COMMERCIAL-IN-CONFIDENCE

                             AMENDMENT NO. 1 TO THE
                       JOINT INVESTMENT AGREEMENT BETWEEN
                    ORION ASIA PACIFIC CORP. AND DACOM CORP.

          This Amendment No. 1 to the Joint Investment Agreement (the
"Amendment")  effective as of July ___,  1997, by and between Orion Asia Pacific
Corp., a corporation  organized and existing under the laws of Delaware,  U.S.A.
("Orion") and DACOM CORP.,  a corporation  organized and existing under the laws
of the Republic of Korea ("DACOM").

                              W I T N E S S E T H:

          WHEREAS,  the Parties have entered into a Joint  Investment  Agreement
dated November 11, 1996 (the  "Agreement"),  for Orion's provision to DACOM of a
payload on Orion 3 consisting of eight (8) 36 Mhz Ku-band transponders and three
(3) spare transponders which will cover the Korean Peninsula; and

          WHEREAS,  a  satellite  manufacturing  contract  for  Orion 3 has been
executed between Orion and Hughes Space and Communications  International,  Inc.
(the  "Satellite   Manufacturer")  on  January  15,  1997  (the   "Manufacturing
Contract")  which  contract  provides  for  certain  specifications  for the DTH
Payload  that are  different  from  those  set  forth in  Exhibit B of the Joint
Investment Agreement dated November 11, 1996; and

          WHEREAS,  the Parties  desire to enter into an  amendment to the Joint
Investment  Agreement to reconcile  differences  between the existing  Exhibit B
(Issue 2.2) of the Joint Investment  Agreement and the proposed Exhibit B (Issue
3.0) resulting from the Manufacturing Contract;

          NOW, THEREFORE,  in consideration of the foregoing and intending to be
legally bound, the Parties hereto agree to amend the Agreement as follows:

1.   Unless otherwise  defined herein,  all capitalized  terms used herein shall
have the meanings given those terms in the Agreement.

2.   Article 1,  Definitions.  The following  definitions  are hereby deleted in
their entirety and replaced with the following:

     o    "Acceptance Test Plan" means the plan for testing the Transponders and
          Spare Transponders, both prior to launch and in-orbit, in the form and
          substance  set forth (or to be set forth) in (a) the  Integrated  Test
          Plan which is attached  hereto as Exhibit F, and (b) the detailed test
          procedures  for the In-Orbit  Test Plan (part of the  Integrated  Test
          Plan) which will be developed,  within  approximately  four (4) months
          prior to launch of Orion 3-- the  objective of the In-Orbit  Test Plan
          will be to verify  ground  test  results  and the  In-Orbit  Test Plan
          procedures will be


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         consistent with customary and reasonable practice within the satellite
         industry.  In  connection  with the  development  of the In-Orbit  Test
         procedures,  Orion and DACOM will work closely to  coordinate  input to
         the Satellite Manufacturer.

     o   "Launch  Failure"  means the  failure of Orion 3 within 180 days after
         launch or the time  prescribed  within  the  insurance  contract  to be
         procured by Orion,  whichever  occurs  first (i) to reach its  assigned
         orbital  location,  or (ii) to have at least _____  ____________ of the
         transponders  meeting their  respective  technical  specifications,  or
         (iii) to have  sufficient  stationkeeping  fuel to achieve its required
         orbital  performance for a minimum of  ________________  of the Orion 3
         fifteen  (15)  year  life  (in-orbit  maneuver  life  specified  in the
         Manufacturing Contract) upon reaching its assigned orbital location, or
         (iv) to otherwise be commercially  usable as a result of destruction or
         damage incurred during launch;

The following definition is hereby be added to this Article:

     o    "DTH Service" shall have the meaning of a single  multiplexed  carrier
          for digital  broadcasting  service  with  equipment  and operated in a
          manner consistent with industry standards and optimized to be received
          by   individual   subscribers   via  dish   antenna  no  larger   than
          ______________________ in diameter.

3.   Section  6.1(b),  Notice of  Transponder  Failure.  This  Section is hereby
deleted in its entirety and replaced with the following:

     Each Party shall notify the other Party as soon as reasonably possible upon
     learning of the commencement of any event which,  with the passage of time,
     could result in a Transponder Failure and of the relevant facts known to it
     concerning  such event.  For purposes of determining  whether a Transponder
     Failure  has  occurred,  the  point  when a  Transponder  fails to meet its
     Technical  Specification  shall be deemed to have commenced upon receipt by
     Orion of written  notification  thereof from DACOM,  sent via telefax (with
     answerback  being deemed evidence of receipt by Orion),  subject to Orion's
     verification  that  the  Transponder  is  not  performing  pursuant  to the
     Technical Specifications in any material respect. The event which, with the
     passage of time,  could result in a Transponder  Failure shall be deemed to
     have ended, and the Transponder shall be deemed to have been restored, upon
     receipt by DACOM,  of written  notification  from  Orion,  sent via telefax
     (with  answerback  being  deemed  evidence of receipt by DACOM),  that such
     Transponder  has  resumed  performance  in  accordance  with the  Technical
     Specifications  in all material  respects or that a Spare  Transponder  has
     been made available to DACOM. For purposes of this Article only,  notice as
     required under this provision shall be sent to the following:


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FOR DACOM:        -----------------------------------
                  Tel:-------------------------------
                  Fax:-------------------------------

FOR ORION:        -----------------------------------
                  Tel:-------------------------------
                  Fax:-------------------------------

     4.   Section 6.1(c), Restoration.  The following is hereby added to the end
of this Section:

          Additionally,  DACOM agrees to fully cooperate with Orion's reasonable
          requests  to test  the  Transponders  in the  event  of a  Transponder
          Failure.  DACOM  understands  that such  testing may require  Orion to
          divert certain traffic on the  Transponders.  Orion shall conduct such
          testing  in a way and  during  periods  in which  there  will be no or
          little  impact to DACOM or its  customers.  Orion shall  consult  with
          DACOM,  consistent with the  requirements  necessitating  the testing,
          regarding   the  need,  if  any,  to  interrupt  the  service  on  the
          Transponders.  Orion  shall  give  DACOM  as much  advance  notice  as
          practicable of the need to interrupt any service on the Transponders.

