Document:

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                                                                     EXHIBIT 4.3

                          ORBITAL SCIENCES CORPORATION

                    12% SERIES A SECOND PRIORITY SECURED NOTE
                                    DUE 2006

                                                               CUSIP: 685564 AD8

No. Q-1                                                             $133,750,000

         Orbital Sciences Corporation, a Delaware corporation (hereinafter
called the "Company" which term includes any successors under the Indenture
hereinafter referred to), for value received, hereby promises to pay to Cede &
Co., or registered assigns, the principal sum of ONE HUNDRED THIRTY THREE
MILLION SEVEN HUNDRED FIFTY THOUSAND DOLLARS, on August 15, 2006.

         Interest Payment Dates: February 15 and August 15, commencing February
         15, 2003.

         Interest Record Dates:   February 1 and August 1

         Reference is made to the further provisions of this Note on the reverse
side, which will, for all purposes, have the same effect as if set forth at this
place.

         This Note has been issued with original issue discount for Federal
income tax purposes. Upon request, the Company will promptly make available to a
holder of this Note information regarding the issue price, the amount of
original issue discount, the issue date, and the yield to maturity of this Note.
Holders should contact Orbital Sciences Corporation, 21839 Atlantic Blvd.,
Dulles, VA 20166, Attention: Chief Financial Officer.
<PAGE>
         IN WITNESS WHEREOF, the Company has caused this instrument to be duly
executed.

                                    ORBITAL SCIENCES CORPORATION,
                                    a Delaware corporation

                                    By:     ___________________________
                                            Name:
                                            Title:

                                    By:     ___________________________
                                            Name:
                                            Title:

                     TRUSTEE'S CERTIFICATE OF AUTHENTICATION

         This is one of the Notes described in the within-mentioned Indenture.

                                    U.S. BANK, N.A.

                                    By:     ____________________________
                                            Authorized Signatory

Dated: August 22, 2002
<PAGE>
                                (Reverse of Note)

               12% Series A Second Priority Secured Note due 2006

THIS GLOBAL NOTE IS HELD BY THE DEPOSITARY (AS DEFINED IN THE INDENTURE
GOVERNING THIS NOTE) OR ITS NOMINEE IN CUSTODY FOR THE BENEFIT OF THE BENEFICIAL
OWNERS HEREOF, AND IS NOT TRANSFERABLE TO ANY PERSON UNDER ANY CIRCUMSTANCES
EXCEPT THAT (I) THE TRUSTEE MAY MAKE SUCH NOTATIONS HEREON AS MAY BE REQUIRED
PURSUANT TO SECTION 2.6 OF THE INDENTURE, (II) THIS GLOBAL NOTE MAY BE EXCHANGED
IN WHOLE BUT NOT IN PART PURSUANT TO SECTION 2.6(a) OF THE INDENTURE, (III) THIS
GLOBAL NOTE MAY BE DELIVERED TO THE TRUSTEE FOR CANCELLATION PURSUANT TO SECTION
2.11 OF THE INDENTURE AND (IV) THIS GLOBAL NOTE MAY BE TRANSFERRED TO A
SUCCESSOR DEPOSITARY WITH THE PRIOR WRITTEN CONSENT OF THE COMPANY.

UNLESS AND UNTIL IT IS EXCHANGED IN WHOLE OR IN PART FOR NOTES IN DEFINITIVE
FORM, THIS NOTE MAY NOT BE TRANSFERRED EXCEPT AS A WHOLE BY THE DEPOSITARY TO A
NOMINEE OF THE DEPOSITARY, OR BY A NOMINEE OF THE DEPOSITARY TO THE DEPOSITARY
OR ANOTHER NOMINEE OF THE DEPOSITARY, OR BY THE DEPOSITARY OR ANY SUCH NOMINEE
TO A SUCCESSOR DEPOSITARY OR A NOMINEE OF SUCH SUCCESSOR DEPOSITARY. UNLESS THIS
CERTIFICATE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE OF THE DEPOSITORY TRUST
COMPANY (55 WATER STREET, NEW YORK, NEW YORK) ("DTC"), TO THE COMPANY OR ITS
AGENT FOR REGISTRATION OF TRANSFER, EXCHANGE OR PAYMENT, AND ANY CERTIFICATE
ISSUED IS REGISTERED IN THE NAME OF CEDE & CO. OR SUCH OTHER NAME AS MAY BE
REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF DTC (AND ANY PAYMENT IS MADE TO
CEDE & CO. OR SUCH OTHER ENTITY AS MAY BE REQUESTED BY AN AUTHORIZED
REPRESENTATIVE OF DTC), ANY TRANSFER, PLEDGE OR OTHER USE HEREOF FOR VALUE OR
OTHERWISE BY OR TO ANY PERSON IS WRONGFUL INASMUCH AS THE REGISTERED OWNER
HEREOF, CEDE & CO., HAS AN INTEREST HEREIN.

THIS SECURITY HAS NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS
AMENDED (THE "SECURITIES ACT"), OR ANY STATE SECURITIES LAWS. NEITHER THIS
SECURITY NOR ANY INTEREST OR PARTICIPATION HEREIN MAY BE REOFFERED, SOLD,
ASSIGNED, TRANSFERRED, PLEDGED, ENCUMBERED OR OTHERWISE DISPOSED OF IN THE
ABSENCE OF SUCH REGISTRATION OR UNLESS SUCH TRANSACTION IS EXEMPT FROM, OR NOT
SUBJECT TO, REGISTRATION. THE HOLDER OF THIS SECURITY BY ITS ACCEPTANCE HEREOF
AGREES TO OFFER, SELL OR OTHERWISE TRANSFER THIS SECURITY, PRIOR TO THE DATE
WHICH IS TWO YEARS (OR SUCH OTHER PERIOD THAT MAY HEREAFTER BE PROVIDED UNDER
RULE 144(K) UNDER THE SECURITIES ACT AS PERMITTING RESALES OF RESTRICTED
SECURITIES BY NON-AFFILIATES WITHOUT RESTRIC-

