1


                                                                    EXHIBIT 10.5

               AMENDED AND RESTATED REGISTRATION RIGHTS AGREEMENT

       Amended and Restated Registration Rights Agreement dated as of May 30,
2001 among CAI CAPITAL PARTNERS AND COMPANY II, L.P., a limited partnership
formed under the laws of the Province of Ontario (the "CANADIAN PARTNERSHIP"),
CAI PARTNERS AND COMPANY II, L.P., a limited partnership formed under the laws
of the Province of Ontario (the "U.S. PARTNERSHIP"), CAI CAPITAL PARTNERS AND
COMPANY II-C, L.P., a limited partnership formed under the laws of the Province
of Ontario ("II-C") and CAI MANAGERS & CO., L.P., a limited partnership formed
under the laws of the State of Delaware and, collectively with the Canadian
Partnership, the U.S. Partnership and II-C , the "CAI ENTITIES" and each a "CAI
ENTITY"), 597858 B.C. LTD., a corporation incorporated under the laws of the
Province of British Columbia ("B.C."), as agent, ONTARIO TEACHERS' PENSION PLAN
BOARD, an entity existing under the laws of the Province of Ontario (the
"INSTITUTIONAL INVESTOR"), MDA HOLDINGS CORPORATION, ("HOLDCO"), a wholly-owned
subsidiary of ORBITAL SCIENCES CORPORATION, a corporation incorporated under the
laws of the State of Delaware ("ORBITAL") and MACDONALD, DETTWILER AND
ASSOCIATES LTD., a corporation amalgamated under the laws of Canada (the
"CORPORATION").

RECITALS:

(a)    The parties hold or may hold common shares (the "COMMON SHARES") in the
       capital of the Corporation.

(b)    The CAI Entities, B.C., Orbital and the Corporation entered into a
       subscription agreement dated as of December 22, 1999, as amended June 29,
       2000 pursuant to which the CAI Entities and B.C. originally acquired an
       equity interest in the Corporation (the "SUBSCRIPTION AGREEMENT").

(c)    The Corporation granted certain registration rights to the CAI Entities,
       B.C. and Orbital which were set forth in Schedule "F" attached to the
       Subscription Agreement (the "REGISTRATION RIGHTS AGREEMENT").

(d)    Following the closing of the Subscription Agreement, Orbital transferred
       all of the Common Shares held by it in the Corporation to its
       wholly-owned subsidiary, Holdco.

(e)    The CAI Entities, B.C. and the Institutional Investor entered into a
       letter agreement dated April 12, 2001 (the "PURCHASE AGREEMENT") with
       Holdco to purchase 12,350,000 of 18,000,000 Common Shares of the
       Corporation held by Holdco (the "PURCHASED SHARES").

(f)    The CAI Entities and B.C. were granted an option to purchase, and
       ancillary rights in respect of, the balance of the 5,650,000 Common
       Shares held by Holdco


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       pursuant to an Amended and Restated Option Agreement dated May 30, 2001
       among Holdco, Orbital, the CAI Entities and B.C.

(g)    The CAI Entities, B.C., the Institutional Investor, Holdco and the
       Corporation have entered into this Agreement for the purpose of setting
       forth the registration rights applicable to certain Common Shares and
       related matters.

       In consideration of the foregoing and the mutual agreements contained
herein (the receipt and adequacy of which are acknowledged), the parties agree
as follows:

                                   ARTICLE 1
                  DEFINITIONS AND PRINCIPLES OF INTERPRETATION

SECTION 1.1   DEFINITIONS

       The terms defined in this Article 1 shall for all purposes of this
Agreement have the meanings herein specified unless the subject matter or
context otherwise requires:

       "ACT" means the Canada Business Corporations Act, as amended;

       "ADDITIONAL PIGGYBACK RIGHTS" has the meaning specified in Section
       2.1(f)(ii);

       "AFFILIATE" shall mean with respect to any Person, any other Person
       directly or indirectly controlling or controlled by or under direct or
       indirect common control with such Person;

       "AMENDED AND RESTATED OPTION AGREEMENT" means the amended and restated
       option agreement dated as of May 30, 2001 among the CAI Entities, B.C.,
       Holdco and Orbital in which Holdco granted an option to purchase the
       Remaining Shares and certain ancillary rights to the CAI Entities and
       B.C.;

       "B.C." means 597858 B.C. Ltd., a corporation incorporated under the laws
       of the Province of British Columbia;

       "BOARD" shall mean the board of directors of the Corporation;

       "CAI ENTITIES" means CAI Capital Partners and Company II, L. P., CAI
       Partners and Company II, L. P., CAI Capital Partners and Company II-C,
       L.P. and CAI Managers & Co., L.P.;

       "CANADIAN PROSPECTUS" shall mean a prospectus prepared in accordance with
       applicable Canadian Securities Laws for the purposes of qualifying
       securities for distribution or distribution to the public, as the case
       may be, in any province or territory of Canada;


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       "CANADIAN SECURITIES LAWS" shall mean the statutes and regulations
       applicable to the trading of securities in any province or territory of
       Canada including applicable rules, policy statements and blanket rulings
       and orders promulgated by Canadian securities regulatory authorities;

       "CLOSING DATE" shall mean May 30, 2001, the date the purchase and sale of
       the Common Shares of the Corporation pursuant to the Purchase Agreement
       is completed;

       "COMMISSION" shall mean the United States Securities and Exchange
       Commission;

       "CONTROLLED" means controlled within the meaning of the Act, and
       "Control" has a similar meaning.

       "CORPORATION" means MacDonald, Dettwiler & Associates Ltd.;

       "CORPORATION SECURITIES" has the meaning specified in Section 2.3(b)(i);

       "DEMAND EXERCISE NOTICE" has the meaning specified in Section 2.1(a);

       "DEMAND REGISTRATION" has the meaning specified in Section 2.1(a);

       "DEMAND REGISTRATION REQUESTS" has the meaning specified in Section
       2.1(a);

       "DOLLARS" shall mean, unless otherwise indicated, Canadian dollars, and
       the symbol "C$" shall refer to Canadian dollars;

       "EXCHANGE ACT" shall mean the United States Securities Exchange Act of
       1934, as amended, and the rules and regulations of the Commission
       thereunder, all as the same shall be in effect at the relevant time;

       "EXERCISING PERSON" has the meaning specified in Section 2.9(a);

       "HOLDCO" means MDA Holdings Corporation, a wholly-owned subsidiary of
       Orbital;

       "HOLDER" or "HOLDERS" shall mean (subject to Section 3.11) (i) each
       Investor while it holds Registrable Securities and (ii) each Person or
       Persons holding Registrable Securities as a result of a transfer or
       assignment made pursuant to Sections 2.2(1), (2) or (6), Sections 2.3 of
       the Resale Restrictions Agreement (as such Sections are in effect on the
       date hereof) or Persons to whom the CAI Entities or B.C., as the case may
       be, Transfer their rights under the Institutional Option Agreement or
       their Remaining Shares pursuant to Sections 3.13(1) and (2) of the Resale
       Restrictions Agreement (as such Sections are in effect on the date
       hereof);

       "INITIATING HOLDERS" has the meaning specified in Section 2.1(a);


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       "INSTITUTIONAL INVESTOR" means the Ontario Teachers' Pension Plan Board;

       "INSTITUTIONAL OPTION AGREEMENT" means the option agreement dated as of
       May 30, 2001 between, among others, the CAI Entities, B.C. and the
       Institutional Investor.

       "INVESTOR SECURITIES" has the meaning specified in Section 2.3(b)(ii);

       "INVESTORS" means CAI Capital Partners and Company II, L.P., CAI Partners
       and Company II, L.P., CAI Capital Partners and Company II-C, L.P., CAI
       Managers & Co., L.P., B.C. and the Institutional Investor;

       "ISSUE PRICE" means $7.50 per Common Share for Common Shares issued
       pursuant to the Subscription Agreement.

       "MAJOR HOLDER" has the meaning specified in Section 2.4(a);

       "ORBITAL" means Orbital Sciences Corporation, a corporation incorporated
       under the laws of the State of Delaware;

       "PERSON" means an individual, corporation, limited liability company,
       body corporate, partnership, limited partnership, joint venture,
       association, trust or unincorporated organization, any trustee, executor,
       administrator or other legal representative, or any government or
       governmental entity;

       "REGISTER" "REGISTERED" and "REGISTRATION" shall refer to a registration
       effected by preparing and filing a registration statement (including the
       prospectus contained therein) in compliance with the U.S. Securities Act
       and the declaration or ordering of the effectiveness of such registration
       statement by the Commission. In addition, unless inconsistent with the
       context:

              (i)    the term "registration" and any references to the act of
                     registering includes the qualification under Canadian
                     Securities Laws of a Canadian Prospectus for which a final
                     receipt has been issued in respect of a distribution or
                     distribution to the public, as the case may be, of Common
                     Shares;

              (ii)   the term "registered" as applied to any Common Shares
                     includes a distribution or distribution to the public, as
                     the case may be, of any Common Shares so qualified;

              (iii)  the term "registration statement" includes a Canadian
                     Prospectus;

              (iv)   any references to a registration statement having become
                     effective, or similar references, shall include a Canadian
                     Prospectus for


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                     which a final receipt has been obtained from the relevant
                     Canadian securities regulatory authorities; and

              (v)    the provisions of this Agreement shall be applied, mutatis
                     mutandis, to any proposed distribution of Common Shares
                     hereunder in any province or territory of Canada or to
                     which the prospectus requirements under any of the Canadian
                     Securities Laws shall otherwise apply;

       "REGISTRABLE SECURITIES" shall mean

              (i)    any Common Shares (which for greater certainty includes the
                     Purchased Shares) held as of the date hereof by the
                     Investors or Holdco;

              (ii)   any Remaining Shares acquired pursuant to the Amended and
                     Restated Option Agreement by the CAI Entities and B.C.;

              (iii)  any additional Common Shares acquired by the CAI Entities
                     or B.C., as the case may be, pursuant to the Institutional
                     Option Agreement;

              (iv)   any Common Shares issued or issuable, directly or
                     indirectly, upon any subdivision, combination or
                     reclassification of such Common Shares (which for greater
                     certainty includes the Purchased Shares), additional Common
                     Shares and Remaining Shares, if applicable, or share
                     dividends in respect of such Common Shares, additional
                     Common Shares and the Remaining Shares, if applicable,
                     referenced in clauses (i), (ii) and (iii) above.