     5.   Section 11.2 is hereby deleted and replaced with the following:

          EXCEPT AS SPECIFICALLY SET FORTH IN ARTICLE 17 HEREOF,  ORION MAKES NO
          REPRESENTATIONS  OR WARRANTIES,  WHETHER  EXPRESS OR IMPLIED AS TO THE
          CONDITION OF ORION 3 OR THE  TRANSPONDERS OR SPARE  TRANSPONDERS.  ALL
          SUCH WARRANTIES ARE HEREBY EXPRESSLY  DISCLAIMED.  DACOM  ACKNOWLEDGES
          THAT ORION MAKES NO  WARRANTIES  BEYOND THOSE  SPECIFICALLY  SET FORTH
          HEREIN,  AND THAT THERE IS NO IMPLIED WARRANTY OF  MERCHANTABILITY  OR
          FITNESS  FOR ANY  PARTICULAR  PURPOSE  ASSOCIATED  WITH ORION 3 OR THE
          TRANSPONDERS  OR SPARE  TRANSPONDERS.  DACOM SHALL INDEMNIFY ORION AND
          HOLD ORION HARMLESS FROM ANY CLAIMS MADE UNDER ANY WARRANTY OTHER THAN
          THOSE SPECIFICALLY SET FORTH HEREIN OR REPRESENTATIONS BY DACOM TO ANY
          THIRD PARTY AS TO ORION 3 OR THE TRANSPONDERS.

     6.   The following is hereby added to the end of Section 13.1:

          Orion shall keep DACOM  informed in writing on a periodic basis of any
          relevant information regarding the frequency coordination issues.

     7.   The  following is hereby  added as a separate  paragraph at the end of
Article 7:
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          Given DACOM's DTH Service objective,  Orion hereby agrees,  during the
          Term,  not to reduce the EIRP  performance  of the DACOM payload below
          the  Technical  Specifications  contained in Exhibit B (Issue 4.0) for
          any  frequency  coordination  purpose  without  DACOM's  prior written
          consent, which consent, having due regard for the DTH Service intended
          for use by DACOM, shall not be unreasonably withheld.

          In the event Orion violates the foregoing with respect to Transponders
          which have not been retained by DACOM pursuant to Section 17.7,  DACOM
          shall be entitled to the following:

          (a)  Injunctive relief; and/or

          (b)  Actual   damages,   as   determined   by  a  court  of  competent
               jurisdiction,    in   an   amount   not   to   exceed   US$71,314
               ____________________________________  multiplied by the number of
               months remaining in the Term for each Transponder  suffering from
               a reduction to the EIRP  performance  (the "Capped  Amount").  In
               this case, as long as the actual damages  determined by the court
               and paid by Orion to DACOM are less than the Capped Amount, DACOM
               is entitled to keep utilizing the  Transponder for any commercial
               purpose,  and if the actual  damages  determined by the court are
               the Capped Amount,  upon payment of such damages by Orion,  DACOM
               shall have no further right to use the Transponders.

     8.   The following is hereby added as Article 17 hereto:

                                   ARTICLE 17.

                        _______________________ WARRANTY


          17.1  _________________  Warranty.  Subject to the  provisions of this
          Article 17, Orion hereby warrants to DACOM the following:

          (a)    During   the    Warranty    Period    (as    defined    below),
          ____________________,  there will be no Degradation (as defined below)
          ______________________ (as defined below); and

          (b)  During the Warranty  Period, _________________,  there will be no
          increase in Degradation  ___________________________________ contained
          in the original  Agreement  dated  November 11, 1996 to that resulting
          from this Amendment (collectively the "Warranty").

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          The above Warranty shall not apply to (a)-----------------------------
          _______________________________;  (b) ___________________;  and/or (c)
          any Successor  Satellite  Orion chooses to launch,  unless the Parties
          mutually agree in writing.

          (c)  For purposes of this Article 17 the following  definitions  shall
          apply:

          i.   ___________________________.

          ii.  ___________________________.

          iii. Warranty Period:  the period of time beginning  November 11, 1996
               and ending at the end of the  second  Additional  Test  completed
               pursuant  to Article  17.7.  or 5 months  after the  Commencement
               Date, whichever is earlier.

          (d)  Limitation of Breach Claims.  DACOM's  remedies for breach of the
          Warranty  under this Article 17 shall be limited to the procedures set
          forth in this Section 17 for Additional  Tests and Arbitration (if the
          facts are disputed); under no circumstances shall DACOM have the right
          to make a subsequent  Warranty  claim  during the  Warranty  Period or
          thereafter.

          17.2  FREQUENCY COORDINATION  TESTING. (a) During In-Orbit Testing and
          after  consultation and coordination  with DACOM,  Orion shall analyze
          the Transponders  for  interference by conducting a spectrum  analyzer
          test in  accordance  with  Exhibit G (the  "Test");  DACOM may, at its
          discretion,  have the opportunity to have a representative attend such
          Test.  The data  resulting  from the Test shall be  provided  to DACOM
          within 7 days  following  completion  of the  Test  for  informational
          purposes  only and  shall  have no  evidentiary  use in any  resulting
          Arbitration.


          (b)  DACOM may, at its discretion, during the Warranty Period, conduct
          tests,  including  a  ______________  as  defined  in  Exhibit  G,  to
          determine the existence of Degradation  ___________________  in breach
          of the  Warranty.  Orion  shall  be  given  notice  and  afforded  the
          opportunity  to attend  such  tests.  In the event  DACOM  chooses  to
          perform  such  _____________,  the  results  of the test  shall be for
          informational  purposes  only and shall not be binding on the  Parties
          nor  shall  such  test  have  any  evidentiary  use in  any  resulting
          arbitration.

          (c) During the Warranty Period, DACOM shall provide to Orion, no later
          than ten  days  following  the end of each  calendar  month,  a report
          setting  forth the details of any outages or other  matters  adversely
          affecting the  performance  of the  Transponders  experienced by DACOM
          during the reporting period.  Orion will consult with DACOM if, during
          the Warranty  Period,  there are matters  affecting the performance of
          the Transponders.


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          17.3 NOTICE FOR ADDITIONAL  Tests.  DACOM may submit a written request
          ("Notice for Additional  Tests") on two separate  occasions during the
          Warranty  Period  for the  performance  of the  additional  tests , as
          outlined in Exhibit G ("Additional  Tests").  The Notice of Additional
          Tests for the second  Additional  Tests shall be submitted to Orion no
          later than a time which permits the completion of the Additional Tests
          within the Warranty Period.

          17.4 ADDITIONAL  TESTS.  (a) Within a reasonable time after receipt of
          the  Notice  for  Additional  Tests,  the  Additional  Tests  shall be
          performed  by DACOM  for a period of 15 days per  Additional  Tests in
          cooperation  with  Orion  (who  shall be  permitted  to  witness  such
          Additional Tests) using DACOM's planned MCPC video transmission.

