EXHIBIT 10.43

             RESEARCH & DEVELOPMENT, MARKETING AND SERVICE AGREEMENT

         THIS  RESEARCH &  DEVELOPMENT,  MARKETING  AND SERVICE  AGREEMENT  (the
"Agreement")  is  entered  into as of 29th day of  June,  2000  (the  "Effective
Date"),  by and between  Motient  Satellite  Ventures  LLC, a limited  liability
company organized under the laws of the State of Delaware, ("Newco") and Motient
Services  Inc.  ("Motient  Services"),  a  wholly-owned  subsidiary  of  Motient
Corporation ("Motient Corporation") both of which are corporations  incorporated
under the laws of the State of Delaware.

         WHEREAS  Motient  Services  owns or otherwise  controls  the  Satellite
Network (as defined below) and related FCC licenses and other  resources,  which
it uses collectively to provide mobile satellite communications services for its
existing customers; and

         WHEREAS Newco wishes to use the Satellite  Network to conduct  research
and development  activities to develop and test new applications and explore new
business opportunities for the Satellite Network; and

         WHEREAS,  Newco is willing  and  desirous  of  purchasing,  and Motient
Services wishes to provide,  access and use of the Satellite Network (as defined
below)  for  research,  development  and  testing  purposes  on  the  terms  and
conditions set forth in this Agreement.

         NOW THEREFORE in  consideration  of the mutual covenants and agreements
set forth below, the Parties hereby agree as follows.

                                    ARTICLE I

                            DEFINITIONS AND SCHEDULES

1.1 Definitions. In this Agreement, the following words and terms shall have the
respective meanings assigned to them as follows:

"Affiliate" shall mean any entity which,  directly or indirectly,  controls,  is
controlled by, or under common control with, a Party hereto.

"Asset Sale Agreement" means that certain Asset Sale Agreement between Newco and
Motient Services of even date herewith.

"Commercialization  Agreement"  shall have the meaning assigned to it in Section
2.4.

"Effective  Date"  is as  defined  immediately  prior  to  the  recitals  at the
beginning of this Agreement.

"Emergency Preemption" shall have the meaning assigned to it in Section 3.5.

"Existing  Business" shall mean,  collectively,  the Satellite Network,  the FCC
License,  and all of the Existing  Satellite Service  agreements between Motient
Services and any third party.

"Existing   Satellite   Services"  shall  mean,   collectively,   the  Satellite
Network-based communications services and applications that are within the scope
of  services  and  applications  provided,   directly  by  Motient  Services  or
indirectly  through  third party  resellers and other  intermediaries,  to third
parties as of the Effective Date, and any services or applications  that are (i)
reasonable  extensions  of the  services  and  applications  offered  by Motient
Services as of the Effective Date; and (ii) developed  independently  by Motient
Services  after the Effective  Date in the normal course of its business and not
arising out of the R&D Activities.

"FCC" shall mean the Federal Communications Commission.

"FCC  License"  means the  license  or  licenses  issued  by the FCC to  Motient
Services  authorizing use of the Satellite Network to provide Existing Satellite
Services within the Territory.

"Intellectual  Property  Rights"  mean any and all  franchise,  patents,  patent
qualifications,  copyrights, know-how, computer software, industrial designs and
drawings and general intangibles of like nature,  trade secrets,  licenses,  and
rights and filings with respect to the foregoing,  and all reissues,  extensions
and renewals thereof, but excluding  trademarks,  tradenames,  service marks and
service names.

"Investment  Agreement"  means  that  certain  Investment  Agreement  among  the
Investors, Newco and Motient Corporation dated June 22, 2000.

"Investors" shall have the meaning assigned to it in the Investment Agreement.

"Losses"  means all  demands,  losses,  claims,  actions  or  causes of  action,
assessments,  damages,  liabilities,  costs  and  expenses,  including,  without
limitation,   interest,   penalties   and   reasonable   attorneys'   fees   and
disbursements.

"Motient  Derivative Works" means any Technology that is developed or created by
or for Newco in connection with the R&D Activities, including without limitation
any  Technology  developed or created for Newco by Motient  Services  during the
course  of  providing  the R&D  Services  for  Newco,  but which  constitutes  a
modification or derivative work of any Motient Technology.

"Motient Services" means Motient Services Inc. and its successors and assigns.

"Motient Technology" means any Technology that is developed or created by or for
Motient Services and/or its Affiliates prior to the Effective Date, or after the
Effective Date but independently of the R&D Activities.

"Newco" means Motient Satellite Ventures LLC, and its successors and assigns.

"Newco  Takeover"  means  Newco's  acquisition  of  the  Existing  Business,  as
contemplated by the Asset Sale Agreement.

"Newco  Technology"  means any Technology  other than a Motient  Derivative Work
that is  developed  or  created  by or for  Newco  in  connection  with  the R&D
Activities, including without limitation any Technology developed or created for
Newco by Motient  Services  during the course of providing  the R&D Services for
Newco.

"New Satellite  Services" shall mean collectively,  the Satellite  Network-based
communications   services   (excluding  the  Existing  Satellite  Services)  and
constituting  new  applications  of the  Satellite  Network  developed  by Newco
pursuant  to the  R&D  Activities  including  without  limitation  fixed  mobile
satellite  services,  mobile  satellite  services,  and  voice,  video  and data
applications  that,  in each such case,  are  different  than  those  offered by
Motient Services as of the Effective Date,  excluding,  however, any services or
applications  that  are both  (i)  reasonable  extensions  of the  services  and
applications  offered by Motient  Services as of the  Effective  Date;  and (ii)
developed  independently  by Motient  Services  after the Effective  Date in the
normal course of its business and not arising out of the R&D Activities.

"Parent  Conversion" means the exchange or conversion of interests in Newco held
by one or more  Investors  into  shares of Motient  Corporation's  common  stock
pursuant to the provisions of the Investment Agreement.

"Party" means Newco or Motient Services.

"Power and Bandwidth  Agreement"  shall mean any agreement with a term in excess
of one (1) year  between  Motient  Services  and a third  party  that  obligates
Motient  Services  to commit to provide  both a  specified  amount of  satellite
transmission  power and a  specified  amount  of  bandwidth,  thereby  depleting
available Satellite Network power and bandwidth capacity.

"Proprietary Information" shall have the meaning assigned to it in Section 9.1.

"R&D Activities" shall have the meaning assigned to it in Section 2.1.

"R&D Services" means, collectively, the Services provided by Motient Services to
Newco to support Newco's R&D Activities, as specified in Section 4.1, and in the
R&D Support Plan to be developed pursuant to Section 4.1.

"Satellite Network" shall mean the satellite-based communications network owned,
leased or  otherwise  controlled  by, and  operated by,  Motient  Services,  and
consisting of the flight satellite,  certain earth stations,  gateways and other
ground  elements,  control  systems  including  telemetry,  tracking and control
systems and network operations centers,  and the related hardware,  software and
networking  resources  which are used  collectively  to  provide  the  Satellite
Services.  The Satellite  Network shall  automatically  include any additions or
modifications to the Satellite  Network made from time to time during the normal
course of Motient Service's business.

"Satellite  Services" shall mean collectively the New Satellite Services and the
Existing Satellite Services.

"Service Fee" shall have the meaning assigned to it in Article V.

"Service Payment Date" shall have the meaning assigned to it in Article V.

"Services"  includes  the R&D  Services  and the Support  Services  provided by
Motient Services to Newco pursuant to this Agreement.

"Support  Services"  shall mean the  services  provided by Motient  Services to
operate and maintain the Satellite  Network,  and any uplink  equipment or other
resources provided by Motient Services to Newco pursuant to this Agreement.

"Technology" means any software components including source code and object code
versions  thereof,  any  documentation,  reports,  analyses or other  printed or
recorded  materials,  whether  in  written,  electronic  or  other  format,  any
hardware,  any  graphics,  audio  or video  objects,  images,  photos,  artwork,
designs, concepts, inventions, methods, ideas, processes, and any other creative
works of authorship.

"Term" shall have the meaning assigned to it in Section 11.1.

"Territory"  is the area within  which  Motient  Services is licensed to use the
Satellite  Network to provide  Existing  Satellite  Services,  which,  as of the
Effective Date includes the United States, Puerto Rico, the U.S. Virgin Islands,
and U.S.  coastal  waters up to 200 miles on or over  ocean  areas  outside  the
territory of any foreign country.

