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                                                                   EXHIBIT 10.12

                               SUBLEASE AGREEMENT

                               SUBLEASE AGREEMENT

1.      PARTIES: The parties to this Sublease Agreement are ARCADIS GERAGHY &
        MILLER, INC., (FORMERLY ACUREX ENVIRONMENTAL CORPORATION), A DELAWARE
        CORPORATION, hereinafter called "Sublessor", and SKYSTREAM CORPORATION
        hereinafter called "Sublessee".

2.      PREMISES: The premises covered in by this Sublease Agreement are
        portions of the building known as 555 Clyde Avenue, Mountain View,
        located in Santa Clara County, California, comprising the following:

        A.      Approximately 21,531 rentable square feet on the first and
                second floors of the building. The leased space is illustrated
                on the attached Exhibit A and B.

        B.      Use of the second floor conference rooms designated on Exhibit
                A. Sublessor at Sublessor's sole discretion can terminate this
                privilege at any time during the Sublease by giving Sublessee
                written notice.

        C.      Maintenance of heating, ventilating and air conditioning (HVAC)
                equipment, plumbing, electrical power, roof, building exterior,
                landscaping and parking lot provided by Sublessor.

3.      TERM: The Sublease of the above premises by Sublessee shall commence on
        January 1, 2000 and shall end on December 31, 2000.

4.      RENT: Sublessee shall pay to Sublessor as rent for the Premises equal
        monthly payments of $46,291.65, in advance, on the first (1st) day of
        each month of the term hereof. Sublessee shall pay Sublessor upon the
        execution hereof as rent for first month's rent of $46,291.65. Rent for
        any period during the term hereof which is for less than one month shall
        be a prorated portion of the monthly installment. Rent shall be payable
        in lawful money of the United States to Sublessor at the address stated
        herein or to such other persons or at such other places as Sublessor may
        designate in writing.

5.      UTILITIES: Utilities, including gas, electricity, water, sewer,
        janitorial and garbage removal shall be provided to Sublessee by
        Sublessor.

6.      TAXES: Real Property taxes are the responsibility of the Sublessor.

7.      INSURANCE: Sublessee at Sublessee's expense shall provide and keep in
        force during the term of this Sublease Agreement a general liability
        insurance policy with a recognized casualty insurance company qualified
        to do business in California,


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     protecting Sublessor, Master Lessor and Sublessee against any and all
     liability occasioned by occurrence in amounts not less than $1,000,000.00
     and satisfactory to Sublessor. Sublessee shall furnish a Certificate of
     Insurance to Sublessor and Master Lessor naming Sublessor and Master Lessor
     as Additional Insured. Sublessor agrees during the Sublease term to carry
     fire and extended coverage insurance insuring Sublessee's interest in the
     premises in such amounts and covering such perils as Sublessor shall
     determine, but Sublessor shall have no obligation to insure against loss
     by Sublessee to Sublessee's property of any kind in or about the premises
     occurring from any cause whatsoever, and Sublessee shall have no interest
     in the proceeds of any insurance carried by Sublessor. If Sublessor's
     insurance rates for the premises are increased at any time during the term
     of the Sublease as a result of the Sublessee's use and occupancy of the
     premises, Sublessee agrees to reimburse Sublessor for the full amount of
     such increase immediately upon receipt of demand from Sublessor.


8.   USE: The Premises shall be used and occupied only for general office and
     for no other purpose.

9.   COMPLIANCE WITH LAW: A. Sublessor warrants to Sublessee that the Premises
     in its existing state, but without regard to the use for which Sublessee
     will use the Premises, does not violate any applicable building code
     regulation or ordinance at the time that this Sublease is executed. In the
     event that it is determined that this warranty has been violated, then it
     shall be the obligation of the Sublessor, after written notice from
     Sublessee, to promptly, at Sublessor's sole cost and expense, rectify any
     such violation. In the event that Sublessee does not give to Sublessor
     written notice of the violation of this warranty within one (1) year from
     the commencement of the term of this Sublease, it shall be conclusively
     deemed that such violation did not exist and the correction of the same
     shall be the obligation of the Sublessee.