       As to any particular Registrable Securities, such securities shall cease
       to be Registrable Securities when (i) a registration statement with
       respect to the sale of such securities shall have been declared effective
       under the applicable Securities Laws and such securities shall have been
       disposed of in accordance with such registration statement; (ii) such
       securities shall have been resold by the Holder thereof pursuant to Rule
       144 (or any successor provision) under the U.S. Securities Act and in
       compliance with the requirements of Rule 144 and are not subject to any
       resale restrictions in the hands of any subsequent holder or holders
       under any Canadian Securities Laws; or (iii) such securities shall have
       been otherwise transferred and new certificates not subject to resale
       restrictions in the hands of any subsequent holder or holders under the
       Securities Laws and not bearing any legend restricting further transfer
       shall have been delivered by the Corporation, and no other applicable and
       legally binding restriction on transfer under Securities Laws shall
       exist;


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       "REMAINING SHARES" means the balance of 5,650,000 Common Shares of the
       Corporation held by Holdco following the Closing Date which Common Shares
       are optioned to (and subject to other rights in favour of) the CAI
       Entities and B.C. pursuant to the Amended and Restated Option Agreement;

       "RESALE RESTRICTIONS AGREEMENT" means the resale restrictions agreement
       dated as of May 30, 2001 among the CAI Entities, B.C. and the
       Institutional Investor;

       "SECTION 2.1 SALE NUMBER" has the meaning specified in Section 2.3(a);

       "SECTION 2.2 SALE NUMBER" has the meaning specified in Section 2.3(b);

       "SECURITIES" has the meaning specified in Section 2.3(b)(i);

       "SECURITIES LAWS" shall mean, collectively, the U.S. Securities Act, the
       U.S. Exchange Act, as amended, and the Canadian Securities Laws;

       "U.S. EXCHANGE ACT" shall mean the U.S. Securities Exchange Act of 1934,
       as amended, and the rules and regulations of the Commission thereunder,
       all as the same shall be in effect at the relevant time;

       "U.S. SECURITIES ACT" shall mean the United States Securities Act of
       1933, as amended, and the rules and regulations of the Commission
       thereunder, all as the same shall be in effect at the relevant time; and

       "VALID BUSINESS REASON" has the meaning specified in Section 2.1(e)(iii).

                                   ARTICLE 2
                              REGISTRATIONS RIGHTS

SECTION 2.1   DEMAND REGISTRATIONS

       (a)    Subject to Section 2.1(e), Section 2.1(f), Section 2.3 and Section
              2.7 below, at any time and from time to time after the Closing
              Date, one or more Investors or Holdco shall have the right to
              require the Corporation to file a registration statement in any
              Canadian jurisdiction and/or in the United States (if the
              Corporation has listed its securities on an exchange in the United
              States or on the NASDAQ Stock Market or has otherwise become
              subject to the reporting requirements of the U.S. Securities Act
              or the U.S. Exchange Act) covering all or part of their respective
              Registrable Securities, by delivering a written request to the
              Corporation specifying the number of Registrable Securities to be
              included in such registration by such Investor(s) or Holdco, as
              applicable, and the intended method of distribution thereof. All
              requests pursuant to this Section 2.1 are referred to as "DEMAND
              REGISTRATION REQUESTS", and the registrations requested are
              referred to as "DEMAND REGISTRATIONS". With respect to any Demand



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              Registration, the Person (being an Investor or Holdco) that
              together with its Affiliates holds a majority of the Registrable
              Securities in respect of which such demand for registration is
              being made shall be referred to as the "INITIATING HOLDERS". As
              promptly as practicable, but no later than ten days after receipt
              of a Demand Registration Request, the Corporation shall give
              written notice (the "DEMAND EXERCISE NOTICE") of such Demand
              Registration Request to all Holders and Holdco.

       (b)    The Corporation, subject to Section 2.3 and Section 2.7, shall
              include in a Demand Registration the Registrable Securities of any
              Holder or Holdco who shall have made a written request to the
              Corporation for inclusion in such registration (which request
              shall specify the maximum number of Registrable Securities
              intended to be disposed of by such Holder or Holdco, as
              applicable) within 30 days after the date of the Demand Exercise
              Notice.

       (c)    The Corporation shall, as soon as practicable following a Demand
              Registration Request, determine the intended method of
              distribution, including the jurisdiction(s) for distribution, and
              use its reasonable best efforts to effect registration of the
              Registrable Securities under the Securities Laws of the relevant
              jurisdiction(s) for distribution in accordance with such intended
              method of distribution.

       (d)    Any Holder or Holdco shall have the right to withdraw its request
              for inclusion of its Registrable Securities in any registration
              statement pursuant to this Section 2.1 by giving written notice to
              the Corporation of its request to withdraw; provided, however,
              that:

              (i)    such request must be made in writing prior to the execution
                     of the underwriting agreement (or such other similar
                     agreement) with respect to such registration; and

              (ii)   such withdrawal shall be irrevocable and, after making such
                     withdrawal, a Holder or Holdco, as applicable, shall no
                     longer have any right to include Registrable Securities in
                     the registration as to which such withdrawal was made;

              and if such withdrawal is made by an Investor or Holdco, as the
              case may be, that initiated the Demand Registration Request in
              accordance with this Section 2.1(d), then such withdrawal shall
              count as a Demand Registration for such Investor or Holdco, as the
              case may be, pursuant to Section 2.1(e)(iv) of this Agreement.

       (e)    The Demand Registration rights granted under Section 2.1 are
              subject to the following limitations:


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              (i)    the Corporation shall not be required to cause a
                     registration pursuant to Section 2.1 if the Demand
                     Registration Request is in respect of less than one million
                     five hundred thousand (1,500,000) Registrable Securities
                     (after giving effect to any withdrawal pursuant to Section
                     2.1(d) hereof);

              (ii)   the Corporation shall not be required to cause a
                     registration pursuant to Section 2.1 to be declared
                     effective within a period of (A) 180 days after the
                     effective date of any registration statement of the
                     Corporation filed pursuant to a Demand Registration Request
                     or (B) 90 days after the effective date of any other
                     registration statement of the Corporation contemplated by
                     Section 2.2; provided, however, that the provisions of this
                     Section 2.1(e)(ii) shall only apply to the first
                     registration statement in any twelve-month period;

              (iii)  if the Board, in its good faith judgement, determines that
                     any registration of Registrable Securities should not be
                     made or continued because it would materially interfere
                     with any material financing, acquisition, corporate
                     reorganization or merger or other transaction involving the
                     Corporation, including Radarsat-3 and National Land
                     Information Services (a "VALID BUSINESS REASON"),

                     (A)    the Corporation may postpone filing a registration
                            statement relating to a Demand Registration Request
                            until such Valid Business Reason no longer exists,
                            but in no event for more than 90 days during any
                            12-month period;

                     (B)    in case a registration statement has been filed
                            relating to a Demand Registration Request, the
                            Corporation may cause such registration statement to
                            be withdrawn and its effectiveness terminated or the
                            Board may postpone amending or supplementing such
                            registration statement until the Valid Business
                            Reason no longer exists, but in no event for more
                            than 90 days during any 12-month period (such period
                            of postponement or withdrawal under subclauses (A)
                            or (B) of this paragraph (d), the "POSTPONEMENT
                            PERIOD"); and

                     (C)    the Corporation shall give written notice of its
                            determination to postpone or withdraw a registration
                            statement and of the fact that the Valid Business
                            Reason for such postponement or withdrawal no longer
                            exists, in each case, promptly after the occurrence
                            thereof; and


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              (iv)   the Corporation shall not be required to effect a
                     registration pursuant to this Section 2.1 with respect to
                     more than two Demand Registration Requests from each of (A)
                     the CAI Entities, collectively, (B) B.C., (C) the
                     Institutional Investor, and (D) Holdco; however, in the
                     event that there has not been a bona fide underwritten
                     secondary and/or treasury public offering within 12 months
                     following the Closing Date, then the CAI Entities, B.C. and
                     the Institutional Investor only, shall have in the
                     aggregate, one additional Demand Registration Right which
                     shall be subject to the limits set forth in Section 2.1(e),
                     Section 2.1(f), Section 2.3 and Section 2.7 herein
                     exercisable by any one of the Investors upon 7 days' notice
                     to the other Investors prior to the exercise of such Demand
                     Registration.