                                       1
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TION) AFTER THE LATER OF THE ORIGINAL ISSUE DATE HEREOF AND THE LAST DATE ON
WHICH THE COMPANY OR ANY AFFILIATE OF THE COMPANY WAS THE OWNER OF THIS SECURITY
(OR ANY PREDECESSOR OF THIS SECURITY) (THE "RESALE RESTRICTION TERMINATION
DATE") ONLY (A) TO THE COMPANY, (B) PURSUANT TO A REGISTRATION STATEMENT WHICH
HAS BEEN DECLARED EFFECTIVE UNDER THE SECURITIES ACT, (C) FOR SO LONG AS THIS
SECURITY IS ELIGIBLE FOR RESALE PURSUANT TO RULE 144A UNDER THE SECURITIES ACT,
IN THE UNITED STATES TO A PERSON IT REASONABLY BELIEVES IS A "QUALIFIED
INSTITUTIONAL BUYER" (AS DEFINED IN RULE 144A UNDER THE SECURITIES ACT) THAT
PURCHASES FOR ITS OWN ACCOUNT OR FOR THE ACCOUNT OF A QUALIFIED INSTITUTIONAL
BUYER TO WHOM NOTICE IS GIVEN THAT THE TRANSFER IS BEING MADE IN RELIANCE ON
RULE 144A UNDER THE SECURITIES ACT, (D) TO AN INSTITUTIONAL "ACCREDITED
INVESTOR" WITHIN THE MEANING OF SUBPARAGRAPH (a)(1), (2), (3) OR (7) OF RULE 501
UNDER THE SECURITIES ACT THAT IS ACQUIRING THIS SECURITY FOR ITS OWN ACCOUNT, OR
FOR THE ACCOUNT OF SUCH AN INSTITUTIONAL "ACCREDITED INVESTOR," FOR INVESTMENT
PURPOSES AND NOT WITH A VIEW TO, OR FOR OFFER OR SALE IN CONNECTION WITH, ANY
DISTRIBUTION IN VIOLATION OF THE SECURITIES ACT, (E) OUTSIDE OF THE UNITED
STATES IN AN OFFSHORE TRANSACTION IN ACCORDANCE WITH RULE 904 UNDER THE
SECURITIES ACT OR (F) PURSUANT TO ANOTHER AVAILABLE EXEMPTION FROM THE
REGISTRATION REQUIREMENTS OF THE SECURITIES ACT, SUBJECT TO THE COMPANY'S AND
THE TRUSTEE'S RIGHT PRIOR TO ANY SUCH OFFER, SALE OR TRANSFER TO REQUIRE THE
DELIVERY OF AN OPINION OF COUNSEL, CERTIFICATIONS AND/OR OTHER INFORMATION
SATISFACTORY TO EACH OF THEM, AND IN EACH OF THE FOREGOING CASES, A CERTIFICATE
OF TRANSFER IN THE FORM APPEARING ON THIS SECURITY IS COMPLETED AND DELIVERED BY
THE TRANSFEROR TO THE TRUSTEE AND IN EACH CASE IN ACCORDANCE WITH APPLICABLE
SECURITIES LAWS OF ANY U.S. STATE OR ANY OTHER APPLICABLE JURISDICTION. THE
HOLDER OF THIS SECURITY AGREES THAT IT WILL DELIVER TO EACH PERSON TO WHOM THIS
SECURITY IS TRANSFERRED A NOTICE SUBSTANTIALLY TO THE EFFECT OF THIS LEGEND.
THIS LEGEND WILL BE REMOVED UPON THE REQUEST OF THE HOLDER AFTER THE RESALE
RESTRICTION TERMINATION DATE.

                                       2
<PAGE>
         Capitalized terms used herein shall have the meanings assigned to them
in the Indenture referred to below unless otherwise indicated.

         1. Interest. Orbital Sciences Corporation, a Delaware corporation (the
"Company"), promises to pay interest on the principal amount of this Note at 12%
per annum from the Issue Date until maturity and shall pay the Liquidated
Damages, if any, payable pursuant to Section 4 of the Note Registration Rights
Agreement referred to below. The Company will pay interest and Liquidated
Damages, if any, semi-annually on February 15 and August 15 of each year, or if
any such day is not a Business Day, on the next succeeding Business Day (each an
"Interest Payment Date"). The first Interest Payment Date shall be February 15,
2003. Interest on the Notes will accrue from the most recent date on which
interest has been paid or, if no interest has been paid, from the Issue Date;
provided that if there is no existing Default in the payment of interest, and if
this Note is authenticated between an Interest Record Date (defined below)
referred to on the face hereof and the next succeeding Interest Payment Date,
interest shall accrue from such next succeeding Interest Payment Date. The
Company shall pay interest (including Accrued Bankruptcy Interest in any
proceeding under any Bankruptcy Law) on overdue principal and premium, if any,
from time to time on demand at the rate then in effect; it shall pay interest
(including Accrued Bankruptcy Interest in any proceeding under any Bankruptcy
Law) on overdue installments of interest and Liquidated Damages, if any,
(without regard to any applicable grace periods) from time to time on demand at
the same rate to the extent lawful. Interest will be computed on the basis of a
360-day year of twelve 30-day months.

         2. Method of Payment. The Company will pay interest on the Notes and
Liquidated Damages, if any, to the Persons who are registered Holders of Notes
at the close of business on the February 1 or August 1 next preceding the
Interest Payment Date (each an "Interest Record Date"), even if such Notes are
cancelled after such Interest Record Date and on or before such Interest Payment
Date, except as provided in Section 2.12 of the Indenture (as defined below)
with respect to defaulted interest. The Notes will be payable as to principal,
premium, if any, and interest (and Liquidated Damages, if any), at the office or
agency of the Company maintained within the City and State of New York for such
purpose, or, at the option of the Company, payment of interest shall be made by
wire transfer to the accounts specified by the Holders or, if no account is
specified, by check mailed to a Holder at its address set forth in the register
of Holders, provided that payment by wire transfer of immediately available
funds to an account within the United States will be required with respect to
principal of, premium, if any and interest (and Liquidated Damages, if any), on
all Global Notes. Such payment shall be in such coin or currency of the United
States of America as at the time of payment is legal tender for payment of
public and private debts.

         3. Paying Agent and Registrar. Initially, U.S. Bank, N.A., the Trustee
under the Indenture, will act as Paying Agent and Registrar. The Company may
change any Paying Agent or Registrar without notice to any Holder. The Company
or any of its Subsidiaries may act in any such capacity.

                                       3
<PAGE>
         4. Indenture. The Company issued the Notes under an Indenture, dated as
of August 22, 2002 ("Indenture"), by and among the Company, the Guarantors party
thereto and the Trustee. The terms of the Notes include those stated in the
Indenture and those made part of the Indenture by reference to the Trust
Indenture Act of 1939, as amended (15 U.S. Code Sections 77aaa-77bbbb).
The Notes are subject to all such terms, and Holders are referred to the
Indenture and such Act for a statement of such terms.

            The Obligations under the Indenture, the Intercreditor Agreement,
the Notes and the Guarantees thereof are secured by the Collateral described in
the Collateral Agreements, subject to the provisions of the Indenture and the
Collateral Agreements. Holders are referred to the Collateral Agreements for a
statement of such terms.

