Document:

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                                                                   EXHIBIT 10.27

                                AMENDMENT NO. 6
                                       TO
                           THIRD AMENDED AND RESTATED
                       CREDIT AND REIMBURSEMENT AGREEMENT

          AMENDMENT No. 6 dated as of December 21, 1999 among ORBITAL SCIENCES
CORPORATION (the "COMPANY"), the BANKS listed on the signature pages hereof and
MORGAN GUARANTY TRUST COMPANY OF NEW YORK, as Administrative Agent (the
"ADMINISTRATIVE AGENT") and as Collateral Agent (the "COLLATERAL AGENT").

                                  WITNESSETH:

          WHEREAS, the parties hereto have heretofore entered into a Third
Amended and Restated Credit and Reimbursement Agreement dated as of December 21,
1998 (as amended from time to time, the "CREDIT AGREEMENT"); and

          WHEREAS, the Company has asked the Banks to waive compliance by the
Company with certain covenants set forth in the Credit Agreement for the period
from and including the Amendment No. 6 Effective Date (as defined in the Credit
Agreement as amended hereby) to and including February 22, 2000 (the "WAIVER
PERIOD"), and the Banks are willing to do so, subject to the terms and
conditions set forth herein; and

          WHEREAS, the parties hereto wish to release certain collateral and
amend certain terms of the Credit Agreement as set forth herein;

          NOW, THEREFORE, the parties hereto agree as follows:

     SECTION 1. Definition; References. Unless otherwise specifically defined
herein, each term used herein that is defined in the Credit Agreement shall have
the meaning assigned to such term in the Credit Agreement. Each reference to
"hereof', "hereunder", "herein" and "hereby" and each other similar reference
and each reference to "this Agreement" and each other similar reference
contained in the Credit Agreement shall from and after the Amendment No. 6
Effective Date (as defined in Section 17 below) refer to the Credit Agreement as
amended hereby.

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     SECTION 2. Additional Definitions. (a) Section 1.01 of the Credit Agreement
is amended by adding therein the following definitions in alphabetical order:

          "ASSET SALE" means any sale, lease or other disposition (including any
     such transaction effected by way of merger or consolidation) by the Company
     or any of its domestic wholly-owned Subsidiaries of any asset, but
     excluding (i) dispositions in the ordinary course of business, (ii)
     dispositions to the Company or a domestic wholly-owned Subsidiary and (iii)
     dispositions of Temporary Cash Investments and cash payments otherwise
     permitted under this Agreement.

          "AMENDMENT NO. 6 EFFECTIVE DATE" means the date of effectiveness of
     Amendment No. 6 to this Agreement.

          "CONSOLIDATED CAPITAL EXPENDITURES" means, for any period, the
     aggregate amount of expenditures by the Company and its Consolidated
     Subsidiaries for plant, property and equipment during such period
     (including any such expenditure by way of acquisition of a Person or by way
     of assumption of indebtedness or other obligations of a Person, to the
     extent reflected as plant, property and equipment).

          "EQUITY ISSUANCE" means any issuance of equity securities by the
     Company or any of its domestic wholly-owned Subsidiaries, other than (i)
     any such issuance to the Company or any of its domestic wholly-owned
     Subsidiaries, (ii) any such issuance pursuant to employee benefit
     arrangements in the ordinary course of business and (iii) any such issuance
     pursuant to the warrants contemplated by Section 16 of Amendment No. 6.

          "EXCLUDED CHARGES" means the non-cash charges taken by the Company
     with respect to certain matters as further described under "Pending
     Matters" in Form 10-Q filed by the Company with the Securities and Exchange
     Commission for the fiscal quarter ended September 30, 1999, a copy of which
     has been delivered by the Company to each Bank prior to the Amendment No. 6
     Effective Date.

          "MDA TRANSACTION" means, collectively, the transactions contemplated
     by the MDA Transaction Agreement.

          "MDA TRANSACTION AGREEMENT" means the Subscription Agreement dated on
     or about December 21, 1999 among CAI CAPITAL PARTNERS AND COMPANY II, a
     limited partnership formed under the laws of the Province of Ontario, CAI
     PARTNERS AND COMPANY II, a

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     limited partnership formed under the laws of the Province of Ontario, CAI
     CAPITAL PARTNERS AND COMPANY II-C, a limited partnership formed under the
     laws of the Province of Ontario (collectively, the "CAI Entities"), a
     newly-formed British Columbia corporation ("NEWCO" and, together with the
     CAI Entities, the "PURCHASERS"), MDA and the Company, containing
     substantially the terms set forth in the summary thereof heretofore
     distributed to the Banks and otherwise in form and substance satisfactory
     to the Administrative Agent.

          "NET CASH PROCEEDS" means, with respect to any Reduction Event, an
     amount equal to the cash proceeds received by the Company or any of its
     domestic wholly-owned Subsidiaries from or in respect of such Reduction
     Event (including any cash proceeds received as interest or similar income
     or other proceeds of any noncash proceeds of any Asset Sale), less (i) any
     fees, costs and expenses reasonably incurred by such Person in respect of
     such Reduction Event and (ii) if such Reduction Event is an Asset Sale, any
     taxes actually paid or to be paid by such Person (as estimated by a senior
     financial or accounting officer of the Company, after giving effect to the
     overall tax position of the Company) in respect of such Asset Sale and the
     amount of any Debt secured by a Lien on an asset which is the subject of
     such Asset Sale and required to be discharged in connection therewith.

          "REDUCTION EVENT" means any Asset Sale or Equity Issuance.

          "RESTRICTED ACCOUNT" means a bank account established pursuant to
     arrangements satisfactory to the Collateral Agent which is subject to a
     Lien in favor of the Agents and the Banks and from which disbursements of
     funds may be authorized only by the Collateral Agent.

     (b) The definition of "CONSOLIDATED EBITDA" set forth in Section 1.01 of
the Credit Agreement is amended to read in its entirety as follows:

          "CONSOLIDATED EBITDA" means, for any period, Consolidated Net Income
     for such period plus, to the extent deducted in determining such
     Consolidated Net Income, without duplication, the aggregate amount of (i)
     consolidated interest expense, (ii) income tax expense, (iii) depreciation,
     amortization and other similar non-cash charges, (iv) one-time accounting
     charges resulting in adjustments to earnings for each of the fiscal
     quarters of the fiscal year ended December 31, 1998, up to an aggregate
     amount equal to $35,600,000, (v) write-offs with respect to the investment
     made by the Company in CCI International N.V. for any fiscal quarter ended
     prior to December 31, 1999, up to an aggregate amount equal to

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     $21,400,000 and (vi) solely for any period ended on or prior to February
     22, 2000, Excluded Charges, up to an aggregate amount equal to $5,000,000.

     (c) The definition of "CONSOLIDATED NET WORTH" set forth in Section 1.01 of
the Credit Agreement is amended to read in its entirety as follows:

          "CONSOLIDATED NET WORTH" means, at any date, the consolidated
     stockholders' equity of the Company and its Consolidated Subsidiaries as of
     such date; provided that Consolidated Net Worth at any date on or prior to
     February 22, 2000 shall be net of the lesser of (i) the effect of any
     Excluded Charges recorded on or prior to such date and (ii) $40,000,000 in
     the aggregate.

     (d) The definition of "EARNINGS AVAILABLE FOR FIXED CHARGES" set forth in
Section 1.01 of the Credit Agreement is amended to read in its entirety as
follows:

          "EARNINGS AVAILABLE FOR FIXED CHARGES" means, for any period,
     Consolidated Net Income for such period (excluding therefrom (i) any
     extraordinary items of gain or loss, (ii) any gain or loss of any other
     Person accounted for pursuant to the equity method, except in the case of
     gain to the extent of cash distributions received from such Person during
     the relevant period), plus the aggregate amounts deducted in determining
     Consolidated Net Income for such period in respect of (i) interest and
     rental expense, (ii) income taxes, (iii) write-offs with respect to the
     investment made by the Company in CCI International N.V. for any fiscal
     quarter ended prior to December 31, 1999, up to an aggregate amount equal
     to $21,400,000 and (iv) solely for any period ended on or prior to February
     22, 2000, Excluded Charges, up to an aggregate amount equal to $5,000,000.

     SECTION 3. Reductions in Commitments. The existing text of Section 2.10 is
redesignated subsection (a) thereof, and the following new subsections (b), (c)
and (d) are added to Section 2.10:

          (b) On the Amendment No. 6 Effective Date, the Commitments shall be
     automatically and ratably reduced to the aggregate amount of $187,000,000.

          (c) The Commitments shall be automatically and ratably reduced on the
     date of consummation of the MDA Transaction, by $22,000,000

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          (d) If a Reduction Event shall occur, the Commitments shall be
     automatically and ratably reduced by an amount equal to the lesser of (i)
     40% of the Net Cash Proceeds of such Reduction Event and (ii) the amount
     necessary to reduce the aggregate amount of the Commitments to
     $125,000,000; provided that if such portion of such Net Cash Proceeds, when
     aggregated with the corresponding portions of the Net Cash Proceeds of all
     other Reduction Events not theretofore so applied, is less than $1,000,000,
     such Net Cash Proceeds shall be deposited in the Restricted Account pending
     application pursuant to this subsection (d) in connection with a subsequent
     Reduction Event. Such reduction shall be effective as of the day of receipt
     by the Company or any of its domestic wholly-owned Subsidiaries, as the
     case may be, of the relevant Net Cash Proceeds.

          (e) To the extent not theretofore reduced to the same or a lesser
     amount, the Commitments shall be automatically and ratably reduced on
     August 1, 2000 to the aggregate amount of $125,000,000.

          (f)) On the date of each reduction of the Commitments pursuant to this
     Section 2.10, the Borrowers shall prepay, together with accrued interest
     thereon, the aggregate principal amount of the Loans in excess of the
     aggregate amount of the Commitments as so reduced.

     SECTION 4. Waiver of Compliance with Certain Covenants. (a) The Banks waive
(i) compliance by the Company with the provisions of Section 5.08 of the Credit
Agreement and (ii) any Default arising under Section 6.01 (c) of the Credit
Agreement by reason of such noncompliance; provided that the waivers granted
pursuant to this Section shall be effective only so long as Consolidated Net
Worth (as defined in the Credit Agreement as amended hereby) at the last day of
any fiscal quarter ended during the Waiver Period will not be less than (i)
$375,000,000 plus (ii) 50% of Consolidated Net Income for each fiscal quarter of
the Company ended on or after September 30, 1999, for which Consolidated Net
Income is positive (but with no deduction on account of any fiscal quarter for
which Consolidated Net Income is negative) plus (iii) 100% of the aggregate
amount by which Consolidated Net Worth shall have been increased by reason of
the issuance and sale after September 30, 1999 and on or prior to such date of
any capital stock or the conversion or exchange of any Debt of the Company into
or with capital stock of the Company consummated after September 30, 1999 and on
or prior to such day.