     B. Except as provided in paragraph 9A, Sublessee shall, at Sublessee's
     expense, comply promptly with all applicable statutes, ordinances, rules,
     regulations, orders, restrictions of record, and requirements in effect
     during the term or any part of the term hereof regulating the use by
     Sublessee of the Premises. Sublessee shall not use or permit the use of the
     Premises in any manner that will tend to create waste or a nuisance or, if
     there shall be more than one tenant of the building containing Premises,
     which shall tend to disturb such other tenants.

10.  CONDITION OF PREMISES: Except as provided in paragraph 9A, Sublessee hereby
     accepts the Premises in their condition existing as of the date of the
     execution hereof, subject to all applicable zoning, municipal, county and
     state laws, ordinances, and regulations governing and regulating the use of
     the Premises, and accepts this Sublease subject thereto and to all matters
     disclosed thereby and by any exhibits attached hereto. Sublessee
     acknowledges that neither Sublessor nor Sublessor's agents have made any
     representation or warranty as to the suitability of the Premises for the
     conduct of Sublessee's business.


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11.  COMPUTER EQUIPMENT/INSTALLATION: Any internal wiring installed other than
     within Sublessee's space shall be installed by the Sublessor's contractors
     or a contractor approved by the Sublessor.

12.  MASTER LEASE: This sublease is subject to all the applicable terms and
     conditions of the Master Lease, initially dated OCTOBER 23, 1976, with
     Amendments, between Sublessor, and the Master Lessor: RICHARD N. MOSEMAN,
     BONNIE MOSEMAN MILLER, and PROPERTIES INTERNATIONAL, ALLRENT, INC., A
     CALIFORNIA CORPORATION. The Master Lease is hereby incorporated into this
     Sublease Agreement, and Sublessee shall assume and perform the obligations
     of the Lessee under this Master Lease to the extent that said terms and
     conditions are applicable to the premises subleased pursuant to this
     Sublease. Sublessee shall not permit or permit to be committed on the
     premises any act or omission which shall violate any term or condition of
     the Master Lease. In the event of termination of Sublessor's interest as
     Lessee under the Master Lease for any reason, then this Sublease shall
     terminate coincidentally therewith without any liability of Sublessor to
     Sublessee.

13.  ASSIGNMENT: Sublessee shall not assign this Sublease or any interest
     therein nor sublet the premises or any part thereof or any right or
     privilege appurtenant thereto nor permit the occupancy of use of any part
     thereof by any person without the prior written consent of Sublessor. Any
     such assignment or subletting without proper prior written consent shall be
     void and, at the option of the Sublessor, may terminate this Sublease.

14.  SIGNAGE: Sublessee shall not place any signs anywhere on the exterior of
     the building or on the land within the property boundaries or inside the
     building in or visible from the common areas without the prior written
     consent of Sublessor.

15.  DEFAULT: Sublessor may terminate this lease for default for violation of
     any term or condition of the Master Lease or this Sublease.

16.  HAZARDOUS MATERIALS: During the term of this Sublease, Sublessee shall
     comply with all federal, state, and local laws, ordinances, and
     regulations relating to the use, storage, sale, transportation or disposal
     to, from, or on the premises of any Hazardous Materials. Upon execution of
     this Sublease and on an ongoing basis, Sublessee shall provide Sublessor
     with a list, no less frequently than quarterly, of Hazardous Materials that
     Sublessee uses or maintains on the premises. Sublessee shall not be
     responsible for any adverse environmental conditions relating to Hazardous
     Materials that are not caused by Sublessee, its agents, employees,
     contractors, or invitees.

     Sublessee shall indemnify, defend (by counsel reasonably acceptable to
     Master Lessor and Sublessor), protect and hold Master Lessor and Sublessor
     and each of their employees, agents, successors, and assigns, free and
     harmless from and against all claims, liabilities, penalties, forfeitures,
     losses, or expenses (including attorneys'


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     fees (arising from or caused by (a) the discharge by Sublessee in or from
     the premises of any Hazardous Materials, or Sublessee's use, storage,
     transportation, discharge, or generation of Hazardous Materials to, in, on,
     under, about or from the premises, or (b) Sublessee's failure to comply
     with any Hazardous Materials Law. In the event that Sublessee becomes
     liable under this section the Sublessee's obligations hereunder shall
     include, without limitation, all costs of any required repair, clean-up,
     or decontamination of the premises, and the preparation and implementation
     of any closure, remedial action, or other required procedures in
     connection therewith. The foregoing indemnity shall survive the expiration
     or the earlier termination of this Sublease.