          (b)  During  the  period  of   Additional   Tests  or  any   resulting
          Arbitration,  DACOM shall be  permitted  to use the  Transponders  not
          subject to Additional Tests or said Arbitration and shall be permitted
          to  use  the   Transponders   subject  to  Additional  Tests  or  said
          Arbitration to the extent said Additional Tests or Arbitration are not
          affected by such use of the Transponder.

          17.5  NOTICES.   The  following   additional   notice  provisions  are
          applicable to this Article 17:

          (a)  NOTICE OF BREACH OF  ____________  WARRANTY.  DACOM may, within 5
          days after completion of the second Additional Test, submit to Orion a
          written statement providing sufficient facts to reasonably demonstrate
          there is Degradation ______________ in violation of the Warranty under
          Article 17 (the "Notice of Breach"). Included as part of the Notice of
          Breach shall be the results of any and all tests conducted pursuant to
          paragraph  17.2(b) or 17.4,  and DACOM  shall  respond  to  reasonable
          requests from Orion for additional  information  intended to establish
          the  existence  of a  factual  basis  for a  claim  of  breach  of the
          Warranty.

          (b)  DEGRADATION NOTICE. If, within 2 days after receipt of the Notice
          of Breach,  DACOM and Orion  agree  there is a breach of  Warranty  in
          violation  of  Article  17,  Orion  shall  send to DACOM  notification
          indicating their agreement  ("Degradation  Notice").  Thereafter,  the
          rights  and  remedies  of Orion  and  DACOM  shall be as set  forth in
          Section 17.7.

          (c)  NOTICE OF DISPUTE. If,  within 2 days after receipt of the Notice
          of  Breach,  Orion  and  DACOM do not agree  that the  results  of the
          Additional Tests and other facts presented by DACOM clearly  establish
          a breach of the Warranty  under Article 17, Orion shall issue to DACOM
          a Notice of Dispute.


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          (d)  NOTICE OF  ARBITRATION. If,  within 2 days  after  receipt of the
          Notice of Dispute,  and DACOM  desires to pursue its remedies  herein,
          DACOM  shall  notify  Orion  and  the  designated   Arbitrators   (the
          "Arbitration  Notice"),  and the matter shall thereupon be resolved in
          accordance with Section 17.6, Dispute Resolution.

          17.6  DISPUTE  RESOLUTION.  In lieu of Section  16.6,  Orion and DACOM
          agree that  disputes  arising  under this  Article 17 shall be settled
          definitively by using an expedited, independent arbitration proceeding
          (the "Arbitration  Proceeding").  The Arbitration  Proceeding shall be
          conducted by three (3) arbitrators (the "Arbitration Panel") who shall
          utilize,  for  guidance  only,  the  rules  set  forth in the Rules of
          Conciliation and Arbitration of the International  Chamber of Commerce
          (ICC).  In order to expedite the  Arbitration  Proceeding,  each Party
          shall  designate one arbitrator 90 days prior to Launch and notify the
          other in writing of its  selection.  At least 30 days prior to launch,
          the  arbitrators  appointed by the Parties  shall  designate the third
          arbitrator in writing.  Each arbitrator  shall be knowledgeable of and
          experienced with the communications  satellite's  design/manufacturing
          or operations industries.

          The  Parties  agree that the issue to be  decided  by the  Arbitration
          Panel  is  whether  the  facts  presented  to  the  Arbitration  Panel
          establish,  by clear and convincing  evidence,  that  Degradation  has
          occurred such as to constitute a breach of the Warranty. In conducting
          the  Arbitration  Proceeding,  the Parties  will  provide any written,
          recorded, or other documentary evidence (the "Evidence") within 3 days
          of the Arbitration  Notice,  and the Arbitration Panel will review and
          consider the Evidence.  Within 10 days after the  Arbitration  Notice,
          the Arbitration Panel shall convene a hearing (not to exceed 5 days in
          duration),  during  which each side shall have up to two days (8 hours
          per each day) to present  its case and,  furthermore,  each side shall
          have one half day (4 hours) to  cross-examine  witnesses for the other
          side.  Following the hearing,  the Parties shall brief the Arbitration
          Panel on any  issues  requested  by the Panel.  Said  briefs to be due
          within 7 days from the  completion  of the  hearing.  The  Arbitration
          Panel shall render its  decision  within 7 days of  submission  of the
          briefs  (there  shall  be  no  reply  briefs).  The  decision  of  the
          Arbitration Panel shall determine whether there has been a Degradation
          in breach of the Warranty and the resulting remedy (in accordance with
          the provisions of Section 17.7);  the  Arbitration  Panel shall not be
          required  to  render  an  opinion  specifying  the  reasoning  for its
          decision.  The decision of the  Arbitration  Panel shall be in writing
          and shall  determine (i) whether there has been  Degradation in breach
          of the  Warranty;  (ii) a reasonable  period of time for Orion to cure
          the  Degradation  but no later than the last day of the Curing  Period
          (as defined below);  and (iii) the appropriate  remedy as set forth in
          Section  17.7  (subject  to DACOM's  election  to  continue to use the
          _________   Transponders)  in  the  event  Orion  fails  to  cure  the
          Degradation with the time period set forth in (ii) above.


<PAGE>


          The  Arbitration  Proceeding  shall take place in  Vancouver,  British
          Columbia,  Canada.  The  applicable law shall be the  substantive  and
          procedural laws of the State of New York. All arbitration  shall be in
          the English language. The arbitration award shall be final and binding
          upon  the  Parties  and  judgment  may be  entered  thereon,  upon the
          application of either Party,  by any court of competent  jurisdiction.
          Each Party shall bear the cost of preparing and  presenting  its case,
          and the cost of the  arbitration  (including  fees and expenses of the
          arbitrators) shall be shared equally by the Parties.

          17.7  REMEDY FOR BREACH OF WARRANTY.  In the event the Parties  agree,
          pursuant to Section 17.5(b) or the Arbitration Panel decides, pursuant
          to  Section  17.6  there  is   Degradation  to  one  or  more  of  the
          Transponders as a result of ____________________________, in breach of
          the  Warranty,  then  Orion  shall  have an  opportunity  to cure  the
          Degradation  up to the last day of the Curing  Period  (defined as the
          period  of time  beginning  with the  Commencement  Date and  ending 6
          months thereafter) or such time as determined by the Arbitration Panel
          pursuant to Section 17.6. If such  Degradation is not cured within the
          Curing Period, DACOM shall be entitled, as its sole remedy and in lieu
          of the remedies set forth in Section 2.3, to the following:

               (i) If three (3) or fewer Transponders  suffer Degradation caused
               by  ___________________________________________________ as of the
               last day of the Curing Period, DACOM shall be entitled either (a)
               to a  refund  of  US$11,125,000  per  __________________  with no
               further  right to use such  ______________;  or (b) to retain the
               rights to use such  __________________  with no  reduction to the
               Joint Investment  Amount.  Such election by DACOM must be made no
               later than 5 days following the final decision of the Arbitration
               Panel  or,  where  the  Parties  agree  there is a breach  of the
               Warranty, within 5 days following the issuance of the Degradation
               Notice under Section 17.5(b).