     (b) The Banks waive (i) compliance by the Company with the provisions of
Section 5.09 of the Credit Agreement and (ii) any Default arising under Section
6.01(c) of the Credit Agreement by reason of such noncompliance; provided that

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the waivers granted pursuant to this Section 3(b) shall be effective only so
long as the Leverage Ratio will at no time during the Waiver Period exceed
5.00:1.

     (c) The Banks waive (i) compliance by the Company with the provisions of
Section 5.10 of the Credit Agreement and (ii) any Default arising under Section
6.01(c) of the Credit Agreement by reason of such noncompliance; provided that
the waivers granted pursuant to this Section 3(c) shall be effective only so
long as the ratio of Earnings Available for Fixed Charges to Consolidated Fixed
Charges, on the last day of any fiscal quarter in each case for the four
consecutive fiscal quarters then ended, will at no time during the Waiver Period
be less than 1.15:1.

     (d) Each of the waivers granted pursuant to this Section shall expire on
the earlier of (i) close of business (New York City time) on the last day of the
Waiver Period and (ii) the first date on which the Company shall, or shall
permit any other Borrower to, breach any of its obligations set forth in Section
11.

     (e) Except as provided in subsections (a), (b) and (c) above, this Section
3 shall not operate as a waiver of any right, remedy, power or privilege of the
Banks under any Financing Document or of any other term or condition of any
Financing Document.

     SECTION 5. Consent to MDA Transaction. The Banks hereby consent to the MDA
Transaction and agree to release the Lien on the capital stock of MacDonald
Dettwiler Holdings Inc. ("MDH") pledged to them under the Pledge Agreement, upon
and subject to the following terms and conditions:

     (a) The MDA Transaction shall be consummated in accordance with the MDA
Transaction Agreement for gross cash proceeds not less than $75,000,000.

     (b) Immediately prior to the merger between MDA and MDH contemplated by the
MDA Transaction Agreement, the Collateral Agent shall release the Lien of the
Banks on the capital stock of MDH so as to permit consummation of such merger
(which shall be consummated on the same day as such release), and immediately
following consummation of such merger and of the other principal components of
the MDA Transaction (all of which shall in any event be consummated on the same
day or the following day), the Company shall deliver to the Collateral Agent in
pledge under the Pledge Agreement all capital stock of MDA owned by the Company
following consummation of the MDA Transaction.

     (c) Upon formation of the new holding company ("NEW MDH") contemplated by
the MDA Transaction Agreement, the Collateral Agent shall release the Lien of
the Pledge Agreement on the capital stock of MDA pledged pursuant to clause (b)
above, provided that (i) New MDH is a wholly owned

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Domestic Subsidiary of the Company and (ii) prior to or substantially
simultaneously with the release of such lien, the Company shall have delivered
all capital stock of New MDH to the Collateral Agent in pledge under the Pledge
Agreement.

     (d) The net cash proceeds to the Company of the MDA Transaction shall be
applied on the date of consummation of the MDA Transaction as follows: (i) an
amount equal to $22,000,000 shall be applied to prepayment of Loans outstanding
under the Credit Agreement (ratably amoung the Banks, to be applied to such
Group or Groups of Loans as the Administrative Agent may determine); (ii) an
amount equal to $10,000,000 shall be deposited in the Restricted Account and
(iii) the balance shall be released to the Company to be used for working
capital purposes. Amounts so deposited in the Restricted Account shall be
released therefrom from time to time upon request of the Company, so long as at
the time no Default shall have occurred and be continuing, as follows: (A) upon
consummation of the security arrangements contemplated by Section 5.19(d) of the
Credit Agreement, $5,000,000 shall be released; (B) at such time as the
aggregate amount of the Commitments shall have been reduced to $150,000,000 or
less, $10,000,000 shall be released; (C) amounts not theretofore released
pursuant to clause (A) or (B) shall be released from time to time, so long as
after giving effect to such release the Company's cash balances do not exceed
$10,000,000 and (D) any such request for release shall be accompanied by a
certificate signed by a duly authorized officer of the Company (on which the
Collateral Agent may conclusively rely) to the effect that the applicable
conditions set forth above have been satisfied in connection with such release.

     (e) The Company agrees to cause the foregoing conditions to be satisfied in
the event that the MDA Transaction is consummated, and agrees that any failure
to do so shall constitute an Event of Default.

     (f) The Banks hereby authorize the Collateral Agent to give the
acknowledgments contemplated by Sections 4.1(2) and (3) of the Unanimous
Shareholders' Agreement contemplated by the MDA Transaction Agreement.

     (g) The Banks hereby waive (i) the requirement under Section 5.19(b) of the
Credit Agreement that New MDH become a Guarantor and (ii) the limitations of
Section 5.14 of the Credit Agreement to the extent, and only to the extent,
necessary to permit New MDH to grant the Lien on the shares of MDA pursuant to
Section 15 of the Secondary Option Agreement contemplated by the MDA Transaction
Agreement, provided that the documentation establishing such Lien is
satisfactory to the Collateral Agent.

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     (h) The figure "60 days" appearing in Section 6.01(i) of the Credit
Agreement is changed to "30 days".

     SECTION 6. Additional Reporting Requirements. Subsections (i) and (j) of
Section 5.01 are amended to read in their entirety as follows:

          (i) (x) no later than 10 Business Days after the Amendment No. 5
     Effective Date, a statement of projected cash flows of the Company and its
     Consolidated Subsidiaries for each month in the six month period from and
     including October 1, 1999 to and including March 31, 2000 and (y) no later
     than the 22nd day after the end of each calendar month (starting with
     October 1999), a statement of projected cash flows of the Company and its
     Consolidated Subsidiaries for each month in the immediately succeeding six
     month period and for the period beginning on the first day after such
     calender month and ending December 31, 2000, taken as a whole, setting
     forth (a) in each case, at least the financial information set forth in the
     projected statement of cash flows of the Company and its Consolidated
     Subsidiaries for the third and fourth fiscal quarters of the fiscal year
     1999 and each fiscal quarter of the fiscal year 2000, a copy of which has
     been delivered to the Banks prior to the Amendment No. 5 Effective Date,
     (b) accounts receivables at the last day of the most recently ended
     calendar month, (c) available cash on hand and amounts available for
     borrowing under this Agreement at the last day of the most recently ended
     calendar month, and (d) in the case of any such statement delivered
     pursuant to clause (y), the actual cash flows of the Company and its
     Consolidated Subsidiaries for the most recently ended calendar month
     setting forth the operating cash flows as a single line item and the
     financing and investing activities as separate line items;

          (j) no later than (x) 10 Business Days after the Amendment No. 5
     Effective Date and (y) the 22nd day after the end of each calendar month
     (starting with October 1999), a summary report setting forth (1)(i) total
     number of units sold by ORBCOMM Global, (ii) total number of units
     installed by ORBCOMM Global and (iii) revenues of ORBCOMM Global derived
     from subscriber airtime usage (i.e. net of product sale revenues), in each
     case (a) for such calendar month (or, in the case of the summary report
     delivered within 10 Business Days after the Amendment No. 5 Effective Date,
     for September 1999 (the "FIRST SUMMARY REPORT")) and (b) for the period
     from creation of ORBCOMM Global to the last day of such calendar month (or
     September 1999, in the case of the First Summary Report), and (2) the
     numbers and revenues described in subclauses (i), (ii) and (iii) of clause
     (1) projected for the immediately succeeding calendar month (or, in the
     case of the First Summary Report, for October 1999) and

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     for the period beginning on the first day after such calender month and
     ending December 31, 2000, taken as a whole; and

     SECTION 7. Additional Permitted Investments. Section 5.07 of the Credit
Agreement is amended by:

          (i) substituting the dollar amount "$157,500,000" for the dollar
     amount "$154,000,000" set forth in clause (d) thereof; and

          (ii) substituting the dollar amount "$45,500,000" for the dollar
     amount "$35,000,000" set forth in subclause (y) under clause (j) thereof.

     SECTION 8. Exception to the Subsidiary Debt Covenant. Section 5.17 of the
Credit Agreement is amended to read in its entirety as follows:

                    SECTION 5.17. Subsidiary Debt. Total Debt of all of the
     Company's Subsidiaries (excluding (i) Loans and Letter of Credit
     Liabilities hereunder, (ii) Debt of a Subsidiary to the Company or to a
     Wholly-Owned Subsidiary of the Company and (iii) Debt consisting of
     performance bonds and letters of credit issued for the account of MDA in an
     aggregate amount not in excess of $30,000,000 to support certain
     contractual obligations, including obligations in an aggregate amount of
     approximately $10,000,000 for construction of the Radarsat 2 satellite, of
     approximately $8,000,000 under a contract with respect to a Malaysian
     ground station, of approximately $3,000,000 under a contract with respect
     to a Taiwanese ground station and of approximately $9,000,000 with respect
     to miscellaneous performance bonds) will at no time exceed 55% of
     Consolidated Tangible Net Worth."

     SECTION 9. Additional Covenants Regarding Collateral. New subsections (d)
and (e) are added immediately after subsection (c) of Section 5.19 of the Credit
Agreement, to read in their entirety as follows:

          (d) The Company shall use its commercially reasonable efforts to
     obtain all necessary consents for the pledge to the Collateral Agent for
     the benefit of the Banks of all of the capital stock and other equity
     interests of Magellan held directly or indirectly by the Company and,
     within 5 days of obtaining such consents, shall (i) enter into, or such
     cause its Subsidiaries to enter into, a pledge agreement in form and
     substance reasonably satisfactory to the Collateral Agent pursuant to which
     the Company or such Subsidiaries, as the case may be, shall grant a
     perfected first priority Lien to the Collateral Agent for the benefit of
     the Banks on all of such capital stock or other equity interests, (ii) take
     all action necessary or (in

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     the opinion of the Collateral Agent or the Required Lenders) desirable to
     perfect and protect the Liens intended to be created by the pledge
     agreement described in clause (i) and (iii) deliver to the Collateral Agent
     and the Lenders such opinions of counsel, in form and substance reasonably
     satisfactory to the Collateral Agent, as the Collateral Agent shall
     reasonably request.