         5.       Optional Redemption.

                  (a) Except as set forth in clause (b) of this Section 5, the
Company shall not have the option to redeem the Notes pursuant to this Section 5
prior to August 15, 2003. The Notes shall be redeemable for cash at the option
of the Company, in whole or in part, at any time on or after August 15, 2003,
upon not less than 30 days nor more than 60 days prior notice mailed by first
class mail to each Holder at its last registered address, at the following
redemption prices (expressed as percentages of the principal amount) if redeemed
during the 12-month period commencing August 15 of the years indicated below, in
each case, together with accrued and unpaid interest (and Liquidated Damages, if
any) thereon, to the date of redemption of the Notes (the "Redemption
Date")(subject to the right of Holders of record on an Interest Record Date to
receive the corresponding interest due (and the corresponding Liquidated
Damages, if any) on the corresponding Interest Payment Date that is on or prior
to such Redemption Date:

<TABLE>
<CAPTION>
               Year                                     Percentage
               ----                                      ----------
<S>            <C>                                      <C>
               2003 ...............................     104.000    %
               2004 ...............................     102.000    %
               2005 and thereafter.................     100.000    %
</TABLE>

                  (b) Notwithstanding the provisions of clause (a) of this
Section 5, at any time or from time to time prior to August 15, 2003, upon a
Public Equity Offering of the Company's common stock for cash, up to 35% of the
aggregate principal amount of the Notes issued pursuant to this Indenture (only
as necessary to avoid any duplication, excluding any replacement Notes) may be
redeemed at the Company's option within 90 days of the closing of any such
Public Equity Offering, on not less than 30 days, but not more than 60 days,
notice to each Holder of the Notes to be redeemed, with cash received by the
Company from the Net Cash Proceeds of such Public Equity Offering, at a
redemption price equal to 112.00% of the principal amount of the Notes (or
portion thereof) to be redeemed, together with accrued and unpaid interest (and
Liquidated Damages, if any) thereon, to the Redemption Date (subject to the
right of Holders of record on an Interest Record Date to receive the
corresponding interest

                                       4
<PAGE>
due (and the corresponding Liquidated Damages, if any) on the corresponding
Interest Payment Date that is on or prior to such Redemption Date); provided,
however, that immediately following such redemption not less than 65% of the
aggregate principal amount of the Notes originally issued pursuant to this
Indenture on the Issue Date remain outstanding (only as necessary to avoid any
duplication, excluding any replacement Notes).

                  (c) Notice of redemption will be mailed by first class mail at
least 30 days but not more than 60 days before the Redemption Date to each
Holder whose Notes are to be redeemed at its registered address. Notes in
denominations larger than $1,000 may be redeemed in part but only in integral
multiples of $1,000, unless all of the Notes held by a Holder are to be
redeemed. On and after the Redemption Date, interest ceases to accrue on Notes
or portions thereof called for redemption unless the Company defaults in the
redemption payment due on the Redemption Date.

         6. Mandatory Redemption. The Company shall not be required to make
mandatory redemption payments with respect to the Notes. The Notes shall not
have the benefit of any sinking fund.

         7.       Offers to Purchase.

                  (a) Change of Control. In the event that a Change of Control
has occurred, each Holder of Notes will have the right, at such Holder's option,
pursuant to an offer (subject only to conditions required by applicable law, if
any) by the Company (the "Change of Control Offer"), to require the Company to
repurchase all or any part of such Holder's Notes (provided, that the principal
amount of such Notes must be $1,000 or an integral multiple thereof) on a date
(the "Change of Control Purchase Date") that is no later than 45 Business Days
after the occurrence of such Change of Control, at a cash price equal to the
following purchase prices (expressed as percentages of the principal amount) if
such Change of Control occurs during the 12-month period commencing August 15 of
the years indicated below (the "Change of Control Purchase Price"), in each
case, together with accrued and unpaid interest and Liquidated Damages, if any,
thereon to the Change of Control Purchase Date.

<TABLE>
<CAPTION>
                Year                                         Percentage
                ----                                         ----------
<S>            <C>                                          <C>
               2002 .................................       106.000    %
               2003 .................................       104.000    %
               2004 .................................       102.000    %
               2005 and thereafter...................       100.000    %
</TABLE>

                  The Change of Control Offer shall be made within 25 Business
Days following a Change of Control and shall remain open for at least 20
Business Days following its commencement (the "Change of Control Offer Period").
Upon expiration of the Change of

                                       5
<PAGE>
Control Offer Period, the Company promptly shall purchase all Notes properly
tendered in response to the Change of Control Offer.

                  On or before the Change of Control Purchase Date, the Company
shall: (i) accept for payment Notes or portions thereof properly tendered
pursuant to the Change of Control Offer; (ii) deposit with the Paying Agent cash
sufficient to pay the Change of Control Purchase Price (together with accrued
and unpaid interest and Liquidated Damages, if any) of all Notes so tendered;
and (iii) deliver to the Trustee the Notes so accepted together with an
Officers' Certificate listing the Notes or portions thereof being purchased by
the Company. The Paying Agent promptly will pay the Holders of Notes so accepted
an amount equal to the Change of Control Purchase Price (together with accrued
and unpaid interest and Liquidated Damages, if any) and the Trustee promptly
will authenticate and deliver to such Holders a new Note equal in principal
amount to any unpurchased portion of the Note surrendered. Any Notes not so
purchased will be delivered promptly by the Company to the Holder thereof. The
Company publicly will announce the results of the Change of Control Offer on or
as soon as practicable after the Change of Control Purchase Date.

                  If the Change of Control Purchase Date is on or after an
Interest Record Date and on or before the associated Interest Payment Date, any
accrued and unpaid interest (and Liquidated Damages, if any) due on such
Interest Payment Date will be paid to the Person in whose name a Note is
registered at the close of business on such Interest Record Date.

                  The Company shall not be required to make a Change of Control
Offer upon a Change of Control if a third party makes the Change of Control
Offer in the manner, at the times and otherwise in compliance with the
requirements set forth in this Indenture applicable to a Change of Control made
by the Company and purchases all Notes validly tendered and not withdrawn under
such Change of Control Offer.

                  (b) Asset Sale. Subject to certain exceptions set forth in the
Indenture, the Company and the Guarantors shall not, and shall not permit any of
the Company's Subsidiaries to, in one or a series of related transactions,
convey, sell, transfer, assign or otherwise dispose of, directly or indirectly,
any of their property, business or assets, including by merger or consolidation
(in the case of a Guarantor or a Subsidiary or Unrestricted Subsidiary of the
Company), and including any sale or other transfer or issuance of any Equity
Interests of any of the Company's Subsidiaries or Unrestricted Subsidiaries,
whether by the Company or one of its Subsidiaries or Unrestricted Subsidiaries
or through the issuance, sale or transfer of Equity Interests by one of the
Company's Subsidiaries or Unrestricted Subsidiaries and including any
sale-leaseback transaction (any of the foregoing, an "Asset Sale"), unless, with
respect to any Asset Sale or related series of Asset Sales involving securities,
property or assets with an aggregate fair market value in excess of $5,000,000
(an Asset Sale (including a series of related Asset Sales) of less than
$5,000,000 shall not be subject to this clause (b)), (a) at least 75% of the
total consideration for such Asset Sale or series of related Asset Sales
consists of cash or Cash Equivalents, and (b) the Company's Board of Directors
determines in good faith that the Company will be receiving or such Subsidiary
will be receiving, as applicable, fair market value for such Asset Sale. Solely
for purposes of the preceding sentence, "cash and Cash Equivalents" shall also
include, (i) Purchase Money Indebtedness secured solely by the assets sold and
assumed by a transferee; provided, that the Company and its Subsidiaries are
fully released from

                                       6
<PAGE>
obligations in connection therewith, (ii) assets for use in a Related Business
or Equity Interests of a Person that becomes a Guarantor which is primarily
engaged in a Related Business, (iii) Indebtedness incurred under the Credit
Agreement that is assumed by a transferee; provided that the Company and its
Subsidiaries are fully released from obligations in connection with the amounts
assumed and the assumed Indebtedness permanently reduced the Indebtedness under
the Credit Agreement (and in the case of a revolver or similar arrangement that
makes credit available, such commitment is permanently reduced by such amount),
(iv) property that within 30 days of such Asset Sale is converted into cash or
Cash Equivalents; provided, that such cash and Cash Equivalents shall be treated
as Net Cash Proceeds attributable to the original Asset Sale for which such
property was received and (v) TMS Indebtedness; provided that the Company and
its Subsidiaries are fully released from obligations in connection with the
amounts assumed.

