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                                                                   EXHIBIT 10.23

                           ORBCOMM SYSTEM CONSTRUCTION
                                       AND
                              OPERATIONS AGREEMENT

        This ORBCOMM System Construction and Operations Agreement ("Agreement")
is made and entered into as of the 26th day of January 2000, by and between
ORBITAL COMMUNICATIONS Corporation, a Delaware corporation ("OCC"), and ORBCOMM
GLOBAL, L.P., a Delaware limited partnership ("ORBCOMM"), and amends and
restates the Restated ORBCOMM System Construction Agreement, dated as of
September 12, 1995, as amended by that certain Amendment No. 1 to Restated
ORBCOMM System Construction Agreement, dated as of July 1, 1996, in each case,
by and between OCC and ORBCOMM (as amended, the "System Construction
Agreement").

                               W I T N E S S E T H

        WHEREAS, Orbital Sciences Corporation, a Delaware corporation
("Orbital"), OCC, Teleglobe Inc., a Canadian corporation ("Teleglobe"), and
Teleglobe Mobile Partners, a Delaware general partnership ("Teleglobe Mobile"),
have entered into agreements for the development, construction, operation and
marketing of a low-Earth orbit satellite communications system that provides
two-way data and message communications services (the "ORBCOMM System") and
related activities in connection therewith;

        WHEREAS, on October 20, 1994, May 17, 1995, June 12, 1995 and March 31,
1998, OCC received from the FCC (as such term is hereinafter defined) licenses
authorizing OCC to construct, launch and operate 48 low-Earth orbit satellites
and to operate the associated ground infrastructure and subscriber units in the
United States (as modified, the "FCC Licenses"), for the purpose of providing
two-way data message communications services in the United States;

        WHEREAS, OCC and ORBCOMM are parties to the System Construction
Agreement, pursuant to which ORBCOMM agreed to develop, construct and launch
satellites and develop and construct certain other assets comprising the ORBCOMM
System in exchange for certain consideration, including the right to market,
sell, lease and franchise ORBCOMM System output capacity in certain locations;
and

        WHEREAS, OCC and ORBCOMM desire to amend and restate the System
Construction Agreement;

        NOW, THEREFORE, in consideration of the mutual covenants and agreements
contained herein and other valuable consideration, the receipt and sufficiency
of which is hereby acknowledged, the parties hereto agree as follows:

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ARTICLE 1 - DEFINITIONS

        Except as otherwise specifically defined herein, capitalized terms shall
have the meanings ascribed to such terms in Appendix C attached to the Restated
Master Agreement dated as of September 12, 1995 among Orbital, OCC, Teleglobe
and Teleglobe Mobile, as amended by that certain Amendment No. 1 to Restated
Master Agreement dated as of February 5, 1997 (as it may be further amended or
restated from time to time, the "Master Agreement"), which Appendix is
incorporated herein by reference.

ARTICLE 2 - TERM

        The term of this Agreement shall commence on the date hereof and shall
continue until such time as OCC and ORBCOMM shall mutually agree to terminate
this Agreement; provided however, that in the event the FCC Licenses are
transferred by OCC to ORBCOMM, this Agreement shall automatically terminate on
such transfer.

ARTICLE 3 - USE OF SYSTEM CAPACITY AND OPERATION OF SYSTEM ASSETS

        SECTION 3.1.  USE OF SYSTEM CAPACITY.

        (a)     Subject to the terms and conditions of this Agreement, OCC
hereby grants to ORBCOMM, which shall in turn be authorized to grant to third
parties, including its resellers, licensees and subscribers: (i) the right to
market, sell, lease and franchise all ORBCOMM System output capacity worldwide
and to use the System Assets located in the United States; and (ii) a
non-exclusive license, to use all logos, service marks, trademarks and trade
names of OCC relating to the ORBCOMM System (the "Marks"), in the course of
ORBCOMM's (or any of such third party's) business, for advertising, promotional
or sales literature, or any other form of publicity for the duration of this
Agreement. ORBCOMM agrees (and shall use all commercially reasonable efforts to
require such third parties to agree) that its use of such Marks conforms (A)
with respect to ORBCOMM's use, to OCC's written requirements, if any, for
display of such Marks, including registry and trademark symbols, and (B) with
respect to such third parties' use, to ORBCOMM's written requirements for
display of such Marks, including registry and trademark symbols.

        (b)     ORBCOMM is hereby granted the right to manage and operate the
ORBCOMM System on behalf of OCC, and ORBCOMM shall provide OCC management and
operational services, including the performance of tracking, telemetry and
control functions, with respect to the ORBCOMM System, all subject to the
oversight, supervision and control of OCC. Notwithstanding any provision of this
Agreement to the contrary, each of OCC and ORBCOMM acknowledges and agrees that:
(i) OCC is in sole control of the FCC Licenses and the ORBCOMM System; and (ii)
OCC is required by FCC regulations to be in sole control of the FCC Licenses so
long as it is the licensee under the FCC Licenses and accordingly, that it has
the right, among other things, to order the discontinuance of operations to
avoid any violations of FCC rules and regulations and the right to unfettered
access to all facilities, sites and equipment used in the operation of the
ORBCOMM System. ORBCOMM further acknowledges and agrees

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that OCC has ultimate control over all decisions affecting the ORBCOMM System
including, but not limited to, the employment, supervision and dismissal of
personnel, notwithstanding any other provision of any of the Definitive
Agreements. ORBCOMM shall assist OCC in complying with all Federal, state and
local rules and regulations regarding operation of the ORBCOMM System, including
all FCC requirements set forth in any of the FCC Licenses.