          (e) On or prior to 30 days after the Amendment No. 6 Effective Date,
     the Company shall (i) execute and deliver to the Collateral Agent a
     mortgage in form and substance reasonably satisfactory to the Collateral
     Agent pursuant to which the Company shall grant to the Collateral Agent for
     the benefit of the Banks a perfected first priority Lien on (x)
     approximately 11.5671 acres of real property, comprising lots 1 and 2 as
     recorded in Deed Book 948, page 1041, among the land records of Loudoun
     County, Virginia, and (y) approximately 9.2922 acres of real property,
     comprising lots 3 and 4, as recorded in Deed Book 948, page 1041, among the
     land records of Loudoun County, Virginia, (ii) deliver to the Collateral
     Agent such surveys, title reports and title insurance as the Collateral
     Agent shall reasonably request, (iii) take all action necessary or (in the
     opinion of the Collateral Agent or the Required Lenders) desirable to
     perfect and protect the Liens intended to be created by the mortgage
     described in clause (i) and (iv) deliver to the Collateral Agent and the
     Lenders such opinions of counsel, in form and substance reasonably
     satisfactory to the Collateral Agent, as the Collateral Agent shall
     reasonably request.

     SECTION 10. Additional Covenant to Limit Consolidated Capital Expenditures.
A new Section 5.20 is added immediately after Section 5.19 of the Credit
Agreement, to read in its entirety as follows:

                    SECTION 5.20. Consolidated Capital Expenditure. At any date
     the aggregate amount of Consolidated Capital Expenditures for the period
     from and including December 1, 1999 to and including such date, will not
     exceed $9,000,000.

     SECTION 11. Bankers Meeting; Strategic Plan. A new section 5.21 to the
Credit Agreement is added immediately after Section 5.20 thereof, to read in its
entirety as follows:

                    SECTION 5.21 January 2000 Bankers Meeting. The Company
     shall:

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          (a) On or prior to January 27, 2000 (i) host a bankers meeting, at
     which meeting the Company shall discuss with the Banks its detailed
     strategic plan to address liquidity for the fiscal year 2000, and (ii)
     provide the Banks in reasonable detail information regarding the strategic
     plans of the Company and its Subsidiaries, as well as any other information
     regarding the Company and its Subsidiaries as any Bank may reasonably
     request.

          (b) At least three Domestic Business Days prior to the date of the
     bankers' meeting referred to in subsection (a) (but in any event no later
     than January 24, 2000), deliver to each of the Lenders a strategic plan
     setting forth in reasonable detail the strategic plans of the Company which
     plan shall include the information set forth in clause (i) of subsection
     (a) of this Section.

     SECTION 12. Additional Events of Default. Section 6.01(c) of the Credit
Agreement is amended to read in its entirety as follows:

          (c) any Borrower shall fail to observe or perform any covenant or
agreement contained in Sections 5.01(g) and 5.07 to 5.21 inclusive;

     SECTION 13. Limitation on New Extensions of Credit. The Company agrees that
neither Company nor any other Borrower shall deliver a Notice of Borrowing under
the Credit Agreement or a request for issuance of a Letter of Credit under the
Credit Agreement or otherwise request any Bank (including the LC Bank) to extend
any credit to the Company or any other Borrower under the Credit Agreement, and
that, notwithstanding any provision of the Credit Agreement (including Sections
2.01, 2.03 and 3.02), on and after the date hereof, no Bank (including the LC
Bank) shall be required to make any Loan, or issue or participate in any Letter
of Credit (it being understood that nothing in this sentence shall be construed
to prohibit the Company from delivering a Notice of Interest Rate Election with
respect to any Loan outstanding prior to the date hereof and continuing or
converting such Loan on the terms set forth in such Notice of Interest Rate
Election).

     SECTION 14. Amendment to Pricing Schedule. The Pricing Schedule to the
Credit Agreement is amended by substituting the date "February 22, 2000" for the
date "December 30, 1999" set forth in paragraph immediately after the table set
forth therein.

     SECTION 15. New York Law. This Amendment shall be governed by and construed
in accordance with the laws of the State of New York.

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     SECTION 16. Warrants. The Company will, not later than January 15, 2000,
deliver to the Administrative Agent for the account of the Approving Banks (as
defined below) ratably in proportion to their Commitments, warrants in form
satisfactory to the Administrative Agent entitling the holder to purchase up to
100,000 shares of Common Stock, par value $.01 per share, of the Company for a
period expiring on the fifth anniversary of the date of issuance thereof at an
exercise price of $0.01 per share, subject to customary antidilution protection
and registration rights.

     SECTION 17. Counterparts, Effectiveness. This Amendment may be signed in
any number of counterparts, each of which shall be an original, with the same
effect as if the signatures thereto and hereto were upon the same instrument.
This Amendment shall become effective on the date (the "AMENDMENT NO. 6
EFFECTIVE DATE") on which the Administrative Agent shall have received:

          (a) duly executed counterparts hereof signed by the Company and the
     Required Banks (or, in the case of any party as to which an executed
     counterpart shall not have been received, the Administrative Agent shall
     have received telegraphic, telex or other written confirmation from such
     party of execution of a counterpart hereof by such party); and

          (b) an amendment fee in the amount of $500,000, for the ratable
     account of those Banks (the "APPROVING BANKS") from which approval of this
     Amendment shall have been received at or prior to the later of (i) the time
     the condition in clause (a) is satisfied and (ii) 12:00 noon, New York City
     time, on December 22, 1999. The determination of the Administrative Agent
     as to timing of the receipt of a Bank's approval shall be conclusive.

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

                         ORBITAL SCIENCES CORPORATION

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

                         MORGAN GUARANTY TRUST COMPANY
                           OF NEW YORK

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

                         THE BANK OF NOVA SCOTIA

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

                         BANK OF AMERICA, N.A., f/k/a
                           NATIONSBANK, N.A.

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

                         FIRST UNION COMMERCIAL CORPORATION

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

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                         DEUTSCHE BANK AG, NEW YORK
                           AND/OR CAYMAN ISLAND BRANCHES

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

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

                         KEYBANK NATIONAL ASSOCIATION

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

                         BANK OF TOKYO-MITSUBISHI TRUST COMPANY

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

                         WACHOVIA BANK, N.A.

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

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                         CHEVY CHASE BANK

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

                         MORGAN GUARANTY TRUST COMPANY
                           OF NEW YORK, as Administrative Agent and as
                           Collateral Agent

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

                                      15<PAGE>   1
                                                                   EXHIBIT 10.28

                                                                [EXECUTION COPY]

                          SECOND AMENDED AND RESTATED

                               SECURITY AGREEMENT

                                  dated as of
                                 June 30, 1992
                           amended and restated as of
                                 August 5, 1997
                     and further amended and restated as of
                               November 30, 1999

                                     among

                         ORBITAL SCIENCES CORPORATION,

                     EACH OF ITS SUBSIDIARIES PARTY HERETO,

                   MORGAN GUARANTY TRUST COMPANY OF NEW YORK,
                              as Collateral Agent

                                      and

                             BANK OF AMERICA, N.A.,
                          as Designated Lockbox Bank

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                 SECOND AMENDED AND RESTATED SECURITY AGREEMENT

         SECOND AMENDED AND RESTATED SECURITY AGREEMENT dated as of June 30,
1992, amended and restated as of August 5, 1997 and further amended and
restated as of November 30, 1999 among ORBITAL SCIENCES CORPORATION (with its
successors, the "COMPANY") and each of the Subsidiaries of the Company listed
on the signature pages hereof and each other Subsidiary of the Company that may
from time to time become a party to this Agreement (each such Subsidiary, with
its successors, a "SUBSIDIARY DEBTOR" and together with the Company, the
"DEBTORS"), MORGAN GUARANTY TRUST COMPANY OF NEW YORK , as Collateral Agent
(with its successors, the "COLLATERAL AGENT") and BANK OF AMERICA, N.A., as
Designated Lockbox Bank (with its successors, the "DESIGNATED LOCKBOX BANK").

                             W I T N E S S E T H :

         WHEREAS, the Company, certain banks (with their respective successors
and assigns, the "BANKS"), Morgan Guaranty Trust Company of New York, as
administrative agent (the "ADMINISTRATIVE AGENT") and the Collateral Agent have
entered into a Third Amended and Restated Credit Agreement dated as of December
21, 1998 (as amended from time to time, the "CREDIT AGREEMENT");

         WHEREAS, the Company and The Northwestern Mutual Life Insurance
Company (with its successors and assigns, "NML") have entered into a Note
Agreement dated as of June 1, 1995 (as amended from time to time, the "NML NOTE
AGREEMENT"); and

         WHEREAS, the Company, the Collateral Agent and the Designated Lockbox
Bank have entered into an Amended and Restated Security Agreement dated as of
June 30, 1992 and amended and restated as of August 5, 1997 (as amended from
time to time prior to the date hereof, the "ORIGINAL COMPANY SECURITY
AGREEMENT"); and

         WHEREAS, pursuant to Section 5.19(a) of the Credit Agreement and
pursuant to the NML Note Agreement, the Company and the Subsidiary Debtors
party hereto are required to enter into a security agreement substantially in
the form hereof; and

         NOW, THEREFORE, in consideration of the premises and other good and
valuable consideration, the receipt and sufficiency of which are hereby

<PAGE>   3
acknowledged, the Original Company Security Agreement is amended and restated
in its entirety as follows:

         SECTION 1. Definitions. Terms defined in the Credit Agreement and not
otherwise defined herein have, as used herein, the respective meanings provided
for therein. The following additional terms, as used herein, have the following
respective meanings:

         "ANCILLARY RIGHTS" means, with respect to each Debtor, rights
incidental or ancillary to the Receivables of such Debtor and the
administration, servicing and collection thereof, including, without
limitation, all collateral security and guarantees of any kind (including
without limitation letters of credit or other forms of credit enhancement)
given by any Person to such Debtor with respect to any Receivable of such
Debtor.

          "BANK COLLATERAL" has the meaning set forth in Section 3(A).

         "BANK SECURED OBLIGATIONS" means:

         (x) with respect to the Company, (a) all principal of and interest
(including, without limitation, any interest which accrues after the
commencement of any case, proceeding or other action relating to the
bankruptcy, insolvency or reorganization of the Company, whether or not allowed
or allowable as a claim in any such proceeding) on any loan to the Company
under, or any note issued by the Company pursuant to, the Credit Agreement, (b)
all Reimbursement Obligations and all interest thereon (including, without
limitation, any interest which accrues after the commencement of any case,
proceeding or other action relating to the bankruptcy, insolvency or
reorganization of the Company, whether or not allowed or allowable as a claim
in any such proceeding), (c) all other amounts payable by the Company under any
Financing Document, and (d) any renewals or extensions of any of the foregoing;
and

         (y) with respect to each Subsidiary Debtor, all obligations of such
Subsidiary Debtor incurred by such Subsidiary Debtor pursuant to Section 22.