               (ii) If more  than  three  (3)  Transponders  suffer  Degradation
               caused  by  ______________________________  as of the last day of
               the  Curing  Period , DACOM  shall be  entitled,  as its sole and
               exclusive  remedy,  either  (a) to retain  the rights to use such
               _____________________  with no reduction to the Joint  Investment
               Amount;  or (b) to a refund  of all  amounts  previously  paid to
               Orion by DACOM pursuant to Sections  5.2(a) - (d), in which case,
               the  Agreement  shall  terminate  and DACOM shall have no further
               rights  hereunder.  Such  election by DACOM must be made no later
               than 5 days following the final decision of the Arbitration Panel
               or,  where the Parties  agree there is a breach of the  Warranty,
               within 5 days  following the issuance of the  Degradation  Notice
               under Section 17.5(b).


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9.   Exhibit B, Issue 2.2, Technical  Specifications of the Agreement are hereby
deleted in their  entirety and replaced with the attached  Exhibit B, Issue 4.0,
dated June 23, 1997.

10.  The attached  Exhibit F, HS601HP,  Integrated Test Plan, has been agreed to
by the Parties and is hereby  incorporated  into the Agreement as the Acceptance
Test Plan.

11.  The  attached  Exhibit G shall be  incorporated  into the  Agreement as the
Frequency Coordination Test Plan.

12.  Notwithstanding  Sections 5.2(b) and 5.6(a),  the Parties  acknowledge that
neither  the  posting  of  the  Letter  of  Credit  due   ___________   nor  the
________________  payment due  _____________  have been made. The Parties hereby
agree there is no default for failure to meet the  aforesaid  requirements,  and
there is no right to interest on any such  amounts.  DACOM shall post the letter
of credit and pay  ________________  by __ days following the date of execution,
by both Parties, of this Amendment.  In the event the aforementioned  payment is
not made as required  under this  provision,  Orion shall be entitled to collect
interest  beginning  on the 16th day after  execution of this  Amendment  and in
accordance with the terms of Section 5.5 of the Agreement.

13.  Section  16.9,  Confidentiality.  The  following  is  hereby  added  to the
beginning of this Section: ---------------

          The  Parties  hereby  acknowledge  that  during  the Term of the Joint
          Investment  Agreement,  it may be  necessary  for  DACOM  to  disclose
          Confidential  Information  to  Permitted  Users for  purposes  of this
          Agreement.  At such time as DACOM desires to make such disclosure,  it
          shall  request,  in writing,  approval  from Orion,  with such request
          identifying the Permitted User and the Confidential  Information DACOM
          seeks to  disclose.  Orion shall  respond  promptly in writing to this
          request  acknowledging  its approval  (which shall not be unreasonably
          withheld) or its  disapproval,  in which case Orion shall  provide the
          reasons for its disapproval.

14.  Orion is currently  working with the  Satellite  Manufacturer  to amend the
Manufacturing Contract such that the technical specification for the DTH Payload
contained in Exhibit B, Appendix A will be substantially identical to Exhibit B,
as adopted hereby. Orion shall notify DACOM within 15 days of the effective date
of this Amendment if the Manufacturing Contract has not been so amended.

15.  Section  16.1,  Further  Assurances.  This  Section is hereby  deleted  and
replaced by the following:

     DACOM  and  Orion  shall  take  all  appropriate  action  and  execute  all
     documents, instruments or conveyances of any kind which may be necessary or
     advisable to carry out any of the  provisions  hereof and to consummate the
     transactions  contemplated  hereby. Orion hereby agrees that (i) the Korean
     National Flag and


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     DACOM's  logo shall be affixed or marked on the Orion 3  launching  vehicle
     conspicuous from the observation  decks;  (ii) the name of Orion 3 in Korea
     shall  be  Orion  3/DACOM,  and  such  name  may be used in  documents  and
     marketing  materials  distributed in Korea;  (iii) through the Term,  DACOM
     shall have the exclusive right to use the  Transponders  for DTH Service in
     Korea, and Orion will not provide comparable transponders on Orion 3 to any
     other entity for the purpose of providing DTH Service in Korea; however, in
     the event any of the  Transponders  are  ____________________  returned  to
     Orion pursuant to Section 17.6, Orion may, in its sole discretion,  provide
     such returned Interfered Transponders or any other returned Transponders to
     any party for the purpose of providing direct to home television service in
     Korea;  (iv)  Orion  shall  inform  DACOM  of any  matters  related  to the
     construction,  launch and  financing  of Orion 3 that would have a material
     adverse effect on DACOM's rights to the Transponders and Spare Transponders
     hereunder  or delay of launch of Orion 3; and (v) Orion  shall  delivery to
     DACOM Orion's form of warrant  containing the terms set forth in the letter
     attached hereto as Exhibit E.

16. Section 10.1(a)(i),  Launch Delay; Launch Failure; Loss of Orbital Position.
This Section is hereby deleted and replaced by the following:

     Subject to clause (ii) below,  if Orion 3 is not  launched by May 31, 1999,
     or if the Commencement Date is delayed beyond June 30, 1999, or if there is
     a Launch  Failure and DACOM does not timely  exercise its option to acquire
     the  right to use  transponders  on a  Replacement  Satellite  pursuant  to
     Section 2.3 (or if such Replacement  Satellite option is not made available
     to DACOM by Orion),  or if the orbital position in which Orion 3 is located
     is not within  the range of 136  degrees  EL to 142  degrees  EL, or in the
     event of a  catastrophic  failure  (i.e.,  destruction of the satellite) or
     other event which would clearly result in a Launch Failure;

17.  Exhibit  C, Form  Letter of Credit is hereby  deleted in its  entirety  and
replaced with the attached revised Exhibit C.

