EXHIBIT 2.2


              VOTING AND EXCHANGE TRUST AGREEMENT


           MEMORANDUM  OF AGREEMENT made as of  the       day  of
,  1995.


B E T W E E N:


                  ORBITAL SCIENCES CORPORATION,
                  a  corporation existing under
                  the  laws  of  the  State  of
                  Delaware,

                  (hereinafter referred to as "Orbital"),

                            - and -

                  MacDONALD DETTWILER HOLDINGS INC.,
                  (formerly known as 3173623 Canada Inc.)
                  a  corporation existing under
                  the laws of Canada,

                  (hereinafter referred to as "Corporation"),

                            - and -

                  STATE STREET BANK AND TRUST COMPANY,
                  a  !  existing under the laws
                  of the United States,

                  (hereinafter referred to as "Trustee").



          WHEREAS pursuant to a combination agreement dated as of
August  31,  1995 (the "Combination Agreement"), by  and  between
Orbital,  the Corporation and MacDonald, Dettwiler and Associates
Ltd.  ("MDA"), the parties agreed that on the Effective Date  (as
defined   in   the  Combination  Agreement),  Orbital   and   the
Corporation would execute and deliver a Voting and Exchange Trust
Agreement  containing  the  terms and  conditions  set  forth  in
Exhibit 2.2 to the Combination Agreement together with such other
terms  and conditions as may be agreed to by the parties  to  the
Combination Agreement acting reasonably;

            AND   WHEREAS   pursuant  to  an   arrangement   (the
"Arrangement")   effected  by  articles  of   arrangement   dated
,  1995  filed pursuant to the Canada Business Corporations  Act,
each  issued and outstanding common share of MDA (an "MDA  Common
Share") was exchanged directly or indirectly for 0.# of an issued
and  outstanding Exchangeable Non-Voting Share of the Corporation
(the "Exchangeable Shares");

           AND WHEREAS the aforesaid articles of arrangement  set
forth   the   rights,  privileges,  restrictions  and  conditions
(collectively the "Exchangeable Share Provisions")  attaching  to
the Exchangeable Shares;

           AND  WHEREAS  Orbital is to provide voting  rights  in
Orbital  to  each holder (other than Orbital and its  Affiliates)
from time to time of Exchangeable Shares, such voting rights  per
Exchangeable  Share  to be equivalent to the  voting  rights  per
share  of  the  common stock, par value U.S. $.01 per  share,  of
Orbital (the "Orbital Common Shares");

          AND WHEREAS Orbital is to grant to and in favour of the
holders (other than Orbital and its Affiliates) from time to time
of  Exchangeable Shares the right, in the circumstances set forth
herein, to require Orbital to purchase from each such holder  all
or any part of the Exchangeable Shares held by the holder;

           AND  WHEREAS  the  parties desire to make  appropriate
provision  and to establish a procedure whereby voting rights  in
Orbital  shall be exercisable by holders (other than Orbital  and
its  Affiliates) from time to time of Exchangeable Shares by  and
through the Trustee, which will hold legal title to one share  of
Orbital Special Voting Preferred Stock, U.S. $.01 par value  (the
"Orbital  Special Voting Stock"), to which voting  rights  attach
for the benefit of such holders and whereby the rights to require
Orbital  to purchase Exchangeable Shares from the holders thereof
shall  be  exercisable  by such holders  from  time  to  time  of
Exchangeable Shares by and through the Trustee, which  will  hold
legal title to such rights for the benefit of such holders;

           AND  WHEREAS these recitals and any statements of fact
in this Agreement are made by Orbital and the Corporation and not
by the Trustee;

           NOW  THEREFORE  in  consideration  of  the  respective
covenants and agreements provided in this Agreement and for other
good  and valuable consideration (the receipt and sufficiency  of
which are hereby acknowledged), the parties agree as follows:


                           ARTICLE 1

                 DEFINITIONS AND INTERPRETATION

1.1        Definitions.  In this Agreement, the  following  terms
shall have the following meanings:

           "Affiliate"  of  any  person means  any  other  person
directly  or  indirectly  controlling, controlled  by,  or  under
common  control  of,  that  person.  For  the  purposes  of  this
definition, "control" (including, with correlative meanings,  the
terms  "controlling", "controlled by" and "under  common  control
of"),  as applied to any person, means the possession by  another
person,  directly or indirectly, of the power to direct or  cause
the  direction  of  the  management and policies  of  that  first
mentioned  person,  whether  through  the  ownership  of   voting
securities, by contract or otherwise.

           "Arrangement" has the meaning ascribed thereto in  the
recitals hereto.

           "Automatic Exchange Rights" means the benefit  of  the
obligation of Orbital to effect the automatic exchange of  shares
of  Orbital  Common  Shares for Exchangeable Shares  pursuant  to
subsection 5.12(c) hereof.

           "Board  of Directors" means the Board of Directors  of
the Corporation.

           "Business  Day" means a day other than a  Saturday,  a
Sunday  or a day when banks are not open for business in  one  or
both  of  Vancouver,  British Columbia and  the  Commonwealth  of
Virginia.

           "Call Rights" means collectively the Liquidation  Call
Right, the Redemption Call Right and the Retraction Call Right.

           "Canadian  Dollar Equivalent" means in respect  of  an
amount  expressed  in a foreign currency (the  "Foreign  Currency
Amount") at any date the product obtained by multiplying (a)  the
Foreign  Currency  Amount by (b) the noon spot exchange  rate  on
such date for such foreign currency expressed in Canadian dollars
as  reported  by  the Bank of Canada or, in the event  such  spot
exchange  rate is not available, such exchange rate on such  date
for such foreign currency expressed in Canadian dollars as may be
deemed  by  the  Board  of Directors to be appropriate  for  such
purpose.

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

           "Current  Market Price" means, in respect  of  Orbital
Common Shares on any date, the Canadian Dollar Equivalent of  the
closing sale price of Orbital Common Shares on such date (or,  if
no  trades of any Orbital Common Shares occurred on such date, on
the last trading day prior thereto on which such trades occurred)
reported on the NASDAQ National Market System, or, if the Orbital
Common  Shares are not then quoted on the NASDAQ National  Market
System,  on  such  other  stock exchange or  automated  quotation
system  on which the Orbital Common Shares are listed or  quoted,
as  the case may be, as may be selected by the Board of Directors
for  such  purpose; provided, however, that if in the opinion  of
the  Board  of  Directors  the  public  distribution  or  trading
activity  of  Orbital Common Shares during such period  does  not
create  a  market that reflects the fair market value of  Orbital
Common  Shares,  then the Current Market Price of Orbital  Common
Shares  shall be determined by the Board of Directors based  upon
the  advice  of such qualified independent financial advisors  as
the  Board of Directors may deem to be appropriate, and  provided
further that any such selection, opinion or determination by  the
Board of Directors shall be conclusive and binding.

           "Current  Orbital  Common Share  Equivalent"  has  the
meaning ascribed thereto in the Exchangeable Share Provisions.

          "Default Event" means any failure, other than by reason
of  an Insolvency Event, of the Corporation to perform any of its
obligations   pursuant  to  the  Exchangeable  Share  Provisions,
including  without  limitation  its  obligation  to  redeem   any
Retracted Shares.

           "Exchange  Right" has the meaning ascribed thereto  in
section 5.1 hereof.

            "Exchangeable  Share  Provisions"  has  the   meaning
ascribed thereto in the recitals hereto.

           "Exchangeable Shares" has the meaning ascribed thereto
in the recitals hereto.

           "Holder  Votes"  has the meaning ascribed  thereto  in
section 4.2 hereof.

           "Holders"  means the registered holders from  time  to
time   of  Exchangeable  Shares,  other  than  Orbital  and   its
Affiliates.

            "Insolvency  Event"  means  the  institution  by  the
Corporation  of any proceeding to be adjudicated  a  bankrupt  or
insolvent or to be dissolved or wound up, or the consent  of  the
Corporation   to  the  institution  of  bankruptcy,   insolvency,
dissolution or winding up proceedings against it, or  the  filing
of  a  petition, answer or consent seeking dissolution or winding
up  under any bankruptcy, insolvency or analogous laws, including
without  limitation  the  Companies  Creditors'  Arrangement  Act
(Canada) and the Bankruptcy and Insolvency Act (Canada), and  the
failure  by  the  Corporation to contest in good faith  any  such
proceedings  commenced  in respect of the Corporation  within  15
days of becoming aware thereof, or the consent by the Corporation
to  the  filing of any such petition or to the appointment  of  a
receiver,  or  the  making  by  the  Corporation  of  a   general
assignment  for  the benefit of creditors, or  the  admission  in
writing  by  the Corporation of its inability to  pay  its  debts
generally  as  they  become  due, or the  Corporation  not  being
permitted,  pursuant to solvency requirements of applicable  law,
to  redeem  any Retracted Shares pursuant to section 5.6  of  the
Exchangeable Share Provisions.

           "Lien" has the meaning ascribed thereto in the Plan of
Arrangement.

           "Liquidation  Call  Right" has  the  meaning  ascribed
thereto in the Plan of Arrangement.

          "Liquidation Event" has the meaning ascribed thereto in
subsection 5.12(a) hereof.

           "Liquidation  Event Effective Date"  has  the  meaning
ascribed thereto in subsection 5.12(c) hereof.

           "List" has the meaning ascribed thereto in section 4.6
hereof.

           "Officer's Certificate" means, with respect to Orbital
or  the Corporation, as the case may be, a certificate signed  by
any  one  of  the  Chairman  of the  Board,  the  President,  any
Vice-President  or  any other senior officer of  Orbital  or  the
Corporation, as the case may be.

           "Orbital  Common  Shares"  has  the  meaning  ascribed
thereto in the recitals hereto.

           "Orbital Consent" has the meaning ascribed thereto  in
section 4.2 hereof.

           "Orbital Meeting" has the meaning ascribed thereto  in
section 4.2 hereof.

          "Orbital Special Voting Stock" has the meaning ascribed
thereto in the recitals hereto.

          "Orbital Successor" has the meaning ascribed thereto in
subsection 10.1(a) hereof.

            "Person"   includes   an   individual,   partnership,
corporation,  company, unincorporated syndicate or  organization,
trust,   trustee,   executor,  administrator  and   other   legal
representative.

           "Plan of Arrangement" means the plan of arrangement of
the Corporation providing for the Arrangement.

           "Redemption  Call  Right"  has  the  meaning  ascribed
thereto in the Plan of Arrangement.

           "Retracted Shares" has the meaning ascribed thereto in
section 5.7 hereof.