                  Within 360 days following such Asset Sale, Net Cash Proceeds
therefrom (the "Asset Sale Amount") shall be: (a) used (i) to retire Purchase
Money Indebtedness secured by the asset which was the subject of the Asset Sale;
or (ii) to retire and permanently reduce Indebtedness incurred under the Credit
Agreement; provided, that in the case of a revolver or similar arrangement that
makes credit available, such commitment is permanently reduced by such amount;
or (b) used to make (i) capital expenditures or (ii) investments in assets and
property (other than notes, bonds, obligations and securities, except in
connection with the acquisition of a Person in a Related Business that becomes a
Guarantor) which in the good faith reasonable judgment of the Company's Board of
Directors will immediately constitute or be a part of a Related Business of the
Company or such Guarantor (if it continues to be a Guarantor) immediately
following such transaction; or the Company shall, within such 360-day period,
enter into a legally binding agreement to apply such Net Cash Proceeds as
described in this clause (b) within six months after such agreement is entered
into and apply such Net Cash Proceeds in accordance with the provisions of this
clause (b); provided, that if such agreement terminates the Company shall have
until the later of (i) 90 days after the date of such termination and (ii) 360
days after the date of the Asset Sale resulting in such Net Cash Proceeds to
effect such application.

                  The accumulated Net Cash Proceeds from Asset Sales and from
any Event of Loss not applied as set forth in the preceding paragraph shall
constitute "Excess Proceeds." Pending the final application of any Net Cash
Proceeds, the Company may temporarily reduce revolving credit borrowings or
otherwise invest or use for general corporate purposes (other than Restricted
Payments that are not solely Restricted Investments) the Net Cash Proceeds in
any manner that is not prohibited by the Indenture. When the Excess Proceeds
equal or exceed $10,000,000, within 10 Business Days the Company shall offer to
repurchase the Notes, together with any other Indebtedness ranking on a parity
with the Notes and with similar provisions requiring the Company to make an
offer to purchase such Indebtedness with the proceeds from such Asset Sale
pursuant to a cash offer (subject only to conditions required by applicable law,
if any), pro rata in proportion to the respective principal amounts of such
Indebtedness (or accreted values in the case of Indebtedness issued with an
original issue discount) and the Notes (the "Asset Sale Offer") at a purchase
price of 100% of the principal amount (or accreted value in the case of
Indebtedness issued with an original issue discount) (the "Asset Sale Offer
Price") together with accrued and unpaid interest and Liquidated Damages, if
any, to the date of payment. The Asset Sale Offer shall remain open for at least
20

                                       7
<PAGE>
Business Days following its commencement (the "Asset Sale Offer Period"). Upon
expiration of the Asset Sale Offer Period, the Company shall apply an amount
equal to the Excess Proceeds (the "Asset Sale Offer Amount") plus an amount
equal to accrued and unpaid interest and Liquidated Damages, if any, to the
purchase of all Indebtedness properly tendered in accordance with the provisions
hereof (on a pro rata basis if the Asset Sale Offer Amount is insufficient to
purchase all Indebtedness so tendered) at the Asset Sale Offer Price (together
with accrued and unpaid interest and Liquidated Damages, if any, to the date of
payment). To the extent that the aggregate amount of Notes and such other pari
passu Indebtedness tendered pursuant to an Asset Sale Offer is less than the
Asset Sale Offer Amount, the Company may use any remaining Net Cash Proceeds as
otherwise permitted by the Indenture. Following the consummation of each Asset
Sale Offer, the Excess Proceeds amount shall be reset to zero.

         8. Subordination. The Notes and the Guarantees are subordinated in
right of payment, to the extent and in the manner provided in Section 10.14 and
Article XI of the Indenture, to the prior payment in full in cash of Senior
Indebtedness and Designated Senior Indebtedness. The Company and the Guarantors
agree, and each Holder by accepting a Note consents and agrees, to the
subordination provided in the Indenture and Intercreditor Agreement and
authorizes the Trustee to give it effect.

         9. Denominations, Transfer, Exchange. The Notes are in registered form
without coupons in denominations of $1,000 and integral multiples of $1,000. The
transfer of Notes may be registered and Notes may be exchanged as provided in
the Indenture. The Registrar and the Trustee may require a Holder, among other
things, to furnish appropriate endorsements and transfer documents, and the
Company may require a Holder to pay any taxes and fees required by law or
permitted by the Indenture. The Company need not exchange or register the
transfer of any Note or portion of a Note selected for redemption, except for
the unredeemed portion of any Note being redeemed in part. Also, it need not
exchange or register the transfer of any Notes for a period of 15 days before a
selection of Notes to be redeemed or during the period between an Interest
Record Date and the corresponding Interest Payment Date.

         10. Persons Deemed Owners. The registered Holder of a Note may be
treated as its owner for all purposes.

         11. Amendment, Supplement and Waiver. Subject to certain exceptions,
the Indenture, the Notes or the Guarantees may be amended or supplemented with
the consent of the Holders of a majority in principal amount of the then
outstanding Notes, and any existing Default or compliance with any provision of
the Indenture, the Notes or the Guarantees may be waived with the consent of the
Holders of a majority in principal amount of the then outstanding Notes.
Notwithstanding the foregoing, other than as provided in Section 9.1 of the
Indenture, without the consent of the Holders of not less than two-thirds in
aggregate principal amount of the Notes at the time outstanding, the Company,
the Guarantors and the Trustee may not amend or supplement the Collateral
Agreements, or waive or modify the rights of the Holders thereunder. Without the
consent of any Holder of a Note, the Indenture, the Notes or the Guarantees may
be amended or supplemented and the Collateral Agreements may be amended,
supplemented, terminated or replaced to cure any ambiguity, defect or
inconsistency; to provide for uncertificated Notes in addition to or in place of
certificated Notes or to alter the provisions of Article II of the Indenture in
a manner that does not adversely affect any Holder; to provide

                                       8
<PAGE>
for the assumption of the Company's obligations to the Holders of the Notes in
the case of a merger or consolidation pursuant to Article V of the Indenture; to
provide for additional Guarantors as set forth in Section 4.17 of the Indenture
or for the release or assumption of a Guarantee in compliance with the
Indenture; to make any change that would provide any additional rights or
benefits to the Holders of the Notes or that does not adversely affect the
rights under the Indenture or under the Collateral Agreements of any Holder of
the Notes; to comply with the provisions of the Depositary, Euroclear or
Clearstream or the Trustee with respect to the provisions of this Indenture or
the Notes relating to transfers and exchanges of Notes or beneficial interests
therein; to comply with requirements of the SEC in order to effect or maintain
the qualification of this Indenture under the TIA; to evidence and provide for
the acceptance of appointment hereunder by a successor Trustee with respect to
the Notes; to evidence and provide for a new or replacement lender under a
Credit Agreement so long as such amended, supplemented or replacement Collateral
Agreements do not, as a whole, adversely affect the second-priority Lien in
favor of the Trustee or the rights of the Holders under the Collateral
Agreements or under the Indenture; to terminate and release control agreements
in respect of deposit accounts and securities accounts in connection with the
closing of any deposit accounts or securities accounts by the Company; or to add
or release Collateral in compliance with the terms of the Indenture and the
Collateral Agreements.