1.2  Schedules.  The following  Schedules are annexed to this  Agreement and are
incorporated  into  this  Agreement  by  reference  and are to be a part of this
Agreement:

                  Schedule A        -       Facilities Requirements
                  Schedule B        -       Compensation for Services



                                   ARTICLE II

                         ACCESS RIGHTS AND RESTRICTIONS

2.1 Access and Use Rights.

Motient  Services hereby grants to Newco,  for the Term of this  Agreement,  the
non-transferable (except in accordance with Article XIV) right to access and use
the Satellite  Network solely for purposes of conducting  technical,  regulatory
and  commercial  research and  development  of New Satellite  Services (the "R&D
Activities").  During the Term of this  Agreement  and  subject to the terms set
forth herein,  Motient  Services agrees that Newco's right to access and use the
Satellite  Network for conducting  the R&D  Activities  will be exclusive in the
respect that Motient  Services will not provide,  or offer to provide,  Services
(or services that are substantially  similar to the Services) to any third party
for the  purpose  of  assisting  such third  party in  conducting  research  and
development of New Satellite  Services.  Motient  Services  further agrees that,
during the Term of this Agreement,  it shall not grant,  or offer to grant,  the
right to promote,  market,  commercialize or offer New Satellite Services to any
other party.

2.2 Allocation of Capacity.

Motient  Services  agrees to provide Newco with up to 1.25 MHz of bandwidth,  in
such channel  configuration  or  configurations  as the parties  shall  mutually
agree,  to enable  Newco to  conduct  the R&D  Activities  contemplated  by this
Agreement.  Unless  otherwise  agreed by the  parties,  Motient  Services  shall
provide a minimum of 6 kHz of bandwidth to Newco.  The  bandwidth to be provided
by Motient  Services shall be in at least one of Motient  Services'  Continental
United States ("CONUS") satellite beams. Subject to the terms of this Agreement,
Motient  Services shall also consider the feasibility of providing  bandwidth in
additional  (or  substitute)  CONUS beams.  Motient  Services  shall provide the
foregoing  bandwidth  to Newco at power  levels  to be  mutually  agreed  by the
parties, in light of Newco's R&D Activities and subject to the  non-interference
provisions and other terms of this Agreement.

Newco  agrees to use its  commercially  reasonable  efforts  to  advise  Motient
Services in writing at least sixty (60) days in advance of the beams in which it
may request  channels.  Newco agrees that Motient Services reserves the right to
plan the use of the satellite  capacity by balancing the  deployment of channels
and of capacity  purchased by Motient Services' other customers.  Once a channel
is activated pursuant to the foregoing provisions,  it shall remain active until
Newco  informs  Motient  Services  that  its use of such  channel  is no  longer
required.  Motient Services' obligations under this Section 2.2 shall be subject
to the limitations of Section 2.3.

2.3 Excess Capacity.

Newco's  right to access and use the  Satellite  Network shall be subject at all
times  to  Motient  Services'  right to use the  Satellite  Network  to  provide
Existing Satellite Services. Newco's right of access and use shall be limited to
use of excess  Satellite  Network  capacity not required by Motient  Services to
provide the Existing Satellite Services.  Newco acknowledges and agrees that the
Satellite Network capacity required to provide the Existing  Satellite  Services
may increase during the Term of this Agreement,  thereby resulting in a decrease
of the excess capacity  available to Newco to conduct its R&D Activities.  Newco
agrees that Motient Services shall have no liability to Newco as a result of any
such decrease in excess capacity.  Motient  Services  reserves the right, in its
sole  discretion,  to deal with all matters  relating to the Satellite  Network,
including without  limitation the operation and allocation of satellite capacity
among  all of its  services  and  customers,  except as  otherwise  agreed to in
Section 2.1.

During the Term,  Motient  Services  shall provide Newco with  reasonable  prior
written notice of any new Power and Bandwidth  Agreements that Motient  Services
proposes  to enter into with any third  party  ("Proposed  Contract").  If Newco
reasonably  determines  that the Proposed  Contract  materially  interferes with
Newco's rights under this Agreement, Newco shall have fifteen (15) days from the
receipt  of such  notice to notify  Motient  Services  of its  objection  to the
Proposed Contract. If Newco fails to provide Motient Services with notice of its
objection  within said  fifteen  (15) day period,  Newco shall be deemed to have
agreed that Motient Services may enter into the Proposed Contract.  In the event
of an objection by Newco as provided  above within said fifteen (15) day period,
Motient Services shall not enter into the Proposed Contract.

2.4 Access Restrictions.

Except to the extent provided for in any Commercialization  Agreement, Newco may
not use the  Satellite  Network for any purpose  other than  conducting  the R&D
Activities.   Without  limiting  the  preceding  sentence,  Newco  is  expressly
prohibited from using the Satellite Network to provide  communications  services
for use in its  ongoing  business  activities  or for the  benefit  of any third
party. Newco may authorize third parties to access and use the Satellite Network
for purposes of assisting Newco to conduct the permitted R&D Activities,  but is
otherwise prohibited from permitting any third party to gain access to or use of
the  Satellite  Network  for any  other  reason,  except  as  authorized  by the
Commercialization  Agreement  (as  defined  below).  During  the  Term  of  this
Agreement,  Newco may promote,  market, and demonstrate any of the New Satellite
Services to third  parties,  but may not  provide,  enter into any  agreement to
provide, or otherwise commercialize,  the New Satellite Services until Newco and
Motient Services have first entered into a separate  network services  agreement
authorizing such activities (the "Commercialization Agreement"). Upon request by
Newco,  Motient Services and Newco will negotiate in good faith the terms of the
Commercialization  Agreement,  provided  that Motient  Services  agrees to offer
Newco terms for the  Commercialization  Agreement that are consistent with those
terms  Motient  Services  offers  generally  to  its  other  Satellite   Service
resellers, and Motient Services further agrees to provide such services at rates
no  less  favorable  than  those  provided  to any of  Motient  Services'  other
similarly  situated Satellite Service resellers that have purchased or committed
to purchase a like volume of Satellite Network power and bandwidth capacity from
Motient  Services.  Newco is prohibited from using the Satellite  Network in any
manner that will or is likely to disrupt or interfere with the Satellite Network
or Motient Service's ability to provide the Existing Satellite Services or both.
Newco further  agrees to comply with the facilities  requirements  applicable to
the Satellite Network, as described in Schedule A.

2.5 Continuing Rights of Motient Services.

Motient  Services shall retain all rights with respect to the Satellite  Network
not  expressly  granted  to  Newco  under  this  Agreement,  including,  without
limitation,  the rights:  (i) to use the Satellite  Network to provide  Existing
Satellite  Services for itself and for third parties in the normal course of its
business;  and (ii) to enter into new  agreements for the provision or resale of
Existing  Satellite  Services  to third  parties on any  basis.  Nothing in this
Agreement shall require Motient Services' to violate its obligations as a common
carrier  licensed  by the FCC with  respect to the  selling of capacity to third
party resellers.

                                   ARTICLE III

                           SATELLITE NETWORK SERVICES

3.1 Provision of Satellite Network Facilities.

Motient  Services  shall operate and maintain the Satellite  Network  during the
Term of this  Agreement  to the extent  required to provide  Existing  Satellite
Services.  Motient Services shall be responsible to provide, at its expense, all
hardware,  software, equipment and other resources necessary to provide, operate
and maintain the Satellite  Network to the extent required for Motient  Services
to provide the Existing Satellite Services.  Motient Services reserves the right
to determine, in its discretion, the particular hardware, software, equipment or
other  resources  to be used to provide,  operate  and  maintain  the  Satellite
Network, the location of any facilities, operations centers, and other resources
used in  connection  with the  Satellite  Network,  the  personnel to be used to
provide Support Services,  and any third party vendors,  service  providers,  or
other suppliers used to source any of the foregoing items.

3.2 Provision of R&D Equipment and Resources.

Newco shall be responsible to provide,  operate and maintain at its expense, any
hardware,  software,  equipment  and other  resources  additional  to that to be
provided  by Motient  Services  pursuant  to Section  3.1,  as and to the extent
required for Newco to conduct its R&D Activities and to develop and test any New
Satellite Services.  Motient Services shall have the right to review and approve
in advance any such additional hardware,  software, equipment or other resources
proposed by Newco to be integrated  with, or otherwise used in connection  with,
the  Satellite  Network  to ensure  that it will not unduly  interfere  with the
Satellite  Network  and/or the provision of Existing  Satellite  Services,  such
approval not to be unreasonably withheld.

3.3 Provision of Uplink Equipment.

Motient  Services  shall,  at its expense,  make  available to Newco  reasonable
access to Motient Services' existing  ground-based  uplink equipment required to
access and use the Satellite Network,  consistent with that used by, or provided
to,  power and  bandwidth  users of the  Existing  Satellite  Services.  Motient
Services  shall  designate  a  facility  for use by  Newco  to  conduct  the R&D
Activities. Motient Services will use commercially reasonable efforts to support
and maintain  such uplink  equipment  consistent  with Section 3.4 below.  Newco
shall,  at its  expense,  be  responsible  to provide,  operate and maintain any
additional uplink equipment required by Newco to conduct the R&D Activities.