           "Retraction  Call  Right"  has  the  meaning  ascribed
thereto in the Plan of Arrangement.

            "Support   Agreement"  means  that  certain   support
agreement  made as of even date herewith between the  Corporation
and Orbital.

          "Trust" means the trust created by this Agreement.

           "Trust  Estate"  means  the Voting  Share,  any  other
securities, the Exchange Right, the Automatic Exchange Rights and
any  money or other property that may be held by the Trustee from
time to time pursuant to this Agreement.

          "Voting Rights" means the voting rights attached to the
Voting Share.

           "Voting Share" means the one share of Orbital  Special
Voting  Stock,  issued  by  Orbital to  and  deposited  with  the
Trustee, which entitles the holder of record to a number of votes
at  meetings  of holders of Orbital Common Shares  equal  to  the
number  of  Exchangeable Shares outstanding from  time  to  time,
other   than  Exchangeable  Shares  held  by  Orbital   and   its
Affiliates,  multiplied  by  the  Current  Orbital  Common  Share
Equivalent at the relevant time.

1.2        Interpretation  not Affected by  Headings,  etc.   The
division of this Agreement into articles, sections and paragraphs
and  the  insertion of headings are for convenience of  reference
only  and shall not affect the construction or interpretation  of
this Agreement.

1.3        Number,  Gender,  etc.  Words importing  the  singular
number  only  shall  include the plural and  vice  versa.   Words
importing the use of any gender shall include all genders.

1.4        Date for any Action.  If any date on which any  action
is  required to be taken under this Agreement is not  a  Business
Day,  such  action  shall be required to be  taken  on  the  next
succeeding Business Day.

1.5        Withholding of Tax.  All amounts required to be  paid,
deposited  or  delivered hereunder shall be  paid,  deposited  or
delivered  after deduction of any amount required  by  applicable
law  to  be  deducted  or  withheld on account  of  tax  and  the
deduction  of  such amounts and remittance to the applicable  tax
authorities   shall,   to  the  extent  thereof,   satisfy   such
requirement to pay, deposit or deliver hereunder.


                           ARTICLE 2

                      PURPOSE OF AGREEMENT

2.1        Establishment of Trust.  The purpose of this Agreement
is  to create the Trust for the benefit of the Holders, as herein
provided.   The Trustee will hold the Voting Share  in  order  to
enable  the Trustee to exercise the Voting Rights and  will  hold
the Exchange Right and the Automatic Exchange Rights in order  to
enable  the  Trustee to exercise such rights,  in  each  case  as
trustee  for  and  on behalf of the Holders as provided  in  this
Agreement.


                           ARTICLE 3

                          VOTING SHARE

3.1         Issue   and  Ownership  of  the  Voting  Share.    In
consideration  of  the granting of the Call  Rights  to  Orbital,
Orbital hereby issues to and deposits with the Trustee the Voting
Share  to  be hereafter held of record by the Trustee as  trustee
for and on behalf of, and for the use and benefit of, the Holders
and in accordance with the provisions of this Agreement.  Orbital
hereby  acknowledges receipt from the Trustee as trustee for  and
on  behalf of the Holders of good and valuable consideration (and
the  adequacy  thereof) for the issuance of the Voting  Share  by
Orbital to the Trustee.  During the term of the Trust and subject
to  the terms and conditions of this Agreement, the Trustee shall
possess  and  be vested with full legal ownership of  the  Voting
Share  and  shall be entitled to exercise all of the  rights  and
powers  of  an  owner with respect to the Voting Share,  provided
that the Trustee shall:

                     (a)   hold  the Voting Share and  the  legal
               title  thereto as trustee solely for the  use  and
               benefit  of  the  Holders in accordance  with  the
               provisions of this Agreement; and

                     (b)   except  as specifically authorized  by
               this  Agreement,  have no power  or  authority  to
               sell, transfer, vote or otherwise deal in or  with
               the Voting Share and the Voting Share shall not be
               used or disposed of by the Trustee for any purpose
               other  than the purposes for which this  Trust  is
               created pursuant to this Agreement.

3.2        Legended  Share Certificates.  The  Corporation  shall
cause  each certificate representing Exchangeable Shares to  bear
an  appropriate  legend notifying the Holders of their  right  to
instruct  the Trustee with respect to the exercise of the  Voting
Rights with respect to the Exchangeable Shares held by Holders.

3.3         Safe   Keeping  of  Certificate.    The   certificate
representing the Voting Share shall at all times be held in  safe
keeping by the Trustee.


                           ARTICLE 4

                         VOTING RIGHTS

4.1       Voting Rights.  The Trustee, as the holder of record of
the  Voting Share, shall be entitled to all of the Voting Rights,
including  the  right to consent to or to vote in  person  or  by
proxy  the  Voting Share, on any matter, question or  proposition
whatsoever  that  may  properly come before the  stockholders  of
Orbital  for  their vote at an Orbital Meeting or  in  connection
with  an Orbital Consent.  The Voting Rights shall be and  remain
vested in and exercised by the Trustee.  Subject to section  6.15
hereof, the Trustee shall exercise the Voting Rights only on  the
basis  of instructions received pursuant to this Article  4  from
Holders entitled to instruct the Trustee as to the voting thereof
at  the  time at which an Orbital Consent is sought or an Orbital
Meeting is held.  To the extent that no instructions are received
from  a  Holder with respect to the Voting Rights to  which  such
Holder is entitled, the Trustee shall not exercise or permit  the
exercise of such Holder's Voting Rights.

4.2        Number  of  Votes.  With respect to  all  meetings  of
stockholders of Orbital at which holders of Orbital Common Shares
are  entitled to vote (an "Orbital Meeting") and with respect  to
all  written  consents sought from the holders of Orbital  Common
Shares  (an "Orbital Consent"), each Holder shall be entitled  to
instruct  the  Trustee  to  cast  and  exercise,  in  the  manner
instructed,  such number of votes comprised in the Voting  Rights
as is equal to the Current Orbital Common Share Equivalent on the
record date established by Orbital or by applicable law for  such
Orbital Meeting or Orbital Consent, as the case may be, for  each
Exchangeable Share owned of record by such Holder on such  record
date (the "Holder Votes") in respect of each matter, question  or
proposition  to  be voted on at such Orbital  Meeting  or  to  be
consented to in connection with such Orbital Consent.

4.3       Mailings to Shareholders.  With respect to each Orbital
Meeting  and Orbital Consent, the Trustee shall mail or cause  to
be mailed (or otherwise communicate in the same manner as Orbital
utilizes  in communications to holders of Orbital Common  Shares)
to  each of the Holders named in the List on the same day as  the
initial  mailing of notice (or other communication) with  respect
thereto  is  given  by  Orbital  or  any  third  party   to   its
stockholders:

                    (a)  a copy of such notice, together with any
               proxy   or   information  statement  and   related
               materials  to  be  provided  to  stockholders   of
               Orbital;

                    (b)  a statement that such Holder is entitled
               to  instruct the Trustee as to the exercise of the
               Holder  Votes with respect to such Orbital Meeting
               or  Orbital  Consent,  as the  case  may  be,  or,
               pursuant  to  section 4.7 hereof, to  attend  such
               Orbital  Meeting  and to exercise  personally  the
               Holder Votes thereat;

                     (c)   a statement as to the manner in  which
               such  instructions may be given  to  the  Trustee,
               including  an express indication that instructions
               may be given to the Trustee to give:

                     (d)   a proxy to such Holder or his designee
               to exercise personally the Holder Votes; or

                                          (i)    a  proxy  to   a
                         designated agent or other representative
                         of the management of Orbital to exercise
                         such Holder Votes;

                    (e)  a statement that if no such instructions
               are received from the Holder, the Holder Votes  to
               which   such  Holder  is  entitled  will  not   be
               exercised;

                     (f)   a form of direction whereby the Holder
               may   so  direct  and  instruct  the  Trustee   as
               contemplated herein; and

                     (g)  a statement of (i) the time and date by
               which  such instructions must be received  by  the
               Trustee  in order to be binding upon it, which  in
               the case of a Orbital Meeting shall not be earlier
               than  the close of business on the second Business
               Day prior to such meeting, and (ii) the method for
               revoking or amending such instructions.

For the purpose of determining Holder Votes to which a Holder  is
entitled  in  respect  of  any such Orbital  Meeting  or  Orbital
Consent, the number of Exchangeable Shares owned of record by the
Holder shall be determined at the close of business on the record
date established by Orbital or by applicable law for purposes  of
determining stockholders entitled to vote at such Orbital Meeting
or  to  give  written  consent in connection  with  such  Orbital
Consent.  Orbital shall notify the Trustee of any decision of the
board of directors of Orbital with respect to the calling of  any
such  Orbital  Meeting  or the seeking by  Orbital  of  any  such
Orbital  Consent and shall provide all necessary information  and
materials  to the Trustee in each case promptly and in any  event
in   sufficient  time  to  enable  the  Trustee  to  perform  its
obligations contemplated by this section 4.3.

4.4        Copies  of  Stockholder  Information.   Orbital  shall
deliver  to the Trustee copies of all proxy materials, (including
notices of Orbital Meetings but excluding proxies to vote Orbital
Common   Shares),  information  statements,  reports   (including
without  limitation all interim and annual financial  statements)
and  other  written communications that are to be distributed  by
Orbital from time to time to holders of Orbital Common Shares  in
sufficient quantities and in sufficient time so as to enable  the
Trustee  to send those materials to each Holder at the same  time
as  such  materials are first sent to holders of  Orbital  Common
Shares.  The Trustee shall mail or otherwise send to each Holder,
at  the expense of Orbital, copies of all such materials (and all
materials specifically directed to the Holders or to the  Trustee
for  the  benefit  of  the Holders by Orbital)  received  by  the
Trustee from Orbital at the same time as such materials are first
sent to holders of Orbital Common Shares.  The Trustee shall make
copies  of  all  such materials available for inspection  by  any
Holder at the Trustee's principal office.

4.5        Other Materials.  Immediately after receipt by Orbital
or  any  stockholder  of Orbital of any material  sent  or  given
generally to the holders of Orbital Common Shares by or on behalf
of  a  third party, including without limitation dissident  proxy
and  information circulars (and related information and material)
and  tender and exchange offer circulars (and related information
and  material),  Orbital  shall use all  commercially  reasonable
efforts  to  obtain and deliver to the Trustee copies thereof  in
sufficient quantities so as to enable the Trustee to forward such
material  (unless the same has been provided directly to  Holders
by  such  third  party)  to  each  Holder  as  soon  as  possible
thereafter.   As soon as practicable after receipt  thereof,  the
Trustee  shall  mail  or otherwise send to each  Holder,  at  the
expense of Orbital, copies of all such materials received by  the
Trustee from Orbital.  The Trustee shall also make copies of  all
such  materials  available for inspection by any  Holder  at  the
Trustee's principal office.