         "COLLATERAL" means the Bank Collateral and the Shared Collateral.

         "COLLATERAL ACCOUNT" has the meaning set forth in Section 5.

         "COPYRIGHT LICENSE" means, with respect to each Debtor, any agreement
now or hereafter in existence granting to such Debtor, or pursuant to which
such Debtor has granted to any other Person, any right to use, copy, reproduce,
distribute, prepare derivative works, display or publish any records or other

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materials on which a Copyright is in existence or may come into existence,
including, without limitation, any agreement identified in Schedule 1 to a
Copyright Security Agreement.

         "COPYRIGHTS" means all the following: (i) all copyrights under the
laws of the United States or any other country (whether or not the underlying
works of authorship have been published), all registrations and recordings
thereof, all copyrightable works of authorship (whether or not published), and
all applications for copyrights under the laws of the United States or any
other country, including, without limitation, registrations, recordings and
applications in the United States Copyright Office or any other country or any
political subdivision thereof, including, without limitation, those described
in Schedule 1 to any Copyright Security Agreement, (ii) all renewals thereof,
(iii) all claims for, and rights to sue for, past or future infringements of
any of the foregoing, and (iv) all income, royalties, damages and payments now
or hereafter due or payable with respect to any of the foregoing, including,
without limitation, damages and payments for past or future infringements
thereof.

         "COPYRIGHT SECURITY AGREEMENT" means a Copyright Security Agreement,
substantially in the form of Exhibit B hereto, executed and delivered by a
Debtor in favor of the Collateral Agent, for the benefit of the Secured
Parties, as amended from time to time.

         "DESIGNATED LOCKBOX BANK" means Bank of America, N.A.

         "EXCLUDED MAGELLAN NOTE" means the Amended and Restated Unsecured
Subordinated Revolving Promissory Note dated November 29, 1999 in the principal
amount of $22,470,846.00 issued by Magellan to the Company.

         "GENERAL INTANGIBLES" means, with respect to each Debtor, all "general
intangibles" (as defined in the UCC) now owned or hereafter acquired by such
Debtor (but excluding any partnership interests or limited liability company
interests of any Person held by such Debtor), including, without limitation,
(i) all obligations or indebtedness owing to such Debtor (other than (x)
Receivables of such Debtor, (y) limited liability company interests or
partnership interests of any Person held by such Debtor and (z) solely with
respect to the Company, any indebtedness evidenced by the Excluded Magellan
Note) from whatever source arising, (ii) Intellectual Property, goodwill, trade
names, service marks, trade secrets, inventions, permits and licenses, (iii)
all rights or claims in respect of refunds for taxes paid and (iv) all rights
in respect of any pension plan or similar arrangement maintained for employees
of any member of the ERISA Group.

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         "INSTRUMENTS" means, with respect to each Debtor, all "instruments",
"chattel paper" or "letters of credit" (each as defined in the UCC) evidencing,
representing, arising from or existing in respect of, relating to, securing or
otherwise supporting the payment of, any of the Receivables of such Debtor,
including (but not limited to) promissory notes, drafts, bills of exchange and
trade acceptances, now owned or hereafter acquired by such Debtor but excluding
the Excluded Magellan Note.

         "INSURANCE ACCOUNT" has the meaning set forth in Section 6.

         "INSURANCE PAYMENTS" means all proceeds payable to the Collateral
Agent as loss payee under, or unearned premiums with respect to, the Insurance
Policies.

         "INSURANCE POLICIES" means the insurance policies evidencing the
insurance the Company and its Subsidiaries are maintaining at any time pursuant
to Section 5.03 of the Credit Agreement other than any such policy solely with
respect to (i) "equipment" (as defined in the UCC) or (ii) real property which
secures a mortgage in favor of any Person other than the Collateral Agent.

         "INTELLECTUAL PROPERTY" means (i) Patents, (ii) Patent Licenses, (iii)
Trademarks, (iv) Trademark Licenses, (v) Copyrights and (vi) Copyright
Licenses, and all rights in or under any of the foregoing.

         "INTELLECTUAL PROPERTY FILING" means (i) with respect to any Patent,
Patent License, Trademark or Trademark License, the filing of the applicable
Patent Security Agreement or Trademark Security Agreement with the United
States Patent and Trademark Office, together with an appropriately completed
recordation form, and (ii) with respect to any Copyright or Copyright License,
the filing of the applicable Copyright Security Agreement with the United
States Copyright Office, together with an appropriately completed recordation
form, in each case sufficient to record the Security Interest granted to the
Collateral Agent in such Intellectual Property.

         "INTELLECTUAL PROPERTY SECURITY AGREEMENT" means a Copyright Security
Agreement, a Patent Security Agreement or a Trademark Security Agreement.

         "LETTER OF CREDIT OBLIGATION" means, at any time, any Reimbursement
Obligations or other obligation to make a payment in connection with a Letter
of Credit issued under the Credit Agreement, including contingent obligations
with respect to amounts which are then, or may thereafter become, available for
drawing under such Letter of Credit.

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<PAGE>   6
         "LIQUID INVESTMENTS" means, with respect to each Debtor, Temporary
Cash Investments; provided that (i) each Liquid Investment shall mature within
30 days after it is acquired by the Collateral Agent and (ii) in order to
provide the Collateral Agent, for the benefit of the Secured Parties (other
than NML), with a perfected security interest therein, each Liquid Investment
shall be either:

                  (i) evidenced by negotiable certificates or instruments, or
         if non-negotiable then issued in the name of such Debtor, which
         (together with any appropriate instruments of transfer) are delivered
         to, and held by, the Collateral Agent or an agent thereof (which shall
         not be such Debtor or any of its Affiliates) in the State of New York;
         or

                  (ii) in book-entry form and issued by the United States and
         subject to pledge under applicable state law and Treasury regulations
         and as to which (in the reasonable opinion of counsel to the
         Collateral Agent) appropriate measures shall have been taken for
         perfection of the Security Interests.

         "MAGELLAN NOTE" means the promissory note dated November 30, 1999 in
the principal amount of $23,000,000.00 issued by Magellan to the Company.

         "MATERIAL GOVERNMENT CONTRACT" means, with respect to each Debtor, any
contract between such Debtor and any United States government agency under
which contract payments to such Debtor in an amount in excess of $3,000,000 may
be made.

         "NML GUARANTY AGREEMENT" means the Guaranty to be entered into among
the Subsidiary Debtors and NML.

         "NML SECURED OBLIGATIONS" means:

         (x) with respect to the Company, (a) all principal of and interest on
any note issued by the Company pursuant to the NML Note Agreement (including,
without limitation, any interest which accrues after the commencement of any
case, proceeding or other action relating to the bankruptcy, insolvency or
reorganization of the Company, whether or not allowed or allowable as a claim
in any such proceeding), (b) all other amounts, including without limitation,
make-whole amount, if any, payable by the Company under the NML Note Agreement
and (c) any renewals or extensions of any of the foregoing; and

         (y) with respect to each Subsidiary Debtor, all obligations of such
Subsidiary Debtor incurred by such Subsidiary Debtor pursuant to the NML
Guaranty Agreement.

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<PAGE>   7
         "PATENT LICENSE" means, with respect to each Debtor, any agreement now
or hereafter in existence granting such Debtor, or pursuant to which such
Debtor has granted to any other Person, any right with respect to any Patent,
now or hereafter in existence, including, without limitation, any agreement
identified in Schedule 1 to a Patent Security Agreement.

         "PATENTS" means (i) all letters patent and design letters patent of
the United States or any other country and all applications for letters patent
and design letters patent of the United States or any other country, including,
without limitation, applications in the United States Patent and Trademark
Office or in any similar office or agency of any other country or any political
subdivision thereof, (ii) all reissues, divisions, continuations,
continuations-in-part, revisions and extensions thereof, (iii) all claims for,
and rights to sue for, past or future infringements of any of the foregoing and
(iv) all income, royalties, damages and payments now or hereafter due or
payable with respect to any of the foregoing, including, without limitation,
damages and payments for past or future infringements thereof.

         "PATENT SECURITY AGREEMENT" means a Patent Security Agreement,
substantially in the form of Exhibit C hereto, executed and delivered by a
Debtor in favor of the Collateral Agent, for the benefit of the Secured
Parties, as amended from time to time.

         "PERFECTION CERTIFICATE" means the certificate, substantially in the
form of Exhibit A, completed and supplemented with the schedules and
attachments contemplated thereby to the satisfaction of the Collateral Agent,
and duly executed by the Debtors.

         "PERMITTED LIENS" means the Liens permitted under Section 5.14 of the
Credit Agreement.

         "PROCEEDS" means all proceeds of, and all other profits, rentals or
receipts, in whatever form, arising from the collection, sale, lease, exchange,
assignment, licensing or other disposition of, or realization upon, Collateral,
including without limitation all claims of each Debtor against third parties
for loss of, damage to or destruction of, or for proceeds payable under, or
unearned premiums with respect to, policies of insurance in respect of, any
Collateral, rights to any returned or repossessed goods relating to any
Collateral, and any condemnation or requisition payments with respect to any
Collateral, in each case whether now existing or hereafter arising.

         "RECEIVABLES" means, with respect to each Debtor, all "ACCOUNTS" (as
defined in the UCC) now owned or hereafter acquired by such Debtor, and shall

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also mean and include all accounts receivable, contract rights, book debts,
chattel paper, notes, drafts and other obligations or indebtedness owing to
such Debtor arising from the sale, lease or exchange of goods or other property
by it and/or performance of services by it (including, without limitation, any
such obligation which might be characterized as an account, contract right or
general intangible under the Uniform Commercial Code in effect in any
jurisdiction) and all of such Debtor's right in, to and under all purchase
orders for goods, services or other property to be provided or sold by it or
any Affiliate, and all of such Debtor's rights to any goods, services or other
property represented by any of the foregoing (including returned or repossessed
goods and unpaid sellers' rights of rescission, replevin, reclamation and
rights to stoppage in transit) and all monies due to or to become due to such
Debtor under all contracts for the sale (as seller), lease (as lessor) or
exchange of goods or other property and/or performance of services by it
(whether or not yet earned by performance on the part of such Debtor), in each
case whether now in existence or hereafter arising or acquired including,
without limitation, the right to receive the proceeds of said purchase orders
and contracts and all collateral security and guarantees of any kind given by
any Person with respect to any of the foregoing.

         "SECURED OBLIGATIONS" means:

         (x) with respect to the Company, (a) the Bank Secured Obligations of
the Company and (b) the NML Secured Obligations of the Company; and

         (y) with respect to each Subsidiary Debtor, (a) the Bank Secured
Obligations of such Subsidiary Debtor and (b) the NML Secured Obligations of
such Subsidiary Debtor.