        SECTION 3.2. CONSIDERATION FOR USE OF SYSTEM CAPACITY. In consideration
of the grant to ORBCOMM of the right to market, sell, lease and franchise
ORBCOMM System output capacity worldwide and to use the System Assets located in
the United States, ORBCOMM hereby agrees as follows:

        (a)     ORBCOMM shall (i) develop, construct, launch and operate the
Satellites comprising the ORBCOMM System and (ii) develop, construct and operate
the other assets comprising the ORBCOMM System located in the United States; and

        (b)     ORBCOMM shall pay the following cash consideration to OCC: (i)
for the period commencing on the date hereof and ending on December 31, 2000,
ORBCOMM shall pay OCC the sum of $100,000; $50,000 of which shall be payable on
June 30, 2000 and $50,000 of which shall be payable on December 31, 2000, and
(ii) for the periods following December 31, 2000, ORBCOMM shall pay OCC such fee
as is mutually agreeable to OCC and ORBCOMM, as determined by negotiation in
good faith by each of OCC and ORBCOMM.

        SECTION 3.3 INSURANCE ON SYSTEM ASSETS. Insurance on the ORBCOMM System
and the System Assets shall be procured by ORBCOMM in such amounts, at such
times and to cover such risks as ORBCOMM shall determine in its sole discretion.

        SECTION 3.4 TRANSFER OF ORBCOMM TRADEMARK AND SERVICE MARK. OCC agrees
to transfer and assign to ORBCOMM, at ORBCOMM's expense, the applications for or
the registered trademark and service mark "ORBCOMM", which transfer and
assignment shall occur upon terms and conditions to be mutually agreed, but in
any event at such time as such registered trademark or service mark comes up for
renewal in the country or territory where it is registered.

        SECTION 3.5 PATENT INDEMNIFICATION. ORBCOMM shall defend, indemnify and
hold harmless OCC and its respective successors and assigns from and against any
claim with respect to an infringement or other violation of any copyright,
trademark or patent or other validly registered enforceable intellectual
property right of any third party for any items ORBCOMM has constructed for OCC
pursuant to the authority granted in Section 3.2 hereof, but only to the same
extent as the indemnification received by ORBCOMM from Orbital, if any, under
the ORBCOMM System Procurement Agreement dated as of September 12, 1995, as
amended from time to time, between Orbital and ORBCOMM and the ORBCOMM
Procurement Agreement dated as of February 1, 1999, as amended from time to time
between Orbital and ORBCOMM.

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ARTICLE 4 - MISCELLANEOUS

        SECTION 4.1 GOVERNING LAW. This Agreement shall be construed in
accordance with and governed by the laws of the State of New York, USA, without
giving effect to the provisions, policies or principles thereof relating to
choice or conflict of laws.

        SECTION 4.2 DISPUTE RESOLUTION. Any controversy or claim that may arise
under, out of, in connection with or relating to this Agreement shall be
resolved in accordance with Section 13.4 of the Master Agreement.

        SECTION 4.3 ENTIRE AGREEMENT. This Agreement constitutes the entire
agreement among the parties with respect to the subject matter hereof and
supersedes any prior writing, agreement or understanding among the parties with
respect to the subject matter hereof.

        SECTION 4.4 AMENDMENT; WAIVER. Except as provided otherwise herein, this
Agreement may not be amended nor may any rights hereunder be waived except by an
instrument in writing signed by the parties hereto.

        SECTION 4.5 BINDING EFFECT; ASSIGNMENT. This Agreement shall be binding
on and shall inure to the benefit of the parties and their respective successors
and permitted assigns. Neither this Agreement nor any interests or obligations
hereunder shall be assigned or transferred (by operation of law or otherwise) to
any Person without the prior written consent of the other party.

        SECTION 4.6 COUNTERPARTS. This Agreement may be executed in any number
of counterparts of the signature pages, each of which shall be considered an
original, but all of which together shall constitute one and the same
instrument.

        SECTION 4.7 HEADINGS. The section and other headings contained in this
Agreement are for reference purposes only and shall not affect the meaning or
interpretation of this Agreement.

        SECTION 4.8 NOTICES. Except as otherwise specified herein, all notices,
requests and other communications required to be delivered to any party
hereunder shall be in writing (including any facsimile transmission or similar
writing), and shall be sent by facsimile or delivered in person addressed as
follows:

        (a)     If to OCC:

                21700 Atlantic Boulevard
                Dulles, Virginia  20166
                Attention: Vice President and Chief Financial Officer
                Facsimile: (703) 406-3502

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        (b)     If to ORBCOMM:

                2455 Horse Pen Road, Suite 100
                Herndon, Virginia  20171
                Attention: Senior Vice President, General Counsel and Secretary
                Facsimile: (703) 406-5933

                with a copy to:

                Teleglobe Inc.
                1000 rue de la Gauchetiere ouest
                Montreal, Quebec
                Canada H3B 4X5
                Attention: Vice President, Legal Affairs and Corporate Secretary
                Facsimile: (514) 868-7438

or to such other persons or addresses as any party may designate by written
notice to the others. Each such notice, request or other communication shall be
effective (i) if given by facsimile, when such facsimile is transmitted and the
appropriate answerback is received, (ii) if given by reputable overnight
courier, one business day after being delivered to such courier, or (iii) if
given by any other means, when received at the address specified in this Section
4.8.

        IN WITNESS WHEREOF, the parties have caused this Agreement to be
executed as of the day and year first above written.

ORBITAL COMMUNICATIONS CORPORATION        ORBCOMM GLOBAL, L.P.

By: /S/ Jeffrey V. Pirone                 By: /s/ Scott L. Webster
    --------------------------                --------------------------
    Name:   Jeffrey V. Pirone                 Name: Scott L. Webster
    Title:  Vice President and                Title:  President and
              Chief Financial Officer                   Chief Executive Officer

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