3.4 Maintenance of Satellite Network.

Motient  Services  shall use  commercially  reasonable  efforts to maintain  the
Satellite Network and any uplink equipment  provided by Motient Services in good
working condition.  Motient Services shall provide Newco with a telephone number
to be used to obtain  support for the Satellite  Network and to report  problems
and defects in the  Satellite  Network or uplink  equipment  provided by Motient
Services.  Motient Services will use commercially  reasonable efforts to correct
problems and defects in the Satellite Network or such uplink equipment  reported
by Newco  within a  reasonable  time.  Motient  Services  reserves  the right to
interrupt  Newco's access and use of the Satellite  Network in order for Motient
Services to perform  scheduled  maintenance  of the Satellite  Network.  Motient
Services shall provide Newco with reasonable  advance written notice of any such
scheduled maintenance.

3.5 Emergency Preemption or Suspension of Service.

Newco's use of the Satellite Network may be preempted,  interrupted or suspended
due to  conditions  or  reasons  beyond  Motient  Services'  reasonable  control
("Emergency  Preemption"),   including  but  not  limited  to:  (i)  maintenance
requirements or emergency conditions  experienced by Motient Services;  (ii) the
protection of Motient Services' personnel,  facilities or services; or (iii) the
provision of priority and preemptive  access to Motient  Services'  satellite as
required by the U.S. Coast Guard, the Federal Aviation  Administration  or other
governmental  agency to provide responsive  emergency support during any natural
or man-made disasters.

3.6 Notice to Newco of Suspension or Emergency Preemption of Service.

In the event of any Emergency Preemption, Motient Services shall notify Newco as
soon as practicable and shall use  commercially  reasonable  efforts to make the
Satellite  Network  available to Newco to conduct R&D  Activities  as quickly as
practicable.

                                   ARTICLE IV

                              R&D SUPPORT SERVICES

4.1 R&D Support Plan.

Motient  Services  agrees to  provide  Newco  with the  system  interfacing  and
engineering  support necessary for Newco to interface with the Satellite Network
as  required  for Newco to perform  its R&D  Activities  under  this  Agreement,
subject to the terms and conditions of this Agreement.  Within a reasonable time
after the Effective Date,  Motient Services and Newco shall develop and mutually
agree upon the details of an R&D support services plan (the "R&D Support Plan"),
identifying the consulting, engineering, technical and other personnel and other
resources  to be  provided  by  Motient  Services  in  support  of  Newco's  R&D
Activities, as well as identifying any third party consultants, engineers and/or
other  third  party  resources  that Newco  will  engage to assist it in its R&D
Activities.  Motient  Services  will provide Newco with  additional  support for
Newco's R&D  Activities as and when  requested by Newco,  to the extent  Motient
Services has the  personnel  required to provide such  support,  and,  except as
provided in Schedule B, such support shall be provided without additional charge
to  Newco.  The  parties  agree  that any third  party  consultants  or  service
providers  engaged by Newco to assist Newco in R&D  Activities  shall execute an
appropriate   non-disclosure  or  confidentiality   agreement  to  preserve  the
confidentiality of Newco's R&D Activities. The R&D Support Plan shall specify in
detail the quantity and type of personnel  resources  and other  resources to be
provided by Motient  Services in order for Newco to conduct its R&D  Activities,
and the  schedule  specifying  when such  resources  will be  required.  Motient
Services shall make the resources specified in the R&D Support Plan available to
Newco in accordance  with such  schedule.  The R&D Support Plan shall be updated
periodically  during  the Term of this  Agreement,  as  reasonably  required  to
support  Newco's  R&D  Activities.  Newco  shall  have  complete  discretion  to
determine  the  scope  and  level of R&D  Activities  in which it may  choose to
engage, to the extent not inconsistent with this Agreement.

4.2 Testing Process.

Motient  Services  agrees  to  make  reasonable  configuration  changes  to  the
Satellite  Network as required to support  Newco's R&D  Activities in accordance
with the following process, provided such changes are conducted in a manner that
will not adversely affect the Existing Satellite Services.  Prior to undertaking
any R&D Activities that will require any such configuration change, or that will
or may adversely affect the Satellite  Network and/or Motient  Service's ability
to provide  Existing  Satellite  Services,  Newco shall provide Motient Services
with  a  test  plan  set  forth  in  writing   which   describes  the  requested
configuration  change,  the testing to be undertaken,  the proposed schedule for
such testing,  the risks to the Satellite Network and/or the Existing  Satellite
Services imposed by such testing, the steps to be taken to eliminate or mitigate
the risks,  and any other  pertinent  information  regarding  the  proposed  R&D
Activities  (each  a "Test  Plan").  Motient  Services  will  have a  reasonable
opportunity to review the Test Plan prior to  commencement  of testing.  Motient
Services may require changes in the Test Plan before approving the Test Plan, if
Motient Services  reasonably believes that such changes are required to minimize
risk to the Satellite  Network and/or its ability to provide Existing  Satellite
Services.  Notwithstanding the foregoing, Motient Services reserves the right to
disapprove  any proposed  Test Plan and to prohibit any proposed  testing in the
event Motient  Services  reasonably  believes that such testing poses a material
risk to the Satellite Network,  and/or its ability to provide Existing Satellite
Services.

4.3 Project Management.

Each Party shall  appoint a project  manager  ("Project  Manager")  who shall be
responsible to oversee such Party's activities and  responsibilities  under this
Agreement  and to  communicate  with the  Project  Manager of the other Party to
coordinate  their  respective  activities  hereunder,  and to resolve issues and
disputes that arise during the Term of this Agreement. Each Party may change its
Project Manager upon prior written notice to the other Party.

4.4 Dispute Resolution.

The parties shall attempt to resolve any disputes  arising out of or relating to
this Agreement by negotiations  between the party's respective Project Managers.
In the event that the Project  Managers  are unable to resolve any such  dispute
within  a  reasonable   time,  such  dispute  shall  be  escalated  in  turn  to
successively higher level managers of each party who will attempt to resolve the
dispute  through  negotiation.  If, despite such attempts,  such dispute remains
unresolved  after a period  of sixty  (60) days  from the date  first  raised by
either  Project  Manager,  then such  dispute  shall be  submitted  to final and
binding arbitration before JAMS/ENDISPUTE  ("JAMS"), or its successor,  pursuant
to the United States  Arbitration Act, 9 U.S.C.  Sec. 1 et seq. Either party may
commence  the  arbitration  process  called  for in this  agreement  by filing a
written demand for arbitration  with JAMS,  with a copy to the other party.  The
arbitration  will  be  conducted  in  accordance  with  the  provisions  of JAMS
Streamlined  Arbitration Rules and Procedures in effect at the time of filing of
the demand for arbitration.  Any such arbitration shall take place at a mutually
agreed location within the Washington,  D.C. metropolitan area. The parties will
cooperate  with JAMS and with one another in selecting an  arbitrator  from JAMS
panel of neutrals,  and in scheduling the arbitration  proceedings.  The parties
covenant that they shall  participate in the arbitration in good faith, and that
they shall share equally in its costs. The provisions of this Section 4.4 may be
enforced  by any  Court  of  competent  jurisdiction.  The  costs  of  any  such
arbitration  shall be shared  equally by the parties;  provided  that each party
shall bear the costs of preparing and presenting  its own case. The  arbitrators
shall have no power to award any punitive damages.  The arbitrator's award shall
be  final  and  binding,   and  may  be  enforced  in  any  court  of  competent
jurisdiction.  The  results  of any  such  arbitration  shall  be  deemed  to be
Proprietary Information under this Agreement.

                                    ARTICLE V

                                     PAYMENT

On or before  July 14,  2000,  Newco  shall pay to  Motient  Services a one-time
service fee in the amount of Twenty Million Dollars  ($20,000,000) (the "Service
Fee") (the date upon which such  payment is made shall be the  "Service  Payment
Date").  Such payment  shall be made by wire transfer of  immediately  available
funds to an account designated in writing by Motient Services.  Motient Services
shall  have no  obligation  to  provide  any  Satellite  Services  or any  other
Services,  or to otherwise  fulfill any of its obligations  under this Agreement
prior to the Service  Payment Date. The Service Fee  represents  full payment in
advance for all support and other services to be provided by Motient Services to
Newco pursuant to this Agreement, except for those services requiring additional
payment,  as specified in Schedule B. Motient  Services  shall be responsible to
pay any sales and use taxes or  similar  such taxes  levied or imposed  upon the
Services provided by Motient Services to Newco pursuant to this Agreement.