4.6        List  of  Persons Entitled to Vote.   The  Corporation
shall,  (a)  prior  to each annual, general and  special  Orbital
Meeting  or the seeking of any Orbital Consent and (b)  forthwith
upon  each  request made at any time by the Trustee  in  writing,
prepare  or cause to be prepared a list (a "List") of  the  names
and  addresses of the Holders arranged in alphabetical order  and
showing the number of Exchangeable Shares held of record by  each
such  Holder, in each case at the close of business on  the  date
specified  by the Trustee in such request or, in the  case  of  a
List prepared in connection with an Orbital Meeting or an Orbital
Consent,  at the close of business on the record date established
by  Orbital  or  pursuant to applicable law for  determining  the
holders  of Orbital Common Shares entitled to receive  notice  of
and/or  to  vote  at such Orbital Meeting or to give  consent  in
connection  with such Orbital Consent.  Each such List  shall  be
delivered   to  the  Trustee  promptly  after  receipt   by   the
Corporation  of such request or the record date for such  meeting
or  seeking  of  consent, as the case may be, and  in  any  event
within  sufficient time as to enable the Trustee to  perform  its
obligations  under this Agreement.  Orbital agrees  to  give  the
Corporation notice (with a copy to the Trustee) of the calling of
any  Orbital  Meeting  or  the seeking of  any  Orbital  Consent,
together  with the record dates therefor, sufficiently  prior  to
the  date  of  the  calling of such meeting or  seeking  of  such
consent   so  as  to  enable  the  Corporation  to  perform   its
obligations under this section 4.6.

4.7        Entitlement to Direct Votes.  Any Holder  named  in  a
List  prepared  in  connection with any Orbital  Meeting  or  any
Orbital Consent shall be entitled (a) to instruct the Trustee  in
the  manner described in section 4.3 hereof with respect  to  the
exercise of the Holder Votes to which such Holder is entitled  or
(b) to attend such meeting and personally to exercise thereat (or
to exercise with respect to any written consent), as the proxy of
the Trustee, the Holder Votes to which such Holder is entitled.

4.8         Voting   by  Trustee,  and  Attendance   of   Trustee
Representative, at Meeting.

                     (a)  In connection with each Orbital Meeting
               and  Orbital Consent, the Trustee shall  exercise,
               either  in person or by proxy, in accordance  with
               the  instructions received from a Holder  pursuant
               to  section  4.3 hereof, the Holder  Votes  as  to
               which  such Holder is entitled to direct the  vote
               (or  any lesser number thereof as may be set forth
               in the instructions); provided, however, that such
               written  instructions are received by the  Trustee
               from  the Holder prior to the time and date  fixed
               by  it  for  receipt of such instructions  in  the
               notice given by the Trustee to the Holder pursuant
               to section 4.3 hereof.

                      (b)    The   Trustee   shall   cause   such
               representatives as are empowered by it to sign and
               deliver,  on  behalf of the Trustee,  proxies  for
               Voting  Rights  to  attend each  Orbital  Meeting.
               Upon  submission by a Holder (or its designee)  of
               identification  satisfactory  to   the   Trustee's
               representatives, and at the Holder's request, such
               representatives  shall sign and  deliver  to  such
               Holder  (or  its  designee) a  proxy  to  exercise
               personally  the  Holder Votes  as  to  which  such
               Holder  is otherwise entitled hereunder to  direct
               the  vote,  if  such  Holder either  (i)  has  not
               previously given the Trustee instructions pursuant
               to  section 4.3 hereof in respect of such meeting,
               or  (ii)  submits to the Trustee's representatives
               written    revocation   of   any   such   previous
               instructions.    At  such  meeting,   the   Holder
               exercising such Holder Votes shall have  the  same
               rights  as the Trustee to speak at the meeting  in
               respect of any matter, question or proposition, to
               vote by way of ballot at the meeting in respect of
               any matter, question or proposition and to vote at
               such  meeting by way of a show of hands in respect
               of any matter, question or proposition.

4.9         Distribution  of  Written  Materials.   Any   written
materials  to  be  distributed by  the  Trustee  to  the  Holders
pursuant to this Agreement shall be delivered or sent by mail (or
otherwise communicated in the same manner as Orbital utilizes  in
communications  to  holders of Orbital  Common  Shares)  to  each
Holder  at  its address as shown on the books of the Corporation.
The  Corporation  shall provide or cause to be  provided  to  the
Trustee for this purpose, on a timely basis and without charge or
other expense:

                    (a)  a List; and

                    (b)  upon the request of the Trustee, mailing
               labels  to  enable the Trustee to  carry  out  its
               duties under this Agreement.

4.10       Termination of Voting Rights.  Except with respect  to
an  Orbital Meeting or Orbital Consent for which the record  date
has  occurred, all of the rights of a Holder with respect to  the
Holder  Votes  exercisable in respect of the Exchangeable  Shares
held  by such Holder, including the right to instruct the Trustee
as  to  the  voting of or to vote personally such  Holder  Votes,
shall  be  deemed to be surrendered by the Holder to Orbital  and
such Holder Votes and the Voting Rights represented thereby shall
cease immediately upon the delivery by such Holder to the Trustee
of  the  certificates  representing such Exchangeable  Shares  in
connection with the exercise by the Holder of the Exchange  Right
or  the  occurrence  of the automatic exchange  pursuant  to  the
Automatic  Exchange Rights (unless in either case  Orbital  shall
not  have  delivered the requisite Orbital Common Shares issuable
in exchange therefor to the Trustee for delivery to the Holders),
or upon the redemption of Exchangeable Shares pursuant to Article
5  or Article 6 of the Exchangeable Share Provisions, or upon the
effective  date of the liquidation, dissolution or winding-up  of
the  Corporation pursuant to Article 4 of the Exchangeable  Share
Provisions, or upon the purchase of Exchangeable Shares from  the
holder thereof by Orbital pursuant to the exercise by Orbital  of
the  Retraction  Call Right, the Redemption  Call  Right  or  the
Liquidation Call Right.

4.11       Issue of Additional Shares.  During the term  of  this
Agreement,  Orbital will not issue any shares of Orbital  Special
Voting Stock, in addition to the Voting Share.


                           ARTICLE 5

             EXCHANGE RIGHT AND AUTOMATIC EXCHANGE

5.1        Grant  and  Ownership  of  the  Exchange  Right.    In
consideration  of  the granting of the Call  Rights  to  Orbital,
Orbital hereby grants to the Trustee as trustee for and on behalf
of,  and  for the use and benefit of, the Holders (a)  the  right
(the  "Exchange  Right"),  upon the  occurrence  and  during  the
continuance of an Insolvency Event or Default Event,  to  require
Orbital  to  purchase from each Holder all or  any  part  of  the
Exchangeable  Shares held by such Holder and  (b)  the  Automatic
Exchange  Rights, all in accordance with the provisions  of  this
agreement.  Orbital hereby acknowledges receipt from the  Trustee
as  trustee for and on behalf of the Holders of good and valuable
consideration  (and the adequacy thereof) for the  grant  of  the
Exchange  Right and the Automatic Exchange Rights by  Orbital  to
the  Trustee.   During the term of the Trust and subject  to  the
terms and conditions of this Agreement, the Trustee shall possess
and be vested with full legal ownership of the Exchange Right and
the  Automatic Exchange Rights and shall be entitled to  exercise
all  of  the  rights and powers of an owner with respect  to  the
Exchange  Right and the Automatic Exchange Rights, provided  that
the Trustee shall:

                      (a)   hold  the  Exchange  Right  and   the
               Automatic  Exchange  Rights and  the  legal  title
               thereto  as trustee solely for the use and benefit
               of  the  Holders in accordance with the provisions
               of this Agreement; and

                     (b)   except  as specifically authorized  by
               this  Agreement,  have no power  or  authority  to
               exercise or otherwise deal in or with the Exchange
               Right  or the Automatic Exchange Rights,  and  the
               Trustee shall not exercise any such rights for any
               purpose  other  than the purposes for  which  this
               Trust is created pursuant to this Agreement.

5.2        Legended  Share Certificates.  The  Corporation  shall
cause  each certificate representing Exchangeable Shares to  bear
an appropriate legend notifying the Holders of:

                    (a)  their right to instruct the Trustee with
               respect  to the exercise of the Exchange Right  in
               respect  of  the  Exchangeable Shares  held  by  a
               Holder; and

                    (b)  the Automatic Exchange Rights.

5.3       General Exercise of Exchange Right.  The Exchange Right
shall  be  and  remain vested in and exercisable by the  Trustee.
Subject  to  section 6.15 hereof, the Trustee shall exercise  the
Exchange  Right  only  on  the  basis  of  instructions  received
pursuant to this Article 5 from Holders entitled to instruct  the
Trustee  as  to  the  exercise thereof.  To the  extent  that  no
instructions  are  received from a Holder  with  respect  to  the
Exchange  Right,  the Trustee shall not exercise  or  permit  the
exercise of the Exchange Right.

5.4        Purchase Price.  The purchase price payable by Orbital
for  each Exchangeable Share to be purchased by Orbital under the
Exchange  Right  shall be an amount per share equal  to  (a)  the
Current  Market  Price multiplied by the Current  Orbital  Common
Share  Equivalent, in each case determined on the day of  closing
of  the  purchase and sale of such Exchangeable Share  under  the
Exchange  Right, which shall be satisfied in full in  respect  of
the Exchangeable Shares in regard to which a Holder has exercised
the Exchange Right by causing to be delivered to such Holder such
whole  number of Orbital Common Shares as is equal to the product
obtained by multiplying the number of such Exchangeable Shares by
the  Current  Orbital Common Share Equivalent (together  with  an
amount  in  lieu of any fractional Orbital Common Share resulting
from  such calculation payable in accordance with section 9.4  of
the Exchangeable Share Provisions), plus (b) the aggregate of all
dividends  declared  and unpaid on each such  Exchangeable  Share
(provided  that  if  the record date for any  such  declared  and
unpaid  dividends occurs on or after the day of closing  of  such
purchase  and  sale  the purchase price shall  not  include  such
declared and unpaid dividends).