                     If the Corporation shall give any notice of postponement or
                     withdrawal of any registration statement, the Corporation
                     shall not, during the Postponement Period register any
                     Common Shares, other than pursuant to a registration
                     statement on Form S-4 or S-8 (or an equivalent registration
                     form then in effect) under the U. S. Securities Act or
                     other than pursuant to a Canadian Prospectus filed (a) in
                     connection with a take-over bid, merger, amalgamation or
                     arrangement transaction including the Corporation or any of
                     its Affiliates, or (b) in order to qualify Common Shares
                     for distribution to employees of the Corporation and its
                     subsidiaries, in each case under Canadian Securities Laws,
                     if required. Each Holder and Holdco agrees that, upon
                     receipt of any notice from the Corporation that the
                     Corporation has determined to withdraw any registration
                     statement pursuant to clause (iii) above, such party will
                     discontinue its disposition of Registrable Securities
                     pursuant to such registration statement and, if so directed
                     by the Corporation, will deliver to the Corporation all
                     copies, other than permanent file copies, then in such
                     party's possession, of the registration statement covering
                     such Registrable Securities that was in effect at the time
                     of receipt of such notice. If the Corporation shall have
                     withdrawn or prematurely terminated a registration
                     statement filed under Section 2.1 (whether pursuant to this
                     paragraph (d) or as a result of any stop order, injunction
                     or other order or requirement of the Commission, any
                     Canadian securities regulatory authority or any other
                     governmental agency or court), the Corporation shall not be
                     considered to have effected an effective registration for
                     the purposes of this Agreement until the Corporation shall
                     have filed a new registration statement covering the
                     Registrable Securities covered by the withdrawn
                     registration statement and such


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                     registration statement shall have been declared effective
                     and shall not have been withdrawn.

       (f)    The Corporation, subject to Section 2.3 and Section 2.7, may elect
              to include in any registration statement and offering made
              pursuant to Section 2.1,

              (i)    authorized but unissued Common Shares issued from the
                     Corporation's treasury; and

              (ii)   any other Common Shares which are requested to be included
                     in such registration pursuant to the exercise of piggyback
                     registration rights granted by the Corporation after the
                     date hereof in accordance with the terms of this Agreement
                     ("ADDITIONAL PIGGYBACK RIGHTS");

              provided, however, that such inclusion shall be permitted only the
              extent that it is pursuant to, and subject to the terms of the
              underwriting agreement or arrangements entered into by the
              Initiating Holders.

SECTION 2.2   PIGGYBACK REGISTRATIONS

       (a)    If at any time, the Corporation proposes or is required to
              register any of its Common Shares under the Securities Laws of
              those jurisdictions selected by the Corporation (other than
              pursuant to a registration statement on Form S-4 or S-8 (or an
              equivalent registration form then in effect) under the U. S.
              Securities Act or other than pursuant to a Canadian Prospectus
              filed (a) in connection with a take-over bid, merger, amalgamation
              or arrangement transaction including the Corporation or any of its
              Affiliates, or (b) in order to qualify Common Shares for
              distribution to employees of the Corporation and its subsidiaries,
              in each case under Canadian Securities Laws, if required, or other
              than in connection with a Demand Registration under Section 2.1 of
              this Agreement), whether or not for its own account, the
              Corporation shall give prompt written notice of its intention to
              do so to each Holder of record and to Holdco. Upon the written
              request of any Holder or Holdco, made within 20 days following the
              date of any such written notice (which request shall specify the
              maximum number of Registrable Securities intended to be disposed
              of by each such Holder or Holdco), the Corporation shall, subject
              to Section 2.2(b), Section 2.3 and Section 2.7 hereof, use its
              reasonable best efforts to cause all the Registrable Securities of
              the Holders or Holdco, as applicable, which have so requested the
              registration thereof, to be registered under such Securities Laws
              (with the securities which the Corporation at the time proposes to
              register) to permit the sale or other disposition by the Holders
              and Holdco, as applicable, of the Registrable Securities to be so
              registered. No registration effected under this


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              Section 2.2(a) shall relieve the Corporation of its obligations to
              effect Demand Registrations under Section 2.1. Each Holder and
              Holdco shall be entitled to have its Common Shares included in an
              unlimited number of registrations pursuant to this Section 2.2(a).

       (b)    If at any time after giving written notice of its intention to
              register any Common Shares and prior to the effective date of the
              registration statement filed in connection with such registration,
              the Corporation shall determine for any reason not to register or
              to delay completion of registration of such Common Shares, the
              Corporation may, at its election, give written notice of such
              determination to all Holders and Holdco, and

              (i)    in the case of a determination not to complete a
                     registration, shall be relieved of its obligation to
                     register any Registrable Securities in connection with such
                     abandoned registration, without prejudice, however, to the
                     rights of Holders and Holdco under Section 2.1; and

              (ii)   in the case of a determination to delay such registration
                     of its Common Shares, shall be permitted to delay the
                     completion of registration of such Registrable Securities
                     for the same period as the delay in registering such other
                     Common Shares.

       (c)    Any Holder or Holdco shall have the right to withdraw its request
              for inclusion of its Registrable Securities in any registration
              statement pursuant to this Section 2.2 by giving written notice to
              the Corporation of its request to withdraw; provided, however,
              that:

              (i)    such request must be made in writing prior to the execution
                     of the underwriting agreement (or such other similar
                     agreement) with respect to such registration; and

              (ii)   such withdrawal shall be irrevocable and, after making such
                     withdrawal, the Holder(s) or Holdco, as applicable, shall
                     no longer have any right to include Registrable Securities
                     in the registration as to which such withdrawal was made.

SECTION 2.3   ALLOCATION OF SECURITIES INCLUDED IN REGISTRATION STATEMENT

       (a)    If any requested registration pursuant to Section 2.1 involves an
              underwritten offering and if the lead managing underwriter shall
              advise the Corporation that, in its view, the number of Common
              Shares requested to be included in such registration (including
              those Common Shares requested by the Corporation to be included in
              such registration) exceeds the largest number (the "SECTION 2.1
              SALE NUMBER") that can be sold in an orderly manner in such
              offering within a price range acceptable


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              to the Initiating Holders, the Corporation shall include in such
              registration:

              (i)    all Registrable Securities requested to be registered by
                     all Investors pursuant to Section 2.1; provided, however,
                     that, if the number of Registrable Securities requested to
                     be registered by all Investors pursuant to Section 2.1
                     exceeds the Section 2.1 Sale Number, then the number of
                     Registrable Securities requested by all Investors to be
                     registered pursuant to Section 2.1 which shall be included
                     in such registration shall be allocated on a pro rata
                     basis, based on the number of Registrable Securities owned
                     by each Investor requesting registration pursuant to
                     Section 2.1 in relation to the number of Registrable
                     Securities then owned by all Investors requesting
                     registration pursuant to Section 2.1;

              (ii)   to the extent that the number of Registrable Securities of
                     the Investors requested to be registered pursuant to
                     Section 2.1 is less than the Section 2.1 Sale Number, all
                     Registrable Securities requested to be registered by all
                     Holders (that are not Investors) pursuant to Section 2.1;
                     provided, however, that if the number of Registrable
                     Securities requested to be registered by all Holders (that
                     are not Investors) pursuant to Section 2.1 exceeds the
                     Section 2.1 Sale Number less the number of Registrable
                     Securities of the Investors requested to be registered,
                     then the number of Registrable Securities requested to be
                     registered by all Holders (that are not Investors) which
                     shall be included in such registration shall be allocated
                     on a pro rata basis, based on the number of Registrable
                     Securities owned by each Holder (that is not an Investor)
                     requesting registration pursuant to Section 2.1 in relation
                     to the number of Registrable Securities then owned by all
                     Holders (that are not Investors) requesting registration
                     pursuant to Section 2.1; and

              (iii)  to the extent that the number of Registrable Securities of
                     the Holders (including the Investors) requested to be
                     registered pursuant to Section 2.1 is less than the Section
                     2.1 Sale Number, all (or such lesser number sufficient to
                     aggregate the Section 2.1 Sale Number when added to the
                     number of Registrable Securities of the Holders (including
                     the Investors) requested to be registered pursuant to
                     Section 2.1) of the Registrable Securities requested to be
                     registered by Holdco pursuant to Section 2.1; and

              (iv)   to the extent that the number of Registrable Securities of
                     the Holders (including the Investors) and Holdco requested
                     to be registered pursuant to Section 2.1 is less than the
                     Section 2.1 Sale


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                     Number, all (or such lesser number sufficient to aggregate
                     the Section 2.1 Sale Number when added to the number of
                     Registrable Securities of the Holders (including the
                     Investors) and Holdco requested to be registered pursuant
                     to Section 2.1) of the Common Shares that the Corporation
                     proposes to register; and

              (v)    to the extent that the number of Registrable Securities
                     and/or Common Shares, as the case may be, of the Holders
                     (including the Investors), Holdco and the Corporation
                     requested to be registered pursuant to Section 2.1 is less
                     than the Section 2.1 Sale Number, all (or such lesser
                     number sufficient to aggregate the Section 2.1 Sale Number
                     when added to the number of Registrable Securities and/or
                     Common Shares, as the case may be, of the Holders
                     (including the Investors), Holdco and the Corporation
                     requested to be registered pursuant to Section 2.1) of the
                     Common Shares that a holder or holders of Additional
                     Piggyback Rights proposes to register.

       If, as a result of the proration provisions of this Section 2.3(a), any
       Holder or Holdco shall not be entitled to include all Registrable
       Securities in a registration that such Holder or Holdco, as applicable,
       has requested be registered, such Holder or Holdco, as applicable, may
       elect to withdraw its request to include Registrable Securities in such
       registration or may reduce the number requested to be included; provided,
       however, that: (A) such request must be made in writing prior to the
       execution of the underwriting agreement with respect to such
       registration, and (B) such withdrawal shall be irrevocable and, after
       making such withdrawal, such Holder or Holdco, as applicable, shall no
       longer have any right to include Registrable Securities in the
       registration as to which such withdrawal was made.