                                   ARTICLE VI

                              REGULATORY COMPLIANCE

6.1 Responsibilities of Motient Services.

In  performing  the Services and  fulfilling  its other  obligations  under this
Agreement,  Motient Services shall comply with all applicable laws, regulations,
rules,  ordinances  and other legal and  administrative  obligations  applicable
thereto,  including without  limitation the terms of any applicable FCC License.
Motient  Services shall be responsible to secure and maintain in effect,  at its
expense,  and shall  use all  commercially  reasonable  efforts  to  secure  and
maintain  all  licenses,  permits,  rights-of-way,   approvals,  and  any  other
arrangements  necessary for providing,  operating and  maintaining the Satellite
Network  and  for  providing  Existing  Satellite  Services,  including  without
limitation  all  required  FCC  or  other  governmental  licenses,   permits  or
approvals.

6.2 Responsibilities of Newco.

In conducting the R&D Activities and fulfilling its other obligations under this
Agreement,  Newco shall comply with all  applicable  laws,  regulations,  rules,
ordinances and other legal and administrative  obligations  applicable  thereto,
including  without  limitation the terms of any  applicable  FCC License.  Newco
shall be  responsible  to secure and  maintain in effect,  at its  expense,  all
licenses,  permits,   rights-of-way,   approvals,  and  any  other  arrangements
necessary  for  carrying  out the R&D  Activities  and for using  the  Satellite
Network to research, develop and test New Satellite Services,  including without
limitation  all  required  FCC  or  other  governmental  licenses,   permits  or
approvals,  but excluding  those items which Motient  Services is responsible to
obtain as  specified in Section  6.1.  Newco shall confer with Motient  Services
prior to obtaining any additional licenses, permits, rights-of-way, approvals or
other  arrangements  for which it is responsible,  to allow Motient  Services to
coordinate  such  activities with its own regulatory  compliance  program.  Upon
request  by  Newco,   Motient  Services  shall  provide  Newco  with  reasonable
cooperation and support to assist Newco in obtaining any such licenses, permits,
rights-of-way,  approvals  or other  arrangements,  and, if  requested by Newco,
Motient Services shall obtain any such license, permit,  right-of-way,  approval
or other  arrangement in its own name;  provided that Newco shall be responsible
to  reimburse  Motient  Services for any costs  incurred by it to obtain  and/or
maintain any FCC licenses,  permits,  and approvals that would  otherwise be the
responsibility  of Newco under this Section 6.2.  Newco shall use the  Satellite
Network only for lawful  purposes and in compliance  with all applicable  rules,
policies and  regulations  of Motient  Services,  the FCC and those of any other
federal, state, or local governmental agencies.

6.3 Relationship to FCC.

The Satellite  Network and any Services  provided by Motient Services under this
Agreement,  are  subject to the  continuing  approval of the FCC.  Newco  hereby
consents to the filing of this  Agreement with the FCC if required by applicable
law and  regulation.  Motient  Services  shall advise Newco in advance of such a
filing.  The Parties will  cooperate to seek such  approvals  and  coordination,
provided that Motient  Services will be solely  responsible  for all FCC matters
relating to the Satellite Network and the Existing Satellite Services, including
but not limited to frequency coordination.

6.4 Notification Regarding FCC Actions.

Each party  shall use  commercially  reasonable  efforts to keep the other party
apprised of its licensing and regulatory activities with respect to the FCC, the
status of any  filings  made by such party with the FCC,  and of any  actions or
rulings  of the FCC of which  such  party is aware,  to the  extent  such  party
reasonably   determines  that  any  of  the  foregoing  materially  affects  the
activities  of the other party with  respect to this  Agreement,  the  Satellite
Network,  or the  R&D  Activities  and  other  activities  contemplated  by this
Agreement.

                                   ARTICLE VII

                      ADDITIONAL OBLIGATIONS OF THE PARTIES

7.1 Ethical Responsibilities of the Parties.

Motient  Services and Newco shall each refrain  from doing  anything  that would
tend to reflect  adversely  upon, or in any manner injure the  reputation of the
other (or their  respective  parent entities and affiliates) or adversely affect
the  other,  or,  in the case of  Motient  Services,  adversely  affect  Motient
Services' status as a licensed common carrier, except that a Party's enforcement
of its rights and  performance of its duties and  obligations  contained  herein
shall not be deemed a violation of this Section 7.1.

7.2 Insurance.

Until the Newco Takeover occurs,  Motient Services is responsible to ensure that
it is covered at all times by  insurance  consistent  with levels of coverage in
effect as of the Effective Date.

                                  ARTICLE VIII

                              INTELLECTUAL PROPERTY

8.1 Newco Technology.

Newco  shall  retain all right,  title and  interest  in and to any of the Newco
Technology  developed or created  during the course of this  Agreement by or for
Newco, including all Intellectual Property Rights therein. To the extent Motient
Services acquires any interest in the Newco Technology,  Motient Services hereby
assigns,  transfers and conveys to Newco all of its right, title and interest in
and to the Newco Technology, including all Intellectual Property Rights therein.

8.2 Motient Technology.

Motient  Services  shall  retain all  right,  title and  interest  in and to any
Motient  Technology  used by or  licensed  to Newco  during  the  course of this
Agreement,  including all  Intellectual  Property Rights therein.  To the extent
Newco  acquires any interest in the Motient  Technology,  Newco hereby  assigns,
transfers and conveys to Motient  Services all of its right,  title and interest
in and to the Motient  Technology,  including all  Intellectual  Property Rights
therein.

8.3 Motient Derivative Works.

Newco  shall  retain  all  right,  title  and  interest  in and  to any  Motient
Derivative  Works developed or created during the course of this Agreement by or
for Newco,  including  all  Intellectual  Property  Rights  therein,  subject to
Motient Service's continued ownership of any Motient Technology contained in any
such  Motient  Derivative  Work.  To the extent  Motient  Services  acquires any
interest in any Motient  Derivative  Works,  Motient  Services  hereby  assigns,
transfers  and conveys to Newco all of its right,  title and  interest in and to
the  Motient  Derivative  Works,  including  all  Intellectual  Property  Rights
therein,  but excluding any underlying Motient Technology  contained in any such
Motient Derivative Works.

8.4 License to Newco.

Motient  Services  hereby  grants  to  Newco a  non-exclusive,  non-transferable
(except in the event of an  assignment  of this  Agreement  in whole by Newco as
authorized in Article XIV), royalty-free license to use, reproduce,  modify, and
to distribute  internally,  but not to sublicense to third parties,  any Motient
Technology  that is needed  for Newco to  perform  the R&D  Activities.  Newco's
licensed rights to the Motient  Technology are restricted solely for the purpose
of conducting the R&D  Activities,  and for system  development,  deployment and
operations  activities  in the conduct of its own business and customer  service
pursuant to any Commercialization  Agreement.  Notwithstanding the foregoing, to
the extent  provided in any  Commercialization  Agreement,  Newco may sublicense
rights to use such Motient Technology to third parties to the extent required by
them to use any New  Satellite  Services  that  may be  provided  by  Newco.  In
addition,  in the event that the Asset Sale  Agreement is  terminated  due to an
event arising under  Section 8.8, 8.9 or 8.10 of the Asset Sale  Agreement,  the
license  granted  above in this  Section 8.4 shall be  modified as follows:  (i)
Newco's  licensed  rights  shall  be  limited  to that  portion  of the  Motient
Technology   that  is  actually   contained   in  a  Motient   Derivative   Work
("Incorporated  Motient  Technology);  (ii) Newco may thereafter use, reproduce,
and  modify  such  Incorporated  Motient  Technology,  and  may  distribute  and
sublicense such Incorporated  Motient Technology for any lawful purpose, so long
as such Incorporated Motient Technology at all times remains a part of a Motient
Derivative  Work;  (iii) Newco may  exercise  such  licensed  rights as modified
without  the  need  to  enter  into  any  Commercialization  Agreement;  (iv) as
modified,   such  licensed  rights  shall  be  perpetual,   notwithstanding  any
termination of this  Agreement;  and (v) as modified,  such license shall remain
transferable  in connection with an assignment of this Agreement as specified in
the first sentence of this Section 8.4.

8.5 Further Assurances.

Each  Party  will upon  request  of the other  Party,  and at the other  Party's
expense,  assist the other Party as reasonably  necessary with  applications for
trademarks,   patents,  copyrights  or  other  forms  of  intellectual  property
protection  with  respect to the  Technology  owned by or licensed to such other
Party  pursuant  to this  Agreement.  Each  Party  will  execute  any  documents
reasonably  requested  by the other  Party for the purpose of  establishing  its
right of  ownership  to such  Technology  without  the  need for any  additional
compensation.