         12. Defaults and Remedies. The Indenture provides that each of the
following constitutes an Event of Default: (a) the failure of the Company to pay
any installment of interest (or Liquidated Damages, if any) on the Notes as and
when the same becomes due and payable and the continuance of any such failure
for 30 days; (b) the failure of the Company to pay all or any part of the
principal, or premium, if any, on the Notes when and as the same becomes due and
payable at maturity, redemption, by acceleration or otherwise, including,
without limitation, payment of the Change of Control Purchase Price or the Asset
Sale Offer Price, on Notes validly tendered and not properly withdrawn pursuant
to a Change of Control Offer or Asset Sale Offer, as applicable; (c) the failure
of the Company or the failure by any of the Guarantors to observe or perform any
other covenant or agreement contained in the Notes or the Indenture and, except
for Sections 4.13 and 4.16 and Article V thereof, which failure continues for a
period of 30 days after written notice is given to the Company by the Trustee or
to the Company and the Trustee by the Holders of at least 25% in aggregate
principal amount of the Notes outstanding; (d) a default occurs and is
continuing (after giving effect to any waivers, amendments, applicable grace
periods or any extension of any maturity date) under the Indebtedness of the
Company or the Indebtedness of any the Company's Subsidiaries with an aggregate
amount outstanding in excess of $10,000,000 (i) resulting from the failure to
pay principal of or interest on such Indebtedness; or (ii) if as a result of
such default, the maturity of such Indebtedness has been accelerated prior to
its stated maturity; (e) final nonappealable unsatisfied judgments not covered
by insurance aggregating in excess of $10,000,000, at any one time rendered
against the Company or any of its Subsidiaries and not stayed, bonded or
discharged within 60 days; (f) any Guarantee of a Guarantor ceases to be in full
force and effect or becomes unenforceable or invalid or is declared null and
void (other than in accordance with the terms of the Guarantee and the
Indenture) or any Guarantor denies or disaffirms its Obligations under its
Guarantee or the Collateral Agreements; (g) any failure to comply with any
material agreement or covenant in, or material provision of, any of the
Collateral Agreements, or any breach of a representation under, the Collateral
Agreements; (h) any of the Collateral Agreements ceases to be in full force and
effect (except as contemplated in the Indenture or the Collateral Agreements) or
any of the

                                       9
<PAGE>
Collateral Agreements ceases to give the Trustee (or, in the case of a Mortgage,
ceases to give the Trustee or any other trustee under such Mortgage) any of the
Liens, rights, powers or privileges purported to be created thereby with respect
to a material portion of the Collateral (except as contemplated in the Indenture
or the Collateral Agreements), or any of the Collateral Agreements is declared
null and void by the Company or a court of competent jurisdiction (except as
contemplated in the Indenture or the Collateral Agreements), or the Company or
any Guarantor denies that it has any further liability under any Collateral
Agreement to which it is a party or gives notice of such effect (in each case
other than by reason of the termination of the Indenture or any such Collateral
Agreement in accordance with its terms or the release of any Guarantor in
accordance with the Indenture); (i) a court having jurisdiction in the premises
enters a decree or order for (A) relief in respect of the Company or any
Significant Subsidiary in an involuntary case under any applicable Bankruptcy
Law now or hereafter in effect, (B) appointment of a receiver, liquidator,
assignee, custodian, trustee, sequestrator or similar official of the Company or
any Significant Subsidiary or for all or substantially all of the property and
assets of the Company or any Significant Subsidiary or (C) the winding up or
liquidation of the affairs of the Company or any Significant Subsidiary and, in
each case, such decree or order shall remain unstayed and in effect for a period
of 60 consecutive days; (j) the Company or any Significant Subsidiary (A)
commences a voluntary case under any applicable Bankruptcy Law now or hereafter
in effect, or consents to the entry of an order for relief in an involuntary
case under any such law, (B) consents to the appointment of or taking possession
by a receiver, liquidator, assignee, custodian, trustee, sequestrator or similar
official of the Company or any Significant Subsidiary or for all or
substantially all of the property and assets of the Company or any Significant
Subsidiary or (C) effects any general assignment for the benefit of creditors;
or (k) failure by the Company or the Guarantors to notify the Trustee within 3
Business Days following its discovery of any Default.

            If a Default occurs and is continuing, the Trustee must, within 90
days after the occurrence of such Default, give to the Holders notice of such
Default, but the Trustee shall be protected in withholding such notice if it in
good faith determines that the withholding of such notice is in the interest of
the Holders, except in the case of a Default in the payment of the principal of,
premium, if any, or interest on any of the Notes when due or in the payment of
any redemption or repurchase obligation.

         13. Trustee Dealings with Company. The Trustee, in its individual or
any other capacity, may make loans to, accept deposits from, and perform
services for the Company or its Affiliates, and may otherwise deal with the
Company or its Affiliates, as if it were not the Trustee.

         14. No Recourse Against Others. No past, present or future, direct or
indirect, stockholder, employee, officer, director agent or representative of
the Company, the Guarantors or any successor entity, as such, shall have any
liability for any Obligations of the Company or the Guarantors under the Notes,
the Guarantees or the Indenture or for any claim based on, in respect of, or by
reason of, such Obligations or their creation, except in their capacity as an
obligor or Guarantor of the Notes in accordance with the Indenture. Each Holder
by accepting a Note waives and releases all such liability. The waiver and
release are part of the consideration for issuance of the Notes.

                                       10
<PAGE>
         15. Authentication. This Note shall not be valid until authenticated by
the manual signature of the Trustee or an authenticating agent.

         16. Abbreviations. Customary abbreviations may be used in the name of a
Holder or an assignee, such as: TEN COM (= tenants in common), TEN ENT (=
tenants by the entireties), JT TEN (= joint tenants with right of survivorship
and not as tenants in common), CUST (= Custodian), and U/G/M/A (= Uniform Gifts
to Minors Act).

         17. Additional Rights of Holders of Transfer Restricted Notes. In
addition to the rights provided to Holders of Notes under the Indenture, Holders
of Transfer Restricted Notes shall have all the rights set forth in the Note
Registration Rights Agreement dated as of the date of the Indenture, by and
among the Company, the Guarantors and the Initial Purchasers (the "Note
Registration Rights Agreement").