       (b)    If any registration pursuant to Section 2.2 involves an
              underwritten offering and the lead managing underwriter shall
              advise the Corporation that, in its view, the number of Common
              Shares requested to be included in such registration exceeds the
              number (the "SECTION 2.2 SALE NUMBER") that can be sold in an
              orderly manner in such registration within a price range
              acceptable to the Corporation, the Corporation shall include in
              such registration:

              (i)    all Common Shares that the Corporation proposes to register
                     for its own account ("CORPORATION SECURITIES");

              (ii)   to the extent that the number of Corporation Securities is
                     less than the Section 2.2 Sale Number, all Registrable
                     Securities requested to be registered by all Investors
                     pursuant to Section 2.2 ("INVESTOR SECURITIES"); provided,
                     however, that, if the number of such


   14
                                     - 14 -


                     Registrable Securities exceeds the Section 2.2 Sale Number
                     less the number of Corporation Securities, then the number
                     of Registrable Securities requested to be registered by all
                     Investors which shall be included in such registration
                     shall be allocated on a pro rata basis, based on the number
                     of Registrable Securities owned by each Investor requesting
                     registration pursuant to Section 2.2 in relation to the
                     number of Registrable Securities then owned by all
                     Investors requesting registration pursuant to Section 2.2;
                     and

              (iii)  to the extent the number of Corporation Securities and
                     Investor Securities is less than the Section 2.2 Sale
                     Number, all Registrable Securities requested to be
                     registered by all other Holders (that are not Investors)
                     pursuant to Section 2.2; provided however, if the number of
                     such Registrable Securities exceeds the Section 2.2 Sale
                     Number less the number of (A) Corporation Securities and
                     (B) Investor Securities, then the number of Registrable
                     Securities requested to be registered by all Holders (that
                     are not Investors) which shall be included in such
                     registration shall be allocated on a pro rata basis, based
                     on the number of Registrable Securities owned by each
                     Holder (that is not an Investor) requesting registration
                     pursuant to Section 2.2 in relation to the number of
                     Registrable Securities then owned by all Holders (that are
                     not Investors) requesting registration pursuant to Section
                     2.2; and

              (iv)   to the extent the number of Corporation Securities and
                     Registrable Securities requested to be registered by all
                     Holders pursuant to Section 2.2 is less than the Section
                     2.2 Sale Number, all (or such lesser number sufficient to
                     aggregate the Section 2.2 Sale Number when added to the
                     Corporation Securities and the number of Registrable
                     Securities of all Holders (including the Investors)
                     requested to be registered pursuant to Section 2.2) of the
                     Registrable Securities requested to be registered by Holdco
                     pursuant to Section 2.2; and

              (v)    to the extent that the number of Corporation Securities and
                     Registrable Securities requested to be registered by all
                     Holders and Holdco pursuant to Section 2.2 is less than the
                     Section 2.2 Sale Number, all (or such lesser number
                     sufficient to aggregate the Section 2.2 Sale Number when
                     added to the Corporation Securities and the number of
                     Registrable Securities of all Holders (including the
                     Investors) and Holdco requested to be registered pursuant
                     to Section 2.2) of the Common Shares requested to be
                     registered by holders of Additional Piggyback Rights.


   15
                                     - 15 -


SECTION 2.4   REGISTRATION PROCEDURES

       If and whenever the Corporation is required by the provisions of this
Agreement to use its reasonable best efforts to effect or cause the registration
of any Registrable Securities under the applicable Securities Laws determined in
the manner contemplated by this Agreement, the Corporation shall, as soon as
reasonably possible:

       (a)    prepare and file with the Commission or Canadian securities
              regulatory authorities a registration statement on an appropriate
              registration form of the Commission or Canadian securities
              regulatory authorities for the disposition of such Registrable
              Securities in accordance with the intended method of disposition
              thereof, which form shall, in the case of a shelf registration, be
              available for the sale of the Registrable Securities by the
              Holders or Holdco and such registration statement shall comply in
              all material respects with the requirements of the applicable form
              and include all financial statements required by the Commission or
              Canadian securities regulatory authorities to be filed therewith,
              and the Corporation shall use its reasonable best efforts to cause
              such registration statement to become and, subject to 2.4(b),
              remain effective (provided, however, that before filing a
              registration statement or any amendments or supplements thereto,
              or comparable statements under securities or "blue sky" laws of
              any United States jurisdiction, the Corporation will furnish to
              counsel (in the case of a registration pursuant to Section 2.1,
              selected by the Initiating Holders and, in the case of a
              registration pursuant to Section 2.2, selected by the Person
              (being a Holder or Holdco), that, together with its Affiliates,
              includes the largest number of Registrable Securities in such
              registration (the "MAJOR HOLDER")) and the underwriters, if any,
              copies of all such documents proposed to be filed (including all
              exhibits thereto), which documents will be subject to the
              reasonable review and reasonable comment of such counsel and the
              underwriter, if any, and the Corporation shall not file any
              registration statement or amendment thereto or any supplement
              thereto to which the Initiating Holders, in the case of a Demand
              Registration Request, the Major Holder in the case of a
              registration pursuant to Section 2.2, or the underwriters, if any,
              shall reasonably object in writing);

       (b)    prepare and file with the Commission or Canadian securities
              regulatory authorities such amendments and supplements to such
              registration statement (including the prospectus contained
              therein) as may be necessary to keep such registration statement
              effective for such period (which shall not be required to exceed
              120 days in the case of a registration pursuant to Section 2.1 or
              90 days in the case of a registration pursuant to Section 2.2) as
              any seller of Registrable Securities pursuant to such registration
              statement may reasonably request and to comply with the provisions
              of the Securities Laws with respect to the sale or other


   16
                                     - 16 -


              disposition of all Registrable Securities covered by such
              registration statement in accordance with the intended methods of
              disposition by the seller or sellers thereof set forth in such
              registration statement;

       (c)    furnish, without charge, to each seller of such Registrable
              Securities and each underwriter, if any, of the securities covered
              by such registration statement such number of copies of such
              registration statement, each amendment and supplement thereto (in
              each case including all exhibits and including any preliminary
              prospectus) included in or constituting such registration
              statement in conformity with the requirements of the applicable
              Securities Laws, and other documents, as such seller and the lead
              managing underwriter may reasonably request in order to facilitate
              the public sale or other disposition of the Registrable Securities
              owned by such seller (the Corporation hereby consenting to the use
              in accordance with all applicable laws of each such registration
              statement (or amendment or post-effective amendment thereto) by
              each such seller of Registrable Securities and the underwriters,
              if any, in connection with the offering and sale of the
              Registrable Securities covered by such registration statement);

       (d)    use its reasonable best efforts to register or qualify the
              Registrable Securities covered by such registration statement
              under such other securities or "blue sky" laws of such
              jurisdictions as any sellers of Registrable Securities or any lead
              managing underwriter, if any, shall reasonably request, and do any
              and all other acts and things which may be reasonably necessary or
              advisable to enable such sellers or the underwriters, if any, to
              consummate the disposition of the Registrable Securities in such
              jurisdictions, except that in no event shall the Corporation be
              required to qualify to do business as a foreign corporation in any
              jurisdiction where it would not, but for the requirements of this
              paragraph (d), be required to be so qualified, to subject itself
              to taxation in any such jurisdiction, to consent to general
              service of process in any such jurisdiction or to qualify the
              Registrable Securities under U.S. Securities Law unless the Common
              Shares are listed and trading on a stock exchange in the United
              States;

       (e)    promptly notify each seller of Registrable Securities covered by
              such registration statement and each lead managing underwriter, if
              any:

              (i)    when the registration statement, any pre-effective
                     amendment, the prospectus or any prospectus supplement
                     included therein or post-effective amendment to the
                     registration statement has been filed and, with respect to
                     the registration statement or any post-effective amendment,
                     when the same has become effective;


   17
                                     - 17 -


              (ii)   of any request by the Commission, any United States state
                     securities authority or any Canadian securities regulatory
                     authority for amendments or supplements to the registration
                     statement or the prospectus included therein or for
                     additional information;

              (iii)  of the issuance by the Commission or any Canadian
                     securities regulatory authority of any stop order
                     suspending the effectiveness of the registration statement
                     or the initiation of any proceedings for that purpose;

              (iv)   of the receipt by the Corporation of any notification with
                     respect to the suspension of the qualification of any
                     Registrable Securities for sale under the securities or
                     "blue sky" laws of any jurisdiction or the initiation of
                     any proceeding for such purpose;

              (v)    of the existence of any fact of which the Corporation
                     becomes aware which results in the registration statement,
                     the prospectus included therein, if any, or any document
                     incorporated therein by reference containing an untrue
                     statement of a material fact or omitting to state a
                     material fact required to be stated therein, or necessary
                     to make any statement therein not misleading or not
                     misleading in light of the circumstances in which it is
                     made; and

              (vi)   if at any time the representations and warranties
                     contemplated by any underwriting agreement, securities
                     sales agreement, or other similar agreement relating to the
                     offering shall cease to be true and correct in all material
                     respects;

       (f)    if the notification relates to an event described in clause (v),
              the Corporation shall promptly prepare and furnish to any seller
              of Registrable Securities and each underwriter, if any, a
              reasonable number of copies of a registration statement
              supplemented or amended so that, as thereafter delivered to the
              purchasers of such Registrable Securities, such registration
              statement shall not include an untrue statement of a material fact
              or omit to state a material fact required to be stated therein or
              necessary to make the statements therein not misleading or not
              misleading in light of the circumstances in which they are made;

       (g)    use its reasonable best efforts (including the payment of any
              listing fees) to obtain the listing of all Registrable Securities
              covered by such registration statement on each securities exchange
              on which securities of the same class are then listed, if the
              listing of such Registrable Securities is then permitted or is
              required under the rules of such exchange;


   18
                                     - 18 -


       (h)    provide and cause to be maintained a transfer agent and registrar
              for all such Registrable Securities covered by such registration
              statement not later than the effective date of such registration
              statement;

       (i)    enter into such customary agreements (including, if applicable, an
              underwriting agreement) and take such other actions as the Major
              Holder (or the Initiating Holders in the case of a Section 2.1
              Demand Registration) shall reasonably request in order to expedite
              or facilitate the disposition of such Registrable Securities;