18. Orion and DACOM have participated jointly in the negotiation and drafting of
this Amendment.  If an ambiguity or question of intent or interpretation arises,
this Amendment  shall be construed as if drafted  jointly by both Parties and no
presumption or burden of proof shall arise favoring or disfavoring  either Party
because  of the  authorship  of any of the  provisions  of this  Amendment.  Any
reference  to any law shall be deemed  also to refer to all rules,  regulations,
orders or decrees promulgated thereunder, unless the context requires otherwise.
The  word   "including"   shall  mean   including   without   limitation.   Each
representation,  warranty and covenant  contained  herein shall have independent
significance.  If either  Party  breaches  in any  respect  any  representation,
warranty,  covenant, or other obligation contained herein or created hereby, the
fact that there exists another representation, warranty, covenant, or obligation
relating  to the same  subject  matter  (regardless  of the  relative  levels of
specificity) which has not been


<PAGE>


breached shall not detract from or mitigate the consequences of such breach. The
Exhibits  specified in this Amendment are  incorporated  herein by reference and
made a part hereof.

Except as amended herein, the Agreement and any prior amendments thereto,  shall
remain in full force and effect in all  respects,  including  but not limited to
price, delivery, schedule, and performance.

IN WITNESS WHEREOF,  the Parties have each duly executed this Amendment No. 1 as
of the day and year first written above.

ORION ASIA PACIFIC CORP.                               DACOM CORP.


By:                                          By:
   --------------------------                   --------------------------------
    W. Neil Bauer                                Kim, Young Chul
    Chief Executive Officer                      Senior Executive Vice President

Date:                                        Date:
     ------------------------                     ------------------------------

<PAGE>




                          COMMERCIAL - IN - CONFIDENCE


                                    Exhibit B
                               ORION ASIA PACIFIC
                             TECHNICAL SPECIFICATION
                                       FOR
                                DACOM DTH PAYLOAD
                                   REVISION B


                                   Issue: 4.0

                             Revised: June 23, 1997




  Signed:                                                       Date:
  On behalf of Orion Network Systems, Inc.


  Signed:                                                       Date:
  On behalf of DACOM Corporation


<PAGE>





                          COMMERCIAL - IN - CONFIDENCE




Exhibit B Revision History

1/11/97           Rev -

2/12/97           Rev A    Pages: 3,4,6,11

6/23/97           Rev B






<PAGE>









                                    Exhibit C
                              Form Letter of Credit










<PAGE>




   [Irrevocable Standby Letter of Credit to be issued by DACOM CORP.'s bank to
                            ORION ASIA PACIFIC CORP.]

                      IRREVOCABLE STANDBY LETTER OF CREDIT


                                 Issuance Date:
                                 Credit Number:


Dear Sirs:

1.   [Name of issuing Bank] (the "Bank") hereby  establishes,  in your favor, at
     the  request  and for the account of DACOM  CORP.,  the Bank's  IRREVOCABLE
     STANDBY  LETTER OF CREDIT NO. ____ (this "Letter of Credit"),  in an amount
     not to exceed United States Dollars  (________USD)  (such amount, as it may
     be reduced from time to time in  accordance  with  Section 3 hereof,  being
     called the "Maximum Drawing Amount"). This Letter of Credit is being issued
     pursuant to the Joint  Investment  Agreement  dated as of November 11, 1996
     (the "Agreement") and the subsequent amendments thereto between DACOM CORP.
     and ORION ASIA PACIFIC CORP. This Letter of Credit is effective immediately
     and will expire at 4:00 p.m., New York time, on the earlier of (a) the date
     (the "Surrender Date") upon which ORION ASIA PACIFIC CORP.  presents to the
     Bank a certificate  in the form of Annex A hereto or (b)  ___________  (the
     "Expiry  Date") (the earlier of the Surrender Date or the Expiry Date being
     referred to herein as the "Termination Date").

2.   The Bank hereby irrevocably  authorizes ORION ASIA PACIFIC CORP. to draw on
     the Bank, in accordance with the terms and conditions hereinafter set


<PAGE>



     forth, an amount not in excess of the Maximum Drawing Amount on the date of
     such drawing (the "Date of Drawing").

3.   The Maximum Drawing Amount shall be modified from time to time as follows:

     (a)  upon payment by the Bank of a drawing  hereunder,  the Maximum Drawing
          Amount  applicable to each Date of Drawing  subsequent to such payment
          shall be automatically reduced by an amount equal to the amount of the
          drawing so paid.

4.   Funds under this Letter of Credit are available to ORION ASIA PACIFIC CORP.
     against  presentation of a draft of ORION ASIA PACIFIC CORP. in the form of
     Annex B hereto and a  certificate  signed by ORION ASIA PACIFIC  CORP. in a
     form of Annex C hereto.  Each such draft and certificate shall be dated the
     date of  presentation  and  shall be  presented  at the  Bank's  office  at
     [address in New York,  U.S.A.]  (Telecopier No. ). The Bank agrees that, so
     long as this Letter of Credit is in effect,  it will maintain an office in,
     or an arrangement reasonably  satisfactory to ORION ASIA PACIFIC CORP. with
     a paying bank having an office in the United States where such presentation
     may be made. The aforesaid  drafts and  certificates  shall have all blanks
     appropriately  completed,  shall be signed by a person  purporting to be an
     authorized  representative of ORION ASIA PACIFIC CORP., and shall be either
     in the form of a letter or a communication  by telecopier  delivered to the
     Bank. Any  communication by telecopier  pursuant to which a drawing is made
     hereunder shall be promptly confirmed to the Bank in writing.  However, the
     Bank shall  have no  responsibility  or  liability  for ORION ASIA  PACIFIC
     CORP.'s failure to confirm any drawing made by telecopier in writing or for
     any  discrepancies  that may  exist  between  the  documents  delivered  by
     telecopier and ORION ASIA PACIFIC CORP.'s written confirmation of same.


<PAGE>



5.   The Bank hereby agrees that all drafts drawn under the terms of this Letter
     of Credit will be duly honored by the Bank upon delivery,  or  transmission
     by  telecopier  (promptly  confirmed  in  writing),m  of the  draft and the
     certificate as specified in Section 2 and if presented (by such delivery or
     transmission) at our aforesaid office on or before 4:00 p.m. New York time,
     on the  Termination  Date. If a drawing is made by ORION ASIA PACIFIC CORP.
     hereunder at or prior to 11:00 a.m.,  New York time,  on a Business Day (as
     hereinafter  defined),   and  provided  that  such  draft  and  certificate
     presented  in  connection  therewith  conform  to the terms and  conditions
     hereof,  payment  shall  be made of the  amount  specified  in  immediately
     available  funds  not later  than 4:00  p.m.,  New York  time,  on the same
     Business  Date. If a drawing is made by ORION ASIA PACIFIC CORP.  hereunder
     after  11:00  a.m.,  New York  time,  and  provided  that  such  draft  and
     certificate  presented  in  connection  therewith  confirm to the terms and
     conditions  hereof,  payment  shall  be made  of the  amount  specified  in
     immediately available funds not later than 1:00 p.m., New York time, on the
     next Succeeding Business Date. Payment under this Letter of Credit shall be
     by wire transfer of immediately available funds to the account specified in
     the draft. As used in this Letter of Credit,  "Business Day" shall mean any
     day, other than a Saturday,  Sunday or other day on which  commercial banks
     in New York, United States are authorized by law to close.