         18. CUSIP Numbers. Pursuant to a recommendation promulgated by the
Committee on Uniform Security Identification Procedures, the Company has caused
CUSIP numbers to be printed on the Notes and the Trustee may use CUSIP numbers
in notices of redemption as a convenience to Holders. No representation is made
as to the accuracy of such numbers either as printed on the Notes or as
contained in any notice of redemption and reliance may be placed only on the
other identification numbers placed thereon, and any such redemption shall not
be affected by any defect in or omission of such numbers.

         19. Notation of Guarantee. As more fully set forth in the Indenture, by
its execution of its Guarantee, each of the Guarantors acknowledges and agrees
that it receives substantial benefits from the Company and that such party is
providing its Guarantee for good and valuable consideration, including, without
limitation, such substantial benefits and services. Accordingly, subject to the
provisions of Article X of the Indenture, each Guarantor, jointly and severally,
unconditionally guarantees on a senior subordinated basis to each Holder of a
Note authenticated and delivered by the Trustee and its successors and assigns
that: (i) the principal of, interest, premium, if any, and Liquidated Damages,
if any, on the Notes shall be duly and punctually paid in full when due, whether
at maturity, by acceleration, call for redemption, upon a Change of Control
Offer, an Asset Sale Offer or otherwise, and interest on overdue principal,
premium, if any, Liquidated Damages, if any, and (to the extent permitted by
law) interest on any interest, if any, on the Notes and all other obligations of
the Company to the Holders or the Trustee under the Notes, the Indenture, the
Collateral Agreements and the Note Registration Rights Agreement (including
fees, expenses or other) shall be promptly paid in full or performed, all in
accordance with the terms of the Indenture; and (ii) in case of any extension of
time of payment or renewal of any Notes or any of such other obligations, the
same shall be promptly paid in full when due or performed in accordance with the
terms of the extension or renewal, whether at stated maturity, by acceleration,
call for redemption, upon a Change of Control, an Asset Sale Offer or otherwise,
subject, however, in the case of clauses (i) and (ii) above, to the limitations
set forth in Section 10.8 of the Indenture.

            When a successor assumes all the obligations of its predecessor
under the Notes and the Indenture, the predecessor may be released from those
obligations.

                                       11
<PAGE>
         20. Governing Law. THE INDENTURE, THE NOTES AND THE GUARANTEES SHALL BE
GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK,
INCLUDING, WITHOUT LIMITATION, SECTIONS 5-1401 AND 5-1402 OF THE NEW YORK
GENERAL OBLIGATIONS LAW AND NEW YORK CIVIL LAWS AND RULES 327(b).

            The Company will furnish to any Holder upon written request and
without charge a copy of the Indenture and/or the Note Registration Rights
Agreement. Requests may be made to:

                       ORBITAL SCIENCES CORPORATION
                       21839 Atlantic Blvd.
                       Dulles, VA 20166
                       Attention: Chief Financial Officer

                                       12
<PAGE>
                                 ASSIGNMENT FORM

To assign this Note, fill in the form below: (I) or (We) assign and transfer
this Note to

__________________________________________________________________________
                  (Insert assignee's soc. sec. or tax I.D. no.)

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

              (Print or type assignee's name, address and zip code)

and irrevocably appoint ______________________________________________________+
to transfer this Note on the books of the Company. The agent may substitute
another to act for it.

__________________________________________________________________________

Date: _______________________

                                  Your Signature:_____________________________
                    (Sign exactly as your name appears on the face of this Note)

Signature Guarantee*

__________________________________________________________________________

*NOTICE: The Signature must be guaranteed by an Institution which is a member of
one of the following recognized signature Guarantee Programs: (i) The Securities
Transfer Agent Medallion Program (STAMP); (ii) The New York Stock Exchange
Medallion Program (MNSP); (iii) The Stock Exchange Medallion Program (SEMP); or
(iv) such other guarantee program acceptable to the Trustee.

                                       13
<PAGE>
                       OPTION OF HOLDER TO ELECT PURCHASE

         If you want to elect to have this Note purchased by the Company
pursuant to Section 4.13 or Section 4.16 of the Indenture, check the box below:

                    [ ]  Section 4.13   [ ] Section 4.16

         If you want to elect to have only part of the Note purchased by the
Company pursuant to Section 4.13 or Section 4.16 of the Indenture, state the
amount you elect to have purchased (in denominations of $1,000 only, except if
you have elected to have all of your Notes purchased): $___________

Date:                                   Your Signature:_________________________
                                 (Sign exactly as your name appears on the Note)

                        Social Security or Tax Identification No.:______________

Signature Guarantee*

________________________________________________________________________________

*NOTICE: The Signature must be guaranteed by an Institution which is a member of
one of the following recognized signature Guarantee Programs: (i) The Securities
Transfer Agent Medallion Program (STAMP); (ii) The New York Stock Exchange
Medallion Program (MNSP); (iii) The Stock Exchange Medallion Program (SEMP); or
(iv) such other guarantee program acceptable to the Trustee.

                                       14
<PAGE>

              SCHEDULE OF EXCHANGES OF INTERESTS IN THE GLOBAL NOTE

         The following exchanges of an interest in this Global Note for an
interest in another Global Notes or for a Definitive Note, or exchanges of an
interest in another Global Note or a Definitive Note for an interest in this
Global Note, have been made:

<TABLE>
<CAPTION>
                          Amount of            Amount of       Principal Amount of           Signature of
                         Decrease in          Increase in        this Global Note       Authorized Officer of
                     Principal Amount of  Principal Amount of  Following Such Decrease    Trustee or Note
   Date of Exchange   this Global Note      this Global Note        or Increase           Custodian
   ----------------   ----------------      ----------------         --------              ---------
<S>                  <C>                  <C>                  <C>                      <C>
</TABLE>

                                       15<PAGE>
                                                                     EXHIBIT 4.4

                                                                133,750 Warrants
                                                             CUSIP No. 685564148

                               Warrant Certificate

                          ORBITAL SCIENCES CORPORATION

         This Warrant Certificate certifies that Cede & Co., or its registered
assigns, is the registered holder of Warrants, expiring August 15, 2006 (the
"WARRANTS"), to purchase common stock, par value $.01 per share (the "COMMON
STOCK"), of Orbital Sciences Corporation, a Delaware corporation (the
"COMPANY"). Each Warrant initially entitles the registered holder upon exercise
at any time from 9:00 a.m., New York City time, on the date immediately
following the Mandatory Separation Date (as defined in the Warrant Agreement)
(the "EXERCISE DATE") until 5:00 p.m., New York City time, on August 15, 2006,
the Expiration Date, to receive from the Company 122.23 fully paid and
nonassessable shares of Common Stock (the "WARRANT SHARES") at the initial
exercise price (the "EXERCISE PRICE") of $3.86 per share payable upon surrender
of this Warrant Certificate and payment of the Exercise Price at the office or
agency of the Warrant Agent, subject to the conditions set forth herein and in
the Warrant Agreement referred to on the reverse hereof. The Exercise Price and
number of Warrant Shares issuable upon exercise of the Warrants are subject to
adjustment upon the occurrence of certain events set forth in the Warrant
Agreement.