                                   ARTICLE IX

                                 CONFIDENTIALITY

9.1 General.

Each Party  acknowledges  that during the course of this  Agreement  it may gain
access to confidential  information belonging to or relating to the other Party,
including  but  not  limited  to  any  business,   financial  and  technological
information   (collectively,   "Proprietary   Information")   which  Proprietary
Information  constitutes  valuable  assets and trade secrets of the other Party.
"Proprietary  Information" of Newco shall include information  regarding the R&D
Activities  to be  conducted  by Newco  under this  Agreement,  and the  results
thereof.  Accordingly, when a Party (the "Receiving Party") receives Proprietary
Information  from the other Party (the  "Disclosing  Party") the Receiving Party
shall,  both  during  the Term of this  Agreement  and for a period of three (3)
years following expiration or termination thereof:

     (a) keep secret and retain in strict confidence any Proprietary Information
received from the Disclosing Party;

     (b)  not   disclose  to  any  third  party  any   Proprietary   Information
received/from   the  Disclosing  Party  for  any  reason  whatsoever  except  as
authorized under this Agreement;

     (c) not disclose any Proprietary  Information  received from the Disclosing
Party to the  Receiving  Party's  and its  Affiliates'  employees,  except  on a
need-to-know basis; and

     (d)  not  make  use  of  any  Proprietary  Information  received  from  the
Disclosing  Party for its own  purposes  or for the  benefit of any third  party
except as authorized by this Agreement.

9.2 Requested or Required Disclosure.

Notwithstanding  Section 9.1, if the Receiving Party is requested or required to
disclose  Proprietary  Information of the Disclosing  Party pursuant to: (i) any
federal or state law or regulation;  or (ii) the order or request of any federal
or state court, or regulatory  entity or agency,  the Receiving Party shall: (A)
in  the  event  of a  request  for  such  Proprietary  Information  by a  court,
regulatory entity or agency,  use commercially  reasonable efforts to obtain the
written consent of the court or agency to maintain the  confidentiality  of such
Proprietary Information; (B) provide written notice to the Disclosing Party; and
(C) furnish only such portion of the  Proprietary  Information  as the Receiving
Party is legally required to disclose.

9.3 Disclosure to Third Parties.

Each  party  covenants  not to  divulge  Proprietary  Information  to any  third
parties,  except as set forth in Section 9.2, without  obtaining a nondisclosure
agreement  from such  party,  wherein  such  third  party  undertakes  to handle
Proprietary  Information  under  confidentiality  terms and  conditions  no less
restrictive than those set forth in this Agreement.

9.4 Exceptions.

The  obligations of this Article IX shall not extend to any  information  which:
(a) is in the public  domain;  (b) comes into the public domain through no fault
of the  parties or their  employees;  (c) is  already  lawfully  known,  free of
restrictions, to the Receiving Party at the time of its receipt; (d) is received
by the  Receiving  Party from a third  party who is not under an  obligation  of
confidence  with  respect  to  such  information;  (e)  is  known  or  developed
independently  of the disclosure by the Disclosing Party as can be proved by the
Receiving Party's  contemporaneous  business  records;  or (f) is required to be
disclosed by a government or regulatory agency, by court order or by law.

9.5 Events upon Termination.

Upon  any  expiration  or  termination  of this  Agreement,  or upon  demand  by
Disclosing  Party,  Receiving Party shall promptly return any documents or other
materials  containing  Proprietary   Information  of  Disclosing  Party  in  its
possession,  or shall certify to Disclosing  Party that such  documents or other
materials containing  Proprietary  Information have been destroyed,  except that
the Receiving  Party need not return or destroy any documents or other materials
containing Proprietary  Information consisting of Technology that is licensed to
the Receiving Party under a license which survives expiration or termination.

9.6 Injunction.

Both  parties  acknowledge  that  remedies  at law for breach of either  party's
obligations  under this  Article IX may be  inadequate,  that the  non-breaching
party may be irreparably harmed by any such breach, and that in the event of any
such  breach,  the  non-breaching  party shall be  entitled  to obtain  specific
performance or injunctive relief without a requirement to post bond.

                                    ARTICLE X

                         REPRESENTATIONS AND WARRANTIES

10.1 Representations and Warranties.

     (a) Motient Services represents and warrants to Newco as follows:

          (i) it has the  authority  to enter into and perform  this  Agreement;
     this Agreement when executed, will be legal, valid and binding upon it, and
     will be  enforceable  in  accordance  with  its  terms;  and it has made no
     misrepresentations  to the other party in connection with the  negotiation,
     execution, or performance of this Agreement; and

          (ii) the execution and performance of this Agreement does not and will
     not  violate  (x) the Series A and Series B 12 1/4%  Senior  Notes due 2008
     Indenture,  dated March 31, 1998, of Motient Holdings Inc.  ("Holdings") or
     (y) any other contract, obligation, or instrument held by it or to which it
     is a party,  or which is  binding  upon it,  including  terms  relating  to
     covenants not to compete and confidentiality obligations; and

          (iii) provided that Newco complies with its obligations  under Section
     6.2, the execution and  performance of this  Agreement by Motient  Services
     does not and will not  violate any  applicable  laws,  regulations,  rules,
     ordinances  and  other  legal  and  administrative  obligations  applicable
     hereto; and

          (iv) it  possesses  all  licenses  issued  by the FCC,  and all  other
     licenses,  permits,  franchisers  and  similar  authorizations,   that  are
     required for the  operation of the  Satellite  Network and for provision of
     Existing Satellite  Services as presently  conducted on the Effective Date,
     and the  ownership,  operation,  lease and  holding by it of the  Satellite
     Network  resources  (the  "Company   Permits").   Motient  Services  is  in
     compliance with the terms of the Company Permits.

     (b) Newco represents and warrants to Motient Services as follows:

          (i) it has the  authority  to enter into and perform  this  Agreement;
     this Agreement when executed, will be legal, valid and binding upon it, and
     will be  enforceable  in  accordance  with  its  terms;  and it has made no
     misrepresentations  to the other party in connection with the  negotiation,
     execution, or performance of this Agreement; and

          (ii) the execution and performance of this Agreement does not and will
     not violate any other contract,  obligation, or instrument held by it or to
     which it is a party, or which is binding upon it,  including terms relating
     to covenants not to compete and confidentiality obligations.

10.2 Disclaimer of Warranty.

EXCEPT AS  OTHERWISE  PROVIDED  IN THIS  AGREEMENT,  MOTIENT  SERVICES  MAKES NO
WARRANTY OR CONDITION,  EXPRESS OR IMPLIED,  REGARDING THE SATELLITE  NETWORK OR
ANY OTHER ITEM OF EQUIPMENT,  HARDWARE,  SOFTWARE OR ANY OTHER RESOURCE PROVIDED
BY MOTIENT SERVICES PURSUANT TO THIS AGREEMENT,  OR THE PROVISION OF ANY SERVICE
PROVIDED BY MOTIENT  SERVICES  PURSUANT  TO THIS  AGREEMENT,  INCLUDING  BUT NOT
LIMITED  TO  THE  IMPLIED  WARRANTIES  OF  MERCHANTABILITY  AND  FITNESS  FOR  A
PARTICULAR PURPOSE.

                                   ARTICLE xi

                              TERM AND TERMINATION

11.1 Term.

This  Agreement  shall commence on the Effective Date and shall remain in effect
for a period of three (3) years after the Effective  Date (the  "Term"),  unless
sooner  terminated in accordance  with Sections 11.3, or 11.4 hereof,  whichever
occurs first.

11.2 Suspension by Motient Services.

Motient Services may immediately suspend Newco's access to the Satellite Network
and the  provision  of any  Service to Newco  without any  liability  of Motient
Services  to Newco or to any  third  party  upon  the  occurrence  of any of the
following:

          (i) Newco's use of the  Satellite  Network or  performance  of the R&D
     Activities  is in violation of any statute or law or of any order,  rule or
     regulation of any court, agency or government authority; or

          (ii) Newco's use of the Satellite  Network or  performance  of the R&D
     Activities  is conducted in a manner that  materially  interferes  with the
     Satellite  Network and/or Motient Services' ability to provide the Existing
     Satellite Services.

Upon the occurrence of any such event,  Motient  Services shall use commercially
reasonable  efforts to provide  prior  written  notice to Newco and a reasonable
opportunity to cure prior to imposing any such suspension,  but Motient Services
reserves the right to suspend  access to the Satellite  Network and provision of
Services  to  Newco  immediately   without  prior  notice  if  Motient  Services
reasonably  believes  that it must act  immediately  to  protect  the  Satellite
Network and its ability to provide Existing  Satellite  Services and/or to avoid
violations  of law.  In  either  event,  access  to the  Satellite  Network  and
provision  of Service  shall be restored  upon cure by Newco of the event giving
rise to the suspension.

11.3 Termination upon Exercise of Newco Takeover.

This  Agreement  shall  automatically  terminate  on the date of  closing of the
transactions associated with the Newco Takeover.