5.5        Exercise  Instructions.   Subject  to  the  terms  and
conditions herein set forth, a Holder shall be entitled, upon the
occurrence and during the continuance of an Insolvency Event,  to
instruct the Trustee to exercise the Exchange Right with  respect
to  all or any part of the Exchangeable Shares registered in  the
name  of  such Holder on the books of the Corporation.  To  cause
the  exercise  of the Exchange Right by the Trustee,  the  Holder
shall  deliver  to  the Trustee, in person  or  by  certified  or
registered  mail, at its principal office or at such other  place
as  the Trustee may from time to time designate by written notice
to  the  Holders, the certificates representing the  Exchangeable
Shares  that  such  Holder  desires  Orbital  to  purchase,  duly
endorsed  in  blank, and accompanied by such other documents  and
instruments   as  may  be  required  to  effect  a  transfer   of
Exchangeable  Shares  under  the CBCA  and  the  by-laws  of  the
Corporation and such additional documents and instruments as  the
Trustee may reasonably require together with (a) a duly completed
form  of  notice of exercise of the Exchange Right, contained  on
the   reverse   of   or   attached  to  the  Exchangeable   Share
certificates,  stating (i) that the Holder thereby instructs  the
Trustee  to exercise the Exchange Right so as to require  Orbital
to  purchase  from  the Holder the number of Exchangeable  Shares
specified  therein, (ii) that such Holder has good title  to  and
owns  all such Exchangeable Shares to be acquired by Orbital free
and clear of all Liens, (iii) the names in which the certificates
representing  Orbital Common Shares issuable in  connection  with
the  exercise of the Exchange Right are to be issued and (iv) the
names  and addresses of the persons to whom such new certificates
should be delivered and (b) payment (or evidence satisfactory  to
the Trustee, the Corporation and Orbital of payment) of the taxes
(if   any)  payable  as  contemplated  by  section  5.8  of  this
Agreement.  If only a part of the Exchangeable Shares represented
by  any certificate or certificates delivered to the Trustee  are
to  be  purchased  by  Orbital under the Exchange  Right,  a  new
certificate for the balance of such Exchangeable Shares shall  be
issued to the holder at the expense of the Corporation.

5.6        Delivery of Orbital Common Shares: Effect of Exercise.
Promptly  after  receipt  of  the certificates  representing  the
Exchangeable Shares that the Holder desires Orbital  to  purchase
under  the  Exchange  Right (together  with  such  documents  and
instruments  of transfer and a duly completed form of  notice  of
exercise of the Exchange Right (and payment of taxes, if any,  or
evidence  thereof in accordance with section 5.8)), duly endorsed
for transfer to Orbital, the Trustee shall notify Orbital and the
Corporation of its receipt of the same, which notice  to  Orbital
and  the  Corporation shall constitute exercise of  the  Exchange
Right by the Trustee on behalf of the holder of such Exchangeable
Shares, and Orbital shall immediately thereafter deliver or cause
to  be  delivered to the Trustee, for delivery to the  Holder  of
such  Exchangeable  Shares (or to such  other  persons,  if  any,
properly  designated  by such Holder), the certificates  for  the
number  of Orbital Common Shares issuable in connection with  the
exercise of the Exchange Right, which shares shall be duly issued
as  fully paid and non-assessable and shall be free and clear  of
any  Liens,  and cheques for the balance, if any,  of  the  total
purchase  price  therefor  (or, if part  of  the  purchase  price
consists  of  dividends  payable in property,  such  property  or
property  the  same  as  or  economically  equivalent   to   such
property).  Immediately upon the giving of notice by the  Trustee
to  Orbital  and the Corporation of the exercise of the  Exchange
Right,  as  provided  in this section 5.6,  the  closing  of  the
transaction  of  purchase and sale contemplated by  the  Exchange
Right  shall be deemed to have occurred, and the Holder  of  such
Exchangeable  Shares  shall  be deemed  to  have  transferred  to
Orbital  all  of  its right, title and interest in  and  to  such
Exchangeable  Shares  and in the related interest  in  the  Trust
Estate and shall cease to be a holder of such Exchangeable Shares
and  shall  not be entitled to exercise any of the  rights  of  a
holder  in  respect thereof, other than the right to receive  the
purchase  price therefor, unless the requisite number of  Orbital
Common Shares (together with a cheque for the balance, if any, of
the  purchase  price therefor or, if part of the  purchase  price
consists  of  dividends  payable in property,  such  property  or
property the same as or economically equivalent to such property)
is  not  allotted, issued and delivered by Orbital to the Trustee
for  delivery  to  such  Holder (or to  other  persons,  if  any,
properly designated by such Holder) within five Business Days  of
the  date  of the giving of such notice by the Trustee, in  which
case  the rights of the Holder shall remain unaffected until such
Orbital  Common Shares are so allotted, issued and  delivered  by
Orbital   and  any  such  cheque  is  so  delivered   and   paid.
Concurrently  with  such  Holder  ceasing  to  be  a  holder   of
Exchangeable  Shares, the Holder shall be considered  and  deemed
for  all  purposes to be the holder of the Orbital Common  Shares
delivered to it pursuant to the Exchange Right.

5.7        Exercise  of Exchange Right Subsequent to  Retraction.
In  the event that a Holder has exercised its right under Article
5 of the Exchangeable Share Provisions to require the Corporation
to  redeem  any  or all of the Exchangeable Shares  held  by  the
Holder   (the  "Retracted  Shares")  and  is  notified   by   the
Corporation  pursuant  to section 5.6 of the  Exchangeable  Share
Provisions that the Corporation is not permitted as a  result  of
solvency  requirements of applicable law to redeem  all  of  such
Retracted  Shares,  and  provided that  Orbital  shall  not  have
exercised the Retraction Call Right with respect to the Retracted
Shares,  the  retraction request shall constitute  and  shall  be
deemed  to  constitute  notice from the  Holder  to  the  Trustee
instructing  the  Trustee  to exercise the  Exchange  Right  with
respect to those Retracted Shares that the Corporation is  unable
to redeem.  In any such event, the Corporation hereby agrees with
the Trustee and in favour of the Holder immediately to notify the
Trustee of such prohibition against the Corporation redeeming all
of the Retracted Shares and immediately to forward or cause to be
forwarded to the Trustee all relevant materials delivered by  the
Holder  to  the  Corporation  or to the  transfer  agent  of  the
Exchangeable Shares (including without limitation a copy  of  the
retraction  request  delivered pursuant to  section  5.1  of  the
Exchangeable  Share Provisions) in connection with such  proposed
redemption  of  the  Retracted  Shares  and  the  Trustee   shall
thereupon  exercise  the  Exchange  Right  with  respect  to  the
Retracted Shares that the Corporation is not permitted to  redeem
and  will  require Orbital to purchase such shares in  accordance
with the provisions of this Article 5.

5.8        Stamp  or  Other Transfer Taxes.   Upon  any  sale  of
Exchangeable Shares to Orbital pursuant to the Exchange Right  or
the   Automatic   Exchange  Rights,  the  share  certificate   or
certificates  representing Orbital Common Shares to be  delivered
in  connection  with the payment of the purchase  price  therefor
shall  be  issued  in the name of the Holder of the  Exchangeable
Shares  so  sold  or in such names as such Holder  may  otherwise
direct   in  writing  without  charge  to  the  holder   of   the
Exchangeable Shares so sold, provided, however, that such  Holder
(a)  shall  pay  (and  neither Orbital, the Corporation  nor  the
Trustee  shall  be  required  to  pay)  any  documentary,  stamp,
transfer or other similar taxes that may be payable in respect of
any  transfer involved in the issuance or delivery of such shares
to  a person other than such Holder or (b) shall establish to the
satisfaction  of  the Trustee, Orbital and the  Corporation  that
such taxes, if any, have been paid.

5.9         Notice   of   Insolvency  Event  or  Default   Event.
Immediately upon the occurrence of an Insolvency Event or Default
Event  or any event that with the giving of notice or the passage
of  time  or both would be an Insolvency Event or Default  Event,
the Corporation and Orbital shall give written notice thereof  to
the  Trustee.  As soon as practicable after receiving notice from
the  Corporation  and  Orbital or from any other  person  of  the
occurrence  of an Insolvency Event or Default Event, the  Trustee
shall mail to each Holder, at the expense of Orbital, a notice of
such  Insolvency  Event  or  Default Event,  which  notice  shall
contain  a  brief  statement of the right  of  the  Holders  with
respect to the Exchange Right.

5.10       Qualification  of Orbital Common Shares.   Unless  the
staff  of  the  United States Securities and Exchange  Commission
(the  "SEC") has confirmed the availability of an exemption  from
registration under the United States Securities Act of  1933,  as
amended  (the "Securities Act") as to the issuance of the Orbital
Common Shares in exchange for the Exchangeable Shares pursuant to
the  Plan  of  Arrangement, the Exchangeable Share Provisions  or
this  Agreement, in response to the No Action Request (as defined
in  the Combination Agreement) or Orbital has received an opinion
of  counsel  reasonably satisfactory to the Corporation  to  such
effect,  then Orbital shall cause such issuance to be  registered
under the Securities Act, and shall file a registration statement
covering  such  issuance with the SEC and  use  all  commercially
reasonable efforts to cause such registration statement to become
effective  as soon as practicable and remain effective throughout
the  period during which the Exchangeable Shares may be exchanged
in  accordance  with  the Plan of Arrangement,  the  Exchangeable
Share  Provisions or this Agreement.  Orbital agrees to file  any
such  required  registration  statement  as  soon  as  reasonably
practicable.  Orbital shall use all reasonable efforts to  obtain
all  orders  required  from  the applicable  Canadian  securities
authorities  to permit the issuance of the Orbital Common  Shares
upon  any  such  exchange  of  the  Exchangeable  Shares  without
registration or qualification with or approval of or  the  filing
of  any document including any prospectus or similar document  or
the  taking of any proceeding with or the obtaining of any order,
ruling  or  consent from any governmental or regulatory authority
under  any  Canadian federal or provincial law or  regulation  or
pursuant to the rules and regulations of any regulatory authority
or  the  fulfilment  of any other legal requirement  before  such
Orbital  Common  Shares  may  be  issued  and  delivered  by  the
Corporation  or Orbital to the holder thereof or  in  order  that
such Orbital Common Shares may be freely traded thereafter (other
than  any restrictions on transfer by reason of a holder being  a
"control  person" of the Corporation or Orbital for  purposes  of
Canadian  federal or provincial securities law or an  "affiliate"
for purposes of United States Federal or state securities law).