       (j)    obtain an opinion from the Corporation's counsel and a "cold
              comfort" letter from the Corporation's independent public
              accountants in customary form and covering such matters as are
              customarily covered by such opinions and "cold comfort" letters
              delivered to underwriters in underwritten public offerings, which
              opinion and letter shall be reasonably satisfactory to the
              underwriters, if any, and to the Major Holder (or the Initiating
              Holders in the case of a Section 2.1 Demand Registration)
              participating in such offering and furnish to each Holder and/or
              Holdco (if participating in the offering) and to each underwriter,
              if any, a copy of such opinion and letter addressed to each such
              Holder and/or Holdco and underwriter, if any;

       (k)    use its reasonable best efforts to obtain the withdrawal of any
              order suspending the effectiveness of the registration statement;

       (l)    provide a CUSIP number for all Registrable Securities, not later
              than the effective date of the registration statement, if
              requested;

       (m)    make reasonably available its employees and personnel and
              otherwise provide reasonable assistance to the underwriters in the
              marketing of Registrable Securities in any underwritten offering;
              provided however, that, the Corporation shall not be required to
              have employees attend or conduct any road shows (which for greater
              certainty will not include conference calls or video conferencing)
              with respect to any Demand Registration pursuant to Section 2.1
              hereof more than one time in any 12 month period, unless the
              Corporation is otherwise selling Common Shares under such
              registration statement and is otherwise conducting road shows;
              provided however, that the Corporation shall require such
              employees and personnel to attend and conduct a road show (which
              for greater certainty, shall be in addition to the road show
              described above and conducted pursuant to Section 2.1 once during
              any 12 month period), including conference calls or video
              conferencing, in respect of an underwritten public offering
              pursuant to Section 3.12 hereof, at any time prior to July 31,
              2001;


   19
                                     - 19 -


       (n)    cooperate with the sellers of Registrable Securities and the
              managing lead underwriter, if any, to facilitate the timely
              preparation and delivery of certificates not bearing any
              restrictive legends representing the Registrable Securities to be
              sold, and cause such Registrable Securities to be issued in such
              denominations and registered in such names in accordance with the
              underwriting agreement prior to any sale of Registrable Securities
              to the underwriters or, if not an underwritten offering, in
              accordance with the instructions of the sellers of Registrable
              Securities at least three business days prior to any sale of
              Registrable Securities;

       (o)    if a Canadian Prospectus is filed in the Province of Quebec,
              obtain opinions of Quebec counsel and of the auditors representing
              the Corporation for the purposes of such registration relating to
              translation into the French language of the applicable
              registration statement, in form and substance as is customarily
              given to underwriters in an underwritten public offering and
              reasonably satisfactory to the underwriter, if any, and to the
              Major Holder (or the Initiating Holders, in the case of a Section
              2.1 Demand Registration) participating in such offering and
              furnish to each Holder and/or Holdco (if participating in the
              offering) and to such underwriters, if any, a copy of such
              opinion, addressed to the underwriter, if any, and to each such
              Holder and/or Holdco; and

       (p)    take all such other commercially reasonable actions as are
              necessary or advisable in order to expedite or facilitate the
              distribution of such Registrable Securities.

       The Corporation may require as a condition precedent to the Corporation's
       obligations under this Section 2.4 that each seller of Registrable
       Securities as to which any registration is being effected furnish the
       Corporation such information regarding such seller and the distribution
       of such securities as the Corporation may from time to time reasonably
       request, provided that such information shall be used only in connection
       with such registration. If any Holder or Holdco, as applicable, fails to
       provide the Corporation with such information within 15 days of the
       Corporation's request, the Corporation's obligations under Section 2.1
       and Section 2.2 hereof with respect to such Holder or Holdco, as
       applicable, or the Registrable Securities owned by such Holder or Holdco,
       as applicable, as to which the registration is being effected, shall be
       suspended until such Holder or Holdco, provides such information.

       Each Holder and Holdco agrees that upon receipt of any notice from the
       Corporation of the happening of any event of the kind described in
       Section 2.4(e)(v), each such Holder and Holdco, as applicable, will
       discontinue such Holder's or Holdco's, as applicable, disposition of
       Registrable Securities pursuant to the registration statement covering
       such Registrable Securities until such Holder's or Holdco's, as
       applicable, receipt of the copies of the registration


   20
                                     - 20 -


       statement contemplated by Section 2.4(f) and, if so directed by the
       Corporation, will deliver to the Corporation all copies, other than
       permanent file copies, then in such Holder's or Holdco's, as applicable,
       possession of the registration statement covering such Registrable
       Securities that was in effect at the time of receipt of such notice. In
       the event the Corporation shall give any such notice, the applicable
       period mentioned in Section 2.4(b) shall be extended by the number of
       days during such period from and including the date of the giving of such
       notice to and including the date when each seller of any Registrable
       Securities covered by such registration statement shall have received the
       copies of the registration statement contemplated by Section 2.4(f).

       If any such registration statement or comparable statement under "blue
       sky" laws refers to any Holder or Holdco by name or otherwise as the
       holder of any Registrable Securities of the Corporation, then such Holder
       or Holdco, as applicable, shall have the right to require:

              (i)    the insertion therein of language, in form and substance
                     satisfactory to such Holder or Holdco, as applicable,
                     acting reasonably, to the effect that the holding by such
                     Holder or Holdco, as applicable, of such securities is not
                     to be construed as a recommendation by such Holder or
                     Holdco, as applicable, of the investment quality of the
                     Corporation's securities covered thereby and that such
                     holding does not imply that such Holder or Holdco, as
                     applicable, will assist in meeting any future financial
                     requirements of the Corporation; or

              (ii)   in the event that such reference to such Holder or Holdco,
                     as applicable, by name or otherwise is not in the judgement
                     of the Corporation, as advised by counsel, required by
                     applicable Securities Laws or any similar federal statute
                     or any state "blue sky" or United States or Canadian
                     securities law then in force, the deletion of the reference
                     to such Holder or Holdco, as applicable.

SECTION 2.5   REGISTRATION EXPENSES

       (a)    "EXPENSES" shall mean any and all fees and expenses incident to
              the Corporation's performance of or compliance with this Article
              2, including, without limitation:

              (i)    Commission, Canadian securities regulatory authorities,
                     United States or Canadian stock exchange registration
                     listing and filing fees;

              (ii)   fees and expenses of compliance with Securities Laws or
                     United States "blue sky" laws and in connection with the
                     preparation of a


   21
                                     - 21 -


                     "blue sky" survey, including, without limitation,
                     reasonable fees and expenses of blue sky counsel;

              (iii)  printing and copying expenses;

              (iv)   messenger and delivery expenses;

              (v)    expenses incurred by the Corporation and any underwriter(s)
                     in connection with any road show;

              (vi)   fees and disbursements of counsel for the Corporation;

              (vii)  fees and disbursements of all independent public
                     accountants (including the expenses of any audit and/or
                     "cold comfort" letter) and fees and expenses of other
                     Persons, including special experts, retained by the
                     Corporation; and

              (viii) subject to clause (d)(ii) below, any other fees and
                     disbursements of underwriters, if any, customarily paid by
                     issuers or sellers of securities.

       (b)    Subject to Section 2.5(c), the Corporation shall pay all Expenses
              with respect to any Demand Registration pursuant to Section 2.1
              (which for greater certainty shall include the Expenses associated
              with a withdrawal of a Demand Registration by an Investor or
              Holdco, as the case may be, pursuant to Section 2.1(d) which
              results in the Corporation abandoning the registration pursuant to
              Section 2.1(e)(i) hereof) whether or not such Demand Registration
              becomes effective or does not remain effective for the period
              contemplated by Section 2.4(b). Subject to Section 2.5(c), the
              Corporation shall pay all Expenses of each Investor and Holdco
              with respect to any registration effected under Section 2.2. Each
              Holder (other than the Investors) shall pay the expenses
              attributable to that Holder with respect to any registration
              effected pursuant to Section 2.2 (such expenses shall be allocated
              amongst the Holders (other than the Investors) on a pro rata basis
              based on the number of Registrable Securities included in such
              offering by each Holder (that is not an Investor) relative to the
              number of Common Shares included in such offering, except to the
              extent Expenses are specifically attributable to a Holder (other
              than an Investor) or to Registrable Securities included in an
              offering by a Holder (other than an Investor)).

       (c)    Each Holder and Holdco participating in a registration pursuant to
              Section 2.1 and each Investor and Holdco participating in a
              registration pursuant Section 2.2, shall pay the fees and expenses
              payable by the Corporation pursuant to Sections 2.5(a)(i) and (ii)
              above that are


   22
                                     - 22 -


              calculated on a "per security" basis, which fees and expenses
              shall be allocated between each Holder and Holdco in a
              registration pursuant to Section 2.1 and between each Investor and
              Holdco in a registartion pursuant to Section 2.2 on a pro rata
              basis based on the number of Registrable Securities included in
              such offering by each party relative to the number of Common
              Shares included in such offering; provided that, if the
              Corporation or any other Person sells any Shares pursuant to a
              registration under Section 2.1 or Section 2.2, then the Holders
              and Holdco participating in a registration under Section 2.1, and
              the Investors and Holdco participating in a registration under
              Section 2.2 shall not be responsible for that portion of the fees
              and expenses payable under Sections 2.5(a)(i) and (ii) that are
              attributable to the Corporation or such Person or Persons as a
              result of participating in such offering or offerings.

