AMENDMENT NO. 5 TO ORBCOMM SYSTEM PROCUREMENT AGREEMENT

   1
                                                                  EXHIBIT 10.5.5

                                AMENDMENT NO. 5 TO
                       ORBCOMM SYSTEM PROCUREMENT AGREEMENT


      This Amendment No. 5 ("Amendment No. 5") to ORBCOMM System Procurement
Agreement is entered into this ___ day of _______, 1998 between ORBCOMM Global,
L.P. ("ORBCOMM Global") and Orbital Sciences Corporation ("Orbital")

                                    WITNESSETH

      WHEREAS, the parties previously entered into ORBCOMM System Procurement
Agreement dated as of September 12, 1995 (the "Procurement Agreement"); and

      WHEREAS, the parties wish to amend certain terms and conditions of the
Agreement as provided herein;

      NOW THEREFORE, the parties agree as follows:


ARTICLE 1 - DEFINITIONS

      Terms used herein and not otherwise defined shall have the meanings
assigned thereto in the Procurement Agreement.


ARTICLE 2 - AMENDMENTS

      Section 2.7 of the Procurement Agreement is hereby deleted in its entirety
and replaced with the following:

            Section 2.7 - Regulatory Matters. Orbital, directly or
      indirectly through its subsidiary ORBCOMM, shall use all commercially
      reasonable efforts (a) to obtain and maintain the required United
      States regulatory authority needed to construct, launch and operate
      the Satellites and operate the ORBCOMM System, (b) to obtain and
      maintain FCC regulatory authority for the operation of type-approved
      subscriber terminals for use in connection with the ORBCOMM System,
      and (c) to take reasonable actions in any regulatory proceedings to
      defend any claims against any regulatory authority granted to Orbital
      or ORBCOMM in connection with the ORBCOMM System or to oppose any
      application by competing systems that use frequencies below 1 GHz.
      In connection therewith, Orbital, directly or indirectly through
      ORBCOMM, may in its reasonable discretion contract with third
      parties, including but not limited to ORBCOMM Global, for the
      provision of such consulting or other services as Orbital may deem
      necessary or desirable to enable it to fulfill its



                                        1
   2

      obligations under this Section 2.7.

ARTICLE 3 - MISCELLANEOUS

      Section 3.1 Except as otherwise provided in Exhibit H, this Amendment 
No. 5 shall be construed in accordance with and governed by the laws of the
Commonwealth of Virginia, without giving effect to the provisions, policies or
principles thereof related to choice or conflict of laws.

      Section 3.2 No changes to the Procurement Agreement are authorized hereby
except as otherwise specified in this Amendment No. 5.



      IN WITNESS WHEREOF, the parties have executed this Amendment No. 5 as of
the day and year first above written.


                                    ORBCOMM GLOBAL, L.P.



                                    By:
                                       --------------------------------
                                       Name:  Xxxxxx X. Xxxxxx
                                       Title: President



                                    ORBITAL SCIENCES CORPORATION



                                    By:
                                       --------------------------------
                                       Name:  Xxxxxxx X. Xxxxxxx
                                       Title: Senior Director, Contracts





                                       2