5.11       Reservation of Orbital Common Shares.  Orbital  hereby
represents  and  warrants  that it has irrevocably  reserved  for
issuance  out of its authorized and unissued capital  stock  such
number  of  Orbital Common Shares as is equal to  the  number  of
Exchangeable Shares outstanding at the date hereof and  covenants
that  it  will at all times keep available, free from pre-emptive
and  other  rights,  out of its authorized and  unissued  capital
stock  such number of Orbital Common Shares (or other  shares  or
securities  into which Orbital Common Shares may be  reclassified
or changed) as is necessary to enable Orbital and the Corporation
to   perform  their  respective  obligations  pursuant  to   this
Agreement,  the  Exchangeable Share Provisions  and  the  Support
Agreement.

5.12      Automatic Exchange on Liquidation of Orbital.

           (a)  Orbital shall give the Trustee notice of each  of
the  following  events (a "Liquidation Event") at  the  time  set
forth below:

                                    (i)   in  the  event  of  any
                    determination  by the Board of  Directors  of
                    Orbital  to  institute voluntary liquidation,
                    dissolution  or  winding-up proceedings  with
                    respect  to  Orbital or to effect  any  other
                    distribution of assets of Orbital  among  its
                    stockholders  for the purpose of  winding  up
                    its  affairs, at least 60 days prior  to  the
                    proposed  effective date of such liquidation,
                    dissolution,     winding-up     or      other
                    distribution; and

                                    (ii)  immediately,  upon  the
                    earlier  of (A) receipt by Orbital of  notice
                    of  and (B) Orbital otherwise becoming  aware
                    of  any threatened or instituted claim, suit,
                    petition or other proceedings with respect to
                    the  involuntary liquidation, dissolution  or
                    winding up of Orbital or to effect any  other
                    distribution of assets of Orbital  among  its
                    stockholders  for the purpose of  winding  up
                    its affairs.

           (b)  Immediately following receipt by the Trustee from
Orbital  of  notice of any Liquidation Event, the  Trustee  shall
give notice thereof to the Holders.  Such notice shall include  a
brief  description  of  the  automatic exchange  of  Exchangeable
Shares  for  Orbital  Common Shares provided  for  in  subsection
5.12(c) below.

           (c)   In  order  that  the Holders  will  be  able  to
participate  on  a  pro rata basis with the  holders  of  Orbital
Common  Shares  in  the  distribution of  assets  of  Orbital  in
connection  with a Liquidation Event, on the fifth  Business  Day
prior  to  the  effective  date  of  a  Liquidation  Event   (the
"Liquidation  Event Effective Date") all of the then  outstanding
Exchangeable Shares shall be automatically exchanged for  Orbital
Common Shares.  To effect such automatic exchange, Orbital  shall
purchase  each  Exchangeable  Share  outstanding  on  the   fifth
Business  Day prior to the Liquidation Event Effective  Date  and
held  by  Holders,  and each Holder shall sell  the  Exchangeable
Shares  held by it at such time, for a purchase price  per  share
equal  to (a) the Current Market Price multiplied by the  Current
Orbital Common Share Equivalent on such fifth Business Day  prior
to the Liquidation Event Effective Date, which shall be satisfied
in full in respect of the Exchangeable Shares held by each Holder
by  Orbital  issuing to such Holder such whole number of  Orbital
Common  Shares as is equal to the product obtained by multiplying
the  number  of  such Exchangeable Shares by the Current  Orbital
Common  Share Equivalent (together with an amount in lieu of  any
fractional  Orbital Common Share resulting from such  calculation
payable in accordance with section 9.4 of the Exchangeable  Share
Provisions), plus (b) an additional amount equal to the aggregate
of  all  dividends declared and unpaid on each such  Exchangeable
Share (provided that if the record date for any such declared and
unpaid  dividends occurs on or after the day of closing  of  such
purchase  and  sale, the purchase price shall  not  include  such
additional amount equal to such declared and unpaid dividends).

          (d)  On the fifth Business Day prior to the Liquidation
Event  Effective Date, the closing of the transaction of purchase
and  sale  contemplated by the automatic exchange of Exchangeable
Shares  for  Orbital  Common  Shares  shall  be  deemed  to  have
occurred, and each Holder of Exchangeable Shares shall be  deemed
to  have transferred to Orbital all of the Holder's right,  title
and  interest in and to such Exchangeable Shares and the  related
interest  in the Trust Estate and shall cease to be a  Holder  of
such  Exchangeable Shares and Orbital shall issue to  the  Holder
the Orbital Common Shares issuable upon the automatic exchange of
Exchangeable  Shares for Orbital Common Shares and shall  deliver
to  the  Trustee  for delivery to the Holder  a  cheque  for  the
balance,  if  any,  of the purchase price for  such  Exchangeable
Shares  (or,  if  any  part  of the purchase  price  consists  of
dividends payable in property, such property or property that  is
the  same  as  or  economically  equivalent  to  such  property).
Concurrently  with  such  Holder  ceasing  to  be  a  holder   of
Exchangeable  Shares, the Holder shall be considered  and  deemed
for  all  purposes to be the holder of the Orbital Common  Shares
issued  to  it pursuant to the automatic exchange of Exchangeable
Shares for Orbital Common Shares and the certificates held by the
Holder  previously representing the Exchangeable Shares exchanged
by  the  Holder with Orbital pursuant to such automatic  exchange
shall thereafter be deemed to represent the Orbital Common Shares
issued  to  the  Holder  by Orbital pursuant  to  such  automatic
exchange.  Upon the request of a Holder and the surrender by  the
Holder  of  Exchangeable Share certificates deemed  to  represent
Orbital Common Shares, duly endorsed in blank and accompanied  by
such  instruments of transfer as Orbital may reasonably  require,
Orbital  shall  deliver or cause to be delivered  to  the  Holder
certificates representing the Orbital Common Shares of which  the
Holder is the holder.


                           ARTICLE 6

                     CONCERNING THE TRUSTEE

6.1        Powers and Duties of the Trustee.  The rights,  powers
and  authorities  of  the Trustee under this  Agreement,  in  its
capacity as trustee of the Trust, shall include:

                    (a)  purchasing the Voting Share from Orbital
               as  trustee  for and on behalf of the  Holders  in
               accordance with the provisions of this Agreement;

                      (b)    granting  proxies  and  distributing
               materials   to   Holders  as  provided   in   this
               Agreement;

                     (c)   voting the Holder Votes in  accordance
               with the provisions of this Agreement;

                     (d)   receiving  the grant of  the  Exchange
               Right  and  the  Automatic  Exchange  Rights  from
               Orbital  as  trustee  for and  on  behalf  of  the
               Holders in accordance with the provisions of  this
               Agreement;

                      (e)   exercising  the  Exchange  Right  and
               enforcing  the  benefit of the Automatic  Exchange
               Rights,  in  each  case  in  accordance  with  the
               provisions  of  this Agreement and  in  connection
               therewith   receiving  from  Holders  Exchangeable
               Shares   and   other   requisite   documents   and
               distributing  to such Holders the  Orbital  Common
               Shares  and cheques, if any, to which such Holders
               are  entitled  upon the exercise of  the  Exchange
               Right   or  pursuant  to  the  Automatic  Exchange
               Rights, as the case may be;

                    (f)  holding title to the Trust Estate;

                     (g)  investing any moneys forming, from time
               to time, a part of the Trust Estate as provided in
               this Agreement;

                     (h)  taking action on its own initiative  or
               at the direction of a Holder or Holders to enforce
               the  obligations of Orbital under this  Agreement;
               and

                    (i)  taking such other actions and doing such
               other things as are specifically provided in  this
               Agreement.

           In  the exercise of such rights powers and authorities
the  Trustee  shall  have (and is granted)  such  incidental  and
additional rights, powers and authority not in conflict with  any
of  the  provisions of this Agreement as the Trustee,  acting  in
good faith and in the reasonable exercise of its discretion,  may
deem necessary, appropriate or desirable to effect the purpose of
the Trust.  Any exercise of such discretionary rights, powers and
authorities by the Trustee shall be final, conclusive and binding
upon  all persons.  For greater certainty, the Trustee shall have
only those duties as are set out specifically in this Agreement.

           The  Trustee in exercising its rights, powers,  duties
and  authorities hereunder shall act honestly and in  good  faith
with  a  view  to  the best interests of the  Holders  and  shall
exercise the care, diligence and skill that a reasonably  prudent
trustee would exercise in comparable circumstances.

6.2       No Conflict of Interest.  The Trustee represents to the
Corporation  and  Orbital  that at  the  date  of  execution  and
delivery  of this Agreement there exists no material conflict  of
interest in the role of the Trustee as a fiduciary hereunder  and
the  role  of  the  Trustee in any other capacity.   The  Trustee
shall, within 30 days after it becomes aware that such a material
conflict  of  interest  exists, either  eliminate  such  material
conflict of interest or resign in the manner and with the  effect
specified in Article 9 hereof.  If, notwithstanding the foregoing
provisions  of this section 6.2, the Trustee has such a  material
conflict  of  interest, the validity and enforceability  of  this
Agreement  shall  not  be affected in any  manner  whatsoever  by
reason  only  of  the  existence of  such  material  conflict  of
interest.  If the Trustee contravenes the foregoing provisions of
this  section 6.2, any interested party may apply to the  Supreme
Court of British Columbia (Trial Division) for an order that  the
Trustee be replaced as trustee hereunder.

6.3        Dealings with Transfer Agents, Registrars,  etc.   The
Corporation  and Orbital irrevocably authorize the Trustee,  from
time to time, to:

                     (a)  consult, communicate and otherwise deal
               with   the   respective  registrars  and  transfer
               agents, and with any such subsequent registrar  or
               transfer  agent,  of the Exchangeable  Shares  and
               Orbital Common Shares; and

                    (b)  requisition, from time to time, (i) from
               any   such   registrar  or  transfer   agent   any
               information  readily available  from  the  records
               maintained  by it which the Trustee may reasonably
               require  for  the  discharge  of  its  duties  and
               responsibilities  under this  Agreement  and  (ii)
               from  the transfer agent of Orbital Common Shares,
               and  any subsequent transfer agent of such shares,
               the  share certificates issuable upon the exercise
               from  time  to  time  of the  Exchange  Right  and
               pursuant to the Automatic Exchange Rights  in  the
               manner specified in Article 5 hereof.

The   Corporation   and  Orbital  irrevocably   authorize   their
respective registrars and transfer agents to comply with all such
requests.   Orbital  covenants that it will supply  its  transfer
agent  with  duly executed share certificates for the purpose  of
completing  the exercise from time to time of the Exchange  Right
and  the  Automatic  Exchange Rights, in each  case  pursuant  to
Article 5 hereof.