         "SECURED PARTIES" means each of the Banks and the Agents and, solely
with respect to the Shared Collateral, NML.

         "SECURITY EVENT" means any event, occurrence or condition which, in
the sole discretion of the Required Banks acting in good faith, "impairs the
prospect of payment" by the Debtors within the meaning of Section 1-208 of the
UCC.

         "SECURITY INTERESTS" means the security interests in the Collateral
granted hereunder securing the Secured Obligations.

         "SHARED COLLATERAL" has the meaning set forth in Section 3(B).

         "TRADEMARK LICENSE" means, with respect to each Debtor, any agreement
now or hereafter in existence granting to such Debtor, or pursuant to which
such Debtor has granted to any other Person, any right to use any Trademark,
including,

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without limitation, any agreement identified in Schedule 1 to any Trademark
Security Agreement.

         "TRADEMARKS" means: (i) all trademarks, trade names, corporate names,
company names, business names, fictitious business names, trade styles, service
marks, logos, brand names, trade dress, prints and labels on which any of the
foregoing have appeared or appear, package and other designs, and any other
source or business identifiers, and general intangibles of like nature, and the
rights in any of the foregoing which arise under applicable law, (ii) the
goodwill of the business symbolized thereby or associated with each of them,
(iii) all registrations and applications in connection therewith, including,
without limitation, registrations and applications in the United States Patent
and Trademark Office or in any similar office or agency of the United States,
any State thereof or any other country or any political subdivision thereof,
including, without limitation, those described in Schedule 1 to any Trademark
Security Agreement, (iv) all renewals thereof, (v) all claims for, and rights
to sue for, past or future infringements of any of the foregoing and (vi) all
income, royalties, damages and payments now or hereafter due or payable with
respect to any of the foregoing, including, without limitation, damages and
payments for past or future infringements thereof.

         "TRADEMARK SECURITY AGREEMENT" means a Trademark Security Agreement,
substantially in the form of Exhibit D hereto, executed and delivered by a
Debtor in favor of the Collateral Agent, for the benefit of the Secured
Parties, as amended from time to time.

         "UCC" means the Uniform Commercial Code as in effect on the date
hereof in the State of New York; provided that if by reason of mandatory
provisions of law, the perfection or the effect of perfection or non-perfection
of the Security Interest in any Collateral is governed by the Uniform
Commercial Code as in effect in a jurisdiction other than New York, "UCC" means
the Uniform Commercial Code as in effect in such other jurisdiction for
purposes of the provisions hereof relating to such perfection or effect of
perfection or non-perfection.

         SECTION 2. Representations and Warranties. Each Debtor represents and
warrants as follows:

         (A) Such Debtor has good title to all of the Collateral, free and
clear of any Liens other than the Permitted Liens. Such Debtor has taken all
actions necessary under the UCC to perfect its interest in any Receivables
purchased or otherwise acquired by it, as against its assignors and creditors
of its assignors.

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         (B) Other than financing statements, mortgages, security agreements or
other similar or equivalent documents or instruments with respect to the
Security Interests and the Permitted Liens, no financing statement, mortgage,
security agreement or similar or equivalent document or instrument covering all
or any part of the Collateral is on file or of record in any jurisdiction in
which such filing or recording would be effective to perfect a Lien on such
Collateral. No Collateral is in the possession of any Person (other than such
Debtor) asserting any claim thereto or security interest therein, except that
the Collateral Agent or its designee may have possession of Collateral as
contemplated hereby.

         (C) Such Debtor has delivered the Perfection Certificate to the
Collateral Agent. The information set forth therein is correct and complete in
all material respects. Promptly after the receipt thereof, such Debtor shall
furnish to the Collateral Agent acknowledgment copies of the filings set forth
in Schedule 7 to the Perfection Certificate.

         (D) The Security Interests constitute valid security interests under
the UCC securing the Secured Obligations to the extent the UCC is applicable
thereto. Upon filing of the financing statements, the Security Interests will
constitute perfected security interests in the Collateral of each Debtor to the
extent that a security interest therein may be perfected by filing pursuant to
the UCC, subject to no Liens except for the Permitted Liens and prior to all
Liens except for the Permitted Liens (other than the Security Interests)
existing on and as of the date on which such Debtor becomes a party to this
Agreement. When, in addition to the filing of UCC financing statements, the
applicable Intellectual Property Filings have been made with respect to each
Debtor's Intellectual Property (including any future filings required pursuant
to Section 4(B)), the Security Interests will constitute perfected security
interests in all right, title and interest of each Debtor in its Intellectual
Property to the extent that security interests therein may be perfected by such
filings, subject to no Liens except for the Permitted Liens and prior to all
Liens except for the Permitted Liens (other than the Security Interests)
existing on and as of the date such Debtor becomes a party to this Agreement.

         (E) Upon the delivery to the Collateral Agent by such Debtor of
assignments and notices of assignment substantially in the forms of Exhibits
E-1 and E-2 hereto, respectively, and the filing of each such notice with the
governmental authority or agency or other office described therein, the
Security Interests shall constitute valid assignments of the Receivables of
such Debtor due under Material Government Contracts of such Debtor to the
extent that such assignment is governed by the Assignment of Claims Act.

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         (F) No Person other than the Collateral Agent has been named as a loss
payee on any of the Insurance Policies. No consent of any Person is required in
connection with the pledge of the Insurance Policies hereunder, other than the
consent of NML set forth in that certain waiver and consent letter, dated
November 30, 1999.

         SECTION 3. The Security Interests. (A) In order to secure the full and
punctual payment of the Bank Secured Obligations in accordance with the terms
thereof, and to secure the performance of all of the obligations of each Debtor
hereunder and under the other Financing Documents, each Debtor hereby grants to
the Collateral Agent for the ratable benefit of the Secured Parties (other than
NML), a continuing security interest in and to all of the following property of
such Debtor, whether now owned or existing or hereafter acquired or arising and
regardless of where located (all being collectively referred to as the "BANK
COLLATERAL"):

                 (1) Receivables;

                 (2) Ancillary Rights;

                 (3) Insurance Payments;

                 (4) Insurance Policies;

                 (5) The Collateral Account, all cash deposited therein from
         time to time, the Liquid Investments made pursuant to Section 5(D) and
         other monies and property of any kind of such Debtor in the possession
         or under the control of the Collateral Agent;

                 (6) The Insurance Account, all cash deposited therein from
         time to time, and the Liquid Investments made pursuant to Section
         6(C);

                 (7) The Magellan Note;

                 (8) All books and records (including, without limitation,
         customer lists, credit files, computer programs, printouts and other
         computer materials and records) of such Debtor pertaining to any of
         the Collateral described in clauses 1 through 7 hereof; and

                 (9) All Proceeds of all or any of the Collateral described in
         clauses 1 through 8 hereof.

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         (B) In order to secure the full and punctual payment of the Secured
Obligations in accordance with the terms thereof, and to secure the performance
of all of the obligations of each Debtor hereunder, under the other Financing
Documents, under the NML Note Agreement and the NML Guaranty, each Debtor
hereby grants to the Collateral Agent for the ratable benefit of the Secured
Parties, a continuing security interest in and to all of following property of
such Debtor, whether now owned or existing or hereafter acquired or arising and
regardless of where located (all being collectively referred to as the "SHARED
COLLATERAL"):

                 (1) Copyrights;

                 (2) Copyright Licenses;

                 (3) Patents;

                 (4) Patent Licenses;

                 (5) Trademarks;

                 (6) Trademark Licenses;

                 (7) General Intangibles (other than Receivables, Ancillary
         Rights, Insurance Payments and Insurance Policies);

                 (8) Instruments (other than the Magellan Note) ;

                 (9) All books and records (including, without limitation,
         customer lists, credit files, computer programs, printouts and other
         computer materials and records) of such Debtor pertaining to any of
         the Collateral described in clauses 1 through 8 hereof; and

                 (10) All Proceeds of all or any of the Collateral described in
         clauses 1 through 9 hereof.

         (C) The Security Interests are granted as security only and shall not
subject the Collateral Agent or any other Secured Party to, or transfer or in
any way affect or modify, any obligation or liability of any Debtor with
respect to any of the Collateral or any transaction in connection therewith.

         SECTION 4. Further Assurances; Covenants. (A) Each Debtor will not
change its name, identity or corporate structure in any manner or change the
location of (i) its chief executive office or chief place of business, or (ii)
the locations where it keeps or holds any Collateral from the applicable
location

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described in the Perfection Certificate unless it shall have given the
Collateral Agent thirty (30) days prior notice thereof, shall have taken all
such action as the Collateral Agent shall reasonably deem necessary to maintain
at all times the perfection of the Security Interests in the Collateral granted
hereunder and shall have delivered an opinion of counsel with respect thereto
in accordance with Section 4(H).

         (B) Each Debtor will, from time to time, at its expense, execute,
deliver, file and record any statement, notice, assignment, instrument,
document, agreement or other paper and take any other action (including,
without limitation, any filings of financing or continuation statements under
the UCC and any Intellectual Property Filings, and, solely with respect to any
Material Government Contract, any such document or action in respect of the
Assignment of Claims Act) that from time to time may be necessary or desirable,
or that the Collateral Agent may reasonably request, in order to create,
preserve, perfect, confirm or validate the Security Interests or to enable the
Collateral Agent and the Secured Parties to obtain the full benefits of this
Agreement, or to enable the Collateral Agent to exercise and enforce any of its
rights, powers and remedies hereunder with respect to any of the Collateral. To
the extent permitted by applicable law, each Debtor hereby authorizes the
Collateral Agent to execute and file financing statements or continuation
statements or Intellectual Property Filings without such Debtor's signature
appearing thereon. Each Debtor agrees that a carbon, photographic, photostatic
or other reproduction of this Agreement or of a financing statement is
sufficient as a financing statement. Each Debtor shall pay the costs of, or
incidental to, any recording or filing of any financing or continuation
statements concerning the Collateral.

         (C) Each Debtor will maintain its qualification to do business and all
necessary licenses, permits and other governmental authorizations necessary in
any jurisdiction to enable such Debtor to perform its obligations in respect of
the Receivables of such Debtor and to administer, service and collect such
Receivables.

         (D) Each Debtor will not, without the consent of the Required Banks,
change its credit or collection policies in a manner that is reasonably likely
to impair the collectability of the Receivables of such Debtor.

         (E) Each Debtor will keep full and accurate books and records relating
to the Collateral, and stamp or otherwise mark such books and records in such
manner as the Required Banks may reasonably require in order to reflect the
Security Interests.