       (d)    Notwithstanding the foregoing:

              (i)    the provisions of this Section 2.5 shall be deemed amended
                     to the extent necessary to cause these expense provisions
                     to comply with United States "blue sky" laws of each state
                     or the securities laws of any other jurisdiction in which
                     the offering is made as contemplated herein;

              (ii)   in connection with any registration hereunder, each Holder
                     and Holdco shall pay all underwriting discounts and
                     commissions and any transfer taxes, if any, attributable to
                     such Holder's or Holdco's, Registrable Securities sold in
                     the offering;

              (iii)  the Corporation shall be responsible for all of its
                     internal expenses (including, without limitation, all
                     salaries and expenses of its officers and employees
                     performing legal or accounting duties);

              (iv)   each Holder and Holdco shall pay the fees and expenses of
                     its own counsel pursuant to a registration under Section
                     2.2. In the case of a registration pursuant to Section 2.1,
                     the Corporation shall pay the reasonable fees and expenses
                     of one special counsel for the Holders and/or Holdco in
                     each applicable country or province, which special counsel
                     shall be designated by the Initiating Holders, and subject
                     to the approval of the Corporation, in an amount not to
                     exceed US$35,000 per registration pursuant to Section 2.1
                     and an aggregate of US$l50,000 for all registrations under
                     Section 2.1.

SECTION 2.6   CERTAIN LIMITATIONS ON REGISTRATION RIGHTS

       In the case of any registration under Section 2.1 pursuant to an
underwritten offering, or in the case of a registration under Section 2.2 if the
Corporation has determined to enter into an underwriting agreement in connection
therewith, all


   23
                                     - 23 -


securities to be included in such registration shall be subject to an
underwriting agreement and no Person may participate in such registration unless
such Person agrees to sell such Person's securities on the basis provided
therein and completes and/or executes all questionnaires and other documents
which must be executed in connection therewith, and provides such other
information to the Corporation or the underwriter as may be necessary to
register such Person's securities; provided that the Corporation and, in the
case of a Demand Registration pursuant to Section 2.1, the Initiating Holders,
first advises with such Holder and/or Holdco, if applicable requesting
Registrable Securities to be included in such registration as to the terms and
conditions of such underwriting agreement. The Corporation shall be entitled to
select the underwriters for all such offerings; provided that in the case of a
Demand Registration, the Initiating Holders shall be entitled to select the
underwriters with the approval of the Corporation, not to be unreasonably
withheld.

SECTION 2.7   LIMITATIONS ON SALE OR DISTRIBUTION OF OTHER SECURITIES.

       If requested in writing by the Corporation or the lead managing
underwriter, if any, of any registration effected pursuant to Section 2.1 or
Section 2.2, each Holder and Holdco agrees not to effect any public sale or
distribution, including any sale pursuant to Canadian Securities Laws or Rule
144 under the U.S. Securities Act, of any Registrable Securities, or of any
other security convertible into or exchangeable or exercisable for any
Registrable Securities (other than as part of such underwritten public offering)
during the time period reasonably requested by the Corporation or the lead
managing underwriter, if any, not to exceed 180 days (and the Corporation hereby
also agrees to cause each holder of 10% or more of the Common Shares or of any
security convertible into or exchangeable or exercisable for 10% or more of the
Common Shares in respect of which the Corporation then has the power to request
or impose such a restriction to agree to an identical restriction on sale or
distribution of any of their Common Shares or securities convertible or
exchangeable or exercisable for Common Shares).

SECTION 2.8   NO REQUIRED SALE

       Nothing in this Agreement shall be deemed to create an independent
obligation on the part of any Holder or Holdco to sell any Registrable
Securities pursuant to any effective registration statement.

SECTION 2.9   INDEMNIFICATION

       (a)    In connection with any registration statement, the Corporation
              shall indemnify and hold harmless each Holder and Holdco which has
              elected to exercise its registration rights under Section 2.1 or
              Section 2.2 hereof ("EXERCISING Person") and each of its
              respective directors and officers and each person controlling such
              Exercising Person within the meaning of Section 15 of the U. S.
              Securities Act from and against any loss, liability, claim, damage
              and expense whatsoever, including any amounts paid in settlement
              of any investigation, litigation, proceeding or claim, joint or

   24
                                     - 24 -


              several, as incurred, arising out of any untrue statement or
              alleged untrue statement of a material fact contained in any
              registration statement (or any amendment or supplement thereto)
              covering Registrable Securities, including all documents
              incorporated therein by reference, or the omission or alleged
              omission therefrom of a material fact required to be stated
              therein or necessary to make the statements therein not misleading
              or not misleading in the light of the circumstances under which
              they were made; provided, that, the Corporation shall not be
              liable under this clause (a) for any settlement of any action
              effected without its written consent, which consent shall not be
              unreasonably withheld or delayed; provided, further, that the
              indemnity provided for in this Section 2.9(a) shall not apply to
              any loss, liability, claim, damage or expense to the extent
              arising out of an untrue statement or omission or alleged untrue
              statement or omission (i) made in reliance upon and in conformity
              with written information furnished to the Corporation by such
              Exercising Person in writing expressly stating that such
              information is being provided by such Exercising Person for use in
              the registration statement (or any amendment thereto) or any
              prospectus (or any amendment or supplement thereto) included
              therein or (ii) contained in any registration statement if such
              Exercising Person failed to send or deliver a copy of the
              registration statement (or any amendment or supplement thereto) to
              the Person asserting such losses, claims, damages or liabilities
              on or prior to the delivery of written confirmation of any sale of
              securities covered thereby to such Person in any case where such
              registration statement (or any amendment or supplement thereto)
              corrected such untrue statement or omission. Any amounts advanced
              by the Corporation to an indemnified party pursuant to this
              Section 2.9 as a result of such losses shall be returned to the
              Corporation if it shall be finally determined by such a court in a
              judgement not subject to appeal or final review that such
              indemnified party was not entitled to indemnification by the
              Corporation.

       (b)    Each Exercising Person, severally and not jointly, shall indemnify
              and hold harmless the Corporation and the other Exercising Persons
              and each of their respective directors and officers (including
              each officer and director (if applicable) of the Corporation who
              signed the registration statement) and each Person, if any, who
              controls the Corporation or any other Exercising Person within the
              meaning of Section 15 of the U. S. Securities Act, from and
              against any loss, liability, claim, damage and expense whatsoever
              described in the indemnity contained in Section 2.9(a) hereof, as
              incurred, but only with respect to untrue statements or omissions,
              or alleged untrue statements or omissions, made in the
              registration statement (or any amendment thereto) or any
              prospectus (or any amendment or supplement thereto) included
              therein in reliance upon and in conformity with written
              information furnished to the Corporation


   25
                                     - 25 -


              by such Exercising Person in writing expressly stating that such
              information is being provided by such Holder for use in the
              registration statement (or any amendment thereto) or any
              prospectus (or any amendment or supplement thereto) included
              therein provided, that the Exercising Person shall not be liable
              under this clause for any settlement of any action effected
              without its written consent, which consent shall not be
              unreasonably withheld.

       (c)    Each party entitled to indemnification under this Section 2.9 (the
              "INDEMNIFIED PARTY") shall give notice to the party required to
              provide indemnification (the "INDEMNIFYING PARTY") promptly after
              such Indemnified Party has actual knowledge of any claim as to
              which indemnity may be sought, but the omission to so notify the
              Indemnifying Party shall not relieve it from any liability which
              it may have to the Indemnified Party pursuant to the provisions of
              this Section 2.9 except to the extent of the actual damages
              suffered by such delay in notification. The Indemnifying Party
              shall assume the defence of such action, including the employment
              of counsel to be chosen by the Indemnifying Party to be reasonably
              satisfactory to the Indemnified Party, and payment of expenses.
              The Indemnified Party shall have the right to employ its own
              counsel in any such case, but the legal fees and expenses of such
              counsel shall be at the expense of the Indemnified Party, unless
              the employment of such counsel shall have been authorized in
              writing by the Indemnifying Party in connection with the defence
              of such action, or the Indemnifying Party shall not have employed
              counsel to take charge of the defence of such action within a
              reasonable time after notice thereof or the Indemnified Party
              shall have reasonably concluded that there may be defences
              available to it or them which are different from or additional to
              those available to the Indemnifying Party (in which case the
              Indemnifying Party shall not have the right to direct the defence
              of such action on behalf of the Indemnified Party), in any of
              which events such fees and expenses shall be borne by the
              Indemnifying Party. No Indemnifying Party, in the defence of any
              such claim or litigation, shall, except with the consent of each
              Indemnified Party, consent to entry of any judgement or enter into
              any settlement which does not include as an unconditional term
              thereof the giving by the claimant or plaintiff to such
              Indemnified Party of a release from all liability in respect to
              such claim or litigation.

       (d)    If the indemnification provided for in this Section 2.9 is
              unavailable to a party that would have been an Indemnified Party
              under this Section 2.9 in respect of any expenses, claims, losses,
              damages and liabilities referred to herein, then each party that
              would have been an Indemnifying Party hereunder shall, in lieu of
              indemnifying such Indemnified Party, contribute to the amount paid
              or payable by such Indemnified Party as a


   26
                                     - 26 -


              result of such expenses, claims, losses, damages and liabilities
              in such proportion as is appropriate to reflect the relative fault
              of the Indemnifying Party on the one hand and such Indemnified
              Party on the other in connection with the statement or omission
              which resulted in such expenses, claims, losses, damages and
              liabilities, as well as any other relevant equitable
              considerations. The relative fault shall be determined by
              reference to, among other things, whether the untrue or alleged
              untrue statement of a material fact or the omission or alleged
              omission to state a material fact relates to information supplied
              by the Indemnifying Party or such Indemnified Party and the
              parties' relative intent, knowledge, access to information and
              opportunity to correct or prevent such statement or omission. The
              Corporation and each Exercising Person agrees that it would not be
              just and equitable if contribution pursuant to this Section were
              determined by pro rata allocation or by any other method of
              allocation which does not take account of the equitable
              considerations referred to above in this Section 2.9(d).