6.4        Books  and Records.  The Trustee shall keep  available
for  inspection by Orbital and the Corporation, at the  Trustee's
principal  office,  correct and complete  books  and  records  of
account  relating to the Trustee's actions under this  Agreement,
including without limitation all information relating to mailings
and  instructions  to  and  from  Holders  and  all  transactions
pursuant  to  the  Voting  Rights, the  Exchange  Right  and  the
Automatic Exchange Rights for the term of this Agreement.  On  or
before  March 31, 1996, and on or before March 31 in  every  year
thereafter,  so long as the Voting Share is on deposit  with  the
Trustee,   the  Trustee  shall  transmit  to  Orbital   and   the
Corporation  a  brief report, dated as of the preceding  December
31, with respect to:

                     (a)   the property and funds comprising  the
               Trust Estate as of that date;

                     (b)  the number of exercises of the Exchange
               Right,  if  any,  and  the  aggregate  number   of
               Exchangeable  Shares received by  the  Trustee  on
               behalf  of  Holders in consideration of the  issue
               and  delivery by Orbital of Orbital Common  Shares
               in  connection with the Exchange Right, during the
               calendar year ended on such date; and

                     (c)   all other actions taken by the Trustee
               in  the  performance  of  its  duties  under  this
               Agreement that it had not previously reported.

6.5       Income Tax Returns and Reports.  The Trustee shall,  to
the  extent  necessary, prepare and file on behalf of  the  Trust
appropriate United States and Canadian income tax returns and any
other returns or reports as may be required by applicable law  or
pursuant  to the rules and regulations of any securities exchange
or other trading system through which the Exchangeable Shares are
traded  and, in connection therewith, may obtain the  advice  and
assistance of such experts as the Trustee may consider  necessary
or advisable.

6.6        Indemnification Prior to Certain Actions  by  Trustee.
The  Trustee  shall  exercise any or all of the  rights,  duties,
powers  or  authorities  vested in it by this  Agreement  at  the
request,  order  or  direction of any  Holder  upon  such  Holder
furnishing  to  the  Trustee  reasonable  funding,  security  and
indemnity against the costs, expenses and liabilities that may be
incurred  by  the  Trustee therein or thereby, provided  that  no
Holder  shall  be  obligated to furnish to the Trustee  any  such
funding, security or indemnity in connection with the exercise by
the  Trustee of any of its rights, duties, powers and authorities
with  respect  to  (i)  the Voting Share pursuant  to  Article  4
hereof,  subject to section 6.15 hereof, (ii) the Exchange  Right
pursuant to Article 5 hereof, subject to section 6.15 hereof, and
(iii) the Automatic Exchange Rights pursuant to Article 5 hereof.

           None  of  the  provisions contained in this  Agreement
shall  require  the Trustee to expend or risk its  own  funds  or
otherwise incur financial liability in the exercise of any of its
rights,  powers,  duties or authorities unless funded  and  given
security and indemnity as aforesaid.

6.7       Actions by Holders.  No Holder shall have the right  to
institute any action, suit or proceeding or to exercise any other
remedy  authorized by this Agreement for the purpose of enforcing
any  of  its  rights or for the execution of any trust  or  power
hereunder unless the Holder has requested the Trustee to take  or
institute  such  action,  suit or proceeding  and  furnished  the
Trustee with the funding, security and indemnity referred  to  in
section  6.6  hereof  and the Trustee shall have  failed  to  act
within  a  reasonable time thereafter.  In  such  case,  but  not
otherwise,  the  Holder shall be entitled to take proceedings  in
any  court  of  competent jurisdiction such as the Trustee  might
have  taken, it being understood and intended that no one or more
Holders  shall have any right in any manner whatsoever to affect,
disturb  or  prejudice  the rights hereby  created  by  any  such
action,  or  to enforce any right hereunder or under  the  Voting
Rights,  the  Exchange  Right or the  Automatic  Exchange  Rights
except  subject  to  the  conditions and  in  the  manner  herein
provided,  and  that  all powers and trusts  hereunder  shall  be
exercised and all proceedings at law shall be instituted, had and
maintained by the Trustee, except only as herein provided, and in
any event for the equal benefit of all Holders.

6.8        Reliance upon Declarations.  The Trustee shall not  be
considered  to be in contravention of any of its rights,  powers,
duties  and authorities hereunder if, when required, it acts  and
relies  in  good  faith  upon  lists,  mailing  labels,  notices,
statutory declarations, certificates, opinions, reports or  other
papers  or documents furnished pursuant to the provisions  hereof
or  required by the Trustee to be furnished to it in the exercise
of  its rights, powers, duties and authorities hereunder and such
lists,   mailing   labels,   notices,   statutory   declarations,
certificates,  opinions,  reports or other  papers  or  documents
comply  with the provisions of section 6.9 hereof, if applicable,
and with any other applicable provisions of this Agreement.

6.9        Evidence  and Authority to Trustee.   The  Corporation
and/or   Orbital  shall  furnish  to  the  Trustee  evidence   of
compliance  with  the conditions provided for in  this  Agreement
relating to any action or step required or permitted to be  taken
by  the  Corporation  and/or Orbital or the  Trustee  under  this
Agreement  or  as a result of any obligation imposed  under  this
Agreement,  including,  without limitation,  in  respect  of  the
Voting  Rights,  the  Exchange Right or  the  Automatic  Exchange
Rights  and  the taking of any other action to be  taken  by  the
Trustee  at  the  request  of  or  on  the  application  of   the
Corporation and/or Orbital forthwith if and when:

                     (a)   such evidence is required by any other
               section of this Agreement to be furnished  to  the
               Trustee  in  accordance with  the  terms  of  this
               section 6.9; or

                     (b)   the  Trustee, in the exercise  of  its
               rights, powers, duties and authorities under  this
               Agreement,  gives the Corporation  and/or  Orbital
               written  notice  requiring  it  to  furnish   such
               evidence  in relation to any particular action  or
               obligation specified in such notice.

          Such evidence shall consist of an Officer's Certificate
of the Corporation and/or Orbital or a statutory declaration or a
certificate  made  by  persons  entitled  to  sign  an  Officer's
Certificate  stating that any such condition  has  been  complied
with in accordance with the terms of this Agreement.

           Whenever such evidence relates to a matter other  than
the  Voting Rights, the Exchange Right or the Automatic  Exchange
Rights,  and  except as otherwise specifically  provided  herein,
such  evidence  may  consist  of  a  report  or  opinion  of  any
solicitor,  auditor, accountant, appraiser, valuer,  engineer  or
other  expert  or  any  other  person whose  qualifications  give
authority  to  a  statement made by him, provided  that  if  such
report or opinion is furnished by a director, officer or employee
of  the Corporation and/or Orbital it shall be in the form of  an
Officer's Certificate or a statutory declaration.

           Each  statutory declaration, certificate,  opinion  or
report furnished to the Trustee as evidence of compliance with  a
condition  provided  for  in  this  Agreement  shall  include   a
statement by the person giving the evidence:

                      (a)    declaring  that  he  has  read   and
               understands  the  provisions  of  this   Agreement
               relating to the condition in question;

                     (b)  describing the nature and scope of  the
               examination or investigation upon which  he  based
               the  statutory declaration, certificate, statement
               or opinion; and

                      (c)    declaring  that  he  has  made  such
               examination  or  investigation as he  believes  is
               necessary to enable him to make the statements  or
               give the opinions contained or expressed therein.

6.10      Experts, Advisers and Agents.

          The Trustee may:

                     (a)   in relation to this Agreement act  and
               rely  on  the  opinion or advice of or information
               obtained  from any solicitor, auditor, accountant,
               appraiser,  valuer,  engineer  or  other   expert,
               whether  retained  by  the  Trustee  or   by   the
               Corporation and/or Orbital or otherwise,  and  may
               employ such assistants as may be necessary to  the
               proper  discharge  of its powers  and  duties  and
               determination of its rights hereunder and may  pay
               proper  and reasonable compensation for  all  such
               legal and other advice or assistance as aforesaid;
               and

                     (b)  employ such agents and other assistants
               as  it  may  reasonably  require  for  the  proper
               discharge of its powers and duties hereunder,  and
               may  pay  reasonable remuneration for all services
               performed  for it in the discharge of  the  trusts
               hereof  and  compensation for  all  disbursements,
               costs  and expenses made or incurred by it in  the
               discharge  of  its  duties hereunder  and  in  the
               management of the Trust.

6.11      Investment of Moneys Held By Trustee.  Unless otherwise
provided  in this Agreement, any moneys held by or on  behalf  of
the  Trustee that under the terms of this Agreement may or  ought
to  be  invested or which may be on deposit with the  Trustee  or
that  may  be  in  the hands of the Trustee may be  invested  and
reinvested  in  the name or under the control of the  Trustee  in
securities  in  which,  under the laws  of  the  Commonwealth  of
Massachusetts,  trustees are authorized to invest  trust  moneys,
provided  that  such securities are stated to mature  within  two
years  after their purchase by the Trustee, and the Trustee shall
so   invest  such  moneys  on  the  written  direction   of   the
Corporation.    Pending  the  investment   of   any   moneys   as
hereinbefore provided, such moneys may be deposited in  the  name
of  the Trustee in any bank in the United States approved by  the
Corporation  or,  with  the consent of the  Corporation,  in  the
deposit  department of the Trustee at the rate of  interest  then
current on similar deposits.

6.12       Trustee  Not Required to Give Security.   The  Trustee
shall not be required to give any bond or security in respect  of
the   execution  of  the  trusts,  rights,  duties,  powers   and
authorities of this Agreement.

6.13       Trustee  Not  Bound  to Act on Corporation's  Request.
Except as in this Agreement otherwise specifically provided,  the
Trustee  shall  not  be  bound  to act  in  accordance  with  any
direction or request of the Corporation and/or Orbital or of  the
directors  thereof  until  a  duly  authenticated  copy  of   the
instrument  or  resolution containing such direction  or  request
shall  have been delivered to the Trustee, and the Trustee  shall
be  empowered to act and rely upon any such copy purporting to be
authenticated and believed by the Trustee to be genuine.

6.14      Authority to Carry on Business.  The Trustee represents
to  the Corporation and Orbital that at the date of execution and
delivery by it of this Agreement it is authorized to perform  its
obligations pursuant to this Agreement under all applicable  laws
but  if, notwithstanding the provisions of this section 6.14,  it
ceases  to  be so authorized, the validity and enforceability  of
this Agreement and the Voting Rights, the Exchange Right and  the
Automatic  Exchange Rights shall not be affected  in  any  manner
whatsoever  by  reason only of such event but the Trustee  shall,
within  30 days after ceasing to be so authorized, either  become
so  authorized  or  resign  in the manner  and  with  the  effect
specified in Article 9 hereof.