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         (F) Each Debtor shall use all commercially reasonable efforts to cause
to be collected from its account debtors, as and when due, any and all amounts
owing under or on account of each Receivable of such Debtor (including, without
limitation, Receivables which are delinquent, such Receivables to be collected
in accordance with lawful collection procedures) and shall apply forthwith upon
receipt thereof all such amounts as are so collected to the outstanding balance
of such Receivables. Subject to the rights of the Collateral Agent and the
Secured Parties hereunder if an Event of Default shall have occurred and be
continuing, each Debtor may allow in the ordinary course of business as
adjustments to amounts owing under the Receivables of such Debtor (i) an
extension or renewal of the time or times of payment, or settlement for less
than the total unpaid balance and (ii) a refund, credit or other adjustment due
as a result of returned, damaged, or non-conforming merchandise, products or
services, all in accordance with such Debtor's sound business judgment. The
costs and expenses (including, without limitation, reasonable attorney's fees)
of collection, whether incurred by such Debtor or the Collateral Agent, shall
be borne by such Debtor.

         (G) Each Debtor will, promptly upon request, provide to the Collateral
Agent all information and evidence it may reasonably request concerning the
Collateral to enable the Collateral Agent to enforce the provisions of this
Agreement.

         (H) Not more than six months nor less than 30 days prior to each date
on which any Debtor proposes to take any action in connection with which an
opinion of counsel is to be delivered pursuant to Section 4(A), such Debtor
shall, at its cost and expense, cause to be delivered to the Secured Parties an
opinion of counsel, reasonably satisfactory to the Collateral Agent, in form
and substance reasonably satisfactory to the Collateral Agent, to the effect
that all financing statements and amendments or supplements thereto,
continuation statements and other documents required to be recorded or filed in
order to continue the perfection of the Security Interests in the Collateral
following the proposed action by such Debtor have been filed in each filing
office necessary for such purpose and that all filing fees and taxes, if any,
payable in connection with such filings have been paid in full.

         (I) Within 30 days after entering into any Material Government
Contract, such Debtor shall deliver to such government agency an instrument of
assignment duly completed and executed by such Debtor substantially in the form
of Exhibit E-1 hereto.

         (J) If any Collateral of any Debtor is at any time in the possession
or control of any warehouseman, bailee or any of such Debtor's agents or
processors, such Debtor shall notify such warehouseman, bailee, agent or
processor of the

                                       13
<PAGE>   15
Security Interests created hereby and to hold all such Collateral for the
Collateral Agent's account subject to the Collateral Agent's instructions.

         (K) Each Debtor will immediately deliver and pledge each Instrument to
the Collateral Agent, appropriately endorsed to the Collateral Agent, provided
that so long as no Event of Default shall have occurred and be continuing, each
Debtor may retain for collection in the ordinary course any Instruments (other
than checks and drafts constituting payments in respect of Receivables of such
Debtor described in clauses (x) or (y) of Section 5(B), as to which the
provisions of such Section shall apply) received by it in the ordinary course
of business and the Collateral Agent shall, promptly upon request of such
Debtor, make appropriate arrangements for making any other Instrument pledged
by such Debtor available to it for purposes of presentation, collection or
renewal (any such arrangement to be effected, to the extent deemed appropriate
to the Collateral Agent, against trust receipt or like document).

         (L) Each Debtor shall notify the Collateral Agent promptly if it knows
that any application or registration relating to any material Intellectual
Property owned or licensed by such Debtor may become abandoned or dedicated, or
of any adverse determination or development (including, without limitation, the
institution of, or any such determination or development in, any proceeding in
the United States Copyright Office, the United States Patent and Trademark
Office or any court) regarding such Debtor's ownership of such material
Intellectual Property, its right to register or patent the same, or its right
to keep and maintain the same. If any of such Debtor's rights to any material
Intellectual Property are infringed, misappropriated or diluted by a third
party, such Debtor shall notify the Collateral Agent within 30 days after it
learns thereof and shall take all actions as such Debtor shall reasonably deem
appropriate under the circumstances to protect such Intellectual Property.

         (M) On the date on which each Debtor becomes a party to this
Agreement, such Debtor will execute and deliver to the Collateral Agent
Intellectual Property Security Agreements with respect to all Intellectual
Property then owned by it. Within 30 days after each March 31 and September 30
thereafter, each such Debtor will execute and deliver to the Collateral Agent
any Intellectual Property Security Agreement necessary to grant Security
Interests in any Intellectual Property owned by it on such March 31 or
September 30 that are not covered by the Security Interests granted in any
previous Intellectual Property Security Agreements so executed and delivered by
it. In each case, each such Debtor will promptly make all Intellectual Property
Filings necessary to record the Security Interests in such Intellectual
Property.

                                       14
<PAGE>   16
         SECTION 5. Collateral Account. (A) The Company has established with
the Collateral Agent a cash collateral account (the "COLLATERAL ACCOUNT") in
the name and under the control of the Collateral Agent into which there shall
be deposited from time to time (i) the cash proceeds of the Collateral of each
Debtor (other than any cash proceeds of the Insurance Payments or the Insurance
Policies) required to be delivered to the Collateral Agent pursuant to
subsection (B) of this Section 5 and (ii) the Borrower LC Amount received by
the Collateral Agent pursuant to Section 6.01 of the Credit Agreement. Any
income received by the Collateral Agent with respect to the balance from time
to time standing to the credit of the Collateral Account, including any
interest or capital gains on Liquid Investments, shall remain, or be deposited,
in the Collateral Account. The cash amounts on deposit from time to time in the
Collateral Account together with any Liquid Investments from time to time made
pursuant to subsection (D) of this Section shall constitute part of the
Collateral hereunder and shall not constitute payment of the Secured
Obligations until applied thereto as hereinafter provided.

         (B) Each Debtor shall instruct all account debtors and other Persons
obligated in respect of (x) all Receivables of such Debtor in an amount in
excess of $1,000,000 and (y) all Receivables (regardless of the amount thereof)
of such Debtor payable pursuant to a contract under which the aggregate amount
of payments to be made exceeds $1,000,000 to make all payments in respect
thereof either (i) directly to the Collateral Agent (by instructing that such
payments be remitted to a post office box which shall be in the name and under
the control of the Collateral Agent) or (ii) to one or more other banks in any
state in the United States (by instructing that such payments be remitted to a
post office box which shall be in the name and under the control of such bank)
under a Lockbox Letter substantially in the form of Exhibit G hereto duly
executed by such Debtor and such bank or under other arrangements, in form and
substance reasonably satisfactory to the Collateral Agent, pursuant to which
such Debtor shall have irrevocably instructed such other bank (and such other
bank shall have agreed) to remit all proceeds of such payments directly to the
Collateral Agent for deposit into the Collateral Account or as the Collateral
Agent may otherwise instruct such bank. All such payments made to the
Collateral Agent shall be deposited in the Collateral Account. In addition to
the foregoing, each Debtor agrees that if the Proceeds of any Collateral
hereunder (including the payments made in respect of Receivables) shall be
received by it, such Debtor shall as promptly as possible deposit such Proceeds
into the Collateral Account. Until so deposited, all such Proceeds shall be
held in trust by such Debtor for the Collateral Agent and the other Secured
Parties and shall not be commingled with any other funds or property of such
Debtor.

         (C) The balance from time to time standing to the credit of the
Collateral Account shall, except upon the occurrence and continuation of a
Security Event or

                                       15
<PAGE>   17
an Event of Default, be distributed to the Company upon the order of the
Company. If immediately available cash on deposit in the Collateral Account is
not sufficient to make any distribution to the Company or referred to in the
previous sentence of this Section 5(C), the Collateral Agent shall liquidate as
promptly as practicable Liquid Investments as required to obtain sufficient
cash to make such distribution and, notwithstanding any other provision of this
Section 5, such distribution shall not be made until such liquidation has taken
place. Upon the occurrence and during the continuation of an Event of Default
the Collateral Agent shall, if so instructed by the Required Banks, apply or
cause to be applied (subject to collection) any or all of the balance from time
to time standing to the credit of the Collateral Account in the manner
specified in Section 10.

         (D) Amounts on deposit in the Collateral Account aggregating
$1,000,000 or more shall be invested and re-invested from time to time in such
Liquid Investments as the Company shall determine, which Liquid Investments
shall be under the control of the Collateral Agent, provided that, if an Event
of Default has occurred and is continuing, the Collateral Agent shall, if
instructed by the Required Banks, liquidate any such Liquid Investment and
apply or cause to be applied the proceeds thereof to the payment of the Secured
Obligations in the manner specified in Section 10.

         SECTION 6. Insurance Accounts. (A) The Company has established with
the Collateral Agent a cash collateral account (the "INSURANCE ACCOUNT") in the
name and under the control of the Collateral Agent into which there shall be
deposited from time to time any amounts received by the Collateral Agent
pursuant to Section 5.03(d) of the Credit Agreement. Any income received by the
Collateral Agent with respect to the balance from time to time standing to the
credit of the Insurance Account, including any interest or capital gains on
Liquid Investments, shall remain, or be deposited, in the Insurance Account.
The cash amounts on deposit from time to time in the Insurance Account together
with any Liquid Investments from time to time made pursuant to subsection (C)
of this Section shall constitute part of the Collateral hereunder and shall not
constitute payment of the Secured Obligations until applied thereto as
hereinafter provided.

         (B) The balance from time to time standing to the credit of the
Insurance Account shall, except upon the occurrence and during the continuation
of a Security Event or an Event of Default, be distributed to the Company upon
the order of the Company. If immediately available cash on deposit in the
Insurance Account is not sufficient to make any distribution to the Company
referred to in the previous sentence of this Section 6(B), the Collateral Agent
shall liquidate as promptly as practicable Liquid Investments as required to
obtain sufficient cash to make such distribution and, notwithstanding any other
provision of this Section 6, such distribution shall not be made until such
liquidation has taken place. Upon

                                       16
<PAGE>   18
the occurrence and during the continuation of an Event of Default, the
Collateral Agent shall, if so instructed by the Required Banks, apply or cause
to be applied (subject to collection) any or all of the balance from time to
time standing to the credit of the Insurance Account in the manner specified in
Section 10.

         (C) Amounts on deposit in the Insurance Account aggregating $1,000,000
or more shall be invested and re-invested from time to time in such Liquid
Investments as the Company shall determine, which Liquid Investments shall be
under the control of the Collateral Agent, provided that, if an Event of
Default has occurred and is continuing, the Collateral Agent shall, if
instructed by the Required Banks, liquidate any such Liquid Investment and
apply or cause to be applied the proceeds thereof to the payment of the Secured
Obligations in the manner specified in Section 10.