6.   Upon receipt of a draft and  certificate  which are not in conformity  with
     terms and conditions of this Letter of Credit,  the Bank will promptly (and
     in any event  within one Business  Day of such  receipt)  notify ORION ASIA
     PACIFIC CORP. of such nonconformity and the reason therefor.

7.   Multiple drawings may be made hereunder.


<PAGE>



8.   Only  ORION ASIA  PACIFIC  CORP.  may make  drawings  under this  Letter of
     credit. Upon payments as provided in Section 5 of the amount specified in a
     draft hereunder, the Bank shall be fully discharged of its obligation under
     this Letter of Credit with respect to such draft.

9.   Should  the  Expiry  Date be a date  prior to the  time in  which  payments
     covered by this Letter of Credit could  potentially be due from DACOM CORP.
     under the Agreement,  then at least 30 days prior to the Expiry Date,  this
     Letter of Credit shall be replaced with a substitute Letter of Credit in an
     amount equal to the Maximum Drawing Amount. If it is not so replaced,  then
     ORION ASIA PACIFIC CORP. may draw upon this Letter of Credit in full.

10.  To the extent not inconsistent  with the express terms hereof,  this Letter
     of Credit  shall be  governed  by the  Uniform  Customs  and  Practice  for
     Documentary  Credits  (1993  revision)  International  Chamber of  Commerce
     Publication No. 500.  Communications  with respect to this Letter of Credit
     shall be in  writing  or  shall  be  transmitted  by  telecopier  (promptly
     confirmed in writing) and shall be addressed to the Bank at [address in New
     York,  U.S.A.] and shall specifically refer to the number of this Letter of
     Credit.

11.  Any drawing under this Letter of Credit will be paid from the general funds
     of the  Bank and not  directly  or  indirectly  from  funds  or  collateral
     deposited  with or for the  account  of the Bank by or on  behalf  of DACOM
     CORP.,  or  pledged  with  or  for  the  account  of  the  Bank  will  seek
     reimbursement  for payments made pursuant to a drawing under this Letter of
     Credit only after such payments have been made.

12.  This Letter of Credit sets forth in full the Bank's  undertaking,  and such
     undertaking shall not in anyway be modified,  amended, amplified or limited
     by reference to any document,  instrument or agreement  referred to herein,
     except


<PAGE>



     only Annexes A, B, and C, and the notices referred to herein;  and any such
     reference  shall not be  deemed to  incorporate  herein  by  reference  any
     document, instrument, or agreement except as set forth above.

Very truly yours,

[ISSUING BANK]
By:


<PAGE>



                     [Where ORION ASIA PACIFIC CORP. DRAWS]
                                                                         ANNEX C
                             CERTIFICATE FOR DRAWING

The undersigned,  a duly authorized  representative of ORION ASIA PACIFIC CORP.,
as a beneficiary  under that certain  IRREVOCABLE  STANDBY  LETTER OF CREDIT No.
________,  dated [the Date of  Issuance],  established  by  [Issuing  Bank] (the
"Bank") (the "Letter of Credit"),  hereby certifies as follows:  A payment(s) in
the amount of US$_____  required to be made to ORION AISA PACIFIC CORP. by DACOM
CORP.  pursuant to the  Agreement  is  overdue.  [1.  Notwithstanding  the first
sentence  of  Section 9 of the Letter of  Credit,  the  Letter of Credit,  which
covers a payment in the amount of  US$__________  payable in the future by DACOM
CORP.  to ORION ASIA  PACIFIC  CORP.,  has not been  replaced  with a substitute
Letter of Credit.]

2.   The aggregate amount of the accompanying  draft does not exceed the Maximum
     Drawing Amount.

Capitalized  Terms used herein and not otherwise  defined  herein shall have the
meaning given to them in the Letter of Credit.

IN WITNESS WHEREOF,  each of the undersigned has executed this Certificate as of
[Date].

ORION ASIA PACIFIC CORP.

By:
[Name and title of Authorized
Representative of ORION ASIA PACIFIC CORP.]


<PAGE>



[Irrevocable Standby Letter of Credit to be issued by ORION ASIA PACIFIC CORP.'s
                              bank to DACOM CORP.]

                      IRREVOCABLE STANDBY LETTER OF CREDIT


                                 Issuance Date:
                                 Credit Number:




Dear Sirs:

1.   [Name of issuing Bank] (the "Bank") hereby  establishes,  in your favor, at
     the  request and for the account of ORION ASIA  PACIFIC  CORP.,  the Bank's
     IRREVOCABLE STANDBY LETTER OF CREDIT NO. ____ (this "Letter of Credit"), in
     an amount not to exceed United States Dollars  (________USD)  (such amount,
     as it may be reduced from time to time in accordance with Section 3 hereof,
     being called the "Maximum Drawing Amount").  This Letter of Credit is being
     issued pursuant to the Joint Investment  Agreement dated as of November 11,
     1996 (the "Agreement") and the subsequent  amendments thereto between DACOM
     CORP.  and ORION ASIA  PACIFIC  CORP.  This  Letter of Credit is  effective
     immediately  UPON  RECEIPT BY THE [Name of bank] of a payment in the amount
     of the Maximum  Drawing  Amount for further  credit to the account of ORION
     ASIA PACIFIC CORP.  (Account No.  _________)  and will expire at 4:00 p.m.,
     Seoul  time,  on the  earlier of (a) the date (the  "Surrender  Date") upon
     which DACOM CORP. presents to the Bank a certificate in the form of Annex A
     hereto


<PAGE>



     or (b) 31 August 1999 (the  "Expiry  Date") (the  earlier of the  Surrender
     Date or the  Expiry  Date  being  referred  to herein  as the  "Termination
     Date").

2.   The Bank hereby irrevocably  authorizes DACOM CORP. to draw on the Bank, in
     accordance  with the terms and conditions  hereinafter set forth, an amount
     not in excess of the  Maximum  Drawing  Amount on the date of such  drawing
     (the "Date of Drawing").

3.   The Maximum Drawing Amount shall be modified from time to time as follows:

     (a)  upon payment by the Bank of a drawing  hereunder,  the Maximum Drawing
          Amount  applicable to each Date of Drawing  subsequent to such payment
          shall be automatically reduced by an amount equal to the amount of the
          drawing so paid.