11.4 Termination Option upon Sale of Existing Business to a Third Party.

If  Motient  Corporation  receives  an  Offer  (as  defined  in the  Asset  Sale
Agreement),  and if Newco  shall  not have  delivered  a Notice to  acquire  the
Satellite  Communications  Business  (as  defined in the Asset  Sale  Agreement)
within sixty (60) days after the Offer Notice Date (as defined in the Asset Sale
Agreement),  and if Motient Corporation or Motient Services elects to pursue the
Offer,  Motient Services shall so notify Newco in writing. If, after electing to
pursue  the  Offer,  the  transactions  contemplated  by the  Offer  fail  to be
consummated,  Motient  Services shall notify Newco in writing of such event,  as
well.  During the period  commencing  on the date of Newco's  receipt of Motient
Services'  notice of the  election  to pursue the Offer and ending on either (i)
the date of consummation of the transactions  contemplated by the Offer, or (ii)
the date of Newco's receipt of written notice that such transactions will not be
consummated  (whichever  applies),  Newco shall refrain from entering enter into
any new Satellite Service agreements with any third party as permitted under the
Commercialization  Agreement,  and from  taking  any action  that would  further
deplete  the  available  Satellite  Network  capacity  or  otherwise  materially
interfere with the  transactions  contemplated  by the Offer.  In the event such
transactions are consummated, Motient Services shall have the right, in its sole
discretion,  and without  consent of Newco,  to terminate  this  Agreement  upon
written notice to Newco and upon compliance with the requirements of Section 8.9
of the Asset Sale Agreement.

11.5 Events upon Termination.

Upon termination of this Agreement pursuant to Section 11.3 or 11.4, Newco shall
immediately  cease  all  access  and use of the  Satellite  Network,  and  shall
promptly,  but in no event less than thirty (30) days after termination,  return
to Motient Services any and all resources provided to Newco by Motient Services,
and remove all Newco Technology from Motient Services' premises and equipment.

                                   ARTICLE xiI

                             LIMITATION OF LIABILITY

12.1 Survival of Representations.

Notwithstanding  anything  to the  contrary  set  forth  in  Section  15.9,  all
representations  and warranties in or pursuant to this  Agreement  shall survive
until  two (2)  years  after  the  date of  expiration  or  termination  of this
Agreement.

12.2 Limitation of Liability.

Motient Services shall in no event be liable for:

          (i) Any Satellite Network service outage or failure; or

          (ii) Any decrease in the excess  capacity of the Satellite  Network or
     of the time  periods in which the  Satellite  Network is made  available to
     Newco to  conduct  the R&D  Activities  as a  result  of  expansion  of the
     Existing Satellite Services in the normal course of business and consistent
     with this Agreement; or

          (iii) The unauthorized access to, or alteration, theft, or destruction
     of  data  and/or   information   of  Newco  by  any  person  other  than  a
     subcontractor  or agent of Motient  Services,  whether through  accident or
     fraudulent  means or  devices,  whether  caused  by  interruption,  errors,
     defects, delays in operation or failure of the Service; or

          (iv) Any claim  arising  out of a breach in the privacy or security of
     communications  transmitted over Motient Services' facilities,  unless such
     breach is caused by Motient Services' willful misconduct; or

          (v) Any change required by any governmental authority to the Satellite
     Network or Motient Services'  facilities,  operations or procedures used in
     connection with the Satellite Network that renders the Satellite Network or
     any such facilities provided by Motient Services or Newco obsolete, or that
     requires Newco to make a material  modification  or alteration of the Newco
     Technology  to  remain  compatible  with  the  Satellite  Network  or  such
     facilities,  or that otherwise  adversely  affect the use or performance of
     the Newco Technology; or

          (vi) Any Loss  incurred  by  reason of or  incidental  to any delay or
     interruption  of the  Service,  other than a delay or  interruption  due to
     Motient Services' willful misconduct; or

          (vii)  Any  failure  by  Motient  Services,   after  exercise  of  all
     commercially reasonable efforts, to obtain and/or maintain any required and
     material FCC or other government approvals for the provision of the Service
     in the Territory;  or the issuance of an effective  final order by the FCC,
     or other government agency having jurisdiction, revoking or denying renewal
     of the mobile satellite services authorization granted to Motient Services.

12.3 Aggregate Damages.

The  Indemnifying   Party  shall  not  be  obligated  to  pay  any  amounts  for
indemnification  under  Article 13 hereof  until the  aggregate  indemnification
obligation  of such  Indemnifying  Party  hereunder  (and  under the Asset  Sale
Agreement)  exceeds  Five-Hundred  Thousand  Dollars  ($500,000) (the "Basket"),
whereupon  the  Indemnifying  Party  shall be liable for all  amounts  for which
indemnification  may  be  sought  which  exceed  $500,000.  Notwithstanding  the
foregoing,  in no event shall the  aggregate  liability  of Motient  Services to
Newco exceed the sum of (i) the aggregate fees  (including the Service Fee) paid
by Newco to Motient Services pursuant to this Agreement, (ii) the Purchase Price
(to the extent actually paid) as defined in the Asset Sale Agreement;  and (iii)
other amounts paid as  consideration  under any  agreements  delivered  pursuant
thereto (collectively,  the sum of (i), (ii) and (iii) constitute the "Liability
Cap").  The  Liability Cap will not apply to any claims made with respect to any
Loss arising as a result of a breach of this Agreement due to Motient  Services'
bad faith or willful misconduct, or to any Losses arising out of a breach of the
representation and warranty set forth in Section 10.1(a)(ii)(x). For purposes of
determining whether the aggregate indemnification  obligation of an Indemnifying
Party exceeds the Basket, the sum of all amounts previously  indemnified by such
Indemnifying  Party for Losses  arising under both this  Agreement and under the
Asset Sale Agreement,  and any agreements  delivered  pursuant  thereto shall be
used to make such determination.

12.4 Exclusive Remedy.

Indemnification  pursuant to Article 13 in accordance with this Article 12 shall
be the  sole  and  exclusive  remedy  for  any  breach  of the  representations,
warranties and covenants contained in this Agreement by either party, other than
claims  relating to fraud or  violations  of  securities  laws;  provided  that,
nothing in this Section 12.4 shall  prevent any party from  obtaining  equitable
relief in order to require the other party to perform its obligations hereunder.

12.5 Limitation of Liability for Motient Services' Suppliers.

To the  extent  that any  portion  of the  Services  or any  facilities  used in
connection  with the Satellite  Network are provided by any third party pursuant
to a separate  agreement  arrangement  between  Motient  Services and such third
party,  the  limitation  of liability  set forth in this Article 12 shall extend
fully to such third party.

                                  ARTICLE xiii

                                    INDEMNITY

13.1 Indemnification by Newco.

Newco shall  indemnify and hold Motient  Services  harmless from and against any
and all Losses  arising out of any claim made by a third party based upon any of
the following:

          (i) The content or addressing of any message  transmitted  by Newco or
     any third party  claim of libel,  slander,  or  infringement  of  copyright
     against   Motient   Services   arising  from  or  in  connection  with  the
     transmission  of  messages  via the  Satellite  Network  by  Newco or third
     parties accessing the Satellite Network through Newco;

          (ii)  Any  negligent  act or  omission  of  Newco,  or  its  officers,
     directors,  employees or agents  resulting in personal  injury or damage to
     tangible or real property; or

          (iii)  Any  breach  by  Newco  of  the   applicable   representations,
     warranties and covenants set forth in this Agreement; or

          (iv) Any portion of the Newco Technology or any portion of the Motient
     Derivative Works (other than the underlying Motient  Technology)  infringes
     the  Intellectual  Property  Rights of a third party;  provided  that Newco
     shall  have  no  obligation  to  indemnify   Motient  Services  under  this
     subsection  (iv) to the extent such an  infringement  claim results  solely
     from  modification of the Newco Technology or the Motient  Derivative Works
     by Motient  Services or any person or entity obtaining access to such Newco
     Technology or Motient Derivative Works through Motient Services.

13.2 Indemnification by Motient Services.

Motient  Services  shall  indemnify and hold Newco harmless from and against any
and all Losses  arising out of any claim made by a third party based upon any of
the following:

          (i)  Any  negligent  act  or  omission  of  Motient  Services,  or its
     officers,  directors,  employees or agents  resulting in personal injury or
     damage to tangible or real property; or

          (ii) Any breach by Motient Services of the applicable representations,
     warranties and covenants set forth in this Agreement; or

          (iii) Any portion of the Motient Technology infringes the Intellectual
     Property Rights of a third party; provided that Motient Services shall have
     no obligation to indemnify Newco under this subsection  (iii) to the extent
     such an  infringement  claim  results  solely from (a) the addition  and/or
     combination by Newco of products not provided by Motient  Services with the
     Motient Technology;  or (b) modification of the Motient Technology by Newco
     or any person or entity obtaining access to such Motient Technology through
     Newco.