6.15       Conflicting Claims.  If conflicting claims or  demands
are  made or asserted with respect to any interest of any  Holder
in  any  Exchangeable Shares, including any disagreement  between
the  heirs, representatives, successors or assigns succeeding  to
all or any part of the interest of any Holder in any Exchangeable
Shares  resulting in conflicting claims or demands being made  in
connection  with  such  interest,  then  the  Trustee  shall   be
entitled,  at its sole discretion, to refuse to recognize  or  to
comply  with  any  such claim or demand.   In  so  refusing,  the
Trustee  may  elect not to exercise any Voting  Rights,  Exchange
Right  or  Automatic Exchange Rights subject to such  conflicting
claims or demands and, in so doing, the Trustee shall not  be  or
become  liable to any person on account of such election  or  its
failure or refusal to comply with any such conflicting claims  or
demands.   The Trustee shall be entitled to continue  to  refrain
from acting and to refuse to act until:

                    (a)  the rights of all adverse claimants with
               respect  to the Voting Rights, Exchange  Right  or
               Automatic   Exchange  Rights   subject   to   such
               conflicting   claims   or   demands   have    been
               adjudicated  by a final judgment  of  a  court  of
               competent jurisdiction; or

                     (b)   all  differences with respect  to  the
               Voting   Rights,  Exchange  Right   or   Automatic
               Exchange Rights subject to such conflicting claims
               or  demands  have been conclusively settled  by  a
               valid  written  agreement  binding  on  all   such
               adverse claimants, and the Trustee shall have been
               furnished with an executed copy of such agreement.

If  the Trustee elects to recognize any claim or comply with  any
demand  made  by  any  such  adverse  claimant,  it  may  in  its
discretion require such claimant to furnish such surety  bond  or
other  security  satisfactory to the Trustee  as  it  shall  deem
appropriate  fully  to  indemnify it as between  all  conflicting
claims or demands.

6.16       Acceptance of Trust.  The Trustee hereby  accepts  the
Trust  created  and  provided for by and in  this  Agreement  and
agrees  to perform the same upon the terms and conditions  herein
set  forth  and  to  hold  all rights,  privileges  and  benefits
conferred hereby and by law in trust for the various persons  who
shall from time to time be Holders, subject to all the terms  and
conditions herein set forth.


                           ARTICLE 7

                          COMPENSATION

7.1        Fees  and  Expenses of the Trustee.  Orbital  and  the
Corporation  jointly and severally agree to pay  to  the  Trustee
reasonable  compensation for all of the services rendered  by  it
under  this  Agreement and will reimburse  the  Trustee  for  all
reasonable  expenses and disbursements, including  the  cost  and
expense  of  any  suit  or litigation of any  character  and  any
proceedings before any governmental agency reasonably incurred by
the  Trustee in connection with its rights and duties under  this
Agreement;  provided that Orbital and the Corporation shall  have
no  obligation  to  reimburse the Trustee  for  any  expenses  or
disbursements  paid, incurred or suffered by the Trustee  in  any
suit  or  litigation in which the Trustee is determined  to  have
acted  fraudulently,  in bad faith or with negligence  or  wilful
misconduct.


                           ARTICLE 8

          INDEMNIFICATION AND LIMITATION OF LIABILITY

8.1        Indemnification  of  the  Trustee.   Orbital  and  the
Corporation  jointly and severally agree to  indemnify  and  hold
harmless  the  Trustee  and  each  of  its  directors,  officers,
employees and agents appointed and acting in accordance with this
Agreement  (collectively the "Indemnified Parties")  against  all
claims,  losses, damages, costs, penalties, fines and  reasonable
expenses  (including reasonable expenses of the  Trustee's  legal
counsel)  which, without fraud, negligence, wilful misconduct  or
bad  faith  on the part of such Indemnified Party, may  be  paid,
incurred or suffered by the Indemnified Party by reason of or  as
a  result  of the Trustee's acceptance or administration  of  the
Trust,  its  compliance  with  its  duties  set  forth  in   this
Agreement, or any written or oral instructions delivered  to  the
Trustee  by  Orbital or the Corporation pursuant hereto.   In  no
case  shall  Orbital  or the Corporation  be  liable  under  this
indemnity  for  any claim against any of the Indemnified  Parties
unless  Orbital  and  the Corporation shall be  notified  by  the
Trustee  of  the written assertion of a claim or  of  any  action
commenced against the Indemnified Parties, promptly after any  of
the  Indemnified  Parties shall have received  any  such  written
assertion of a claim or shall have been served with a summons  or
other first legal process giving information as to the nature and
basis  of  the  claim.  Subject to (ii), below, Orbital  and  the
Corporation shall be entitled to participate at their own expense
in the defense and, if Orbital or the Corporation so elect at any
time after receipt of such notice, either of them may assume  the
defence  of  any  suit brought to enforce any  such  claim.   The
Trustee  shall have the right to employ separate counsel  in  any
such suit and participate in the defence thereof but the fees and
expenses  of such counsel shall be at the expense of the  Trustee
unless: (i) the employment of such counsel has been authorized by
Orbital or the Corporation; or (ii) the named parties to any such
suit include both the Trustee and Orbital or the Corporation  and
the  Trustee  shall  have been advised by counsel  acceptable  to
Orbital  or  the Corporation that there may be one or more  legal
defences available to the Trustee that are different from  or  in
addition  to  those available to Orbital or the  Corporation  and
that an actual or potential conflict of interest exists (in which
case  Orbital  and the Corporation shall not have  the  right  to
assume  the  defence of such suit on behalf of  the  Trustee  but
shall  be  liable  to  pay the reasonable fees  and  expenses  of
counsel for the Trustee).

8.2       Limitation of Liability.  The Trustee shall not be held
liable  for any loss that may occur by reason of depreciation  of
the value of any part of the Trust Estate or any loss incurred on
any investment of funds pursuant to this Agreement, except to the
extent  that  such loss is attributable to the fraud, negligence,
wilful misconduct or bad faith on the part of the Trustee.


                           ARTICLE 9

                       CHANGE OF TRUSTEE

9.1        Resignation.   The Trustee, or any  trustee  hereafter
appointed,  may  at any time resign by giving written  notice  of
such  resignation to Orbital and the Corporation  specifying  the
date  on  which it desires to resign, provided that  such  notice
shall  never  be  given  less than 60 days  before  such  desired
resignation  date  unless Orbital and the  Corporation  otherwise
agree  and provided further that such resignation shall not  take
effect  until the date of the appointment of a successor  trustee
and  the acceptance of such appointment by the successor trustee.
Upon  receiving  such  notice  of resignation,  Orbital  and  the
Corporation shall promptly appoint a successor trustee by written
instrument in duplicate, one copy of which shall be delivered  to
the  resigning  trustee  and one copy to the  successor  trustee.
Failing  acceptance by a successor trustee, a  successor  trustee
may  be  appointed  by an order of the Supreme Court  of  British
Columbia upon application of one or more of the parties hereto.

9.2         Removal.   The  Trustee,  or  any  trustee  hereafter
appointed, may be removed with or without cause, at any  time  on
60  days' prior notice by written instrument executed by  Orbital
and  the  Corporation, in duplicate, one copy of which  shall  be
delivered to the trustee so removed and one copy to the successor
trustee.

9.3       Successor Trustee.  Any successor trustee appointed  as
provided  under  this  Agreement shall execute,  acknowledge  and
deliver  to  Orbital and the Corporation and to  its  predecessor
trustee an instrument accepting such appointment.  Thereupon  the
resignation  or removal of the predecessor trustee  shall  become
effective  and such successor trustee, without any  further  act,
deed  or  conveyance, shall become vested with  all  the  rights,
powers,  duties  and  obligations of its predecessor  under  this
Agreement, with like effect as if originally named as trustee  in
this  Agreement.  However, on the written request of Orbital  and
the  Corporation or of the successor trustee, the trustee ceasing
to act shall, upon payment of any amounts then due it pursuant to
the  provisions  of  this  Agreement,  execute  and  deliver   an
instrument transferring to such successor trustee all the  rights
and powers of the trustee so ceasing to act.  Upon the request of
any  such  successor trustee, Orbital, the Corporation  and  such
predecessor  trustee  shall execute any and  all  instruments  in
writing for more fully and certainly vesting in and confirming to
such successor trustee all such rights and powers.

9.4        Notice  of  Successor  Trustee.   Upon  acceptance  of
appointment  by  a successor trustee as provided herein,  Orbital
and  the  Corporation  shall cause to be  mailed  notice  of  the
succession of such trustee hereunder to each Holder specified  in
a  List.  If Orbital or the Corporation shall fail to cause  such
notice   to  be  mailed  within  10  days  after  acceptance   of
appointment by the successor trustee, the successor trustee shall
cause such notice to be mailed at the expense of Orbital and  the
Corporation.


                           ARTICLE 10

                       ORBITAL SUCCESSORS

10.1       Certain  Requirements in Respect of Combination,  etc.
Orbital shall not enter into any transaction (whether by  way  of
reconstruction, reorganization, consolidation, merger,  transfer,
sale, lease or otherwise) whereby all or substantially all of its
undertaking, property and assets would become the property of any
other  person  or,  in the case of a merger,  of  the  continuing
corporation resulting therefrom, unless:

                      (a)    such   other  person  or  continuing
               corporation  is a corporation (herein  called  the
               "Orbital  Successor") incorporated under the  laws
               of  any state of the United States or the laws  of
               Canada or any province thereof; and

                     (b)  Orbital Successor, by operation of law,
               becomes,  without  more, bound by  the  terms  and
               provisions of this Agreement or, if not so  bound,
               executes, prior to or contemporaneously  with  the
               consummation  of  such  transaction  an  agreement
               supplemental hereto and such other instruments (if
               any)  as  are  satisfactory to the Trustee  acting
               reasonably  to evidence the assumption by  Orbital
               Successor of liability for all moneys payable  and
               property deliverable hereunder and the covenant of
               such Orbital Successor to pay and deliver or cause
               to  be  delivered  the same and its  agreement  to
               observe   and   perform  all  the  covenants   and
               obligations of Orbital under this Agreement.

10.2        Vesting   of  Powers  in  Successor.   Whenever   the
conditions  of  section 10.1 hereof have been duly  observed  and
performed,  the  Trustee, if required, by  section  10.1  hereof,
Orbital  Successor and the Corporation shall execute and  deliver
the  supplemental agreement provided for in Article 11 hereof and
thereupon Orbital Successor shall possess and from time  to  time
may exercise each and every right and power of Orbital under this
Agreement  in  the name of Orbital or otherwise and  any  act  or
proceeding by any provision of this Agreement required to be done
or performed by the board of directors of Orbital or any officers
of  Orbital may be done and performed with like force and  effect
by the directors or officers of such Orbital Successor.