4.   Funds under this  Letter of Credit are  available  to DACOM  CORP.  against
     presentation  of a draft of DACOM CORP. in the form of Annex B hereto and a
     certificate  signed by DACOM CORP.  in a form of Annex C hereto.  Each such
     draft and certificate  shall be dated the date of presentation and shall be
     presented at the Bank's office at [address in Seoul, Korea] (Telecopier No.
     ). The Bank agrees that, so long as this Letter of Credit is in effect,  it
     will maintain an office in, or an arrangement  reasonably  satisfactory  to
     DACOM  CORP.  with a paying  bank  having  an office  in Korea  where  such
     presentation may be made. The aforesaid drafts and certificates  shall have
     all blanks appropriately completed,  shall be signed by a person purporting
     to be an authorized  representative  of DACOM CORP., and shall be either in
     the form of a letter or a  communication  by  telecopier  delivered  to the
     Bank. Any  communication by telecopier  pursuant to which a drawing is made
     hereunder shall be promptly confirmed to the Bank in writing.  However, the
     Bank shall have no responsibility or liability for DACOM CORP.'s failure to
     confirm any


<PAGE>



     drawing made by  telecopier  in writing or for any  discrepancies  that may
     exist  between the  documents  delivered by  telecopier  and DACOM  CORP.'s
     written confirmation of same.

5.   The Bank hereby agrees that all drafts drawn under the terms of this Letter
     of Credit will be duly honored by the Bank upon delivery,  or  transmission
     by  telecopier  (promptly  confirmed  in  writing),m  of the  draft and the
     certificate as specified in Section 2 and if presented (by such delivery or
     transmission) at our aforesaid office on or before 4:00 p.m. Seoul time, on
     the Termination  Date. If a drawing is made by DACOM CORP.  hereunder at or
     prior  to  11:00  a.m.,  Seoul  time,  on a  Business  Day (as  hereinafter
     defined),  and  provided  that such  draft  and  certificate  presented  in
     connection  therewith conform to the terms and conditions  hereof,  payment
     shall be made of the amount  specified in immediately  available  funds not
     later than 4:00 p.m.,  Seoul time, on the same Business  Date. If a drawing
     is made by DACOM CORP. hereunder after 11:00 a.m., Seoul time, and provided
     that such draft and certificate  presented in connection  therewith confirm
     to the terms and  conditions  hereof,  payment  shall be made of the amount
     specified in immediately  available  funds not later than 1:00 p.m.,  Seoul
     time, on the next  Succeeding  Business Date. If a drawing is made by DACOM
     CORP.  hereunder  on a Business  Day but which day is a Saturday or Sunday,
     New York,  U.S.A.  time or other day on which commercial banks in New York,
     U.S.A.  are  authorized  by law to close and  provided  that such draft and
     certificate  presented  in  connection  therewith  conform to the terms and
     conditions  hereof,  payment  shall  be made  of the  amount  specified  in
     immediately available funds not later than 10:00 a.m., Seoul time, on a day
     after the next succeeding Business Day. Payment under this Letter of Credit
     shall be by wire  transfer of  immediately  available  funds to the account
     specified in the draft.  As used in this Letter of Credit,  "Business  Day"
     shall  mean any day,  other than a  Saturday,  Sunday or other day on which
     commercial banks in Seoul, Korea are authorized by law to close.


<PAGE>



6.   Upon receipt of a draft and  certificate  which are not in conformity  with
     terms and conditions of this Letter of Credit,  the Bank will promptly (and
     in any event within one Business Day of such receipt) notify DACOM CORP. of
     such nonconformity and the reason therefor.

7.   Multiple drawings may be made hereunder.

8.   Only  DACOM  CORP.  may make  drawings  under this  Letter of credit.  Upon
     payments  as  provided  in  Section 5 of the  amount  specified  in a draft
     hereunder,  the Bank shall be fully discharged of its obligation under this
     Letter of Credit with respect to such draft.

9.   Should the Expiry Date be a date prior to the time in which refunds covered
     by this Letter of Credit could  potentially  be due from ORION ASIA PACIFIC
     CORP. under the Agreement,  then at least 30 days prior to the Expiry Date,
     this Letter of Credit shall be replaced with a substitute  Letter of Credit
     in an amount equal to the Maximum Drawing Amount. If it is not so replaced,
     then DACOM CORP. may draw upon this Letter of Credit in full.

10.  To the extent not inconsistent  with the express terms hereof,  this Letter
     of Credit  shall be  governed  by the  Uniform  Customs  and  Practice  for
     Documentary  Credits  (1993  revision)  International  Chamber of  Commerce
     Publication No. 500.  Communications  with respect to this Letter of Credit
     shall be in  writing  or  shall  be  transmitted  by  telecopier  (promptly
     confirmed  in writing)  and shall be  addressed  to the Bank at [address in
     Seoul,  Korea] and shall specifically refer to the number of this Letter of
     Credit.

11.  Any drawing under this Letter of Credit will be paid from the general funds
     of the  Bank and not  directly  or  indirectly  from  funds  or  collateral
     deposited with or


<PAGE>



     for the account of the Bank by or on behalf of ORION ASIA PACIFIC CORP., or
     pledged  with or for the  account of the Bank will seek  reimbursement  for
     payments  made pursuant to a drawing under this Letter of Credit only after
     such payments have been made.

12.  This Letter of Credit sets forth in full the Bank's  undertaking,  and such
     undertaking shall not in anyway be modified,  amended, amplified or limited
     by reference to any document,  instrument or agreement  referred to herein,
     except only  Annexes A, B, and C, and the notices  referred to herein;  and
     any such reference  shall not be deemed to incorporate  herein by reference
     any document, instrument, or agreement except as set forth above.

Very truly yours,

[ISSUING BANK]

By:


<PAGE>



                                                                         ANNEX A

                                   [UNCHANGED]

                                                                         ANNEX B

                                   [UNCHANGED]



<PAGE>



                            [Where DACOM CORP. DRAWS]
                                                                         ANNEX C
                             CERTIFICATE FOR DRAWING

The  undersigned,  a  duly  authorized  representative  of  DACOM  CORP.,  as  a
beneficiary  under  that  certain  IRREVOCABLE  STANDBY  LETTER  OF  CREDIT  No.
________,  dated [the Date of  Issuance],  established  by  [Issuing  Bank] (the
"Bank") (the "Letter of Credit"), hereby certifies as follows:

1.   A refund(s) in the amount of US$_____ required to be made to DACOM CORP. by
     ORION  ASIA  PACIFIC  CORP.  pursuant  to the  Agreement  is  overdue.  [1.
     Notwithstanding  the first  sentence  of Section 9 of the Letter of Credit,
     the Letter of Credit, which covers a payment in the amount of US$__________
     potentially  payable  in the future by ORION ASIA  PACIFIC  CORP.  to DACOM
     CORP., has not been replaced with a substitute Letter of Credit.]