         No Warrant may be exercised after 5:00 p.m., New York City time, on the
Expiration Date, and to the extent not exercised by such time Warrants shall
become void.

         Reference is hereby made to the further provisions of this Warrant
Certificate set forth on the reverse hereof and such further provisions shall
for all purposes have the same effect as though fully set forth at this place.

         This Warrant Certificate shall not be valid unless countersigned by the
Warrant Agent, as such term is used in the Warrant Agreement.

         This Warrant Certificate shall be governed by and construed in
accordance with the laws of the State of New York applicable to contracts made
and to be performed in New York, including, without limitation Sections 5-1401
and 5-1402 of the New York General Obligations Law and Rule 327(b) of the New
York Civil Practices Laws and Rules.
<PAGE>
         IN WITNESS WHEREOF, the Company has caused this Warrant Certificate to
be signed below.

DATED:  August 22, 2002
                                             ORBITAL SCIENCES CORPORATION

                                             By: _______________________________
                                                 Name:
                                                 Title:

Countersigned:
U.S. BANK, N.A.
as Warrant Agent

By:______________________________
      Authorized Signature

                                        2
<PAGE>
                         Reverse of Warrant Certificate

         THE WARRANTS EVIDENCED BY THIS CERTIFICATE ARE INITIALLY ISSUED AS PART
OF AN ISSUANCE OF 135,000 UNITS (THE "UNITS"), EACH OF WHICH CONSISTS OF $1,000
PRINCIPAL AMOUNT AT MATURITY OF THE 12% SECOND PRIORITY SECURED NOTES DUE 2006,
SERIES A, OF THE COMPANY (THE "NOTES") AND ONE WARRANT INITIALLY ENTITLING THE
HOLDER THEREOF TO PURCHASE 122.23 SHARES OF COMMON STOCK, PAR VALUE $.01 PER
SHARE, OF THE COMPANY.

         PRIOR TO THE EARLIEST OF (I) THE DATE ON WHICH A REGISTRATION STATEMENT
WITH RESPECT TO A REGISTERED EXCHANGE OFFER FOR THE NOTES IS DECLARED EFFECTIVE
UNDER THE ACT, AND (II) THE DATE ON WHICH A SHELF REGISTRATION STATEMENT WITH
RESPECT TO THE NOTES OR THE WARRANTS AND WARRANT SHARES IS DECLARED EFFECTIVE
UNDER THE SECURITIES ACT, THE WARRANTS EVIDENCED BY THIS CERTIFICATE MAY BE
TRANSFERRED OR EXCHANGED SEPARATELY FROM EACH OTHER AT THE OPTION OF THE HOLDER
UPON NOTICE TO THE WARRANT AGENT.

         THIS GLOBAL WARRANT IS HELD BY THE DEPOSITARY (AS DEFINED IN THE
WARRANT AGREEMENT GOVERNING THIS WARRANT) OR ITS NOMINEE IN CUSTODY FOR THE
BENEFIT OF THE BENEFICIAL OWNERS HEREOF, AND IS NOT TRANSFERABLE TO ANY PERSON
UNDER ANY CIRCUMSTANCES EXCEPT THAT (I) THE WARRANT AGENT MAY MAKE SUCH
NOTATIONS HEREON AS MAY BE REQUIRED PURSUANT TO SECTION 3.5 OF THE WARRANT
AGREEMENT, (II) THIS GLOBAL WARRANT MAY BE EXCHANGED IN WHOLE BUT NOT IN PART
PURSUANT TO SECTION 3.5(a) OF THE WARRANT AGREEMENT, (III) THIS GLOBAL WARRANT
MAY BE DELIVERED TO THE WARRANT AGENT FOR CANCELLATION PURSUANT TO SECTION 3.8
OF THE WARRANT AGREEMENT AND (IV) THIS GLOBAL WARRANT MAY BE TRANSFERRED TO A
SUCCESSOR DEPOSITARY WITH THE PRIOR WRITTEN CONSENT OF THE COMPANY.

         THIS SECURITY AND THE SECURITIES ISSUABLE UPON EXERCISE OF THIS
SECURITY HAVE NOT BEEN REGISTERED UNDER THE U.S. SECURITIES ACT OF 1933, AS
AMENDED (THE "SECURITIES ACT"), AND, ACCORDINGLY, MAY NOT BE OFFERED, SOLD,
PLEDGED

                                        3
<PAGE>
OR OTHERWISE TRANSFERRED WITHIN THE UNITED STATES OR TO, OR FOR THE ACCOUNT OR
BENEFIT OF, U.S. PERSONS, EXCEPT AS SET FORTH IN THE NEXT SENTENCE HEREOF. BY
ITS ACQUISITION HEREOF OR OF A BENEFICIAL INTEREST HEREIN, THE HOLDER:

         (1) REPRESENTS THAT (A) IT IS A "QUALIFIED INSTITUTIONAL BUYER" (AS
         DEFINED IN RULE 144A UNDER THE SECURITIES ACT)(A "QIB") OR (B) IT IS AN
         INSTITUTIONAL "ACCREDITED INVESTOR" (AS DEFINED IN RULE 501(A)(1), (2),
         (3) OR (7) OF REGULATION D UNDER THE SECURITIES ACT (AN "IAI"),

         (2) AGREES THAT IT WILL NOT RESELL OR OTHERWISE TRANSFER THIS SECURITY
         EXCEPT (A) TO THE COMPANY OR ANY OF ITS SUBSIDIARIES, (B) TO
         A PERSON WHOM THE SELLER REASONABLY BELIEVES IS A QIB PURCHASING FOR
         ITS OWN ACCOUNT OR FOR THE ACCOUNT OF A QIB IN A TRANSACTION MEETING
         THE REQUIREMENTS OF RULE 144A, (C) IN A TRANSACTION MEETING THE
         REQUIREMENTS OF RULE 144 UNDER THE SECURITIES ACT, (D) TO AN IAI THAT,
         PRIOR TO SUCH TRANSFER, FURNISHES THE WARRANT AGENT A SIGNED LETTER
         CONTAINING CERTAIN REPRESENTATIONS AND AGREEMENTS RELATING TO THE
         TRANSFER OF THIS SECURITY (THE FORM OF WHICH CAN BE OBTAINED FROM THE
         WARRANT AGENT) AND, IF THE COMPANY SO REQUESTS, AN OPINION OF COUNSEL
         ACCEPTABLE TO THE COMPANY THAT SUCH TRANSFER IS IN COMPLIANCE WITH THE
         SECURITIES ACT, (E) IN ACCORDANCE WITH ANOTHER EXEMPTION FROM THE
         REGISTRATION REQUIREMENTS OF THE SECURITIES ACT (AND BASED UPON AN
         OPINION OF COUNSEL ACCEPTABLE TO THE COMPANY) OR (F) PURSUANT TO AN
         EFFECTIVE REGISTRATION STATEMENT AND, IN EACH CASE, IN ACCORDANCE WITH
         THE APPLICABLE SECURITIES LAWS OF ANY STATE OF THE UNITED STATES OR ANY
         OTHER APPLICABLE JURISDICTION, AND

         (3) AGREES THAT IT WILL DELIVER TO EACH PERSON TO WHOM THIS NOTE OR AN
         INTEREST HEREIN IS TRANS-

                                       4
<PAGE>
         FERRED A NOTICE SUBSTANTIALLY TO THE EFFECT OF THIS LEGEND.