         SECTION 7. General Authority. Each Debtor hereby irrevocably appoints
the Collateral Agent its true and lawful attorney, with full power of
substitution, in the name of such Debtor, the Agents, any other Secured Parties
or otherwise, for the sole use and benefit of the Collateral Agent and the
Secured Parties, but at such Debtor's expense, to the extent permitted by law
(including, without limitation, applicable laws, rules, regulations and orders)
to exercise, at any time and from time to time while and only after an Event of
Default has occurred and is continuing, all or any of the following powers with
respect to all or any of the Collateral:

                 (i) to demand, sue for, collect, receive and give acquittance
         for any and all monies due or to become due thereon or by virtue
         thereof;

                 (ii) to settle, compromise, compound, prosecute or defend any
         action or proceeding with respect thereto;

                 (iii) to sell, transfer, assign or otherwise deal in or with
         the same or the proceeds or avails thereof, as fully and effectually
         as if the Collateral Agent were the absolute owner thereof; and

                 (iv) to extend the time of payment of any or all thereof and
         to make any allowance and other adjustments with reference thereto;

provided that the Collateral Agent shall give such Debtor not less than ten
days' prior written notice of the time and place of any sale or other intended
disposition of any of the Collateral of such Debtor, except any Collateral
which is perishable or threatens to decline speedily in value or is of a type
customarily sold on a recognized market. Each Debtor agrees that such notice
constitutes "reasonable notification" within the meaning of Section 9-504(3) of
the UCC.

                                       17
<PAGE>   19
         SECTION 8. Remedies upon Event of Default. (A) If any Event of Default
has occurred and is continuing, the Collateral Agent may at the direction of
the Required Banks, exercise on behalf of the Secured Parties all rights of a
secured party under the UCC (or, if the Uniform Commercial Code is not in
effect in the jurisdiction where such rights are exercised, the UCC as in
effect in the State of New York to the extent not prohibited by the laws of
such jurisdiction), and, in addition, the Collateral Agent may, at the
direction of the Required Banks, without being required to give any notice,
except as herein provided or as may be required by mandatory provisions of law,
(i) withdraw all cash and Liquid Investments in the Collateral Account and the
Insurance Account and apply such cash and Liquid Investments and other cash, if
any, then held by it as Collateral as specified in Section 10 and (ii) if there
shall be no such cash or Liquid Investments or if such cash and Liquid
Investments shall be insufficient to pay all the Secured Obligations in full,
sell the Collateral (subject to any applicable laws, rules, regulations and
orders) or any part thereof at public or private sale, for cash, upon credit or
for future delivery, and at such price or prices as the Collateral Agent may
reasonably deem satisfactory. The Collateral Agent or any other Secured Party
may be the purchaser of any or all of the Collateral (subject to any applicable
laws, rules, regulations and orders) so sold at any public sale (or, if the
Collateral is of a type customarily sold in a recognized market or is of a type
which is the subject of widely distributed standard price quotations, at any
private sale). Each Debtor will execute and deliver such documents and take
such other action as the Collateral Agent reasonably deems necessary or
advisable in order that any such sale may be made in compliance with law. Upon
any such sale the Collateral Agent shall have the right to deliver, assign and
transfer to the purchaser thereof the Collateral so sold (subject to any
applicable laws, rules, regulations and orders). Each purchaser at any such
sale shall (subject to any applicable laws, rules, regulations and orders) hold
the Collateral so sold to it absolutely and free from any claim or right of
whatsoever kind, including any equity or right of redemption of any Debtor
which may be waived, and each Debtor, to the extent permitted by law, hereby
specifically waives all rights of redemption, stay or appraisal which it has or
may have under any law now existing or hereafter adopted. The notice (if any)
of such sale required by Section 7 shall (1) in the case of a public sale,
state the time and place fixed for such sale, and (2) in the case of a private
sale, state the day after which such sale may be consummated. Any such public
sale shall be held at such time or times within ordinary business hours and at
such place or places as the Collateral Agent may fix in the notice of such
sale. At any such sale the Collateral may be sold in one lot as an entirety or
in separate parcels, as the Collateral Agent may determine. The Collateral
Agent shall not be obligated to make any such sale pursuant to any such notice.
The Collateral Agent may, without notice or publication, adjourn any public or
private sale or cause the same to be adjourned from time to time by
announcement at the time and place fixed for the sale, and

                                       18
<PAGE>   20
such sale may be made at any time or place to which the same may be so
adjourned. In case of any sale of all or any part of the Collateral on credit
or for future delivery, the Collateral so sold may be retained by the
Collateral Agent until the selling price is paid by the purchaser thereof, but
the Collateral Agent shall not incur any liability in case of the failure of
such purchaser to take up and pay for the Collateral so sold and, in case of
any such failure, such Collateral may again be sold upon like notice. The
Collateral Agent, instead of exercising the power of sale herein conferred upon
it (subject to any applicable laws, rules, regulations and orders) may, at the
direction of the Required Banks, proceed by a suit or suits at law or in equity
to foreclose the Security Interests and sell the Collateral, or any portion
thereof, under a judgment or decree of a court or courts of competent
jurisdiction.

         (B) For the purpose of enforcing any and all rights and remedies under
this Agreement the Collateral Agent may (i) require each Debtor to, and each
Debtor agrees that it will, at its expense and upon the request of the
Collateral Agent, forthwith assemble all or any part of the Collateral as
directed by the Collateral Agent and make it available at a place reasonably
designated by the Collateral Agent which is, in its opinion, reasonably
convenient to the Collateral Agent and such Debtor, whether at the premises of
such Debtor or otherwise, (ii) to the extent permitted by applicable law,
enter, with or without process of law and without breach of the peace, any
premise where any of the Collateral is or may be located, and without charge or
liability to it seize and remove such Collateral from such premises, (iii) have
access to and use each Debtor's books and records relating to the Collateral
and (iv) prior to the disposition of the Collateral, store or transfer it
without charge in or by means of any storage or transportation facility owned
or leased by any Debtor, process, repair or recondition it or otherwise prepare
it for disposition in any reasonable manner and to the extent the Collateral
Agent deems reasonable, appropriate and, in connection with such preparation
and disposition, use without charge any trademark, trade name, copyright,
patent or technical process used by any Debtor.

         (C) Without limiting the generality of the foregoing, if an Event of
Default shall have occurred and be continuing,

                 (i) the Collateral Agent may license, or sublicense, whether
         general, special or otherwise, and whether on an exclusive or
         non-exclusive basis, any Intellectual Property included in the
         Collateral throughout the world for such term or terms, on such
         conditions and in such manner as the Collateral Agent shall in its
         sole discretion determine;

                 (ii) the Collateral Agent may (without assuming any
         obligations or liability thereunder), at any time and from time to
         time, in its sole and reasonable discretion, enforce (and shall have
         the exclusive right to

                                       19
<PAGE>   21
         enforce) against any licensee or sublicensee all rights and remedies
         of any Debtor in, to and under any of its Intellectual Property and
         take or refrain from taking any action under any thereof, and each
         Debtor hereby releases the Collateral Agent and each of the other
         Secured Parties from, and agrees to hold the Collateral Agent and each
         of the other Secured   arties free and harmless from and against any
         claims and expenses arising out of, any lawful action so taken or
         omitted to be taken with respect thereto, except for claims and
         expenses arising from the Collateral Agent's or such Secured Party's
         gross negligence or willful misconduct; and

                 (iii) upon request by the Collateral Agent (which shall not be
         construed as implying any limitation on the rights or powers of the
         Collateral Agent), each Debtor will execute and deliver to the
         Collateral Agent a power of attorney, in form and substance
         satisfactory to the Collateral Agent, for the implementation of any
         lease, assignment, license, sublicense, grant of option, sale or other
         disposition of any Intellectual Property owned by such Debtor or any
         action related thereto. In the event of any such disposition pursuant
         to this Section, subject to confidentiality restrictions imposed on
         such Debtor in any license or similar agreement, such Debtor shall
         supply its know-how and expertise relating to or the products or
         services made or rendered in connection with Patents, and its customer
         lists and other records relating to such Intellectual Property and to
         the distribution of said products or services, to the Collateral
         Agent.

         SECTION 9. Limitation on Duty of Collateral Agent in Respect of
Collateral. Beyond the exercise of reasonable care in the custody thereof, the
Collateral Agent shall have no duty as to any Collateral in its possession or
control or in the possession or control of any agent or bailee or any income
thereon or as to the preservation of rights against prior parties or any other
rights pertaining thereto. The Collateral Agent shall be deemed to have
exercised reasonable care in the custody of the Collateral in its possession if
the Collateral is accorded treatment substantially equal to that which it
accords its own property, and shall not be liable or responsible for any loss
or damage to any of the Collateral, or for any diminution in the value thereof,
by reason of the act or omission of any warehouseman, carrier, forwarding
agency, consignee or other agent or bailee selected by the Collateral Agent in
good faith.

         SECTION 10. Application of Proceeds. (A) Upon the occurrence and
during the continuance of an Event of Default, the proceeds of any sale of, or
other realization upon, all or any part of the Collateral of each Debtor and
any cash held in the Collateral Account and Insurance Account shall be applied
by the Collateral Agent in the following order of priorities:

                                       20
<PAGE>   22
                 first, to payment of the expenses of such sale or other
         realization, including reasonable compensation to agents and counsel
         for the Collateral Agent, and all expenses, liabilities and advances
         incurred or made by the Collateral Agent in connection therewith, and
         any other unreimbursed expenses for which the Collateral Agent, the
         Administrative Agent, any Bank or NML is to be reimbursed pursuant to
         the Credit Agreement or the NML Note Agreement, as the case may be,
         and unpaid fees owing to the Agents under the Credit Agreement;

                 second, to the ratable payment of accrued but unpaid interest
         on the Bank Secured Obligations (or, solely with respect to the
         proceeds of any sale of, or other disposition or realization upon, the
         Shared Collateral, to the ratable payment of accrued but unpaid
         interest on the Bank Secured Obligations and the NML Secured
         Obligations);

                 third, to the ratable payment of Bank Secured Obligations
         consisting of unpaid principal of Loans and, subject to the second
         sentence of subsection (B), Letter of Credit Obligations (or, solely
         with respect to the proceeds of any sale of, or other disposition or
         realization upon, the Shared Collateral, to the ratable payment of (x)
         the Bank Secured Obligations consisting of unpaid principal of Loans
         and, subject to the second sentence of subsection (B), Letter of
         Credit Obligations and (y) the NML Secured Obligations);

                 fourth, to the ratable payment of all other Bank Secured
         Obligations (or, solely with respect to the proceeds of any sale of,
         or other disposition or realization upon, the Shared Collateral, to
         the ratable payment of all other Bank Secured Obligations and NML
         Secured Obligations), until all such Secured Obligations have been
         repaid in full; and

                 finally, to payment to such Debtor or its successors or
         assigns, or as a court of competent jurisdiction may direct, of any
         surplus then remaining from such proceeds.