          "Hazardous Materials" shall mean any hazardous or toxic substances,
     material, or wastes including, but not limited to, those substances,
     materials, and wastes regulated now or in the future by any federal,
     state, or local regulatory body.

17.  NOTICE TO VACATE: Prior to the expiration of the Sublease, Sublessee must
     give Sublessor not less than six (6) months notice in writing of its
     intent to vacate the premises. If Sublessee does not give Sublessor notice
     on or before July 1, 2000 of its intent to vacate, the sublease will not
     terminate on December 31, 2000 but on the sixth (6) month anniversary of
     the actual notice given. By example, if Sublessee gives written notice on
     September 1, 2000, the Sublease will not expire until February 28, 2001.
     Sublessee will be obligated to pay all rents and other charges due up to
     and including the actual date of vacation of the premises.

18.  KEYS: Sublessee shall be provided with two (2) keys to the front door of
     the 555 Clyde building. Sublessee has the option to have locks installed
     on the office door, but must bear the burden of this cost. All locksmith
     work must be performed and coordinated through Sublessor's vendor.
     Additional keys may be purchased for a fee of $5.00 each.

19.  ENTIRE AGREEMENT: The foregoing constitutes the entire agreement between
     the parties and may be modified only by a written amendment signed by both
     parties.

20.  ATTORNEY'S FEES: If any party or the Broker named herein brings an action
     to enforce the terms hereof or to declare rights hereunder, the prevailing
     party in any such action, on trial and appeal, shall be entitled to his
     reasonable attorney's fees to be paid by the losing party as fixed by the
     Court the provision of this paragraph shall inure to the benefit of the
     Broker named herein who seeks to enforce a right hereunder.

THE SUBLEASE HAS BEEN PREPARED FOR SUBMISSION TO YOUR ATTORNEY FOR HIS
APPROVAL. NO REPRESENTATION OR RECOMMENDATION IS MADE BY THE REAL ESTATE BROKER
OR ITS AGENTS OR EMPLOYEES AS TO THE LEGAL SUFFICIENCY, LEGAL EFFECT, OR TAX
CONSEQUENCES OF THIS SUBLEASE OR THE TRANSACTION RELATING THERETO.

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Sublessor:                             Sublessee:
ARCADIS Geraghty & Miller, Inc.        Skystream Corporation


/s/  [SIGNATURE ILLEGIBLE]             /s/ SUSAN KETCHAM
--------------------------             -------------------------
ARCADIS Geraghty & Miller, Inc.        VP Finance
555 Clyde Avenue
Mountain View, CA 94043

Date: 12/31/99                         Date: 12/29/99
     -------------                          ------------


CONSENT TO SUBLEASE: Without releasing Lessee in the Master Lease from the
obligations hereunder, the undersigned hereby consents to the foregoing
Sublease Agreement between ARCADIS Geraghty & Miller, Inc., Lessee under the
Master Lease, and SkyStream Corporation, Sublessee, provided that this consent
shall no be construed as a consent to any further subletting.

         Dated:
               -----------------                   -----------------------

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

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


                                                   Richard N. Moseman, Bonnie
                                                   Moseman Miller and Properties
                                                   International, Allrent, Inc.,
                                                   Lessor under the Master Lease
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                         BUILDING 6 -- 555 CLYDE AVENUE
                                   DOWNSTAIRS

                                   EXHIBIT A
                                  NOT TO SCALE

                            [FLOOR DIAGRAM OMITTED]

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                         BUILDING 6 -- 555 CLYDE AVENUE

                                    UPSTAIRS

                                   EXHIBIT B
                                  NOT TO SCALE

                            [FLOOR DIAGRAM OMITTED]