       (e)    No Person guilty of fraudulent misrepresentation (within the
              meaning of Section 11(f) of the U.S. Securities Act) shall be
              entitled to contribution from any Person who was not guilty of
              such fraudulent misrepresentation.

       (f)    Notwithstanding any provision of this Agreement or any other
              agreement, in no event will any Exercising Person be liable for
              indemnification hereunder for an amount greater than the amount of
              proceeds that such Exercising Person received in any particular
              offering of Common Shares in which its Registrable Securities were
              sold.

                                    ARTICLE 3
                                     GENERAL

SECTION 3.1   RULE 144

       If the Corporation shall have filed a registration statement pursuant to
the requirements of Section 12 of the U.S. Exchange Act or a registration
statement pursuant to the requirements of the U.S. Securities Act in respect of
the Common Shares or securities of the Corporation convertible into or
exchangeable or exercisable for Common Shares, the Corporation covenants that:

       (a)    so long as it remains subject to the reporting provisions of the
              U.S. Exchange Act, it will timely file the reports required to be
              filed by it under the U.S. Securities Act or the U.S. Exchange Act
              (including, without limitation, the reports under Sections 13 and
              15(d) of the U.S. Exchange Act referred to in subparagraph (c)(l)
              of Rule 144 under the U.S. Securities Act); and


   27
                                     - 27 -


       (b)    to the extent required from time to time to enable such Holder to
              sell Registrable Securities without registration under the U.S.
              Securities Act within the limitation of the exemptions provided by
              (a) Rule 144 under the U.S. Securities Act, as such Rule may be
              amended from time to time, or (b) any similar rule or regulation
              hereafter adopted by the Commission. Upon the request of any
              Holder or Holdco, the Corporation will deliver to such Holder or
              Holdco, as applicable, a written statement as to whether it has
              complied with such requirements.

SECTION 3.2   NOMINEES FOR BENEFICIAL OWNERS

       If Registrable Securities are held by a nominee for the beneficial owner
thereof, the beneficial owner thereof may, at its option, be treated as the
holder of such Registrable Securities for purposes of any request or other
action by any holder or holders of Registrable Securities pursuant to this
Agreement (or any determination of any number or percentage of Common Shares
constituting Registrable Securities held by any holder or holders of Registrable
Securities contemplated by this Agreement); provided, however, that the
Corporation shall have received written assurances reasonably satisfactory to it
of such beneficial ownership.

SECTION 3.3   AMENDMENTS

       The terms and provisions of this Agreement may be modified or amended, or
any of the provisions hereof waived, temporarily or permanently, pursuant to the
prior written consent of the Corporation and the party adversely affected by
such modification or waiver.

SECTION 3.4   NOTICES

       All notices, requests, consents and other communications hereunder to any
party shall be deemed to be sufficient if contained in a written instrument
delivered in person or sent by telecopy, nationally recognized overnight courier
or first class registered or certified mail, return receipt requested, postage
prepaid, addressed to such party at the address set forth below or such other
address as may hereafter be designated in writing by such party to the other
parties:

       (a)    if to the CAI Entities, to:

              c/o CAI Managers & Co., L. P.
              767 Fifth Avenue
              New York, NY 10153

              Attention: Manfred Yu

              Telephone: (212) 319-3023
              Facsimile: (212) 319-0232


   28
                                     - 28 -


              with a copy to (which shall not constitute notice for the purposes
              of this Agreement):

              Stikeman Elliott
              Commerce Court West
              Suite 5300, 199 Bay Street
              Toronto, ON M5L lB9

              Attention: Simon Romano

              Telephone: (416) 869-5596
              Facsimile: (416) 947-0860

       (b)    if to B.C., to:

              Randall Mullan
              c/o McCullough O'Connor Irwin
              1100-888 Dunsmuir Street
              Vancouver, BC V6C 3K4

              Attention: Jonathon McCullough

              Telephone: (604) 687-7077
              Facsimile: (604) 687-7079

       (c)    if to the Institutional Investor, to:

              5650 Yonge Street
              Toronto, Ontario, Canada M2M 4H5

              Attention: Roy Graydon

              Telephone: (416) 730-6167
              Facsimile: (416) 730-5143

              with a copy to (which shall not constitute notice for the purposes
              of this Agreement):

              Goodmans
              Suite 2400
              250 Yonge Street
              Toronto, Ontario M5B 2M6

              Attention: Jonathan Lampe

              Telephone: (416) 979-2211
              Facsimile: (416) 979-1234


   29
                                     - 29 -


       (d)    if to Holdco, to:

              c/o 21700 Atlantic Boulevard
              Dulles, Virginia
              20166

              Attention:    Legal Department

              Telephone:    (703) 406-5000
              Facsimile:    (703) 406-5572

              with a copy to (which shall not constitute notice for the purposes
              of this Agreement):

              Hogan & Hartson, L.L.P.
              555 13th Street, N.W.
              Washington, D.C.
              20004 - 1109

              Attention:    Eve N. Howard

              Telephone:    (202) 537-5627
              Facsimile:    (202) 537-5910

              (e)    if to the Corporation, to:

              13800 Commerce Parkway
              Richmond, BC V6V 253

              Attention: Chief Executive Officer

              Telephone: (604) 278-3411
              Facsimile: (604) 278-l837

              with a copy to (which shall not constitute notice for the purposes
              of this Agreement):

              Farris Vaughan Wills & Murphy
              P. O. Box 10026
              Pacific Centre South
              Toronto Dominion Bank Tower
              700 West Georgia Street
              Vancouver, B.C. V7Y lB3

              Attention: Elizabeth Harrison, Esq.


   30
                                     - 30 -


              Telephone: (604) 661-9367
              Facsimile: (604) 661-9349

Each party, by written notice given to the Corporation in accordance with this
Section 3.4, may change the address to which such notice or other communications
are to be sent to such party. All such notices, requests, consents and other
communications shall be deemed to have been given when received.

SECTION 3.5   REGISTRATION RIGHTS OF ORBITAL

       Subject to Section 3.8:

       (a)    For good and valuable consideration, the receipt and sufficiency
              of which is hereby acknowledged by each of Orbital, the
              Corporation, the CAI Entities and B.C., Orbital, the Corporation,
              the CAI Entities and B.C. covenant and agree that the registration
              rights granted to Orbital pursuant to the Registration Rights
              Agreement in respect of its Registrable Securities as defined in
              the Registration Rights Agreement are cancelled and terminated as
              and from the date of this Agreement and all the provisions of the
              Registration Rights Agreement as they relate to Orbital are hereby
              declared to be null and void and of no further force and effect.

       (b)    Orbital and the Corporation hereby release each other, their
              successors and assigns and the CAI Entities and B.C. from any
              claims or demands arising under or pursuant to the Registration
              Rights Agreement as it relates to the rights granted to Orbital.

       (c)    Orbital acknowledges that the registration rights previously
              granted to it under the Registration Rights Agreement have been in
              effect granted to Holdco pursuant to this Agreement.

SECTION 3.6   SUBORDINATION OF REGISTRATION RIGHTS OF HOLDCO

       Holdco's registration rights in respect of the Corporation set forth in
this Agreement shall in all respects be subordinate to the rights of the Holders
herein.

SECTION 3.7   CERTAIN COVENANTS OF ORBITAL AND HOLDCO IN FAVOUR OF THE CAI
ENTITIES AND B.C.

       The CAI Entities, B.C., Orbital and Holdco covenant and agree as follows:

       (a)    For so long as (i) the CAI Entities and B.C. collectively own the
              lesser of (a) at least 10% of the outstanding Common Shares, and
              (b) Common Shares representing at least U.S.$25 million based on
              their Issue Price, and (ii) Orbital Controls Holdco, Holdco shall
              not at any time incur or guarantee any indebtedness for borrowed
              money (including borrowings represented by a note, bond, debenture
              or other evidence of indebtedness) or other obligations, or
              pledge, grant security over or otherwise encumber

   31
                                     - 31 -



              any of its assets, or dispose of any of its assets except for
              transfers of Common Shares in accordance with the Amended and
              Restated Option Agreement, without the consent of the CAI Entities
              and B.C.

       (b)    For so long as (i) the CAI Entities and B.C. collectively own the
              lesser of (a) at least 10% of the outstanding Common Shares, and
              (b) Common Shares representing at least U.S.$25 million based on
              their Issue Price, and (ii) Orbital Controls Holdco, Holdco shall
              not, without the consent of the CAI Entities and B.C., amend its
              articles (except immaterial amendments) or be the subject of any
              reorganization, continuance, amalgamation, arrangement, merger,
              winding-up, liquidation or dissolution.

       (c)    Orbital will at all times, for so long as Orbital Controls Holdco,
              ensure that any security existing with respect to any shares of
              Holdco held by Orbital shall comply with the following: Orbital
              shall be entitled to pledge any or all of its shares of Holdco to
              a bona fide arm's length lender or lenders (the "LENDER") of
              Orbital from time to time as security for indebtedness of Orbital
              owed to such Lender provided that such Lender acknowledges in
              writing to the CAI Entities, B.C. and Holdco that (i) until a
              default under the pledge, the pledged shares shall continue to be
              registered in the name of Orbital and Orbital shall be entitled to
              exercise all rights in respect thereof (including voting rights
              and director nomination rights), and (ii) if the Lender commences
              enforcement proceedings or otherwise realizes on the pledged
              shares following default, the Lender shall immediately notify the
              CAI Entities, B.C. and Holdco and its interest in the pledged
              shares shall be subject to the provisions of this Section
              applicable thereto, as and to the same extent as though the Lender
              were Orbital.