         (B) The Collateral Agent may make distributions hereunder in cash or
in kind or, on a ratable basis, in any combination thereof. If at any time any
monies collected or received by the Collateral Agent are distributable pursuant
to this Section in respect of a Letter of Credit Obligation which is a
contingent obligation at such time, then the Collateral Agent shall invest such
amounts in Liquid Investments selected by it and shall hold all such amounts so
distributable and all such Liquid Investments and the net proceeds thereof in
trust for application to the payment of such Letter of Credit Obligation at
such time as such Letter of Credit

                                       21
<PAGE>   23
Obligation is no longer a contingent obligation. If the Collateral Agent holds
any amounts which were distributable in respect of any Letter of Credit
Obligations after all Letters of Credit have expired and all amounts payable
with respect thereto have been paid, such amounts shall be applied in the order
set forth in subsection (A) above.

         (C) In making the determinations and allocations required by this
Section, the Collateral Agent shall have no liability to any Secured Party for
actions taken in reliance on information supplied by such Secured Party as to
the amounts of the Secured Obligations held by them. All distributions made by
the Collateral Agent pursuant to this Section shall be final, and the
Collateral Agent shall have no duty to inquire as to the application by any
Secured Party of any amount distributed to them. However, if at any time the
Collateral Agent determines that an allocation or distribution previously made
pursuant to this Section was based on a mistake of fact (including, without
limiting the generality of the foregoing, mistakes based on any assumption that
principal or interest has been paid by payments which are subsequently
recovered from the recipient thereof through the operation of any bankruptcy,
reorganization, insolvency or other laws or otherwise), the Collateral Agent
may in its discretion, but shall not be obligated to, adjust subsequent
allocations and distributions hereunder so that, on a cumulative basis, the
Collateral Agent and the other Secured Parties receive the distributions to
which they would have been entitled if such mistake of fact had not been made.

         SECTION 11. Appointment of Co-agents. At any time or times, in order
to comply with any legal requirement in any jurisdiction, the Collateral Agent
may appoint another bank or trust company or one or more other Persons, either
to act as collateral co-agent or collateral co-agents, jointly with the
Collateral Agent, or to act as separate collateral agent or collateral agents
on behalf of the Secured Parties with such power and authority as may be
necessary for the effectual operation of the provisions hereof and may be
specified in the instrument of appointment (which may, in the discretion of the
Collateral Agent, include provisions for the protection of each such collateral
co-agent or separate collateral agent similar to the provisions of Article 7 of
the Credit Agreement).

         SECTION 12. Designated Lockbox Bank. The Designated Lockbox Bank shall
have the rights and obligations of the Collateral Agent in respect of the
Collateral Account specified in Section 5 of this Agreement, provided that if
an Event of Default has occurred and is continuing, the Designated Lockbox Bank
shall exercise such rights and perform such obligations at the direction of the
Collateral Agent. In exercising such rights and performing such obligations the
Designated Lockbox Bank shall have the benefit of all privileges, immunities
and

                                       22
<PAGE>   24
indemnities provided for the Collateral Agent under this Agreement. The
Designated Lockbox Bank may resign as Designated Lockbox Bank in accordance
with the provisions of Section 7.08 of the Credit Agreement.

         SECTION 13. Expenses. Each Debtor agrees that it will, on demand, pay
to the Collateral Agent the amount of any and all reasonable out-of-pocket
expenses, including the reasonable fees and disbursements of counsel and of any
other experts, which the Collateral Agent may incur in connection with (x) the
administration or enforcement of this Agreement, including such expenses as are
incurred to preserve the value of the Collateral and the validity, perfection,
rank and value of any Security Interest, (y) the collection, sale or other
disposition of any of the Collateral or (z) the exercise by the Collateral
Agent of any of the rights conferred upon it hereunder. The obligation to pay
any such amount shall be an additional Secured Obligation hereunder, and each
such amount shall bear interest from the time of demand at the rate applicable
to Base Rate Loans.

         SECTION 14. Termination of Security Interests; Release of Collateral.
(A) Upon the repayment in full of all Bank Secured Obligations, the termination
of the Commitments under the Credit Agreement and the cancellation or
expiration of all Letters of Credit, the Security Interests and all obligations
of each Debtor under this Agreement shall terminate and all rights to and
interests in the Collateral shall revert to such Debtor.

         (B) Subject to the rights of the Secured Parties hereunder if an Event
of Default shall have occurred and be continuing and subject always to the
rights of the Banks and the Administrative Agent under the Credit Agreement and
to the rights of NML under the NML Note Agreement, upon any sale or other
disposition of any Collateral permitted under Section 5.15 of the Credit
Agreement (any such sale or other disposition, a "PERMITTED COLLATERAL SALE"),
the Security Interests in the Collateral subject to such Permitted Collateral
Sale (but not in any Proceeds thereof) shall cease immediately without any
further action on the part of the Collateral Agent. The Collateral Agent shall
be fully protected in relying on a certificate from any Debtor stating that a
sale or other disposition of any Collateral constitutes a Permitted Collateral
Sale.

         (C) In addition to releases of Collateral effected by subsection (B),
at any time and from time to time prior to the termination of the Security
Interests, the Collateral Agent may release any of the Collateral with the
prior written consent of the Required Banks; provided that the Collateral Agent
may release all or substantially all of the Collateral (for purposes of this
proviso only, as defined in the Credit Agreement) only with the prior written
consent of all of the Banks.

                                       23
<PAGE>   25
         (D) Upon the termination of the Security Interests or any release of
any Collateral effected or permitted by this Section, the Collateral Agent will
promptly, at the expense of each Debtor, execute and deliver to such Debtor
such documents as such Debtor shall reasonably request to evidence the
termination of the Security Interests or the release of such Collateral, as the
case may be, including UCC termination statements, and will duly assign,
transfer and deliver to such Debtor or to whomever lawfully shall be entitled
to receive the same, such of the Collateral as may be in the possession of the
Collateral Agent.

         (E) Upon the repayment in full of all NML Secured Obligations, NML's
rights under this Agreement shall terminate. Upon any such termination, NML
will, at the expense of the Debtors, execute and deliver to the Debtors such
documents as any Debtor may reasonably request to evidence such termination.
SECTION 15. Notices. All notices, communications and distributions to any party
hereunder shall be given in accordance with Section 10.01 of the Credit
Agreement.

         SECTION 16. Waivers, Non-Exclusive Remedies. No failure on the part of
the Collateral Agent to exercise, and no delay in exercising and no course of
dealing with respect to, any right under this Agreement shall operate as a
waiver thereof; nor shall any single or partial exercise by the Collateral
Agent of any right under this Agreement preclude any other or further exercise
thereof or the exercise of any other right. The rights in the Financing
Documents are cumulative and are not exclusive of any other remedies provided
by law.

         SECTION 17. Successors and Assigns. This Agreement is for the benefit
of the Collateral Agent and the other Secured Parties and their successors and
assigns, and in the event of an assignment of all or any of the Secured
Obligations, the rights hereunder, to the extent applicable to the indebtedness
so assigned, may be transferred with such indebtedness. This Agreement shall be
binding on each Debtor and the Collateral Agent and their respective successors
and assigns.

         SECTION 18. Changes in Writing. Neither this Agreement nor any
provision hereof may be changed, waived, discharged or terminated orally, but
only in writing signed by each Debtor and the Collateral Agent with the consent
of the Required Banks (or, in the case of Section 14(A) or to the number of
Banks whose consent shall be required for the Collateral Agent to take any
action under this Section or any other provision of this Agreement, the consent
of all the Banks).

                                       24
<PAGE>   26
         SECTION 19. New York Law. This Agreement shall be construed in
accordance with and governed by the laws of the State of New York, except as
otherwise required by mandatory provisions of law and except to the extent that
remedies provided by the laws of any jurisdiction other than New York are
governed by the laws of such jurisdiction.

         SECTION 20. Severability. If any provision hereof is invalid or
unenforceable in any jurisdiction, then, to the fullest extent permitted by
law, (i) the other provisions hereof shall remain in full force and effect in
such jurisdiction and shall be liberally construed in favor of the Collateral
Agent and the other Secured Parties in order to carry out the intentions of the
parties hereto as nearly as may be possible; and (ii) the invalidity or
unenforceability of any provision hereof in any jurisdiction shall not affect
the validity or enforceability of such provision in any other jurisdiction.

         SECTION 21. Counterparts. This Agreement may be signed in any number
of counterparts, each of which shall be an original, with the same effect as if
the signatures thereto and hereto were upon the same instrument.

         SECTION 22. Guaranty. Each Subsidiary Debtor hereby agrees to be bound
by the provisions of Article 9 of the Credit Agreement and to be subject to all
of the obligations of a "Guarantor" thereunder, and the limitations set forth
in Section 9.05 of the Credit Agreement shall apply to such obligations of such
Subsidiary Debtor.

         SECTION 23. Additional Debtors. Any Subsidiary of the Company may
become a "Subsidiary Debtor" party hereto and bound hereby by executing a
counterpart hereof and delivering same to the Collateral Agent.

                                       25
<PAGE>   27
         IN WITNESS WHEREOF, the parties hereto have caused this Agreement to
be duly executed by their respective authorized officers as of the day and year
first above written.

                                             ORBITAL SCIENCES CORPORATION

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

                                             ENGINEERING TECHNOLOGIES, INC.

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

                                             ORBITAL SPACE SYSTEMS, INC.

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

                                             ORBITAL COMMERCIAL SYSTEMS, INC.

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

                                             ORBITAL INTERNATIONAL, INC.

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

                                       26
<PAGE>   28
                                             ORBITAL SERVICES CORPORATION

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

                                             ORBITAL NAVIGATION CORPORATION

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

                                             ORBLINK LLC

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

                                             MORGAN GUARANTY TRUST
                                                COMPANY OF NEW YORK,
                                                as Collateral Agent

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

                                             BANK OF AMERICA, N.A.,
                                                as Designated Lockbox Bank

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

                                       27
<PAGE>   29
                                             THE NORTHWESTERN MUTUAL LIFE
                                                INSURANCE COMPANY

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

                                       28

Source: [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00000-of-00352.parquet"}, [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00000-of-00352.parquet"}]]