13.3 Notification for Indemnification.

All claims for  indemnification  hereunder  shall be resolved in accordance with
the following procedures:

          (i) If the party seeking indemnification (the "Indemnified Party") has
     incurred or  reasonably  believes  that it may incur any  Losses,  it shall
     deliver   promptly   written   notice  to  the   indemnifying   party  (the
     "Indemnifying Party"), setting forth the nature and amount of the Losses or
     potential Losses, if possible, and further referencing the sections of this
     Agreement or in any other document delivered pursuant hereto upon which the
     claim for indemnification  for such Losses is based (a "Claim Notice").  If
     an Indemnified  Party receives  notice of a third-party  claim for which it
     intends to seek indemnification  hereunder,  it shall give the Indemnifying
     Party  written  notice  of such  claim,  so that the  Indemnifying  Party's
     defense of such claim under this  Agreement may be timely  instituted.  The
     failure by an  Indemnified  Party to provide such written  notice shall not
     constitute a waiver of the  Indemnified  Party's right to indemnity  unless
     such failure has prejudiced the Indemnifying Party's ability to defend such
     claim, and then only to the extent of such prejudice.

          (ii) If,  after  receiving  a Claim  Notice,  the  Indemnifying  Party
     desires to dispute such claim or the amount claimed in the Claim Notice, it
     shall deliver to the Indemnified Party a written objection to such claim or
     payment  setting forth the basis for disputing such claim or payment.  Such
     notice shall be delivered  within thirty (30) days after the date the Claim
     Notice to which it relates is received  by the  Indemnifying  Party.  If no
     such  notice is  received  within the  aforementioned  30-day  period,  the
     Indemnified  Party  shall be  entitled  to payment for such Losses from the
     Indemnifying Party within ten (10) days of the end of such 30-day objection
     period.

          (iii) If the Indemnifying Party shall agree that it is responsible for
     all amounts that may be recovered in connection  with a third-party  claim,
     action or suit  (including  waiving  any  deductible  or limit  that  might
     otherwise  apply  under  this  Article 13 or Section  12.3  hereof)  and is
     financially  capable of satisfying  its  indemnification  obligations,  the
     Indemnifying  Party  shall have the right to conduct  and  control  through
     counsel of its own choosing,  which counsel shall be reasonably  acceptable
     to the Indemnified Party, any third-party claim, action or suit;  provided,
     that the Indemnifying Party diligently contests and defends such claim. The
     Indemnified  Party  shall  be  entitled  at any  time,  at its own cost and
     expense   (except  that  such  cost  and  expense  shall  be  paid  by  the
     Indemnifying Party if the Indemnified Party reasonably  determines that the
     Indemnifying Party is not adequately representing or, because of a conflict
     of interest,  may not adequately represent the interests of the Indemnified
     Party) to participate in such defense and to be represented by attorneys of
     its  choosing.  Except with the prior  written  consent of the  Indemnified
     Party no  Indemnifying  Party,  in the defense of such claim or litigation,
     shall consent to entry of any judgment or order,  interim or otherwise,  or
     enter into any settlement that provides for injunctive or other nonmonetary
     relief  affecting  the  Indemnified  Party or that does not  include  as an
     unconditional term thereof the giving by each claimant or plaintiff to such
     Indemnified  Party of a release  from all  liability  with  respect to such
     claim or litigation.

          (iv) In the event that the Indemnifying Party does not elect to defend
     against any third-party  claim,  the  Indemnified  Party may defend against
     such claim in such manner as it may deem  appropriate and the  Indemnifying
     Party  shall be  liable  for any  legal  expenses  reasonably  incurred  in
     connection with such defense;  provided that, the  Indemnified  Party shall
     not, without the consent of the Indemnifying Party, which consent shall not
     be unreasonably  withheld,  settle or consent to the entry of judgment with
     respect to such third-party claim.

          (v) In the event of any claim by a third  party,  the  parties  hereto
     agree that they will cooperate fully with each other in connection with the
     defense or settlement of such matter.

13.4 No Duplication of Remedies.

To the extent any party may have more than one remedy for any Losses incurred by
it, it may pursue all  available  remedies  but in no event shall be entitled to
collect and retain any amount hereunder in excess of its Losses.

13.5 Subrogation.

If any Indemnified Party receives any payment or other indemnification  pursuant
to this Agreement from an Indemnifying Party with respect to any claim or demand
by any third party against the Indemnified  Party, the Indemnifying  Party shall
be subrogated to the extent of such payment or  indemnification to all rights in
respect of the subject  matter of such claim or demand to which the  Indemnified
Party may be entitled, to institute appropriate action for the recovery thereof,
and the Indemnified Party agrees to provide  reasonable levels of assistance and
cooperation to such subrogated party, in enforcing such rights.

                                   ARTICLE xiV

                                   ASSIGNMENT

Motient  Services  shall not  assign  its  rights  and  obligations  under  this
Agreement,  in whole or in  part,  whether  by  operation  of law or  otherwise,
without the prior  written  consent of Newco.  Newco shall not assign its rights
and obligations under this Agreement,  in whole or in part, whether by operation
of law or otherwise,  unless the assignee agrees to be bound by all of the terms
and conditions hereof applicable to Newco hereunder,  and provided that any such
assignment  shall be  subject to any prior  approval  required  by the FCC,  and
compliance with any conditions and restrictions  imposed by the FCC with respect
to such  assignment.  Any  assignment  contrary to the terms of this Article XIV
shall  be null  and  void and of no force  and  effect.  In no event  shall  the
assignment  by Motient  Services or Newco of such party's  respective  rights or
obligations  under this Agreement,  whether before,  at or after the Closing (as
defined  in the Asset Sale  Agreement),  release  such  party from such  party's
respective liabilities and obligations hereunder.

                                   ARTICLE Xv

                            MISCELLANEOUS PROVISIONS

15.1 Successors and Assigns.

This  Agreement  shall be  binding  upon and shall  inure to the  benefit of the
parties  hereto and their  permitted  assigns.  This  Agreement  is entered into
solely for the benefit of such parties.

15.2 No Third Party Beneficiaries.

The provision by Motient  Services to Newco of the Satellite  Network and of the
Services  is not part of any  principal  and agent  relationship,  employer  and
employee relationship,  or joint venture or partnership between Motient Services
and Newco.  This  Agreement  is entered  into  solely for the benefit of Motient
Services and Newco and is for the  exclusive  benefit of such  parties.  Nothing
contained  in  this   Agreement  will  be  deemed  to  create  any  third  party
beneficiaries  or confer  any  benefit or rights on or to any person not a party
hereto,  and no  person  not a  party  hereto  (including,  without  limitation,
customers,  vendors,  or  creditors  of Newco)  shall be entitled to enforce any
provisions hereof or exercise any rights hereunder.

15.3 Notices.

All notices,  demands,  requests,  or other  communications  which may be or are
required to be given,  served,  or sent by any party to any other party pursuant
to this  Agreement  shall be in  writing  and shall be hand  delivered,  sent by
overnight courier or mailed by first-class, registered or certified mail, return
receipt  requested,  postage  prepaid,  or transmitted by telecopy  addressed as
follows:

     (a) If to Newco:

                           Motient Satellite Ventures LLC
                           10802 Parkridge Boulevard
                           Reston, Virginia  20191-5416
                           Attn:  Randy S. Segal, Esq.
                           Telecopy No.:  703-758-6134

     with a copy to:

                           Motient Satellite Ventures LLC
                           211 North Union Street, Suite 300
                           Alexandria, Virginia  22314
                           Attn:  Hal Perkins
                           Telecopy No.:  703-706-3801

     (b) If to Motient Services:

                           Motient Services Inc.
                           10802 Parkridge Boulevard
                           Reston, Virginia  20191-5416
                           Attn:  Randy S. Segal, Esq.
                           Telecopy No.:  703-758-6134

Each party may designate by notice in writing a new address to which any notice,
demand,  request or  communication  may thereafter be so given,  served or sent.
Each notice,  demand,  request,  or communication which shall be hand delivered,
sent,  mailed  or  telecopied  in the  manner  described  above  shall be deemed
sufficiently given, served, sent, received or delivered for all purposes at such
time as it is delivered to the addressee (with the return receipt,  the delivery
receipt,  or (with respect to a telecopy or telex) the  answerback  being deemed
conclusive,  but not  exclusive,  evidence of such  delivery) or at such time as
delivery is refused by the addressee upon presentation.

15.4 Applicable Law.

This Agreement shall be governed by and construed in accordance with the laws of
the  Commonwealth of Virginia,  without regard to its principles of conflicts of
law  that  would  give  effect  to  the   application  of  the  law  of  another
jurisdiction.  Each of the parties hereto hereby irrevocably and unconditionally
consents  to  submit  to  the  exclusive  jurisdiction  of  the  courts  of  the
Commonwealth  of  Virginia  and of the United  States of  America,  in each case
having  jurisdiction over the County of Fairfax,  for any litigation arising out
of or relating to this Agreement and the  transactions  contemplated  hereby and
thereby (and agrees not to commence any  litigation  relating  thereto except in
such courts), and further agrees that service of any process, summons, notice or
document by U.S.  registered  mail to its  respective  address set forth in this
Agreement  shall be  effective  service of process  for any  litigation  brought
against it in any such court. Each of the parties hereto hereby  irrevocably and
unconditionally  waives any  objection to the laying of venue of any  litigation
arising out of this  Agreement or the  transactions  contemplated  hereby in the
courts of the Commonwealth of Virginia or the United States of America,  in each
case  having  jurisdiction  over the  County  of  Fairfax,  and  hereby  further
irrevocably and  unconditionally  waives and agrees not to plead or claim in any
such court that any such  litigation  brought in any such court has been brought
in an inconvenient forum.

15.5 Waiver.

Neither the waiver by either of the  Parties  hereto of a breach of or a default
under any of the provisions of this Agreement,  nor the failure of either of the
Parties,  on one or more  occasions  to enforce  any of the  provisions  of this
Agreement or to exercise any right or privilege  hereunder  shall  thereafter be
construed as a waiver of any subsequent  breach of default of a similar  nature,
or as a waiver of any provisions,  rights, or privileges  hereunder.  Any waiver
under this Agreement must be in writing.

15.6 Severability.

In the event that any one or more of the provisions of this  Agreement  shall be
held by a court of competent  jurisdiction to be invalid or unenforceable in any
respect,  such  invalidity  and  unenforceability  shall  not  affect  any other
provision of this Agreement, and the Agreement shall be construed as though such
invalid  and/or  unenforceable  provision(s)  had never been  contained  herein,
unless such invalid and/or  unenforceable  provision(s) are an essential part of
the agreed exchange.

15.7 Modification.

No amendment or  modification  to this  Agreement  shall be valid unless made in
writing  and signed by the  authorized  representatives  of the  parties.  As to
Motient Services, the "authorized  representatives" means both Motient Services'
(a) General Counsel and (b) President or any Vice President.

15.8 Headings.

The headings and numbering of paragraphs in this  Agreement are for  convenience
only and shall not be  construed  to define or limit any of the terms  herein or
affect the meaning of interpretation hereof.

15.9 Survival.

The  provisions  of Sections  4.4, 8.1, 8.2, 8.3, 8.4 (to the extent the license
granted therein becomes  perpetual),  8.5, 11.5,  15.2, 15.4, 15.8, and 15.9 and
Articles  V, IX, X (subject to Section  12.1),  XII,  XIII and XV shall  survive
expiration or termination of this Agreement.

15.10 No Joint Venture or Agency.

Neither  Party  will be  deemed  to be an  employee,  agent,  partner  or  legal
representative  of the other for any purpose  and  neither  will have any right,
power or authority to create any obligation or  responsibility  on behalf of the
other.

15.11 Force Majeure.

Motient  Services  shall not be liable  for any  failure of  performance  due to
causes beyond its  reasonable  control,  including,  but not limited to, acts of
God, fires, floods or other catastrophes;  national emergencies,  insurrections,
riots or wars;  strikes,  lockouts,  work stoppages or other labor difficulties;
and any law,  order,  regulation or other action of any  governing  authority or
agency thereof (collectively,  "Force Majeure Events"). A failure of performance
by Motient Services caused solely by acts or omissions of Motient Corporation or
any of  its  Affiliates  (except  to the  extent  such  acts  or  omissions  are
themselves  due to a Force  Majeure  Event) or by reason  of  Motient  Services'
insolvency or bankruptcy or other such condition of financial distress shall not
be deemed to be a Force Majeure Event with respect to Motient Services.

15.12 Entire Agreement.

This Agreement,  including all Schedules  hereto,  and the Asset Sale Agreement,
constitutes the entire  agreement  between the parties hereto and supersedes all
prior oral or written  agreements,  representations,  statements,  negotiations,
understandings,  proposals,  and undertakings with respect to the subject matter
hereof.






                  IN WITNESS  WHEREOF,  the  Parties  hereto  have  caused  this
Research  and  Development  Agreement  to be executed on the date first  written
above by their duly authorized officers.

                                             MOTIENT SATELLITE VENTURES LLC
                                             By Motient Corporation, Sole Member

                                             By:     /s/Gary M. Parsons
                                                     Gary M. Parsons
                                                     Chairman


                                             MOTIENT SERVICES INC.

                                             By:     /s/Gary M. Parsons
                                                     Gary M. Parsons
                                                     Chairman






                                   SCHEDULE A

                             FACILITIES REQUIREMENTS

         Newco's  access  to the  Satellite  Network  for the  purposes  of this
Agreement  shall be  subject to its  compliance  with the  following  Facilities
Requirements:

         (1) Compliance with Motient Services requirements and standards:  Newco
will  adhere  to  Motient  Services'  standard   interfacing   requirements  and
specifications  when  interconnecting  external  equipment and facilities to the
Satellite  Network.  Newco's  activities  under this Agreement shall comply with
Motient Services' acceptable use policy and other applicable policies, rules and
regulations (including without limitation those promulgated by the FCC) that are
intended to protect the integrity of the Satellite Network,  to prevent unlawful
or  improper  use of the  Satellite  Network,  and to  prevent  harm to  Motient
Services'  personnel.  Notwithstanding  the generality of the  foregoing,  Newco
shall adhere to Motient Services' IF Interface Access Requirements, as in effect
from  time  to  time.  Motient  Services  reserves  the  right  to  change  such
requirements from time to time, upon reasonable notice to Newco.

         (2) Licenses  and permits:  Newco shall be  responsible  for  obtaining
those licenses,  permits,  rights-of-way,  approvals, and any other arrangements
for which it is  responsible,  as set forth in  Section  6.2.  Motient  Services
agrees to provide Newco with  reasonable  cooperation  and  assistance to enable
Newco to obtain  such  licenses,  permits,  rights-of-way,  approvals  and other
arrangements. Newco agrees that, unless otherwise requested in writing by Newco,
all of Newco's governmental approvals and licensing activities will be conducted
by  Motient  Services'  regulatory  counsel;  provided  that  Motient  Services'
regulatory  counsel will handle requests by Newco for Motient Services to obtain
licenses,   permits,   approvals  and  other  such  items  for  which  Newco  is
responsible, as provided for in Section 6.2.

         (3) Motient  Services  right of access:  For the  protection of Motient
Services'  network,  services,  facilities  and  personnel,  Newco hereby grants
Motient  Services the right at any time, and from time to time,  upon reasonable
prior notice  except in the case of an  emergency,  to inspect all equipment and
communications  facilities  or  services  used or provided by Newco for use with
Motient  Services'  mobile satellite system for compliance with FCC regulations,
this Agreement, and Motient Services' emission requirements, and other technical
requirements.





                                   SCHEDULE B

                            COMPENSATION FOR SERVICES

Unless agreed otherwise by the parties from time to time, Motient Services shall
be compensated by Newco for the Services to be provided under the Agreement,  in
accordance with this Schedule B.

Motient Services shall not charge Newco for the following Services:

          (i) assistance to Newco in establishing  access and/or connectivity of
     Newco and/or Newco mobile  terminals  and other  equipment to the Satellite
     Network;

          (ii) provision of technical  descriptions of the Satellite Network and
     descriptions   and   explanations  of  Motient   Services'   technical  and
     operational requirements for Newco's use of the Satellite Network;

          (iii) restart of Newco's uplink equipment in the event of an equipment
     failure,  pursuant to  procedures  to be defined in the R&D Support Plan or
     another document; and

          (iv) other similar  services and assistance of a general  nature,  not
     focused on a particular R&D Activity or other special project.

In the event Newco requests in writing for Motient Services to provide any major
or  extraordinary  technical  assistance  required  for Newco to perform its R&D
Activities,  including but not limited to  consulting,  engineering,  strategic,
technical or similar Services provided in support of the R&D Activities, Motient
Services shall be: (a) compensated for Motient  Services  employees at the rates
set forth below, plus reimbursement for reasonable  out-of-pocket  expenses; (b)
compensated for third party  consultants and other personnel  engaged by Motient
Services  for Newco (at written  request of Newco) at Motient  Services'  actual
costs,  plus  reimbursement  for  reasonable   out-of-pocket  expenses  and  (c)
reimbursed,  at Motient Services' cost, for equipment  requested to be purchased
by Newco in connection with the Services.

The billing rates are as follows:



                                                         Hourly Rate
                                                         -----------
                                                         
        Senior  Engineering/
        Technical/Regulatory                                $   135
        Junior Engineering/
        Technical/Regulatory                                $    90


Motient  Services  shall submit an invoice for all  Services  rendered for which
compensation  is due,  within thirty (30) days following the end of the month in
which  such  Services  were  provided.   Such  invoice  shall  include  a  brief
description  of the Services  rendered,  indicating  the amount charged for each
Service rendered.  Invoices shall be payable by Newco within thirty (30) days of
the invoice date.