2.   The aggregate amount of the accompanying  draft does not exceed the Maximum
     Drawing Amount.

Capitalized  Terms used herein and not otherwise  defined  herein shall have the
meaning given to them in the Letter of Credit.

IN WITNESS WHEREOF,  each of the undersigned has executed this Certificate as of
[Date].

DACOM CORP.
By:
[Name and title of Authorized
Representative of DACOM CORP.]


<PAGE>




                          COMMERCIAL - IN - CONFIDENCE







                                    Exhibit F

                              Acceptance Test Plan.




<PAGE>




                                                                          HUGHES
                                                                   HS601 HP -XXX



--------------------------------------------------------------------------------

                                      ORION

--------------------------------------------------------------------------------


                              INTEGRATED TEST PLAN

                                   AUGUST 1996



                                ----------------
                                 Approved by HSC





                               ------------------
                                Approved by ORION





                               HUGHES PROPRIETARY

         This document contains proprietary information, and except with
         written permission of Hughes Space and Communications Company,
        such information shall not be published, or disclosed to others,
        or used for any purpose and the document shall not be duplicated
                              in whole or in part.

                                 Copyright 1996
                     Hughes Space and Communications Company
                                Unpublished Work


<PAGE>



                                 LIST OF FIGURES
<TABLE>
<CAPTION>

                                                                                                            Page

<S>                                                                                                          <C>
A-1 HS601 HP Integration and Test Documentation ..........................................................   iii
1-1 Top Level Acceptance Spacecraft Test Flow.............................................................   1-3
1-2 HS601 HP Acceptance Spacecraft Integration and Test Flow Details......................................   1-4
</TABLE>





                                 LIST OF TABLES
<TABLE>
<CAPTION>

                                                                                                            Page
<S>                                                                                                          <C>
3.1.1 HS601 HP Product Line Heritage / Qualification Matrix ...............................................  3-3
3.2 Unit Thermal Cycle and Thermal Vacuum Cycle Requirements ..............................................  3-6

4.  Subsystem and System Test Matrices ....................................................................  4-2
                  4.1 Mechanical ..........................................................................  4-2
                  4.2 Electrical Power Subsystem...........................................................  4-4
                  4.3 Attitude Control Subsystem...........................................................  4-6
                  4.4 Liquid Propulsion Subsystem (LPS) ...................................................  4-8
                  4.5 Xenon Ion Propulsion Subsystem (XIPS)................................................ 4-10
                  4.6 T&C Subsystem Digital Equipment ..................................................... 4-12
                  4.7 T&C Subsystem RF Hardware ........................................................... 4-13
                  4.8 Communications Subsystem............................................................. 4-14

5.2 In Orbit Test (JOT) Matrices...........................................................................  5-2
                  5.2.1 Electrical Power Subsystem ........................................................  5-2
                  5.2.2 Attitude Control Subsystem.........................................................  5-3
                  5.2.3 Communications Subsystem ..........................................................  5-4
                  5.2.4 Telemetry and Command Subsystem....................................................  5-5
</TABLE>


<PAGE>



                                TABLE OF CONTENTS
<TABLE>
<CAPTION>

                                                                                                             Page

<S>                                                                                                          <C>
ACRONYMS AND ABBREVIATIONS.................................................................... NOT NUMBERED

FOREWORD          .........................................................................................i
         A. Integrated Test Plan (ITP) and HS601 HP Integration and Test Documentation.....................   ii
         B. HS601 HP Product Line Test Philosophy..........................................................   iv
         C. Program-Specific Information for the _____________________  Spacecraft.........................   vi

1.  INTRODUCTION...........................................................................................  1-1
         1.1 Plan Scope ...................................................................................  1-2
         1.2 Test Program Flow.............................................................................  1-2
         1.3 Plan Content..................................................................................  1-2
         1.4 Customer Participation .......................................................................  1-2

2.  TEST PROVISIONS........................................................................................  2-1
         2.1 HS601 HP Product Line Test Philosophy.........................................................  2-2
         2.2 Test Requirements.............................................................................  2-2
                  2.2.1 Development Testing................................................................  2-3
                  2.2.2 Qualification Testing .............................................................  2-3
                  2.2.3 Acceptance Testing ................................................................  2-4
                  2.2.4 Life Testing.......................................................................  2-4
         2.3 Test Phase Descriptions.......................................................................  2-5
                  2.3.1 Unit Level.........................................................................  2-5
                  2.3.2 Subsystem Level ...................................................................  2-7
                  2.3.3 System Level ......................................................................  2-9
                  2.3.4 In Orbit Testing (IOT)............................................................. 2-14

3.  UNIT/EQUIPMENT LEVEL TESTING ..........................................................................  3-1
         3.1 Unit/Equipment Heritage I Qualification/Heritage..............................................  3-2
                  3.1.1 HS601 HP Product Line Heritage / Qualification Matrix .............................  3-3
         3.2 Unit Thermal Cycle and Thermal Vacuum Cycle Requirements .....................................  3-6
         3.3 Life Testing .................................................................................  3-9

4.  SUBSYSTEM AND SYSTEM LEVEL ACCEPTANCE TESTING .........................................................  4-1
         4. Test Matrices .................................................................................  4-2
                  4.1 Mechanical ..........................................................................  4-2
                  4.2 Electrical Power Subsystem...........................................................  4-4
                  4.3 Attitude Control Subsystem...........................................................  4-6
                  4.4 Liquid Propulsion Subsystem (LPS) ...................................................  4-8
                  4.5 Xenon ion Propulsion Subsystem (XIPS)................................................ 4-10
                  4.6 T&C Subsystem Digital Equipment ..................................................... 4-12
                  4.7 T&C Subsystem RF Hardware ........................................................... 4-13
                  4.8 Communications Subsystem............................................................. 4-14

5.  IN ORBIT TESTING (IOT).................................................................................  5-1
         5.1 Overview......................................................................................  5-2
         5.2 Tests.........................................................................................  5-2
                  5.2.1 Electrical Power Subsystem ........................................................  5-2
                  5.2.2 Attitude Control Subsystem.........................................................  5-3


<PAGE>



<CAPTION>

                  5.2.3 Communications Subsystem...........................................................  5-4
                  5.2.4 Telemetry and Command Subsystem....................................................  5-5
</TABLE>


<PAGE>






                          COMMERCIAL - IN - CONFIDENCE





                                    Exhibit G

                               Interference Tests.