         The Warrants evidenced by this Warrant Certificate are part of a duly
authorized issue of Warrants expiring at 5:00 p.m., New York City time, on the
Expiration Date, entitling the holder on exercise to receive shares of Common
Stock, and are issued or to be issued pursuant to a Warrant Agreement, dated as
of August 22, 2002 (the "WARRANT AGREEMENT"), duly executed and delivered by the
Company to U.S. Bank, N.A., as warrant agent (the "WARRANT AGENT"), which
Warrant Agreement is hereby incorporated by reference in and made a part of this
instrument and is hereby referred to for a description of the rights, limitation
of rights, obligations, duties and immunities thereunder of the Warrant Agent,
the Company and the holders (the words "HOLDERS" or "HOLDER" meaning the
registered holders or registered holder) of the Warrants. A copy of the Warrant
Agreement may be obtained by the holder hereof upon written request to the
Company.

         Warrants may be exercised commencing at the opening of business on the
Exercise Date and until 5:00 p.m., New York City time, on the Expiration Date,
provided that holders shall be able to exercise their Warrants only if a
Registration Statement relating to the exercise of the Warrants is then in
effect, or the exercise of such Warrants is exempt from the registration
requirements of the Securities Act of 1933, as amended (the "SECURITIES ACT"),
and such securities are qualified for sale or exempt from qualification under
the applicable securities laws of the states in which the various holders of the
Warrants or other Persons to whom it is proposed that the Warrant Shares be
issued on exercise of the Warrants reside. In order to exercise all or any of
the Warrants represented by this Warrant Certificate, the holder must deliver to
the Warrant Agent at the address set forth in Section 15 of the Warrant
Agreement or at the Warrant Agent's New York corporate trust office this Warrant
Certificate and the form of election to purchase included in this Warrant
Certificate duly filled in and signed, which signature shall be medallion
guaranteed by an institution which is a member of one of the following
recognized signature guarantee programs: (i) The Securities Transfer Agent
Medallion Program (STAMP); (ii) the New York Stock Exchange Medallion Program
(MNSP); (iii) the Stock Exchange Medallion Program (SEMP); or (iv) such other
guarantee program acceptable to the Warrant Agent, and payment to the Warrant
Agent for the account of the Company of the Exercise Price, as adjusted as
provided in the Warrant Agreement, for the number of Warrant Shares in respect
of which such Warrant is then exercised.

         The Warrant Agreement provides that upon the occurrence of certain
events the Exercise Price set forth on the face hereof may, subject to certain
condi-

                                       5
<PAGE>
tions, be adjusted. If the Exercise Price is adjusted, the Warrant Agreement
provides that the number of shares of Common Stock issuable upon the exercise of
each Warrant shall be adjusted. No fractions of a share of Common Stock will be
issued upon the exercise of any Warrant, but the Company, at its option, will
pay the cash value thereof determined or round to the next full share of Common
Stock, as provided in the Warrant Agreement. No adjustment shall be made for any
dividends on any Common Stock issuable upon exercise of this Warrant.

         Warrant Certificates, when surrendered at the office of the Warrant
Agent by the registered holder thereof in person or by legal representative or
attorney duly authorized in writing, may be exchanged, in the manner and subject
to the limitations provided in the Warrant Agreement, but without payment of any
service charge, for another Warrant Certificate or Warrant Certificates of like
tenor evidencing in the aggregate a like number of Warrants.

         Upon due presentation for registration of transfer of this Warrant
Certificate at the office of the Warrant Agent, a new Warrant Certificate or
Warrant Certificates of like tenor and evidencing in the aggregate a like number
of Warrants shall be issued to the transferee(s) in exchange for this Warrant
Certificate, subject to the limitations provided in the Warrant Agreement,
without charge except for any tax or other governmental charge imposed in
connection therewith.

         The Company and the Warrant Agent may deem and treat the registered
holder(s) thereof as the absolute owner(s) of this Warrant Certificate (notwith-
standing any notation of ownership or other writing hereon made by anyone), for
the purpose of any exercise hereof, or any distribution to the holder(s) hereof,
and for all other purposes, and neither the Company nor the Warrant Agent shall
be affected by any notice to the contrary. Neither the Warrants nor this Warrant
Certificate entitles any holder hereof to any rights of a stockholder of the
Company.

                                       6
<PAGE>
                          Form of Election to Purchase

                    (To Be Executed Upon Exercise Of Warrant)

         The undersigned hereby irrevocably elects to exercise the right,
represented by this Warrant Certificate, to receive ________ shares of Common
Stock and herewith tenders payment for such shares to the order of Orbital
Sciences Corporation, in the amount of $_______ in accordance with the terms
hereof or the tender of $_____ aggregate principal amount of Notes in accordance
with the terms hereunder. The undersigned requests that a certificate for
such shares be registered in the name of _______________, whose address is
__________________ and that such shares be delivered to ___________, whose
address is ____________________________. If said number of shares is less than
all of the shares of Common Stock purchasable upon exercise of the Warrant(s)
represented by this Warrant Certificate, the undersigned requests that a new
Warrant Certificate representing the number of Warrants exercisable for the
remaining balance of such shares be registered in the name of
______________________, whose address is ____________________, and that such
Warrant Certificate be delivered to _______________________________ whose
address is ________________________.

                                                     ___________________________
                                                     Signature

Date:  _____________________

         _____________________________
         Signature Guaranteed*

                                       7
<PAGE>
*NOTICE: The Signature must be guaranteed by an Institution which is a member of
one of the following recognized signature Guarantee Programs: (i) The Securities
Transfer Agent Medallion Program (STAMP); (ii) The New York Stock Exchange
Medallion Program (MNSP); (iii) The Stock Exchange Medallion Program (SEMP); or
(iv) such other guarantee program acceptable to the Trustee.

                                       8
<PAGE>
                       SCHEDULE OF EXCHANGES OF INTERESTS
                               OF GLOBAL WARRANTS

The initial number of warrants evidenced by this Global Warrant is 33,750. The
following exchanges of a part of this Global Warrant have been made:

<TABLE>
<CAPTION>
                          Amount of                                         Number of
                         Decrease in                                     Warrants in this
                          Number of               Amount of               Global Warrant           Signature of
                         Warrants in         Increase in Number           Following Such            Authorized
     Date of Ex          this Global         of Warrants in this          Decrease or In            Officer of
       change              Warrant             Global Warrant                 crease              Warrant Agent
    ------------------------------------------------------------------------------------------------------------
<S>                      <C>                 <C>                         <C>                      <C>

</TABLE>

                                       9

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