10.3       Wholly-Owned Subsidiaries.  Nothing  herein  shall  be
construed  as  preventing  the  amalgamation  or  merger  of  any
wholly-owned subsidiary of Orbital with or into Orbital.


                           ARTICLE 11

          AMENDMENTS AND SUPPLEMENTAL TRUST AGREEMENTS

11.1      Amendments, Modifications, etc.  This Agreement may not
be amended or modified except by an agreement in writing executed
by  the Corporation, Orbital and the Trustee and approved by  the
Holders in accordance with section 8.2 of the Exchangeable  Share
Provisions.

11.2      Ministerial Amendments.  Notwithstanding the provisions
of  section  11.1  hereof, the parties to this Agreement  may  in
writing,  at any time and from time to time, without the approval
of  the  Holders, amend or modify this Agreement for the purposes
of:

                    (a)  adding to the covenants of any or all of
               the  parties  hereto  for the  protection  of  the
               Holders hereunder;

                     (b)  making such amendments or modifications
               not  inconsistent with this Agreement  as  may  be
               necessary or desirable with respect to matters  or
               questions  that, in the opinion of  the  Board  of
               Directors  of each of Orbital and Corporation  and
               in  the opinion of the Trustee, having in mind the
               best  interests of the Holders as a whole, it  may
               be expedient to make, provided that such boards of
               directors and the Trustee shall be of the  opinion
               that such amendments and modifications will not be
               prejudicial to the interests of the Holders  as  a
               whole; or

                     (c)   making  such  changes  or  corrections
               required  for the purpose of curing or  correcting
               any  ambiguity or defect or inconsistent provision
               or clerical omission or mistake or manifest error,
               provided  that  the  Trustee  and  the  Board   of
               Directors  of each of the Corporation and  Orbital
               shall  be  of  the  opinion that such  changes  or
               corrections  will  not  be  prejudicial   to   the
               interests of the Holders as a whole.

11.3       Meeting  to Consider Amendments.  The Corporation,  at
the  request of Orbital, shall call a meeting or meetings of  the
Holders for the purpose of considering any proposed amendment  or
modification  requiring  approval  pursuant  hereto.   Any   such
meeting  or meetings shall be called and held in accordance  with
the by-laws of the Corporation, the Exchangeable Share Provisions
and all applicable laws.

11.4       Changes  in  Capital of Orbital and  the  Corporation.
Notwithstanding section 11.1, at all times after  the  occurrence
of   any   Orbital   Common  Share  Reorganization   or   Capital
Reorganization  (as such terms are respectively  defined  in  the
Exchangeable  Share  Provisions) or other change  in  either  the
Orbital  Common Shares or the Exchangeable Shares or  both,  this
Agreement shall forthwith be amended and modified as necessary in
order  that  it  shall apply with full force and effect,  mutatis
mutandis, to all new securities into which Orbital Common  Shares
or the Exchangeable Shares or both are so changed and the parties
hereto  shall execute and deliver a supplemental agreement giving
effect   to   and   evidencing  such  necessary  amendments   and
modifications.

11.5         Execution   of   Supplemental   Trust    Agreements.
Notwithstanding  section 11.1, from time to time the  Corporation
(when  authorized  by  a resolution of the Board  of  Directors),
Orbital  (when  authorized  by  a  resolution  of  its  board  of
directors) and the Trustee may, subject to the provisions hereof,
and  they shall, when so directed by these presents, execute  and
deliver by their proper officers, Agreements or other instruments
supplemental hereto, which thereafter shall form part hereof, for
any one or more of the following purposes:

                     (a)   evidencing the succession  of  Orbital
               Successors  to  Orbital and the covenants  of  and
               obligations assumed by each such Orbital Successor
               in  accordance with the provisions of  Article  10
               and  the  succession of any successor  trustee  in
               accordance with the provisions of Article 9;

                     (b)  making any additions to, deletions from
               or alterations of the provisions of this Agreement
               or  the  Voting Rights, the Exchange Right or  the
               Automatic Exchange Rights that, in the opinion  of
               the   Trustee  acting  reasonably  will   not   be
               prejudicial to the interests of the Holders  as  a
               whole  or  are  in the opinion of counsel  to  the
               Trustee   necessary  or  advisable  in  order   to
               incorporate,   reflect   or   comply   with    any
               legislation  the  provisions  of  which  apply  to
               Orbital,  the  Corporation, the  Trustee  or  this
               Agreement; and

                     (c)  for any other purposes not inconsistent
               with  the  provisions of this Agreement including,
               without  limitation,  to  make  or  evidence   any
               amendment  or  modification to this  Agreement  as
               contemplated hereby, provided that, in the opinion
               of  the  Trustee acting reasonably, the rights  of
               the Trustee and the Holders as a whole will not be
               prejudiced thereby.


                           ARTICLE 12

                          TERMINATION

12.1       Term.    The  Trust  created by this  Agreement  shall
continue until the earliest to occur of the following events:

                     (a)  no outstanding Exchangeable Shares  are
               held by any Holder;

                     (b)   each  of the Corporation  and  Orbital
               elects in writing to terminate the Trust and  such
               termination  is  approved by the  Holders  of  the
               Exchangeable Shares in accordance with Section 8.2
               of the Exchangeable Share Provisions; and

                     (c)   21  years after the death of the  last
               survivor  of  the descendants of His Majesty  King
               George  VI of the United Kingdom of Great  Britain
               and  Northern Ireland living on the  date  of  the
               creation of the Trust.

12.2       Survival.  The provisions of Articles 7 and  8  hereof
shall  survive any termination of the Trust pursuant  to  section
12.1.


                           ARTICLE 13

                            GENERAL

13.1       Severability.  If any provision of this  Agreement  is
held  to  be  invalid,  illegal or unenforceable,  the  validity,
legality  or  enforceability of the remainder of  this  Agreement
shall  not  in any way be affected or impaired thereby  and  this
Agreement  shall  be  carried  out  as  nearly  as  possible   in
accordance  with  its  original terms and  conditions;  provided,
however,  that  if  the provision or provisions  so  held  to  be
invalid, in the reasonable judgment of the parties, is or are  so
fundamental  to  the intent of the parties and the  operation  of
this  Agreement  that  the enforcement of  the  other  provisions
hereof,  in  the absence of such invalid provision or provisions,
would  damage irreparably the intent of the parties  in  entering
into  this  Agreement, the parties shall agree (i)  to  terminate
this  Agreement,  or  (ii)  to amend  or  otherwise  modify  this
Agreement  so as to carry out the intent and purposes hereof  and
the transactions contemplated hereby.

13.2       Inurement.  This Agreement shall be binding  upon  and
inure  to  the benefit of the parties hereto and their respective
successors  and  permitted assigns and  to  the  benefit  of  the
Holders.

13.3        Notices   to   Parties.   All   notices   and   other
communications between the parties hereunder shall be in  writing
and shall be deemed to have been given if delivered personally or
by  confirmed telecopy to the parties at the following  addresses
(or at such other address for such party as shall be specified in
like notice):

                    (a)  if to Orbital at:

               Orbital Sciences Corporation
               21700 Atlantic Boulevard
               Dulles, Virginia 20166
               U.S.A.

               Attention:     General Counsel

               Telecopy: (703) 406-5572

          (b)  if to the Corporation at:

               MacDonald Dettwiler Holdings Inc.
               13800 Commerce Parkway
               Vancouver, British Columbia
               V6V 2J3

               Attention:     #

               Telecopy: (604) #

                (with a copy to Orbital at the address set out in
(a))

                    (c)  if to the Trustee at:

               #

                         Attention:     #

                         Telecopy: (#) #

Any  notice  or  other  communication given personally  shall  be
deemed to have been given and received upon delivery thereof  and
if  given  by  telecopy shall be deemed to have  been  given  and
received on the date of receipt thereof unless such day is not  a
Business Day in which case it shall be deemed to have been  given
and received upon the immediately following Business Day.

13.4      Notice to Holders.  Any and all notices to be given and
any  documents to be sent to any Holders may be given or sent  to
the  address of such Holder shown on the register of  Holders  in
any  manner permitted by the by-laws of the Corporation from time
to  time in force in respect of notices to shareholders and shall
be deemed to be received (if given or sent in such manner) at the
time  specified in such by-laws, the provisions of  which  bylaws
shall apply mutatis mutandis to notices or documents as aforesaid
sent to such Holders.

13.5      Risk of Payments by Post.  Whenever payments are to  be
made or documents are to be sent to any Holder by the Trustee  or
by  the  Corporation,  or by such Holder to  the  Trustee  or  to
Orbital or the Corporation, the making of such payment or sending
of  such  document sent through the post shall be at the risk  of
the  Corporation, in the case of payments made or documents  sent
by the Trustee or the Corporation, and the Holder, in the case of
payments made or documents sent by the Holder.

13.6       Counterparts.   This  Agreement  may  be  executed  in
counterparts, each of which shall be deemed an original, but  all
of  which  taken  together  shall constitute  one  and  the  same
instrument.

13.7       Jurisdiction.  This Agreement shall be  construed  and
enforced  in accordance with the laws of the Province of  British
Columbia and the laws of Canada applicable therein.

13.8        Attornment.   Orbital  agrees  that  any  action   or
proceeding  arising out of or relating to this Agreement  may  be
instituted  in  the  courts of the Province of British  Columbia,
waives  any  objection that it may have now or hereafter  to  the
venue  of  any such action or proceeding, irrevocably submits  to
the  jurisdiction  of  the said courts  in  any  such  action  or
proceeding, agrees to be bound by any judgment of the said courts
and  agrees  not to seek, and hereby waives, any  review  of  the
merits  of  any  such  judgment  by  the  courts  of  any   other
jurisdiction   and  hereby  appoints  the  Corporation   at   its
registered office as Orbital's attorney for service of process.

          IN WITNESS WHEREOF, the parties hereto have caused this
Agreement to be duly executed as of the date first above written.


                                   ORBITAL SCIENCES CORPORATION

                                   by ___________________________


                                      ___________________________

                                   MACDONALD DETTWILER HOLDINGS
                                   INC.

                                   by ___________________________


                                      ___________________________

                                   STATE  STREET BANK  AND  TRUST
                                   COMPANY


                                   by ___________________________


                                      ___________________________