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                                                                 EXHIBIT 10.2.10

                        TENTH AMEMDMENT TO NOTE AGREEMENT
                                       AND
                               EXTENSION OF WAIVER


       THIS TENTH AMENDMENT TO NOTE AGREEMENT AND EXTENSION OF WAIVER ("Tenth
Amendment"), is made and entered into as of the 22nd day of February, 2000,
between ORBITAL SCIENCES CORPORATION, a Delaware corporation (the "Company"),
and THE NORTHWESTERN MUTUAL LIFE INSURANCE COMPANY, a Wisconsin corporation (the
"Purchaser").

                                    RECITALS:

       A.     The Purchaser is the holder of $13,333,333 12% Senior Notes of the
Company due June 14, 2001 (the "Notes"). The Company and the Purchaser are
parties to that certain Note Agreement, dated as of June 1, 1995, the First
Amendment to Note Agreement dated as of June 30, 1995, the Second Amendment to
Note Agreement dated as of March 15, 1996, the Third Amendment to Note Agreement
dated as of July 31, 1996, the Fourth Amendment to Note Agreement dated as of
March 31, 1997, the Fifth Amendment to Note Agreement dated as of December 23,
1997, the Sixth Amendment to Note Agreement dated as of August 14, 1998, the
Seventh Amendment to Note Agreement dated as of May 27, 1999, the Eighth
Amendment to Note Agreement dated as of December 20, 1999, and the Ninth
Amendment to Note Agreement dated as of January 31, 2000 (as amended,
supplemented or otherwise modified, the "Note Agreement") whereby the Purchaser
purchased the Notes from the Company.

       B.     The Company and the Purchaser entered into that certain Waiver
Letter, dated as of October 31, 1999 (the "Waiver Letter"), whereby the
Purchaser waived certain Defaults or Events of Default arising or existing under
Sections 5.7, 5.8 and 5.9 of the Note Agreement until 11:59 p.m. C.S.T. on
December 31, 1999. Pursuant to that certain Letter Agreement, dated as of
December 23, 1999, between the Company and the Purchaser, the date and time of
termination of the Default Waiver Term (as defined in Section 1 of the Waiver
Letter) was extended to 5:00 p.m. C.S.T. on February 22, 2000. The Company and
the Purchaser now desire to further extend the Default Waiver Term on the terms
set forth in this Tenth Amendment.

       C.     In addition, the Company and the Purchaser desire to amend certain
provisions of the Note Agreement as of February 22, 2000 (the "Effective Date")
in the respects, but only in the respects, set forth in this Tenth Amendment.

       D.     Capitalized terms used in this Tenth Amendment have their
respective meanings ascribed thereto in the Note Agreement unless defined in
this Tenth Amendment or the context otherwise requires.


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       NOW, THEREFORE, upon full and complete satisfaction of the conditions
precedent to the effectiveness of this Tenth Amendment set forth in Section 4
below, the Company and the Purchaser agree as follows:

SECTION 1.  EXTENSION OF WAIVER.

       The Company and the Purchaser agree that the Default Waiver Term, as
defined in Section 1 of the Waiver Letter, shall be extended so that the Default
Waiver Term shall terminate at 5:00 p.m. C.S.T. on April 30, 2000.

SECTION 2.  AMENDMENTS.

       2.1    Section 5.11 of the Note Agreement is hereby amended in its
entirety to read as follows:

              5.11. Restricted Investments. Neither the Company nor any of its
       Subsidiaries will declare, make or authorize any Restricted Investment on
       or after February 22, 2000. Any entity which becomes a Subsidiary after
       the date of this Agreement shall be deemed to have made, on the 90th day
       following the date on which it became a Subsidiary, all Restricted
       Investments of such corporation existing on such 90th day after it
       becomes a Subsidiary.

       2.2    Clause (d) of the definition of "Restricted Investments" appearing
in Section 8.1 of the Note Agreement is hereby amended in its entirety to read
as follows:

              (d) Investments made by the Company (i) after the Closing Date but
       prior to February 22, 2000, in connection with the development and growth
       of the business of ORBCOMM Partnership, provided that the aggregate
       amount of such Investments shall not exceed $157,500,000; (ii) pursuant
       to that certain Omnibus Agreement, dated January 1, 2000, by and among
       the Company, ORBCOMM, Teleglobe Inc., Teleglobe Mobile Partners, and
       ORBCOMM Partnership (the "Omnibus Agreement"), whereby the Company,
       through ORBCOMM, (x) will acquire $33,081,650.22 of partnership interests
       in ORBCOMM Partnership by converting loans, advanced by the Company to
       ORBCOMM Partnership prior to January 1, 2000, to such partnership
       interests, and (y) will contribute the GEMtrak Business (as defined in
       the Omnibus Agreement) to ORBCOMM Partnership; (iii) after December 31,
       1996, in connection with the formation and development of the business of
       ORBIMAGE, provided that the aggregate amount of such Investments shall
       not exceed $52,000,000; (iv) in common stock of Earthwatch Incorporated,
       provided that the aggregate amount of such Investments shall not exceed
       $1,800,000; and (v) in preferred stock of Wireless Link Corp., provided
       that the aggregate amount of such Investments shall not exceed
       $2,000,000.


SECTION 3.  REPRESENTATIONS AND WARRANTIES OF THE COMPANY.


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       To induce the Purchaser to execute and deliver this Tenth Amendment, the
Company represents and warrants to the Purchaser (which representations will
survive the execution and delivery of this Tenth Amendment) that:

              (a)    this Tenth Amendment has been duly authorized, executed and
       delivered by the Company and constitutes the legal, valid and binding
       obligation of the Company, enforceable against it in accordance with its
       terms, except as enforcement may be limited by bankruptcy, insolvency,
       reorganization, moratorium or similar laws or equitable principles
       relating to fraudulent conveyance or limiting creditors' rights
       generally;

              (b)    the Note Agreement, as modified by this Tenth Amendment,
       constitutes the legal, valid and binding obligation of the Company,
       enforceable against it in accordance with its terms, except as
       enforcement may be limited by bankruptcy, fraudulent conveyance,
       insolvency, reorganization, moratorium or similar laws or equitable
       principles relating to or limiting creditors' rights generally;

              (c)    the execution, delivery and performance by the Company of
       this Tenth Amendment (i) has been duly authorized by all requisite
       corporate action and, if required, shareholder action, (ii) does not
       require the consent or approval of any governmental or regulatory body or
       agency, and (iii) will not (A) violate (1) any provision of law, statute,
       rule or regulation or its certificate of incorporation or bylaws, (2) any
       order of any court or any rule, regulation or order of any other agency
       or government binding upon it, or (3) any material provision of any
       material indenture, agreement or other instrument to which it is a party
       or by which its properties or assets are or may be bound, or (B) result
       in a material breach or constitute (alone or with due notice or lapse of
       time or both) a default under any indenture, agreement or other
       instrument referred to in clause (iii)(A)(3) of this Section 2(c); and

              (d)    as of the ate hereof and after giving effect to this Tenth
       Amendment, no Default or Event of Default has occurred which is
       continuing.

SECTION 4.  CONDITIONS AND AGREEMENTS.

       Upon fulfillment or receipt of all of the following, as the case may be,
this Tenth Amendment will on the Effective Date become effective:

              (a)    executed counterparts of this Tenth Amendment, duly
       executed by the Company and the Purchaser, have been delivered to the
       Purchaser.

              (b)    the representations and warranties of the Company set forth
       in Section 3 of this Tenth Amendment will be true and correct on and with
       respect to the date hereof; and

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              (c)    the Company has obtained any consents or approvals required
       to be obtained from any holder or holders of any outstanding security of
       the Company and any amendments or agreements pursuant to which any
       security may have been issued which will be necessary to permit the
       consummation of the transactions contemplated by this Tenth Amendment.

SECTION 5.  MISCELLANEOUS.

       5.1    This Tenth Amendment will be construed in connection with the Note
Agreement, and except as modified by this Tenth Amendment, all terms, conditions
and covenants contained in the Note Agreement and the Note are hereby ratified
and will be and remain in full force and effect.

       5.2    The descriptive headings of the various Sections or parts of this
Tenth Amendment are for convenience only and will not affect the meaning or
construction of any of the provisions hereof.

       5.3    This Tenth Amendment will be governed by and construed in
accordance with the internal laws of the State of Illinois.

       5.4    This Tenth Amendment may be executed in any number of
counterparts, each executed counterpart constituting an original, but all
together only one agreement.

       IN WITNESS WHEREOF, the Company and the Purchaser have caused this Tenth
Amendment to be executed and delivered by their respective duly authorized
representatives.

                                  ORBITAL SCIENCES CORPORATION


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

                                  THE NORTHWESTERN MUTUAL LIFE
                                     INSURANCE COMPANY


                                  By:
                                     ----------------------------------

                                     Its Authorized Representative