       (d)    Orbital will at all times, for so long as Orbital Controls Holdco,
              ensure that Holdco, if applicable, and the Corporation and its
              subsidiaries shall operate consistent with the following: Orbital
              shall ensure that Holdco complies with the Amended and Restated
              Option Agreement and, for so long as the CAI Entities and B.C.
              hold at least 10% of the outstanding Common Shares or Common
              Shares representing at least U.S.$25 million based on their Issue
              Price, Orbital shall ensure that Holdco complies with its charter
              documents (which shall continue to have limitations satisfactory
              to the CAI Entities and B.C., acting reasonably, on its activities
              to ensure its separateness and independence).

       (e)    The provisions of this Section 3.7 shall terminate two years from
              the date hereof.

SECTION 3.8   EFFECTIVENESS OF CERTAIN AGREEMENTS

       The Registration Rights Agreement is terminated, amended, restated,
replaced and superseded by this Agreement effective immediately.


   32
                                     - 32 -


SECTION 3.9   PERMITTED TRANSFEREES OF THE CAI ENTITIES

       Each Person or Persons holding Registrable Securities as a result of a
transfer or assignment by the CAI Entities contemplated by Section 2.3 of the
Resale Restrictions Agreement, shall be deemed collectively for the purposes of
this Agreement a CAI Entity and such investors shall agree to act for the
purposes of this Agreement through one of the CAI Entities or their general
partners for the earlier of the term of this Agreement and 12 months following
the Closing Date, and shall not, for greater certainty, exercise a Demand
Registration pursuant to Section 2.1 without the prior consent of one of the CAI
Entities or their general partners.

SECTION 3.10  CAI

       The parties to this Agreement (including any other Person or Persons that
become bound by the terms of this Agreement) agree that the CAI Entities shall
be treated collectively for purposes of the computations found in Sections
3.7(a), (b) and (d) and shall be deemed to be Affiliates for the purposes
hereof.

SECTION 3.11  HOLDERS

       This Agreement shall cease to apply to a Holder (that is a transferee
pursuant to Section 2.2(2) or Sections 3.13(1) or (2) of the Resale Restrictions
Agreement as in effect on the date hereof) following June 30, 2002.

SECTION 3.12  REMAINING SHARES

(1)    Notwithstanding anything to the contrary contained in this Agreement,

       (a)    if the CAI Entities or B.C., as the case may be (each an
              "EXERCISING OPTIONHOLDER"), exercises its right under Section 5(b)
              of the Amended and Restated Option Agreement to require Holdco to
              sell the Remaining Shares pursuant to an underwritten public
              offering at any time prior to the Termination Date (as defined in
              the Amended and Restated Option Agreement), then Holdco shall
              promptly thereafter exercise a Demand Registration pursuant to
              Section 2.1 of the Amended and Restated Registration Rights
              Agreement to sell, by way of an underwritten public offering, any
              or all of the Remaining Shares and the Exercising Optionholder
              shall be entitled to (i) select the underwriter(s) for such public
              offering; and (ii) exercise the decision-making powers of Holdco
              in respect of such Demand Registration as if it was Holdco
              (notwithstanding that the Demand Registration is being exercised
              by Holdco), and the Exercising Optionholder shall be treated in
              all other respects as the Initiating Holder for the purposes of
              such offering; and

       (b)    none of the Holders (other than the Exercising Optionholder),
              Holdco, the Corporation or the holders of Additional Piggyback
              Rights shall be entitled to participate in the Demand Registration
              and/or underwritten


   33
                                     - 33 -


              public offering without the prior written consent of the
              Exercising Optionholder, in its sole discretion; and

       (c)    for greater certainty, Section 2.3(a) and Section 2.1(b) shall not
              apply in such circumstances.

(2)    The Corporation, Holdco and Orbital agree to cooperate in full with the
       Exercising Optionholder, in connection with the sale of the Remaining
       Shares pursuant to an underwritten public offering, including without
       limitation, participating in the prospectus process, assisting with
       access for due diligence purposes, and signing any requested underwriting
       or indemnification agreements on terms not materially more adverse to
       them than those applicable in the Corporation's initial public offering.

(3)    The exercise by Holdco of a Demand Registration in accordance with
       Section 2.1(1) shall count as one of Holdco's Demand Registrations
       pursuant to Section 2.1(e)(iv) of this Agreement.

SECTION 3.13  BOARD APPROVAL

       The terms and conditions of this Agreement shall not take effect until
ratified, confirmed and approved by the board of directors of the Corporation
(it being understood that all members of the board of directors of the
Corporation shall be entitled, notwithstanding their interest, to vote thereon
given the immateriality of this Agreement).

SECTION 3.14  MISCELLANEOUS

       (a)    This Agreement shall be binding upon and enure to the benefit of
              and be enforceable by the parties hereto and the respective
              successors, personal representatives and permitted assigns of the
              parties hereto, whether so expressed or not, provided that, for
              greater certainty, no Person other than a Holder or Holdco shall
              be entitled to any benefits under this Agreement, except as
              otherwise expressly provided herein. This Agreement and the rights
              of the parties hereunder may be assigned in whole by any of the
              parties hereto to any transferee (other than a Holder) of
              Registrable Securities with the consent of the Corporation, which
              consent shall not be unreasonably withheld, provided that upon the
              consummation of, and as a condition to, any such assignment the
              transferee assumes the obligations of the assignor under, and
              agrees to be bound by the terms of this Agreement.

       (b)    This Agreement and the other writings referred to herein or
              delivered pursuant hereto which form a part hereof contain the
              entire agreement among the parties with respect to the subject
              matter hereof and supersede all prior and contemplated
              arrangements and understandings with respect thereto, including
              but not limited to, Schedule "F" of the


   34
                                     - 34 -


              Subscription Agreement dated as of June 29, 2000, as amended among
              CAI Capital Partners and Company II, L.P., CAI Partners and
              Company II, L.P., CAI Capital Partners and Company II-C, L.P.,
              597858 B.C. LTD., Orbital Sciences Corporation, MacDonald,
              Dettwiler Holdings Inc. and MacDonald, Dettwiler and Associates
              Ltd.

       (c)    This Agreement shall be governed by and construed in accordance
              with the laws of the Province of British Columbia without giving
              effect to the principles of conflicts of law thereof.

       (d)    The headings of the sections of this Agreement have been inserted
              for convenience of reference only and shall not be deemed to be a
              part of this Agreement.

       (e)    This Agreement may be executed in any number of counterparts, and
              each such counterpart hereof shall be deemed an original
              instrument, but all such counterparts together shall constitute
              but one instrument.

       (f)    Whenever possible, each provision of this Agreement shall be
              interpreted in such manner as to be effective and valid, but if
              any provision of this Agreement is held to be invalid or
              unenforceable in any respect, such invalidity or unenforceability
              shall not render invalid or unenforceable any other provision of
              this Agreement.

       (g)    It is hereby agreed and acknowledged that it will be impossible to
              measure in money the damages that would be suffered if the parties
              fail to comply with any of the obligations herein imposed on them
              and that in the event of any such failure, an aggrieved Person
              will be irreparably damaged and will not have an adequate remedy
              at law. Any such Person, therefore, shall be entitled to
              injunctive relief, including specific performance, to enforce such
              obligations, without the posting of any bond, and, if any action
              should be brought in equity to enforce any of the provisions of
              this Agreement, none of the parties hereto shall raise the defence
              that there is an adequate remedy at law.

       (h)    Each party hereto shall do and perform or cause to be done and
              performed all such further acts and things and shall execute and
              deliver all such other agreements, certificates, instruments, and
              documents as any other party hereto reasonably may request in
              order to carry out the intent and accomplish the purposes of this
              Agreement and the consummation of the transactions contemplated
              hereby.

   35
                                     - 35 -



       IN WITNESS WHEREOF the parties have executed this Agreement.


                                   CAI CAPITAL PARTNERS AND COMPANY II, L.P. BY
                                   ITS GENERAL PARTNER, CAI CAPITAL PARTNERS GP
                                   & CO., L.P., BY ONE OF ITS GENERAL PARTNERS
                                   36 PIERREPONT ST. II. CO.

                                   By:
                                         ---------------------------------------
                                         Name:     Peter Restler
                                         Title:    President


                                   CAI PARTNERS AND COMPANY II,  L.P. BY ITS
                                   GENERAL PARTNER, CAI PARTNERS GP & CO., L.P.,
                                   BY ONE OF ITS GENERAL PARTNERS, 36 PIERREPONT
                                   ST. II. CO.

                                   By:
                                         ---------------------------------------
                                         Name:     Peter Restler
                                         Title:    President


                                   CAI CAPITAL PARTNERS AND COMPANY II-C, L.P.,
                                   BY ITS GENERAL PARTNER, CAI CAPITAL PARTNERS
                                   GP II-C INC.

                                   By:
                                         ---------------------------------------
                                         Name:     Manfred Yu
                                         Title:    Assistant Secretary


                                   CAI MANAGERS & CO., L.P.

                                   By:
                                         ---------------------------------------
                                         Name:     Manfred Yu
                                         Title:    Vice-President and Secretary


   36
                                     - 36 -


                                   597858 B.C. LTD., AS AGENT

                                   By:
                                         ---------------------------------------
                                         Name:     Randall Mullan
                                         Title:    Director


                                   ONTARIO TEACHERS' PENSION PLAN BOARD

                                   By:
                                         ---------------------------------------
                                         Name:     Roy Graydon
                                         Title:    Vice-President, Relationship
                                                   Investing


                                   MACDONALD, DETTWILER AND ASSOCIATES LTD.

                                   By:
                                         ---------------------------------------
                                         Name:     Anil Wirasekara
                                         Title:    Chief Financial Officer


                                   MDA HOLDINGS CORPORATION

                                   By:
                                         ---------------------------------------
                                         Name:
                                         Title:


                                   ORBITAL SCIENCES CORPORATION
                                   ONLY FOR THE PURPOSES OF SECTIONS 3.5 , 3.7
                                   AND 3.8

                                   By:
                                         ---------------------------------------
                                         Name:
                                         Title: