<PAGE>

                                                                   EXHIBIT 10.21

7 July 1993

Mr. Alain Cohen
MIL 3
3400 International Dr.,
Suite 4L
N.W., Washington D.C.  20008

Subject:  Letter Agreement on Administration of Building Common Areas

In connection with the Agreement of lease between INTELSAT and MIL 3, Inc.
(INTEL-L-1433) dated 16 June 1993, INTELSAT ("Landlord") and MIL 3 ("Tenant")
hereby agree to the terms of this letter agreement which further clarify the
Lease and Building Rules and Regulations.  The Landlord hereby agrees to make
appropriate adjustments within its procedures to adhere to the following
clarifications:

4.  Signage:

The Landlord shall develop uniform building signage standards for all Multi-
Tenant common areas which shall include directory locations, suite numbers and
proprietary signage at suite entrances, on glass, doors or adjacent vicinity
within the pod floor.  No signage shall be installed without prior written
consent of Landlord.  (INTELSAT is currently working with an outside vendor to
assist in developing signage standards and will convey the results to the Tenant
no later that 31 August 1993.)

6.  Art work:

No tenant art work shall be installed within the Multi-Tenant common areas
without prior written consent of Landlord, who shall first obtain the consent of
all affected parties.  The Landlord shall bear no liability for any such art
work.

10.  Quiet Enjoyment:

The Landlord agrees to protect the Tenant's quiet enjoyment of the demised
premises in a commercially reasonable fashion and if the Landlord permits
receptions to be held within the building areas adjacent to the Tenant's
premises, Landlord shall (1) provide five (5) days advance notice of the
reception, unless Landlord itself has less than five (5) days notice, in which
case, Landlord shall notify tenant as soon as reasonably possible, (2) prevent
the placement of obstacles in front of the double doors leading to the atrium
adjacent to Pod 4L to maintain a minimum safe clearance of five (5) feet, and
(3) prevent the placement of wires and/or cabling
<PAGE>

by suite entrances or by the double doors leading to the atrium adjacent to Pod
4L which do not protect the safety of the building occupants.

40. (of the lease) Reporting of Payments:

With regard to the Reporting of Payments clause, INTELSAT has concluded that the
requirement for a certification by MIL 3's auditors under the Reporting of
Payments clause does not apply as it is INTELSAT's view that the net value of
this contract falls below the $500,000 threshold.

If you are in agreement with the above clarifications please sign below as an
acknowledgement and return to me.

Sincerely,


/s/ Robert A. Lambert
-----------------------------------------
Robert A. Lambert
Department Manager,
Facilities Management and Office Services

Acknowledgement:     /s/ Alain Cohen      Date:   7/16/93
                  ------------------            ---------

                  MIL 3 ( or designated representative)

cc:  C. Lewis
     D. Meltzer
     Mil 3 Lease file
<PAGE>

                                                                   5 August 1993

Mr. Alain Cohen
MIL 3, Inc.
3400 International Dr., N.W.
Suite 4L
Washington D.C.  20008

Dear Alain:

     Attached for your files is a fully signed original of INTEL-L-1433 and a
copy of the signed letter agreement, dated 7 July 1993.

     All rental payments and inquiries should be directed to Tuula Sumpter,
Shannon & Luchs Polinger, at (202) 944-8235.  If you have any questions
regarding the Lease, please feel free to contact me.

                              Sincerely,


                              /s/ Cecilia R. Lewis
                              ------------------------------
                              Cecilia R. Lewis
                              Special Projects Administrator

Attachment

cc:  K. Gross/MIL 3, Inc.
     R. Lambert  w/o attachment
     D. Meltzer  w/o attachment
     file
<PAGE>

                                                                    INTEL-L-1433



                               AGREEMENT OF LEASE

                                    BETWEEN

                        INTERNATIONAL TELECOMMUNICATIONS

                             SATELLITE ORGANIZATION

                                      AND

                                   MIL 3, INC

                                                             DATE:  18 June 1993
<PAGE>

                               TABLE OF CONTENTS

<TABLE>
<CAPTION>
Article No.    Title                                            Page
-----------    -----                                            ----
<S>            <C>                                              <C>
     1.        DEMISED PREMISES...............................     1

     2.        TERM...........................................     2

     3.        USE............................................     3

     4.        RENTAL.........................................     4

     5.        RENTAL ESCALATION..............................     8

     6.        SECURITY DEPOSIT...............................    10

     7.        PREOCCUPANCY WORK AGREEMENT....................    10

     8.        ASSIGNMENT AND SUBLETTING......................    11

     9.        CLEANING AND MAINTENANCE BY TENANT.............    13

     10.       ALTERATIONS....................................    13

     11.       SIGNS AND FURNISHINGS..........................    14

     12.       ENTRY FOR HOUSEKEEPING, REPAIRS AND INSPECTIONS    15

     13.       INSURANCE RATING...............................    15

     14.       TENANT'S EQUIPMENT.............................    16

     15.       INDEMNITY AND PUBLIC LIABILITY INSURANCE.......    17

     16.       SERVICES AND UTILITIES.........................    18

     17.       METERED UTILITIES..............................    22

     18.       RESPONSIBILITY FOR DAMAGE TO DEMISED PREMISES..    23

     19.       LIABILITY FOR DAMAGE TO PERSONAL PROPERTY AND
               PERSONS........................................    23

     20.       FIRE AND OTHER CASUALTY DAMAGE TO DEMISED
               PREMISES.......................................    24

</TABLE>
                                      -i-
<PAGE>

<TABLE>
<CAPTION>
Article No.    Title                                            Page
-----------    -----                                            ----
<S>            <C>                                              <C>
     21.       BANKRUPTCY OR INSOLVENCY.......................    25

     22.       DEFAULT OF TENANT..............................    28

     23.       WAIVER.........................................    31

     24.       FIRST MORTGAGE.................................    31

     25.       ATTORNMENT.....................................    32

     26.       CONDEMNATION...................................    32

     27.       RULES AND REGULATIONS..........................    33

     28.       RIGHT OF LANDLORD TO CURE TENANT'S DEFAULT;
               LATE PAYMENTS..................................    33

     29.       NO PARTNERSHIP.................................    34

     30.       NO REPRESENTATIONS BY LANDLORD.................    34

     31.       BROKERS........................................    34

     32.       NOTICES........................................    35

     33.       ESTOPPEL CERTIFICATES..........................    35

     34.       COVENANTS OF LANDLORD..........................    36

     35.       SURRENDER OF DEMISED PREMISES..................    36

     36.       HOLDING OVER...................................    37

     37.       LIEN FOR RENT..................................    37

     38.       UNDERLYING LEASE...............................    37

     39.       SALES AND EXCISE TAXES.........................    38

     40.       REPORTING OF PAYMENTS..........................    38

     41.       GENDER.........................................    39

     42.       BENEFIT AND BURDEN.............................    39

</TABLE>
-ii-
<PAGE>

<TABLE>
<CAPTION>
Article No.    Title                                            Page
-----------    -----                                            ----
<S>            <C>                                              <C>
     43.       GOVERNING LAW..................................    39

     44.       WAIVER OF TRIAL BY JURY........................    39

     45.       OPTION TO LEASE ADDITIONAL OFFICE SPACE........    39

     46.       PARKING OPTION.................................    40

     47.       MISCELLANEOUS..................................    40

     48.       ENTIRE AGREEMENT...............................    41

Exhibit A      Plan of Demised Premises                           1A

Exhibit B      Preoccupancy Work                                  1B

Exhibit C      Rules and Regulations                              1C

Exhibit D      Plan of Phase I of the Office Building             1D

Exhibit E      Letter of 17 December 1992                         1E

</TABLE>

                                     -iii-
<PAGE>

                                     LEASE
                                     -----

     THIS LEASE number INTEL-L-1433 is made and entered into this 18th day of
June, 1993, by and between the International Telecommunications Satellite
Organization ("Landlord") and MIL 3, Inc. ("Tenant").

     In consideration of the agreements hereinafter set forth, the parties
hereto mutually agree as follows:

1.   DEMISED PREMISES
     ----------------

     Landlord hereby leases to Tenant, and Tenant hereby leases from Landlord,
four (4) separate areas of office space (the "demised premises"), outlined on
Exhibit A attached hereto, located on the second and fourth levels of Pod L of
Phase II of the office building situated at 3400 International Drive, N.W.,
Washington, D.C. 20008-3098.  All references in this lease to the "Building"
shall mean only Phase II of the office building, a plan of which is provided in
Exhibit D attached hereto.  The demised premises constitute a total of 7,172
square feet of rentable area, which includes a proportionate share of the common
areas of Pod L as well as a proportionate share of the common areas of the
Building.  The four separate areas of office space constituting the demised
premises have been measured by Landlord to be 1,441 and 1,261 square feet of
rentable area in Pod 4L; and 2,151 and 2,319 square feet of rentable area in Pod
2L.  The rentable area calculation consists of the net useable area of office
space (NU) plus the proportionate share of common corridor areas within a pod
floor (P), multiplied by the proportionate share of the common areas of the
Building (Core Factor)(1.08) (i.e., [NU + P] x 1.08).  Tenant shall have the
right, at its sole expense, to measure one or more of the spaces after
construction is completed to verify Landlord's measurements.  If Tenant's
measurements (based on the most recent version of the Washington Board of
Realtor's Standard Method of Measurement) reveals a discrepancy of more than 1%
between the rentable area provided in this Lease and the rentable area based on
said measurement, the parties agree to amend the terms of this Lease to conform
to the actual measurement.  Tenant hereby agrees that Landlord shall have the
right, for the purposes of accommodating other tenants of Pod L or otherwise, to
increase or decrease the dimensions, change the configuration, or to otherwise
alter the common corridors;
<PAGE>

however, any such alteration of the common areas shall not increase or decrease
the amount of common area attributable to Tenant as specified in this Article.

2.  TERM
    ----

    A.  The term of this Lease (hereinafter referred to as the "term") shall be
    for a period of five (5) years commencing on the date (the "Lease
    Commencement Date") which corresponds to the later of (a) the date that
    Landlord notifies Tenant that Landlord's Work (as set forth in Exhibit B of
    this Lease) is substantially complete and the demised premises are available
    for occupancy by Tenant (which notification shall be given on or about 15
    April 1993) or (b) three (3) business days following execution of this lease
    by both parties. The term shall expire at midnight on the date (the "Lease
    Expiration Date") which is five (5) years after the Lease Commencement Date.

    B.  Option to Renew
        ---------------

          Tenant shall have and is hereby granted the option to renew or extend
     the term of this Lease for an additional period of five (5) years (the
     "Renewal Period").  Subject to the provisions of paragraph C of this
     Article, the renewal option shall be exercisable by Tenant giving written
     notice to Landlord of the exercise of such renewal option at least six (6)
     months prior to the expiration of the initial term of this Lease.  The
     Renewal Period shall be upon the same terms, covenants and conditions as
     set forth herein with respect to the initial term of this Lease, except
     that (i) the fixed monthly rental payable pursuant to Article 4 during such
     Renewal Period shall be equal to the greater of (a) the fixed monthly
     rental payable hereunder during the Lease Adjustment Year (hereafter
     defined) immediately prior to the commencement of such Renewal Period, or
     (b) the market rate of fixed monthly rental for comparable office space in
     the area prevailing at the commencement of such Renewal Period; provided,
     however, that the fixed monthly rental payable for the first year of the
     Renewal Period shall not exceed by more than 3% the fixed monthly rental
     payable by Tenant during the last Lease Adjustment Year of the initial
     term.  Thereafter, the fixed monthly rental may be adjusted annually at 30%
     of the increase in the Consumer Price Index; however, each year's increase
     shall not exceed 3% of the fixed monthly rental for the previous Lease
     Adjustment Year.  All references in

                                      -2-
<PAGE>

     this Lease to the term hereof shall be construed to mean the initial term
     and such Renewal Period, unless the context clearly indicates another
     meaning is intended.

     C.  Conditions of Exercise of Option to Renew
         -----------------------------------------

          The renewal option referred to in paragraph B of this Article may not
     be exercised by Tenant if, at the time specified in paragraph B for
     exercising such option, (i) this Lease shall not be in full force and
     effect, (ii) Tenant shall not be in possession of the demised premises, or
     (iii) an Event of Bankruptcy (as defined in Article 21) or an event of
     default (as defined in Article 22) shall have occurred and shall be
     continuing.  If Tenant shall fail to exercise the renewal option granted
     hereunder during the time or in the manner provided in paragraph B for the
     exercise thereof, or if at the time specified for the exercise of such
     renewal option, Tenant shall not be entitled to exercise such option
     because of the provisions of this paragraph C, then and in any such event,
     such renewal option shall be absolutely void and of no force and effect.

3.  USE
    ---

    Tenant shall use and occupy the demised premises solely for office use in
accordance with applicable regulations, and for no other purpose; provided,
however, that Tenant may use the demised premises for the production and sales
of computer software and documentation.  Tenant will not use or occupy the
demised premises for any unlawful, disorderly, or hazardous purpose, and will
comply with all present and future laws, ordinances, regulations and orders of
all governmental authorities having jurisdiction over the demised premises.
Tenant will not suffer any act to be done or any condition to exist on the
demised premises which may interfere unreasonably with the use of any other
property or improvements within the International Center.  Notwithstanding
anything to the contrary, Tenant may bring and keep ordinary office supplies
within the demised premises.


                                      -3-
<PAGE>

4.  RENTAL
    ------

    A.  Fixed Monthly Rental
        --------------------

    Tenant shall pay to Landlord a fixed monthly rental of Five Thousand Four
Hundred and One Dollars ($5,401.00) for the office spaces located in Pod 2L and
Five Thousand and Forty Four Dollars ($5,044.00) for the office spaces located
in Pod 4L due and payable in advance on the first (1st) day of each and every
calendar month during the term of this Lease and any renewals of such term
pursuant to Article 2; however, the fixed monthly rental for the first full
month of the first lease year (exclusive of the abatement for this month) shall
be due and payable upon execution of this Lease.

Landlord shall abate fifty percent (50%) of the fixed monthly rental for each of
the first twelve (12) months of the first lease year.

    B.  Operating Costs
        ----------------

        (1) In addition to the fixed monthly rental set forth in paragraph A
        above, Tenant shall pay to Landlord throughout the term of this Lease,
        as additional rental, two percent (2%) (being the approximate and agreed
        upon proportion which the floor area of the demised premises [7,172]
        bears to the architectural and engineering (A&E) design figure for total
        area of the Building [296,733]) of the Actual Operating Expenses. Tenant
        shall receive an annual credit in the amount of $300 to be applied
        toward payment of Operating Expenses.

        (2) The Projected Operating Expenses are estimated to be Four Dollars
        and Fifty Cents ($4.50) per square foot of total area of the Building
        for 1993.

        (3) Upon the Lease Commencement Date, and thereafter at the beginning of
        each calendar year during the term of this Lease, Landlord shall provide
        Tenant with a statement showing Landlord's Projected Operating Expenses
        for such calendar year. Tenant's proportionate share of the Projected
        Operating Expenses shall be due and payable, in equal monthly
        installments, in advance, on the first (1st) day of each and every
        calendar month of such year.


                                      -4-
<PAGE>

        (4) Within the period of ninety (90) days (or as soon thereafter as
        possible) after the close of each calendar year during the term of this
        Lease, Landlord shall give Tenant a statement of such year's Actual
        Operating Expenses and a comparison of same with the Projected Operating
        Expenses. Tenant's proportionate share of the amount by which the Actual
        Operating Expenses for such year exceeds the Projected Operating
        Expenses for such year shall be due and payable by Tenant within thirty
        (30) days of receipt of said statement. If any year-end statement
        provided by Landlord to Tenant pursuant to this paragraph shows that the
        Actual Operating Expenses during the year covered by that statement was
        less than the Projected Operating Expenses on which monthly payments
        were made for that year, Tenant's proportionate share of the
        overpayments for that year may be deducted by Tenant from its next
        payment or payments of fixed monthly rental. Any such overpayments by
        Tenant during the last calendar year of the term of this Lease shall be
        refunded within ninety (90) days after the close of such calendar year,
        unless an event of default shall have occurred and shall be continuing.

        (5) "Actual Operating Expenses", as that term is used herein, shall
        consist of all operating expenses of the Building. Actual Operating
        Expenses shall be computed on the accrual basis and shall include all
        expenditures to maintain all facilities in operation of the Building and
        such additional facilities in subsequent years as may be reasonably
        determined by Landlord to be necessary. Actual Operating Expenses shall
        mean all expenses, costs and disbursements (but not replacement of
        capital investment items or specific costs especially billed to and paid
        by specific tenants or any fines and penalties imposed upon Landlord or
        its agents, except if incurred by Landlord as a result of an act or
        omission of Tenant) of every kind and nature which Landlord shall pay or
        become obligated to pay because of or in connection with the ownership
        and operation of the Building, including but not limited to, the
        following:

            (a) Wages and salaries of all employees engaged in the operation,
            maintenance, housekeeping, or security of the Building and grounds,
            including payroll, taxes, insurance and benefits relating thereto.


                                      -5-
<PAGE>

            (b) All supplies and materials used in the operation, maintenance,
            housekeeping, and security of the Building and grounds.

            (c) Cost of all utilities including surcharges for the Building and
            the cost of water, sewer, power, heating, lighting, air conditioning
            and ventilation for the Building.

            (d) Cost of all maintenance, housekeeping, and service agreements
            for the grounds, the Building and the equipment therein, including
            but not limited to, security and energy management services, window
            cleaning, snow removal, elevator maintenance, and janitorial
            service.

            (e) Cost of all insurance relating to the Building and grounds,
            including the cost of casualty and liability insurance applicable to
            the Building and grounds, and Landlord's personal property used in
            connection therewith.

            (f) Cost of repairs and general maintenance (excluding repairs and
            general maintenance paid by proceeds of insurance or by Tenant or
            other third parties, and alterations attributable solely to tenants
            of the Building other than Tenant).

            (g) Management fees for the management of the Building.

            (h) The costs of any additional services not provided to the
            Building or grounds at the Lease Commencement Date but thereafter
            provided by Landlord in the prudent management of the Building as a
            whole.

            (i) The cost of any capital improvements made to the Building or
            grounds after the Lease Commencement Date that reduce other
            operating expenses or are required under any governmental law or
            regulation that was not applicable to the Building or grounds at the
            time it was constructed, such cost thereof to be amortized over such
            reasonable period as Landlord shall determine in accordance with
            Generally Accepted Accounting Principles

                                      -6-
<PAGE>

            (GAAP) together with interest on the unamortized balance at the rate
            of 10% per annum.

            (j) Property taxes imposed upon the demised premises by the District
            of Columbia or the Government of the United States, but only to the
            extent the rate of such taxes exceeds $2.15 for each $100 of
            assessed market value.

        (6) Operating Expenses shall be "net" only, and for that purpose shall
        be reduced by the amounts of any reimbursement, refund or credit
        received or receivable by Landlord with respect to any item of cost that
        is included in operating expenses. The following items shall be excluded
        from the definition of operating expenses as used herein:

            (a) Interest on debt or amortization payments on any mortgage or
            rental under any ground lease or other underlying lease;

            (b) Any real estate brokerage commissions or other cost incurred in
            procuring other tenants;

            (c) Any advertising expenses;

            (d) Salaries of officers and employees of Landlord to the extent not
            engaged in the management of the Building;

            (e) The cost of any items for which Landlord is reimbursed by
            insurance or otherwise; and

            (f) The cost of any repairs, alterations, improvements or other
            items which are made in order to prepare for a new tenant's
            occupancy.

        (7) Tenant at its expense shall have the right at all reasonable times
        to audit Landlord's books and records relating to Actual Operating
        Expenses under this Lease for any year or years for which additional
        rental payments pursuant to this

                                      -7-
<PAGE>

        paragraph B become due; or at Landlord's sole discretion Landlord will
        provide such audit prepared by an independent certified public
        accountant.

        (8) Tenant's obligation for amounts set forth herein shall survive the
        termination or expiration of this Lease, provided that said amounts were
        incurred before the date of expiration or termination.

    C.  Tenant shall pay all rental without demand, deduction, setoff or
    counterclaim, by check to such party and address as Landlord may designate
    by written notice to Tenant. If Landlord shall at any time or times accept
    said rental after it shall become due and payable, such acceptance shall not
    excuse delay upon subsequent occasions, or constitute a waiver of any or all
    of Landlord's rights hereunder. If the Lease Commencement Date occurs on a
    day other than the first day of a calendar month, or the lease term ends on
    a day other than the last day of a calendar month, the fixed monthly rental,
    for the partial month(s), shall be appropriately prorated at the rate of
    one-thirtieth (1/30th) of said fixed monthly rental for each day of such
    partial months during which this Lease is in effect. If the Lease
    Commencement Date occurs on a day other than the first day of a calendar
    month, the prorated fixed monthly rental for the first partial month shall
    be payable in advance on the Lease Commencement Date. If the Lease
    Commencement Date occurs on a day other than the first day of a calendar
    year, or the lease term ends on a day other than the last day of a calendar
    year, the additional rental for increases in operating costs, for the
    partial year(s), shall be appropriately prorated at the rate of one-three
    hundred and sixty fifth (1/365th) of said additional rental for each day of
    such partial years during which this Lease is in effect.

5.  RENTAL ESCALATION
    -----------------

    The fixed monthly rental shall be adjusted (but not decreased) for each
calendar year of the term, commencing on January 1, 1994 and on January 1 for
each succeeding calendar year (the "Adjustment Year"), on the following terms
and conditions: The fixed monthly rental for each Adjustment Year shall be the
sum of (i) the fixed monthly rental for the prior calendar year and (ii) thirty
percent of the product of the fixed monthly rental for the prior calendar year
and a fraction, the numerator of which shall be the difference (but not less
than zero) between (a) the


                                      -8-
<PAGE>

Consumer Price Index for All Urban Consumers, All Items, Washington, D.C.
Metropolitan Area, Base 1982-84=100, issued by the Bureau of Labor Statistics of
the U.S. Department of Labor (hereinafter referred to as the "Consumer Price
Index") for November prior to the first day of such Lease Adjustment Year and
(b) the Consumer Price Index for November prior to the commencement of the prior
calendar year and the denominator of which shall be the Consumer Price Index for
the November prior to the commencement of the prior calendar year; provided,
however, that each year's increase in fixed monthly rental based upon the
Consumer Price Index shall not exceed 3% of the fixed monthly rental for the
previous Lease Adjustment Year; provided, however, that the fixed monthly rental
for the 1994 calendar year shall be the sum of the fixed monthly rental for the
1993 calendar year and fifty percent (50%) of item (ii) above. With the first
payment of fixed monthly rental during a Lease Adjustment Year which is due at
least fifteen (15) days after Tenant's receipt of a statement (the "Escalation
Statement") from Landlord specifying the fixed monthly rental payable during
such Lease Adjustment Year (computed as aforesaid), Tenant shall pay the fixed
monthly rental specified therein for such month and, in addition, shall pay the
difference for all prior months of such Lease Adjustment Year between the fixed
monthly rental so specified and the fixed monthly rental which Tenant was
theretofore required to pay for such prior months. Thereafter, Tenant shall pay
the fixed monthly rental specified in the Escalation Statement until the first
fixed monthly rental payment due at least fifteen (15) days after Tenant
receives the next Escalation Statement, when Tenant shall make the payments
specified in the preceding sentence.

     If the Consumer Price Index is replaced by a successor index published by
the Department of Labor (or successor agency), such successor index shall be
substituted for the Consumer Price Index with such adjustments as may be
published by the Department of Labor (or successor agency) to reconcile such
successor index with the Consumer Price Index.  If the Consumer Price Index (or
such successor index) shall be discontinued with no successor index, the parties
shall attempt to agree upon a substitute index.  If the parties are unable to
agree upon a substitute index, then the matter shall be determined by
arbitration in accordance with the then prevailing rules of the American
Arbitration Association, and judgment upon the award rendered shall be final and
binding upon the parties, and may be entered in any court of competent
jurisdiction.


                                      -9-
<PAGE>

6.  SECURITY DEPOSIT
    ----------------

     Concurrently with Tenant's execution of this Lease, Tenant shall deposit
the sum of Ten Thousand Four Hundred and Forty Five Dollars ($10,445.00), less
amounts already deposited with Landlord under INTEL-L-811 ($6,636.00) which
shall be applied by Landlord towards satisfying Tenant's obligation under this
Article, with Landlord as security for the full and faithful performance by
Tenant of each and every term, provision, covenant, and condition of this Lease.
Landlord shall not be required to keep the security deposit separate from its
other funds and Tenant shall not be entitled to any interest on the security (it
is noted that in lieu of interest, Landlord and Tenant have agreed to an annual
credit of $300 towards Tenant's Operating Expenses payments as indicated in
paragraph 4(b)(1)).  In the event that Tenant is in default of any of the terms,
provisions, covenants, and conditions of this Lease, including but not limited
to payment of any rental, Landlord may use, apply, or retain the whole or any
part of the security so deposited for the payment of any such sum in default, or
for any other sum which Landlord may expend or be required to expend by reason
of Tenant's default, including any damages or deficiencies in the reletting of
the premises, whether such damage or deficiency may occur before or after any
repossession proceeding or other reentry by Landlord.  If the Landlord utilizes
any of the security deposit in curing a default on the part of Tenant, Tenant
shall immediately pay Landlord the amount necessary to restore the security
deposit to its original amount.  The security deposit or any lesser amount
properly remaining under this Lease, shall be returned to Tenant within thirty
(30) days after expiration of the term of this Lease.  The holding, use,
application, or retention of the security deposit by Landlord shall not be
deemed to restrict Landlord's right to possession of the demised premises or to
limit Tenant's liability, under this Lease while the Lease is in full force and
effect.  Upon termination or expiration of this Lease, the holding, use,
application, or retention of the security deposit (or some portion thereof) by
Landlord will reduce Tenant's monetary obligations to Landlord by the amount
held, used, applied, or retained.

7.  PREOCCUPANCY WORK AGREEMENT
    ---------------------------

     Landlord at its sole expense will provide the design services and will
finish the demised premises in accordance with the provisions set forth in
Exhibit B attached hereto and made a part


                                     -10-
<PAGE>

hereof. Landlord shall have no obligation to make any alternations, additions or
improvements to the demised premises except as set forth in Exhibit B; provided,
however, Tenant may, at its own expense, substitute a higher grade item for that
of a building-standard item (e.g., door locks) in which case Tenant shall
receive a credit from INTELSAT for the cost of the building-standard item being
replaced. Immediately following the Lease Commencement Date, Landlord shall work
diligently to complete any remaining construction items identified by Landlord
and Tenant in connection with the required construction. Landlord shall exercise
its best efforts to assure that all such construction items are completed no
later than sixty (60) days following the Lease Commencement Date. Within this
period, Tenant shall inform Landlord in writing of any such construction items,
and Landlord shall work diligently to complete such items within the sixty (60)
day period.

8.  ASSIGNMENT AND SUBLETTING
    -------------------------
    A.  Landlord's Consent Required
        ---------------------------

          Tenant may not assign, transfer, mortgage or encumber this Lease, nor
     sublet the demised premises, or any part thereof, nor shall any assignment
     or transfer of this Lease be effectuated by operation of law or otherwise,
     without first obtaining the prior written consent of Landlord, whose
     consent shall not be unreasonably withheld or delayed.  Any attempted
     assignment, transfer, mortgage, encumbrance or subletting without such
     consent shall be wholly void and shall confer no rights upon any third
     parties.  The consent of Landlord to any assignment, transfer, or
     subletting to any third party shall not be construed as a waiver or release
     of Tenant from the terms of any covenant or obligation under this Lease,
     nor shall the collection or acceptance of rental from any such assignee,
     transferee, subtenant or occupant constitute a waiver or release of Tenant
     of any covenant or obligation contained in this Lease, nor shall any such
     assignment, transfer or subletting be construed to relieve Tenant from
     obtaining the consent in writing of Landlord to any further assignment or
     subletting.  In the event that Tenant defaults hereunder, Tenant hereby
     assigns to Landlord the rental due from any subtenant of Tenant and hereby
     authorizes each such subtenant to pay said rental directly to Landlord.



                                     -11-
<PAGE>

    B.  Tenant's Application (Assignment and Sublease)
        ----------------------------------------------

          In the event that Tenant desires at any time to assign this Lease or
     to sublet the demised premises or any portion thereof, Tenant shall submit
     notice thereof to Landlord at least sixty (60) days prior to the proposed
     effective date of the assignment or sublease ("Proposed Effective Date"),
     in writing, which shall include: (a) a request for permission to assign or
     sublease, setting forth the Proposed Effective Date, which shall be no less
     than sixty (60) nor more than ninety (90) days after the date such notice
     was submitted; (b) the name of the proposed subtenant or assignee; (c) the
     nature of the proposed subtenant's or assignee's business to be carried on
     in the demised premises; (d) the terms, provisions, covenants and
     conditions of the proposed sublease or assignment; and (e) current
     financial information (audited, if available) of Tenant and the proposed
     subtenant or assignee, Tenant shall also promptly submit such additional
     information as Landlord may request in order to make a reasoned judgment.

    C.  Recapture
        ---------

          If Tenant proposes to assign this Lease or to sublet the demised
     premises or any portion thereof, Landlord may, at its option, exercisable
     upon written notice to Tenant within thirty (30) days after receipt of the
     notice from Tenant set forth in paragraph B above, elect to recapture the
     demised premises or portion thereof which Tenant proposes to sublease, and
     terminate this Lease with respect to such recaptured premises.  If Landlord
     does not elect to recapture pursuant to this paragraph C, Tenant may
     thereafter enter into a valid assignment or sublease with respect to the
     demised premises provided Landlord consents thereto, and provided further
     that (a) such assignment or sublease is executed within ninety (90) days
     after notification to Landlord of such proposal, and (b) the rental
     therefrom is not more than that stated in such notification.

    D.  Sharing of Sublet Profits
        -------------------------

          In the event that Tenant sublets the demised premises or any portion
     thereof in accordance with the provisions of this Article, Tenant shall pay
     to Landlord, in addition


                                     -12-
<PAGE>

     to all other payments required by this Lease, 25% of the amount by which
     the proceeds of such sublease exceed Tenant's payments to Landlord for any
     monthly period.

9.  CLEANING AND MAINTENANCE BY TENANT
    ----------------------------------

     Tenant will keep the demised premises and the fixtures and equipment
therein in clean, safe and sanitary condition, will take good care thereof, will
suffer no waste or injury thereto, and will at its sole cost and expense,
promptly make all repairs and perform all maintenance, in and to the demised
premises that are necessary to keep the demised premises in good order and
repair and in a safe and rentable condition, but Tenant shall not be responsible
for maintenance items assumed by Landlord under the terms of this Lease.
Without limiting the generality of the foregoing, Tenant, at its sole cost and
expense, is specifically required to make promptly all repairs (i) to the
demised premises, and (ii) to the interior glass windows, plate glass doors, and
any fixtures or appurtenances composed of glass.  Tenant shall make all repairs
to the demised premises caused by any act or omission of Tenant, or its
employees, agents or invitees.  In the event Tenant fails to maintain the
demised premises in good order, condition and repair, Landlord may (but shall
not be obligated to) give Tenant notice to do such acts as are reasonably
required to so maintain the demised premises.  In the event that after such
notice Tenant shall fail to promptly commence such work and diligently prosecute
it to completion, then Landlord shall have the right to do such acts and expend
such funds at the expense of Tenant as are reasonably required to perform such
work.  Any amount so expended by Landlord shall be paid by Tenant promptly after
demand with interest at the Default Interest Rate defined in Article 28 of this
Lease.  Landlord shall have no liability to Tenant for any damage,
inconvenience, or interference with respect to the use of the demised premises
by Tenant as a result of performing any such work.

10.  ALTERATIONS
     -----------

     Tenant will not make or permit anyone to make any alterations, additions or
improvements, structural or otherwise (hereinafter referred to as
"Alterations"), in or to the demised premises or the Building, without the prior
written consent of Landlord, which consent shall not be unreasonably withheld.
Tenant may wire the demised premises for low-voltage electrical signal purposes
provided the wiring is routed through wall conduits, above panel


                                     -13-
<PAGE>

ceilings, or below panel flooring and provided such wiring is approved in
writing in advance by Landlord. All Alterations made or permitted to be made by
Tenant shall be at Tenant's sole cost and expense. If any mechanic's lien is
filed against the demised premises, the Building, and/or the Land, for work or
materials done for, or furnished to, Tenant (other than for work or materials
supplied by Landlord), such mechanic's lien shall be discharged by Tenant within
ten (10) days thereafter, at Tenant's sole cost and expense, by the payment
thereof or by the filing of any bond required by law. If Tenant shall fail to
discharge any such mechanic's lien, Landlord may, at its option, discharge the
same and treat the cost thereof as additional rental hereunder, payable with the
monthly installment of rental next becoming due; and such discharge by Landlord
shall not be deemed to waive the defaulting of Tenant in not discharging the
same. Tenant will indemnify and hold Landlord harmless from and against any and
all expenses, liens, claims, or damages to person or property which may or might
arise by reason of the making of any Alterations. If any Alteration is made
without the prior written consent of Landlord, Landlord may correct or remove
same, and Tenant shall be liable for all costs and expenses so incurred by
Landlord. All Alterations in or to the demised premises or the Building made by
either party shall immediately become the property of Landlord; provided,
however, nothing in this Article shall be construed to impair Tenant's rights in
its personal property, and its trade fixtures, machinery and equipment which
were installed by Tenant, at its sole cost and expense.

11.  SIGNS AND FURNISHINGS
     ---------------------

     With the exception of notices and signs posted by Tenant within the demised
premises which cannot be seen from the common areas within the Building or from
the grounds outside the Building, no sign, advertisement or notice shall be
inscribed, painted, affixed or displayed by Tenant on any part of the outside or
the inside of the Building except as is approved in advance by Landlord in
writing, which approval shall not be unreasonably withheld, and if any such
sign, advertisement or notice is exhibited, without Landlord's approval,
Landlord shall have the right to remove the same and Tenant shall be liable for
any and all costs and expenses incurred by Landlord by said removal.  Landlord
shall have the right to prescribe the weight and position of safes and other
heavy equipment or fixtures that Tenant desires to install in the demised
premises.  Tenant shall not place a load upon any floor exceeding the floor load
per square foot area which such floor was designed to carry, as specified by
Landlord upon request.  Any and all


                                     -14-
<PAGE>

damage or injury to the demised premises or the Building caused by moving the
property of Tenant into or out of the demised premises, or due to the same being
on the demised premises, shall be repaired by and at the sole cost and expense
of Tenant. No furniture, equipment or other bulky matter of any description will
be received into the Building or carried in the elevators except with prior
consent of Landlord. Tenant shall give Landlord twenty-four (24) hours' prior
notice of the timing of all moving of furniture, machinery, equipment and other
material within the public areas and all such moving shall be conducted in such
manner as Landlord may reasonably require in the interests of all tenants in the
Building. Prior consent of Landlord is not required for Tenant personnel
carrying small hand-held items and equipment under 100 lbs. that can be
conveniently transported through the Building common areas and into the
elevators by a single person using a "luggage-style" handcart with rubber tires;
however, Tenant personnel shall transport such items through the Building common
areas only in a safe and courteous fashion. Tenant may hang pictures, logos, and
other wall furnishings, using small finishing nails, screws or hooks, within the
demised premises provided that substantial damage to the interior walls is not
inflicted. Tenant agrees to remove promptly from the sidewalks adjacent to the
Building any of Tenant's furniture, machinery, equipment or other property.

12.  ENTRY FOR HOUSEKEEPING, REPAIRS AND INSPECTIONS
     -----------------------------------------------

     Tenant will permit Landlord, or its representatives, to enter the demised
premises, at all reasonable times, without diminution of the rental payable by
Tenant, to examine, inspect, protect and maintain the same, to make such
alterations and/or repairs as in the judgment of Landlord may be deemed
necessary to perform housekeeping chores, and, during the last one hundred
eighty (180) days of the term of this Lease, to exhibit the demised premises to
prospective tenants after five business days advance notification to Tenant.

13.  INSURANCE RATING
     ----------------

     Tenant will not conduct or permit to be conducted any activity or place any
machinery, equipment or other property in or about the demised premises, which
will in any way, increase the rate of insurance premiums on the Building; and if
any increase in the rate of insurance premiums is stated by any insurance
company or by the applicable Insurance Rating Bureau to be due to any such
activity or property in or about the demised premises, such statement shall be



                                     -15-
<PAGE>

conclusive evidence that the increase in such rate is due to such activity or
property and, as a result thereof, Tenant shall be liable for such increase, as
additional rental hereunder, and shall reimburse Landlord therefor; provided,
however, that Landlord has provided Tenant with notice of such activity.

14.  TENANT'S EQUIPMENT
     ------------------

     Tenant will not install or operate in the demised premises any electrically
operated equipment, machinery or other property, other than electric
typewriters, calculators, personal computers, desktop or deskside engineering
workstation computers, laser printers, radios, tape recorders and other audio
equipment, televisions and other video equipment, refrigerators, desktop
electronics test, measurement, and prototyping equipment, standard size office
copiers, telex and fax machines, other standard office equipment, and any
special equipment approved in writing by Landlord, provided such equipment or
pieces of equipment does not require special outlet or current exceeding 16 amps
per 20 amp. circuits and such equipment does not exceed the floor loads set
forth in Exhibit B, without first obtaining the prior written consent of
Landlord and a mutually acceptable separate written agreement setting forth the
terms and conditions on which additional electrical power for such items is to
be furnished, including among other things, a provision for payment by Tenant of
additional rental in compensation for such excess consumption of utilities and
for the cost and expense of such additional wiring as may be occasioned by the
operation of said equipment, machinery or other property.  Tenant shall not
install, any other property of any kind or nature whatsoever which may
necessitate any changes, replacements or addition to, or in the use of, the
water, heating, plumbing, air conditioning, or electrical systems of the
Building without first obtaining the prior written consent of Landlord.
Business machines and mechanical equipment or other property belonging to Tenant
which cause noise or vibration that may be transmitted to any part of the
Building to such a degree as to be objectionable to Landlord or to any tenant in
the Building shall be installed and maintained by Tenant, at Tenant's sole cost
and expense, on vibration eliminators or other devices sufficient to eliminate
such noise and vibration.


                                     -16-
<PAGE>

15.  INDEMNITY AND PUBLIC LIABILITY INSURANCE
     ----------------------------------------

     Tenant will indemnify and hold harmless Landlord from and against any loss,
damage, liability, claim, cost or expense (including reasonable attorneys' fees)
incurred by or claimed against Landlord occasioned by or resulting from any
default of Tenant hereunder or any act or omission on the part of Tenant, its
agents, employees, or invitees or arising from or in connection with Tenant's
use or occupancy of the demised premises or which relates to the business of
Tenant, except to the extent due to the negligence or willful misconduct of
Landlord or Landlord's employees or agents.  Notwithstanding the foregoing,
Tenant shall not be liable to Landlord for any loss or damage to personal
property or injury to persons, whether or not the result of any act or omission
of Tenant, to the extent that Landlord is compensated therefor by Landlord's
insurance.  The preceding sentence shall not constitute a waiver of any
subrogation rights of Landlord's insurer.  Tenant shall not be liable for any
interruption or loss to Landlord's business from any cause.  Tenant shall obtain
and maintain in effect at all times during the term of this Lease a policy of
comprehensive public liability insurance, naming Landlord and any mortgagee of
the Building as additional insureds, protecting Landlord, Tenant and any such
mortgagee against any liability for bodily injury, death or property damage
occurring upon, in or about any part of the Building, the grounds, or the
demised premises arising from any of the items set forth in this Article against
which Tenant is required to indemnify Landlord, with such policies to afford
protection (i) with respect to bodily injury or death to the limit of not less
than One Million Dollars ($1,000,000) to any one person and to the limit of not
less than Three Million Dollars ($3,000,000) with respect to any one accident,
and (ii) with respect to damage to the property of any one owner to the limit of
not less than Five Hundred Thousand Dollars ($500,000).  Such insurance policies
shall be issued by responsible insurance companies licensed to do business in
the District of Columbia.  A certificate of insurance evidencing the issuance of
such insurance policy, together with evidence of payment of premiums thereon,
shall be delivered to Landlord upon Landlord's written request prior to the
Lease Commencement Date and at least thirty (30) days before the expiration date
of any policy evidenced by a certificate previously furnished.  Neither the
issuance of any insurance policy required under this Lease, nor the minimum
limits specified herein with respect to Tenant's insurance coverage, shall be
deemed to limit or restrict in any way Tenant's liability arising under or out
of this Lease.


                                     -17-
<PAGE>

Landlord shall maintain in effect at all times property and liability insurance
policies providing a commercially reasonable level of insurance commensurate
with a first-class office building.

16.  SERVICES AND UTILITIES
     ----------------------

    A.  Landlord shall provide, without cost or expense to Tenant, the necessary
    mains, feeders, pipes, ducts and conduits to bring electricity services and
    heating, ventilation and air conditioning (HVAC) services to the demised
    premises. Landlord shall also provide all connections and all outlets,
    risers, wiring, piping, duct work or other means of interior distribution of
    electricity and HVAC service within the demised premises.

    B.  As long as Tenant is not in default under any of the provisions of this
    Lease, Landlord shall provide the following facilities and services to
    Tenant without additional charge to Tenant (except as otherwise provided
    herein):

        (1)   Landlord will provide restroom facilities and necessary lavatory
        supplies, including hot and cold running water, at those points of
        supply provided for general use of other tenants in the Building, and
        routine maintenance, painting and electric lighting service for all
        public areas and special service areas of the Building in the manner and
        to the extent that is standard for similar first-class buildings in
        Washington, D.C.

        (2)   Landlord will provide access to the demised premises on a full-
        time twenty-four hour a day basis, subject to such reasonable
        regulations as Landlord may impose for security purposes.

        (3)   Landlord will provide heating, ventilation and air conditioning
        (HVAC) services as follows:

            (a)   Landlord will provide HVAC services Monday through Friday from
            8:00 A.M. to 6:00 P.M., and Saturday from 9:00 A.M. to 1:00 P.M.
            (holidays recognized by Landlord excepted but not to exceed fourteen
            (14) holidays per year unless otherwise agreed in writing between
            Landlord and Tenant) on an all year round basis.


                                     -18-
<PAGE>

            (b)   Landlord will maintain the building HVAC system, as well as
            the means of interior distribution within the demised premises, and
            will use all reasonable care to maintain the system in proper and
            efficient operating condition. Landlord will not be responsible for
            the failure of the air conditioning system to meet normal
            requirements, if such failure results from the occupancy of the
            demised premises by more than an average of one person for each 100
            square feet, or from faults in any interior distribution system
            provided by Tenant.

            (c)   Tenant agrees to keep and cause to be kept closed, at all
            times, exterior doors in the demised premises, except for normal
            ingress and egress, and Tenant agrees to cooperate fully with
            Landlord and to abide by all the regulations and requirements which
            Landlord may reasonably prescribe for the proper functioning and
            protection of said HVAC system.

            (d)   Landlord will maintain the above building standard air
            conditioning unit identified in Exhibit B for one (1) year and will
            be responsible for all service and repairs of problems reported by
            Tenant within one (1) year of the Lease Commencement Date. Landlord
            will be responsible for design defects for a period of five years.
            In the event of a dispute between Landlord and Tenant as to whether
            a repair is required due to a design defect, such dispute shall be
            finally settled by a third party contractor. Electricity will be
            provided to this air conditioning unit on a full-time twenty-four
            hour a day basis.

        (4)   Landlord will provide hot and cold running water on a full-time
        twenty-four hour a day basis, subject to such reasonable regulations as
        Landlord may impose. Landlord will use all reasonable care to maintain
        the building plumbing system, as well as the interior plumbing within
        the demised premises, in proper and efficient operating condition. In
        the event that a problem with the building plumbing system or the
        interior plumbing within the demised premises is caused


                                     -19-
<PAGE>

        by an act or omission of Tenant, Landlord will correct such problem at
        Tenant's sole cost and expense.

        (5)   Landlord will provide electrical energy which Tenant requires in
        the demised premises for lighting purposes and for operation of
        electrical office equipment, machinery and other property normally
        associated with use of space for office purposes but not including any
        additional requirement of Tenant caused by installation or operation of
        equipment, machinery or property as to which prior written consent of
        Landlord is required under Article 14. Overhead lighting will be
        provided Monday through Friday from 7:00 A.M. to 11:00 P.M., and
        Saturday from 7:00 A.M. to 3:00 P.M. (holidays recognized by Landlord
        excepted but not to exceed fourteen (14) holidays per year unless
        otherwise agreed in writing between Landlord and Tenant).

        (6)   Landlord will provide after hours lighting and HVAC services at
        reasonable hourly rates; provided, that Tenant shall give notice to
        Landlord prior to 1:00 P.M. on the day such service is required in the
        case of after hours service on weekdays, prior to 3:00 P.M. on the
        Friday preceding the day such service is required in the case of after
        hours service on weekends, and prior to 1:00 P.M. on the last business
        day preceding the holiday on which such service is required in the case
        of after hours service on holidays.

        (7)   Landlord will provide after hours Monday through Friday
        maintenance and housekeeping services, including replacement of
        fluorescent bulbs, glass cleaning, dusting, sweeping, vacuuming, and
        removal of trash, in a manner consistent with the standard for similar
        first-class office buildings in Washington, D.C. Such services shall
        also include cleaning the showers, sinks, and kitchen areas within the
        demised premises.

        (8)   Landlord will make available for Tenant's ordinary business usage
        conference rooms and meeting rooms, provided that Tenant shall give
        Landlord forty-eight (48) hours advance notice, and provided that such
        facilities are not scheduled to be used by Landlord or committed for use
        to other eligible users. Tenant's use of


                                     -20-
<PAGE>

        Landlord's conference rooms, adjacent atria, and other areas designed
        for common use by Building occupants for receptions shall require prior
        written permission from Landlord for each individual occasion, which
        permission shall not unreasonably be withheld. Permission shall be
        considered reasonably withheld if such facilities are scheduled for use
        by Landlord or committed for use to other eligible users. Any added
        costs for services such as set-up, restoration, security, engineering
        and catering arising from Tenant's use of Landlord's reception rooms or
        other facilities for any purpose shall be paid by Tenant on a direct
        cost basis plus any general administrative costs to INTELSAT. Catering
        service is available in the Building.

        (9)   Landlord shall maintain the Building common areas in good, safe,
        and sanitary condition and repair.

        (10)   Landlord shall maintain security which is adequate in Landlord's
        reasonable judgment for the Building.

        (11)   Landlord shall provide at least one operational elevator in the
        Building at all times. After notice of an elevator problem, Landlord
        shall undertake to make appropriate repairs with due diligence.

        (12)   Tenant shall be entitled to full access to the cafeteria
        facilities during normal hours of operation.

    C. If Landlord fails to provide any of the services specified in this
    Article, and any such failure continues for fourteen (14) days after
    Landlord receives written notification from Tenant, if such failure renders
    the demised premises unsuitable for normal commercial purposes, then
    Tenant's obligation to pay rent hereunder shall be reduced in proportion to
    the extent the premises are rendered unsuitable for normal commercial
    purposes. If Landlord's failure to provide services affects a substantial
    portion of the demised premises, and renders the demised premises unsuitable
    for normal commercial purposes, and continues for more than thirty (30)
    days, Tenant may, by written notice to

                                     -21-
<PAGE>

    Landlord, terminate this Lease upon a date not less than thirty (30) days
    after the date of such notice.

    D.  Any failure by Landlord to furnish the foregoing services as a result of
    governmental restrictions, energy shortages or from any cause beyond the
    control of Landlord shall not render Landlord liable in any respect for
    damages to either person or property, or loss of Tenant's business, nor be
    construed as an eviction of Tenant, nor work an abatement of rental, nor
    relieve Tenant from Tenant's obligations hereunder. If the Building
    equipment should cease to function properly, Landlord shall use reasonable
    diligence to repair the same. Landlord shall also use reasonable diligence
    to rectify any problem adversely affecting any of the above services and
    utilities.

17.  METERED UTILITIES
     -----------------

     Notwithstanding any contrary provision of this Lease, Tenant agrees to bear
no less than that portion of the cost of the services provided by Landlord as
described in Article 16 above, which clearly reflects the use by Tenant upon or
with respect to the demised premises and the services provided by Landlord with
respect thereto, such as computer utility costs and unusual electricity, air
conditioning, heat or water requirements; and Landlord may, in its sole
discretion, increase or decrease, from time to time during the term of this
Lease, the portion of such costs of such services to be paid by Tenant which
reasonably approximates Tenant's use thereof in excess of the Building Standards
established by Landlord from time to time for normal use of the demised
premises.  Landlord's engineering department may determine or estimate Tenant's
excess use of utility services using industry standards or Landlord may, in its
sole discretion, install separate meters or submeters to measure Tenant's actual
consumption of utility resources in excess of the Building Standards established
by Landlord from time to time for normal use of the demised premises.  The costs
and expenses related to installing such meters or submeters shall be borne by
Landlord.  In the event of excess consumption of utility services, Landlord
shall bill Tenant periodically for utility usage upon or with respect to the
demised premises, in excess of the Building Standards established by Landlord
from time to time for normal use, together with a reasonable administration
charge.  The amount specified in such bill shall

                                     -22-
<PAGE>

become additional rental due and payable with the installment of fixed monthly
rental next becoming due under the terms of this Lease.

18.  RESPONSIBILITY FOR DAMAGE TO DEMISED PREMISES
     ---------------------------------------------

     All injury or damage to the demised premises or the Building caused by
Tenant or any of its agents, employees and invitees, shall be repaired promptly
by Tenant at Tenant's sole cost and expense.  If Tenant shall fail to so repair,
Landlord shall have the right to make such repairs or replacements and any cost
or expense so incurred by Landlord shall be paid by Tenant, in which event such
cost and expense shall become additional rental due and payable with the
installment of fixed monthly rental next becoming due under the terms of this
Lease.  All injury or damage to the demised premises or the Building caused by
the act or omission of Landlord, or any of its agents, employees and invitees,
shall be the responsibility of Landlord and shall be repaired with due diligence
and as soon as practicable, at Landlord's sole cost and expense, and in no event
shall Tenant be liable for any such injury or damage caused by the act or
omission of Landlord or any of its agents, employees and invitees.

19.  LIABILITY FOR DAMAGE TO PERSONAL PROPERTY AND PERSONS
     -----------------------------------------------------

     All personal property of Tenant and its employees, agents and invitees in
or about the demised premises shall be and remain at their sole risk.  Landlord
shall not be liable for any damage to or loss of such personal property arising
from any act or omission of any person, or from any cause other than any damage
or loss except to the extent that it results directly from the negligence or
willful misconduct of Landlord.  Landlord shall not be liable for any personal
injury, including death, to Tenant, its employees, agents, or invitees, arising
from the use, occupancy or condition of the demised premises except to the
extent it arises from the negligence or willful misconduct of Landlord.
Notwithstanding the foregoing, Landlord shall not be liable to Tenant for any
loss or damage to personal property or injury, including death, to persons,
whether or not the result of Landlord's negligence or willful misconduct, to the
extent that Tenant is compensated therefor by Tenant's insurance.  The preceding
sentence shall not constitute a waiver of subrogation rights of Tenant's
insurer.  Landlord shall not be liable for any interruption or loss to Tenant's
business from any cause.

                                     -23-
<PAGE>

20.  FIRE AND OTHER CASUALTY DAMAGE TO DEMISED PREMISES
     --------------------------------------------------
     A.  Damage Generally
         ----------------

          If the demised premises shall be damaged by fire or other cause, other
     than a cause resulting from the act or omission of Tenant or its agent,
     employee or invitee, Landlord shall as soon as practicable after such
     damage occurs (taking into account the time necessary to effectuate a
     satisfactory settlement with any insurance company) repair the demised
     premises to the condition originally furnished by Landlord, at the sole
     cost and expense of Landlord, on the Lease Commencement Date, and the
     rental shall be reduced in proportion to the extent the demised premises
     are rendered untenantable, as reasonably agreed to by Landlord and Tenant,
     until such repairs are completed.  Landlord shall not be obligated to
     restore any alterations, additions or improvements to the demised premises
     installed by Tenant, including but not limited to those installed pursuant
     to Articles 7 and 10, it being expressly agreed and understood that Tenant
     shall carry insurance to cover such alterations, additions and improvements
     and Landlord shall not be required to insure such alterations, additions
     and improvements under such insurance as Landlord may carry upon the
     demised premises.  No compensation or reduction of rent will be paid or
     allowed by Landlord by reason of inconvenience, annoyance, or injury to
     business arising from the necessity of repairing the demised premises or
     any portion of the Building or the grounds.

     B.  Exceptions to Obligation to Rebuild
         -----------------------------------

          Notwithstanding the provisions of paragraph A of this Article, if
     substantial alteration or reconstruction of the Building shall, in the
     opinion of Landlord, be required as a result of damage by fire or other
     cause (whether or not the demised premises shall have been damaged by such
     fire or other cause and whether or not such damage is covered by insurance
     carried by Landlord), or if the proceeds of available insurance are less
     than one hundred percent (100%) of the cost of restoration, or if the
     damage to the demised premises or the Building is a result of an uninsured
     risk, then this Lease and the term and estate hereby granted may be
     terminated by Landlord by its giving to Tenant, within one hundred twenty
     (120) days after the date of such damage, a notice specifying a

                                     -24-
<PAGE>

     date, not less than sixty (60) days after giving of such notice, for such
     termination. In the event of the giving of such notice of termination, this
     Lease and the term and estate hereby granted shall cease and terminate as
     of the date specified therefor in such notice, and the fixed monthly rental
     and all other rental payable hereunder shall be prorated as of the date of
     termination. Additionally, it is agreed that if the demised premises or the
     Building is so substantially destroyed that reconstruction cannot be
     substantially completed within one hundred twenty (120) days from the date
     of destruction, Tenant may elect to terminate this Lease by giving Landlord
     written notice of such election within sixty (60) days after the date of
     such damage. Such termination shall be effective as of the date specified
     in such notice, which date shall not be less than sixty (60) days after
     said notice. Notwithstanding the foregoing, in the event that the demised
     premises are not damaged but the Building is substantially destroyed,
     Tenant shall have the above termination rights only in the event that said
     destruction of the Building (considering all relevant factors) results in
     the demised premises being unsuitable for normal commercial purposes.

21.  BANKRUPTCY OR INSOLVENCY
     ------------------------

     A.  Events of Bankruptcy
     --------------------
          The following shall be Events of Bankruptcy under this Lease:

          (1)   Tenant's becoming insolvent, as that term is defined in Title 11
          of the United States Code, entitled Bankruptcy, 11 U.S.C., Para. 101
          et seq. (The "Bankruptcy Code"), or under the applicable insolvency
          laws of any State, District, Commonwealth or Territory of the United
          States ("Insolvency Laws");

          (2)   The appointment of a receiver or custodian for any or all of
          Tenant's property or assets, or the institution of a foreclosure
          action upon any of Tenant's real or personal property;

          (3)   The filing of a voluntary petition under the provisions of the
          Bankruptcy Code or Insolvency Laws;

                                     -25-
<PAGE>

          (4)   The filing of an involuntary petition against Tenant as the
          subject debtor under the Bankruptcy Code or Insolvency Laws, which is
          either not dismissed within sixty (60) days of filing, or results in
          the issuance of an order for relief against the debtor, whichever is
          later; or

          (5)   Tenant's making or consenting to an assignment for the benefit
          of creditors or a common law composition of creditors.

     B.  Landlord's Remedies
     -------------------

          (1)    Termination of Lease
                 --------------------

               Upon the occurrence of an Event of Bankruptcy, Landlord shall
          have the right to terminate this Lease by giving written notice to
          Tenant; provided, however, that this subparagraph B.(1) shall have no
          effect while a case in which Tenant is the subject debtor under the
          Bankruptcy Code is pending, unless Tenant or its Trustee in bankruptcy
          is unable to comply with the provisions of subparagraphs B.(4) and
          B.(5) hereof; otherwise this Lease shall automatically cease and
          terminate, and Tenant shall be immediately obligated to quit the
          premises upon the giving of notice pursuant to this subparagraph
          B.(1).  Any other notice to quit or notice of Landlord's intention to
          reenter is hereby expressly waived.  If Landlord elects to terminate
          this Lease, everything contained in this Lease on the part of Landlord
          to be done and performed shall cease without prejudice; however, such
          termination shall not effect the right of Landlord to recover from
          Tenant all rental and any other sums accrued up to the time of
          termination or recovery of possession by Landlord, whichever is later,
          and any other monetary damages or loss of reserved rental sustained by
          Landlord.

                                     -26-
<PAGE>

          (2)    Suit for Possession
                 -------------------

               Upon termination of this Lease pursuant to subparagraph B.(1)
          hereof, Landlord may proceed to recover possession of the demised
          premises under and by virtue of the provisions of the laws of the
          District of Columbia, or by such other proceedings, including reentry
          and possession, as may be applicable.

          (3)    Reletting of Demised Premises
                 -----------------------------

               Upon termination of this Lease pursuant to subparagraph B.(1)
          hereof, the demised premises may be relet by Landlord for such rental
          and upon such terms as are not unreasonable under the circumstances
          and, if the full rental reserved under this Lease (and any of the
          cost, expenses or damages incurred by Landlord) shall not be realized
          by Landlord, Tenant shall be liable for all such costs, expenses and
          damages sustained by Landlord in accordance with the provisions of
          Article 22 hereof.

          (4)   Assumption or Assignment by Trustee
                -----------------------------------

               In the event Tenant becomes the subject debtor in a case pending
          under the Bankruptcy Code, Landlord's right to terminate this Lease
          pursuant to this Article 21 shall be subject to the rights of the
          Trustee in bankruptcy to assume or assign this Lease.  The Trustee
          shall not have the right to assume or assign this Lease unless the
          Trustee (a) promptly cures all defaults under this Lease, (b) promptly
          compensates Landlord for monetary damages incurred as a result of such
          default, and (c) provides adequate assurance of future performance.

          (5)   Adequate Assurance of Future Performance
                ----------------------------------------

               Landlord and Tenant hereby agree in advance that adequate
          assurance of future performance, as used in subparagraph B.(4) hereof
          shall mean that all of the following minimum criteria must be met: (a)
          the Trustee must pay to Landlord at the time the next installment of
          monthly rental is then due and payable under this Lease, in addition
          to payment of such fixed monthly rental, an amount equal

                                     -27-
<PAGE>

          to the next three (3) months monthly rental due under this Lease, said
          amount to be held by Landlord as an additional security deposit in
          accordance with the provisions of Article 6 and this Article 21, until
          either the Trustee or Tenant defaults in its payments of rental or
          other obligations under this Lease (whereupon Landlord shall have the
          right to draw on such funds) or until the expiration of this Lease
          (whereupon the funds shall be returned to the Trustee or Tenant); (b)
          the Tenant or Trustee must agree to pay to Landlord, at any time the
          Landlord is authorized and does draw on the funds, the amount
          necessary to restore such funds to the original level required by said
          provision; and (c) the Trustee must agree that the use of the premises
          as stated in this Lease will remain unchanged.

          (6)   Failure to Provide Adequate Assurance
                -------------------------------------

               In the event Tenant is unable to (a) cure its defaults, (b)
          reimburse Landlord for its monetary damages, (c) pay the rental due
          under this Lease, or any other payments required of Tenant under this
          Lease, on time (or within ten (10) days of the due date), and (d) meet
          the criteria and obligations imposed by subparagraph B.(5) hereof,
          then Tenant agrees in advance that it has not met its burden to
          provide adequate assurance of future performance, and this Lease may
          be terminated by Landlord in accordance with paragraph B hereof.

22.  DEFAULT OF TENANT
     -----------------
     A.  Breach of Obligations
         ---------------------

          If Tenant shall (a) fail to pay any installment of rental as aforesaid
     or fail to timely make any other payment required by the terms and
     provisions hereof and such failure to pay shall continue for more than ten
     (10) days after written notice thereof to Tenant by Landlord; or (b)
     violate or fail to perform any of the other terms, conditions, provisions,
     covenants or agreements herein made by Tenant, and if such violation or
     failure shall continue for a period of ten (10) days after written notice
     thereof to Tenant by Landlord, or if in a case involving a failure to
     perform an obligation not involving the payment of money where such failure
     to perform cannot be corrected with reasonable diligence

                                     -28-
<PAGE>

     within ten (10) days, Tenant does not begin to correct the failure to
     perform within ten (10) days after written notice thereof to Tenant by
     Landlord and/or Tenant thereafter does not use reasonable diligence to
     correct the failure to perform; or (c) if Tenant shall abandon or vacate
     the demised premises before the Lease Expiration Date, then and in any of
     said events Landlord shall have the right, at its election, then or at any
     time thereafter while such event of default shall continue to give Tenant
     written notice of its intent to terminate this Lease on the date of such
     notice or on any later date specified therein, and on the date specified in
     such notice Tenant's right to possession of the demised premises shall
     cease and this Lease shall thereupon be terminated.

     B.  Liability of Tenant
         -------------------

          If Landlord terminates this Lease pursuant to this Article 22, Tenant
     shall remain liable (in addition to accrued liabilities) for (i) the rental
     and all other sums provided for in this Lease which would have been due and
     payable to Landlord had such termination not occurred, or any and all costs
     and expenses incurred by Landlord in reentering the demised premises,
     repossessing the same, making good any default of Tenant, painting,
     altering or dividing the demised premises, putting the same in proper
     repair, protecting and preserving the same by placing therein watchmen and
     caretakers, reletting the same (including any and all attorney's fees and
     disbursements and brokerage fees incurred in so doing), and any and all
     costs and expenses which Landlord may incur during the occupancy of any new
     tenant or subtenant; less (ii) the net proceeds of any reletting prior to
     the date when this Lease would have expired if it had not been terminated.
     Tenant agrees to pay to Landlord the difference between items (i) and (ii)
     to the foregoing sentence with respect to each month during the term of
     this Lease, at the end of such month.  Any suit, action or proceeding
     brought by Landlord to enforce collection of such difference for any one
     month shall not prejudice Landlord's right to enforce the collection of any
     difference for any subsequent month.  In addition to the foregoing, and
     without regard to whether this Lease is terminated, Tenant shall pay to
     Landlord all costs and expenses incurred, including reasonable attorney's
     fees, with respect to any successful lawsuit or action instituted by
     Landlord to enforce the provisions of this Lease.  Landlord shall have the
     right, at its sole option, to relet the whole or any part of the demised


                                     -29-
<PAGE>

     premises for the whole of the unexpired term of this Lease, or longer, or
     from time to time for shorter periods, for any rental then obtainable,
     giving such concessions of rental and making such special repairs,
     alterations, improvements, additions, decorations and paintings for any new
     tenant as Landlord, in its sole and absolute discretion, may deem
     advisable.  Tenant's liability as aforesaid shall survive the institution
     of summary proceedings and the issuance of any warrant thereunder.
     Landlord shall be under no obligation to relet the demised premises, but
     agrees to use reasonable efforts to do so.  If Landlord terminates this
     Lease pursuant to this Article 22, Landlord shall have the right, at any
     time, at its option, to require Tenant to pay to Landlord, on demand, as
     liquidated and agreed final damages in lieu of Tenant's liability for
     damages hereunder, the rental and all other charges which would have been
     payable from the date of such demand to the date when this Lease would have
     expired if it had not been terminated, minus the fair rental value of the
     demised premises for the same period.  If the demised premises shall have
     been relet for all or part of the remaining balance of the term by Landlord
     after a default but before presentation of proof of such liquidated
     damages, the amount of rental reserved upon such reletting, absent proof to
     the contrary, shall be deemed the fair rental value of the demised premises
     for purposes of the foregoing determination of liquidated damages.  Upon
     payment of such liquidated and agreed final damages, Tenant shall be
     released from all further liability under this Lease with respect to the
     period after the date of such demand.  For purposes of this Article 22, the
     term rental shall include fixed monthly rental, additional rental and all
     other charges to be paid by Tenant under this Lease.  All rights and
     remedies of Landlord under this Lease shall be cumulative and shall not be
     exclusive of any other rights and remedies provided to Landlord under
     applicable law.

     C.  Attorneys' Fees
         ---------------

          If as a result of any breach or default by Tenant in the performance
     of any of the provisions of this Lease, Landlord uses the services of an
     attorney in order to secure compliance with such provisions, recover
     damages therefor, terminate this Lease or evict Tenant, Tenant shall
     reimburse Landlord upon demand for all reasonable attorneys' fees and
     expenses so incurred by Landlord, but only if Landlord prevails in such
     pursuits.

                                     -30-
<PAGE>

          If as a result of any breach or default by Landlord in the performance
     of any of the provisions of this Lease, Tenant uses the services of an
     attorney in order to secure compliance with such provisions, recover
     damages therefor, or terminate this Lease, Landlord shall reimburse Tenant
     upon demand for all reasonable attorneys' fees and expenses so incurred by
     Tenant, but only if Tenant prevails in such pursuits.

23.  WAIVER
     ------

     If under the provisions hereof Landlord shall institute proceedings and a
compromise or settlement thereof shall be made, the same shall not constitute a
waiver of any covenant herein contained nor of any Landlord's rights hereunder.
No waiver by Landlord of any breach of any term, covenant, provision, condition
or agreement herein contained shall operate as a waiver of such term, covenant,
provision, condition, or agreement itself, or of any subsequent breach thereof.
No payment by Tenant or receipt by Landlord of a lesser amount than the
stipulated installments of fixed monthly rental or additional rental shall be
deemed to be other than on account of the earliest stipulated fixed monthly
rental or additional rental, respectively, nor shall any endorsement or
statement on any check or letter accompanying a check for payment of rental or
any other amounts owed to Landlord be deemed an accord and satisfaction and
Landlord may accept such check or payment without prejudice to Landlord's right
to recover the balance of such rental or other amount owed or to pursue any
other remedy provided in this Lease.  No reentry by Landlord, and no acceptance
by Landlord of keys from Tenant, shall be considered an acceptance of a
surrender of this Lease.

24.  FIRST MORTGAGE
     --------------

     This Lease is subject and subordinate to the lien of any first mortgage
(which term "mortgage" shall include both construction and permanent financing
and shall include deeds of trust and similar security instruments) which may now
or hereafter encumber or otherwise affect the Land and the Building or
Landlord's interest therein, and to all and any renewals, extensions,
modifications, recastings or refinancings thereof, but shall not be subordinate
to any mortgage other than a first mortgage.  In confirmation of such
subordination, Tenant shall, at Landlord's request, promptly execute any
requisite or appropriate certificate or other document.  Tenant agrees that in
the event that any proceedings are brought for the foreclosure of any such


                                     -31-
<PAGE>

mortgage, Tenant shall attorn to the purchaser at such foreclosure sale, if
requested to do so by such purchaser, and shall recognize such purchaser as the
Landlord under this Lease, and Tenant waives the provisions of any statute or
rule of law, now or hereafter in effect, which may give or purport to give
Tenant any right to terminate or otherwise adversely affect this Lease and the
obligations of Tenant hereunder in the event that any such foreclosure
proceeding is prosecuted or completed.

25.  ATTORNMENT
     ----------

     In the event of (a) a transfer of Landlord's interest in the Land or
Building, (b) the termination of any ground or underlying lease of the Land or
Building, or (c) the purchase of the Building or Landlord's interest therein at
a foreclosure sale or by deed in lieu of foreclosure under any first mortgage or
pursuant to a power of sale contained in any first mortgage, then in any of such
events Tenant shall attorn to and recognize the transferee or purchaser of
Landlord's interest or the lessor under the terminated ground or underlying
lease, as the case may be, as Landlord under this Lease for the balance of the
then remainder of the term, and thereafter this Lease shall continue as a direct
lease between such person, as Landlord, and Tenant, and such lessor, transferee
or purchaser shall not be liable for any act or omission of Landlord prior to
such person's succession to title, nor be subject to any offset, defense or
counterclaim, accruing prior to such lease termination or prior to such person's
succession to title, nor be bound by any payment of fixed monthly rental or
additional rental prior to such lease termination or prior to such person's
succession to title for more than two (2) months in advance.  Tenant agrees
that, within five (5) days after written request therefor, it will, from time to
time, execute and deliver any instrument or other document required by any
mortgagee, transferee, purchaser or other interested person to confirm such
attornment and/or such obligation to attorn.

26.  CONDEMNATION
     ------------

     If the whole or a substantial part of the demised premises shall be taken
or condemned by any governmental authority for any public or quasi-public use or
purpose, then the term of this Lease shall cease and terminate as of the date
when title vests in such governmental authority, and the rental shall be abated
on such date.  In the event that Tenant accepts replacement office space offered
by Landlord, the rental shall be equitably adjusted for the period of time, if
any,

                                     -32-
<PAGE>

between the date that title vests in such governmental authority and the date
that such replacement office space is available for occupancy by Tenant. If less
than a substantial part of the demised premises is taken or condemned by any
governmental authority for any public or quasi-public use or purpose, the rental
shall be equitably adjusted on the date when title vests in such governmental
authority and this Lease shall otherwise continue in full force and effect. For
purposes hereof, a substantial part of the demised premises shall be considered
to have been taken if more than fifteen percent (15%) of the demised premises
are unusable by Tenant. In the case of any such taking or condemnation, whether
or not involving the whole or a substantial part of the demised premises, Tenant
shall have no claim against Landlord for any portion of the amount that may be
awarded as damages as a result of such taking or condemnation or for the value
of any unexpired term of this Lease.

27.  RULES AND REGULATIONS
     ---------------------

     Tenant, its agents, employees and invitees shall abide by and observe the
rules and regulations attached hereto as Exhibit C.  Tenant, its agents,
employees and invitees, shall abide by and observe such other rules or
regulations as may be promulgated from time to time by Landlord for the
operation and maintenance of the Building provided that the same are not
inconsistent with the provisions of this Lease and a copy thereof is sent to
Tenant.  Landlord shall be obligated to enforce, in a commercially reasonable
manner, the Building's rules and regulations as against all tenants in the
Building.  In particular, Landlord will take commercially reasonable steps to
protect Tenant's quiet enjoyment of its premises.

28.  RIGHT OF LANDLORD TO CURE TENANT'S DEFAULT; LATE PAYMENTS
     ---------------------------------------------------------

     If Tenant defaults in the making of any payment or in the doing of any act
herein required to be made or done by Tenant, then after twenty (20) days notice
from Landlord, Landlord may, but shall not be required to, make such payment or
do such act, and the amount of the cost and expense thereof, if made or done by
Landlord, with interest thereon at the Default Interest Rate (hereafter defined)
from the date paid by Landlord, shall be paid by Tenant to Landlord and shall
constitute additional rental hereunder due and payable with the next installment
of fixed monthly rental; but the making of such payment or the doing of such act
by Landlord shall not operate to cure such default or to estop Landlord from the
pursuit of any remedy to which Landlord would

                                     -33-
<PAGE>

otherwise be entitled. If Tenant fails to pay any installment of rental on or
within five (5) days after the day when such installment is due and payable,
such unpaid installment shall bear interest at the rate of the Default Interest
Rate from the date which is five (5) days after the date when such installment
became due and payable to the date of payment thereof by Tenant. In addition,
Tenant shall pay to Landlord, as a "late charge," four percent (4%) of any
payment herein required to be made by Tenant which is more than ten (10) days
late to cover the costs of collecting amounts past due. Such interest and late
charge shall constitute additional rental hereunder due and payable with the
next installment of fixed monthly rental. For purposes hereof, the Default
Interest Rate shall be the prime interest rate charged by Riggs National Bank
during the period of such default plus two percent (2%) per annum.

29.  NO PARTNERSHIP
     --------------

     Nothing contained in this Lease shall be deemed or construed to create a
partnership or joint venture of or between Landlord and Tenant or to create any
other relationship between the parties hereto other than that of Landlord and
Tenant.

30.  NO REPRESENTATIONS BY LANDLORD
     ------------------------------

     Neither Landlord nor any agent, employee or representative of Landlord has
made any representations or promises with respect to the demised premises or the
Building except as herein expressly set forth, and no rights, privileges,
easements or licenses are granted to Tenant except as herein set forth.
Furthermore, Tenant understands and agrees that Landlord has made no commitment
and is under no obligation to utilize Tenant's services, to purchase any goods
from Tenant or to enter into any relationship with Tenant other than that of
Landlord and Tenant as established pursuant to the provisions of this Lease.
Tenant also acknowledges and agrees that it has not entered into this Lease in
reliance upon, nor are its obligations hereunder conditioned upon Landlord
utilizing any of its services, purchasing any goods from it, or entering into
any relationship with Tenant other than that of Landlord and Tenant.

31.  BROKERS
     -------

     Tenant shall indemnify and hold Landlord harmless from all damages
(including reasonable attorneys' fees and costs) resulting from any claims that
may be asserted against

                                     -34-
<PAGE>

Landlord by any broker, finder or other person with whom Tenant has dealt.
Tenant understands and agrees that any representation or statement by any third
party engaged by Landlord as an independent contractor which is made with regard
to the demised premises or the Building shall not be binding upon Landlord nor
serve as a modification of this Lease and Landlord shall have no liability
therefor, except to the extent such representation is also contained herein or
is approved in writing by Landlord.

32.  NOTICES
     -------

     All notices or other communications hereunder shall be in writing and shall
be deemed duly given if delivered in person or sent by certified or registered
mail, return receipt requested, first class, postage prepaid,

                  (i)  if to Landlord, at:

                       INTELSAT
                       3400 International Drive, N.W.
                       Washington, D.C.  20008-3098

                       Attn:  Department Manager, Facilities Management and
                              Office Services

                  (ii) if to Tenant, at:

                       MIL 3, Inc.
                       Pod 4L
                       3400 International Drive, N.W.
                       Washington, D.C.  20008-3098

                       Attn:  Mr. Alain Cohen

prior to the Lease Commencement Date and, with respect to Tenant, at the demised
premises after the Lease Commencement Date, unless notice of a change of address
is given pursuant to the provisions of this Article.

33.  ESTOPPEL CERTIFICATES
     ---------------------

     Tenant agrees, at any time and from time to time, upon not less than ten
(10) days prior written notice by Landlord, to execute, acknowledge and deliver
to Landlord a statement in

                                     -35-
<PAGE>

writing (i) certifying that this Lease has been unmodified since its execution
and is in full force and effect (or if there have been modifications, that this
Lease is in full force and effect, as modified, and stating the modifications),
(ii) stating the dates, if any, to which the fixed monthly rental and additional
rental hereunder have been paid by Tenant, (iii) stating whether or not to the
knowledge of Tenant, there are then existing any defaults under this Lease (and,
if so, specifying the same), and (iv) stating the address to which notices to
Tenant should be sent. Any such statement delivered pursuant hereto may be
relied upon by Landlord or any prospective purchaser or mortgagee of the Land
and/or Building or any part thereof or estate therein.

34.  COVENANTS OF LANDLORD
     ---------------------

     Landlord covenants that it has the right to make this Lease, and that if
Tenant shall pay the rental and perform all of Tenant's obligations under this
Lease, Tenant shall, during the term hereof, freely, peaceably and quietly
occupy and enjoy the full possession of the demised premises without molestation
or hindrance by Landlord or any party claiming through or under Landlord.  In
the event of any sale or transfer of Landlord's interest in the demised
premises, the covenants and obligations of Landlord under this Lease accruing
after the date of such sale or transfer shall be imposed upon such successor-in-
interest (subject to the provisions of Articles 24 and 25 hereof) and any prior
Landlord shall be freed and relieved of all covenants and obligations of
Landlord hereunder accruing after the date of such sale or transfer.

35.  SURRENDER OF DEMISED PREMISES
     -----------------------------

     Upon the expiration or termination of the term of this Lease, Tenant shall
quit and surrender to Landlord the demised premises, including all improvements,
additions or alterations made or permitted pursuant to Articles 7 and 10, broom
clean, in good order and condition, ordinary wear and tear and acts of God
excepted, and Landlord shall have the right to reenter and resume possession of
the demised premises.  Tenant shall, prior to expiration or termination of this
Lease, and at its sole cost and expense, remove all of its personal property,
trade fixtures, machinery and equipment installed in the demised premises and
restore the demised premises to the condition existing at the commencement of
the lease allowing for reasonable wear and tear, or as otherwise agreed by
Landlord and Tenant, and if such property is not removed by Tenant prior to
expiration or termination of this Lease, it shall, at Landlord's option, become
the

                                     -36-
<PAGE>

property of Landlord and shall be surrendered with the demised premises as a
part thereof. Should Tenant fail (i) to remove any of its personal property,
trade fixtures, machinery and/or equipment, as required hereunder, or (ii) to
restore the demised premises as aforesaid, Landlord may remove same and restore
the demised premises at Tenant's sole cost and expense and Tenant shall
reimburse Landlord for all cost, expense, damages and losses which Landlord
sustains by reason of such failure by Tenant to remove and/or restore. When
Tenant surrenders the premises, Tenant may remove the upgraded locks installed
by Tenant at no cost to Tenant.

36.  HOLDING OVER
     ------------

     If Tenant shall hold possession of the demised premises after the end of
the term of this Lease, Tenant shall be deemed to be occupying the demised
premises as a Tenant from month to month, at one and one half times the monthly
rental then in effect if such holdover occurs without the Landlord's written
consent and at the monthly rental then in effect if such holdover occurs with
the Landlord's written consent, and subject to all the other terms, conditions,
provisions, covenants and obligations of this Lease insofar as the same are
applicable, or as same shall be adjusted, to a month-to-month tenancy.

37.  LIEN FOR RENT
     -------------

     If Tenant does not cure a default under this Lease within ten (10) days
after receiving notice of such default from Landlord, or if Tenant vacates the
premises without Landlord's approval, then in either event, Landlord shall have
a lien on all property of Tenant contained within the demised premises at the
time of the default and such property shall be and remain subject to such lien
of Landlord for payment of all rental and all other sums agreed to be paid by
Tenant herein or for services or costs and expenses relating to the demised
premises that Tenant may hereafter become liable to pay to Landlord.

38.  UNDERLYING LEASE
     ----------------

     Tenant acknowledges that it has been advised of the Lease Agreement between
the Government of the United States as Lessor and Landlord as Lessee dated 8
June 1982, as amended on 22 February 1985, which is sometimes herein referred to
as the Underlying Lease.

                                     -37-
<PAGE>

Tenant agrees that it will not do or cause to be done anything which would
constitute a breach of obligations of Landlord as Lessee under said Underlying
Lease.

39.  SALES AND EXCISE TAXES
     ----------------------

     If during the term of this Lease any governmental authority shall impose a
sales, use, excise or any other tax, with the exception of taxes based upon
Landlord's gross income, on the rentals payable by Tenant hereunder, Tenant
shall pay such tax (or reimburse Landlord for any such tax paid by Landlord)
within ten (10) days after request therefor by Landlord to Tenant.

40.  REPORTING OF PAYMENTS
     ---------------------

     A.  The Tenant agrees to provide to INTELSAT any and all information
     concerning any form of inducement or payment, with a value exceeding U.S.
     $100 ("gratuity") which is given, directly or indirectly, at any time, by
     or on behalf of the Tenant to any INTELSAT Official in connection with this
     Lease. If the value of this Lease exceeds U.S. $500,000, the Tenant shall
     also cause its firm of independent certified public accountants to certify
     to the internal auditor of INTELSAT annually that all such information
     known to such firm has been so provided.

     B.  If INTELSAT determines that any such gratuity has been given for the
     purpose of obtaining this Lease or favorable treatment under this Lease,
     INTELSAT shall be entitled to treat the giving of such gratuity as a
     material breach of this Lease, to terminate this Lease by giving written
     notice of termination to Tenant, and to receive from Tenant punitive
     damages in addition to any other damages .

     C.  The rights and remedies of INTELSAT under this Article are in addition
     to any other rights and remedies provided by law or under this Lease.

     D.  For the purposes of this Article, "INTELSAT Official" includes any
     officer, agent, servant or employee of INTELSAT, its Signatories, or its
     Parties, and any person accredited to attend meetings of INTELSAT organs.


                                     -38-
<PAGE>

41.  GENDER
     ------

     Feminine or neuter pronouns shall be substituted for those of the masculine
form, and the plural shall be substituted for the singular, in any place or
places herein in which the context may require such substitution.

42.  BENEFIT AND BURDEN
     ------------------

     The provisions of this Lease shall be binding upon and inure to the benefit
of the parties hereto and each of their permitted successors and assigns.
Landlord may freely and fully assign its interest or delegate its obligations
hereunder.

43.  GOVERNING LAW
     -------------

     It is the intention of the parties hereto that this Lease (and the terms,
conditions, provisions and covenants hereof) shall be construed and enforced in
accordance with the laws of the District of Columbia.  Landlord and Tenant each
hereby waive any objection to the venue of any action filed by either party in
any court situated in the District of Columbia and each party further waives any
right, claim or power, under the doctrine of forum non conveniens or otherwise,
to transfer any such action filed by any party to any other court.

44.  WAIVER OF TRIAL BY JURY
     -----------------------

     Each party hereby waives all right to trial by jury in any claim, action,
proceeding or counterclaim by either party against the other on any matters
arising out of or in any way connected with this Lease, the relationship of the
parties, Tenant's use or occupancy of the demised premises and/or any claim of
injury or damage.

45.  OPTION TO LEASE ADDITIONAL OFFICE SPACE
     ---------------------------------------

     In the event space in addition to the demised premises becomes available
for commercial use at any time during the Term (including any extensions
thereof) in Pods 2L, 4L or 7L, and Landlord does not require such additional
space for its own use, Landlord shall provide written notice to Tenant of the
availability of such additional space and Tenant shall have an option,
exercisable by providing written notice to Landlord no later than ten (10) days
from the date of

                                     -39-
<PAGE>

receipt of Landlord's notice, to lease from Landlord, in addition to the demised
premises, the additional space referenced in Landlord's notice; provided,
however, that based upon Landlord's own need for office space Landlord may make
its offering of space in Pod 7L conditional upon Tenant vacating office space
within its leased premises located in Pods 4L and 2L.

46.  PARKING OPTION
     --------------

     During the term of this Lease, Tenant shall have the right to rent from
Landlord, on a monthly basis, up to six (6) underground parking space at rates
now or hereinafter established by Landlord (currently $75.00), which rates shall
not be in excess of the monthly parking rates generally charged other Tenants in
the Building for similar parking spaces.  The parking fee may be modified from
time to time at the sole discretion of Landlord, provided that the parking fee
may not exceed the market rental for similar commercial parking space in the
area.

47.  MISCELLANEOUS
     -------------

     Window Blinds - Landlord, at its sole expense, shall promptly install
     -------------
window blinds on the exterior windows of Pod 4L pending a decision by the
appropriate governmental authority.  If such blinds are damaged prior to
Tenant's occupancy of the 4L space, Landlord shall repair the damage or replace
the blinds.  Such window blinds shall not be removed or replaced by Landlord
unless and until such blinds are expressly prohibited by appropriate
governmental authority.  Tenant may, at its sole option and expense, install
such blinds or screens in Pod 2L as soon as the appropriate governmental
approvals have been obtained.

     Cable Television - Landlord shall cooperate with Tenant's efforts to obtain
     ----------------
cable television in its offices; however, all cabling costs associated with such
efforts and services shall be borne by Tenant.

     Smoking - Throughout the term of the Lease Agreement, INTELSAT shall
     -------
enforce in a commercially reasonable fashion the smoking policy set forth in the
INTELSAT Rules and Regulations (Exhibit C).

     Quiet Enjoyment - Tenant's quiet enjoyment of the demised premises shall be
     ---------------
protected by Landlord in a commercially reasonable fashion.

                                     -40-
<PAGE>

     Final Lease Agreement - This Lease Agreement shall supersede in full the
     ---------------------
existing Lease Agreement between the parties, INTEL-L-811, as of the Lease
Commencement Date provided herein.

48.  ENTIRE AGREEMENT
     ----------------

     This Lease, including all exhibits, schedules and addenda attached hereto,
constitutes the entire agreement of the parties hereto, and supersedes all prior
representations, inducements, or agreements, oral or otherwise, between the
parties with respect to the subject matter hereof.  No addition to, deletion of
or deviation from the provisions of this Lease shall be binding unless in
writing and duly signed by the party against whom the same is sought to be
enforced.

                                     -41-
<PAGE>

     IN WITNESS WHEREOF, on the day and year first hereinabove written, the
undersigned have executed two (2) copies of this Lease under seal.

                                        LANDLORD
                                        --------

                                        International Telecommunications
                                           Satellite Organization
                                        3400 International Drive, N.W.
                                        Washington, D.C.  20008-3098

Attest:                                 By:    /s/ David T. Tudge
       -------------------------               ------------------
                                                      Signed

                                                   David T. Tudge
                                               ------------------
                                                      Typed

                                        Title:    Vice President and
                                                  Chief Financial Officer
                                                  -----------------------
[Seal]

                                        TENANT
                                        ------

                                        MIL 3, Inc.
                                        3400 International Drive, N.W.
                                        Pod 4L
                                        Washington, D.C.  20008-3098

Attest: /s/ Steven P. Bonarial (sp)     By:    /s/ Alain Cohen
        ------------------------------         ------------------
                                               Signed

                                                 Alain Cohen
                                               ------------------
                                                 Typed

[Corporate Seal]                        Title:   President
                                               ------------------


                                     -42-
<PAGE>

                                                         Exhibit A - Page 1 of 2

                                                                     MIL 3, Inc.

                                                                          Pod 2L




                               Atrium - 6 Diagram
<PAGE>

                                                         Exhibit A - Page 2 of 2

                                                                     MIL 3, Inc.

                                                                          Pod 4L






                                    Diagram
<PAGE>

                                                          Exhibit B, Page 1 of 3


                        PREOCCUPANCY WORK - MIL 3, INC.
                               INTELSAT BUILDING
             (PERTAINING TO RENTAL SPACES REQUIRING MODIFICATIONS)

Partitioning:         . Partitioning between suites and units to be slab to slab
                        and sound insulated.
                      . Partitioning to be constructed of 3 5/8" steel studs at
                        24 inches o.c. and 5/8" gypsum wallboard.
                      . Partitioning provided by landlord will be one linear
                        foot for each twelve (12) feet of rentable space.

Painting:             . Three coats flat finish paint building standard color
                        for all office partitioning.
                      . Interior doors to be stained building standard red oak
                        or equal.
                      . Hallways will be covered with building standard vinyl
                        wallcover.

Doors:                . Interior doors of rift cut red oak veneer, or equal with
                        glass sidelights, will be provided for each office in
                        the rentable space.
                      . Doors to be 2'-8" x 7'10" solid core, metal frame
                        equipped with building standard latch set.
                      . One suite entrance door will be provided for each tenant
                        with metal frame, equipped with building standard lock
                        set.

Floor Covering:       . Building standard carpet tile 18" x 18", special grey,
                        including 2-1/2 vinyl straight base will be provided.

Ceiling:              . Building standard suspended, acoustical tile ceiling
                        system provided.

Electrical:           . One 120 volt duplex wall electrical outlet will be
                        provided for each 150 square feet of rentable space.

Telephone:            . One telephone outlet will be provided for each 200
                        square feet of rentable space.

Outlets:              . Any special cable or amperage requirements are not
                        included, but will be provided by the landlord at
                        tenant's expense.

Lighting:             . One 2' x 4' recessed fluorescent lighting fixture with
                        parabolic lens per 80 square feet of rentable space.

Heating and           . Building standard heating and cooling for normal
Air Conditioning        office use and one thermostat for each 200 square
                        feet of rentable space is provided.
                      . Excess capacity, special controls and exhaust
                        requirements are not included, but will be provided by
                        landlord at tenant's expense.
<PAGE>

                                                          Exhibit B, Page 2 of 3


Window Covering:      . No window covering allowed.


Floor Loads:          . Floor loads are designed for 60 pounds per square foot
                        of live load and an additional allowance of 20 pounds
                        per square foot for partitioning.

Plumbing:             . Landlord will provide rough plumbing from nearest
                        plumbing stack to one location within space at landlords
                        option; 1,500 square feet of rentable space minimum.

Design Services:      . Consultation with landlord's space designer is provided
                        to prepare the documentation for tenant's space plan and
                        interior layout.
                      . Two (2) two- (2) hour planning sessions are provided and
                        one (1) major and two (2) minor revisions in the space
                        plans are allowed at no cost to tenant.

Allowance:            . Enumerated above are maximum allowance quantities to be
                        provided by landlord at no cost to tenant. There will be
                        no credits for unused portions of allowance quantities.

ABS Items:            . See Exhibit B, Page 3
<PAGE>

                                                          Exhibit B, Page 3 of 3

                        PREOCCUPANCY WORK - MIL 3, INC.
                                INTELSAT BUILDING

    Landlord will provide, at Landlord's sole expense, the following:

1.  One folding door in 4L;

2.  Millwork in existing 4L space necessary to modify existing counter and
    cabinets in connection with expansion of the Demo Room as illustrated. No
    ABS millwork will be provided by Landlord in 2L space;

3.  Two showers, two sinks, and plumbing associated with such showers and sinks
    in 2L;

4.  Computer Room air conditioner (three ton) in 2L;

5.  Shower exhaust fans, ducts in 2L;

6.  All Power Upgrades necessary to support Tenant's electrical requirements in
    both 2L and 4L as enumerated in Tenant's Letter of 17 December 1992
    (attached hereto as Exhibit E).

7.  Existing vinyl wall covering in the hallway within the new space in 4L shall
    be repaired or cleaned by Landlord where necessary.

8.  All carpet tiles within the new spaces in 4L and 2L shall be homogeneous in
    appearance.

9.  Landlord shall repaint Tenant's preexisting office space within six (6)
    months of taking occupancy under this Lease.

10. All thermostats controlling the climate within Tenant's demised premises
    shall be located somewhere within Tenant's demised premises where
    mechanically and commercially feasible. Landlord shall provide Tenant with a
    diagram or list of the thermostats and the areas which they control.

11. Landlord shall relocate the exit sign in the 4L conference room to a less
    obtrusive location.

     If there are any other ABS items which are necessary to construct the
office space as illustrated in Exhibit A, Landlord shall provide such items at
its sole expense.  Tenant reserves the right to alter the plans during the space
planning process.  If either Landlord or Tenant alters the plans (Exhibit A) in
a way that requires additional ABS items, such items shall be paid by the party
who alters the plans.
<PAGE>

                                                                       EXHIBIT C

                             RULES AND REGULATIONS
                             ---------------------

     The following rules and regulations have been formulated for the safety and
well-being of all the tenants of the Building.  Strict adherence to these rules
and regulations is necessary so that each and every tenant will enjoy a safe and
unannoyed occupancy in the Building.  Any violation of these rules and
regulations by any tenant which continues after notice from Landlord shall be
sufficient cause for termination of this Lease at the option of the Landlord.
In the event of a conflict between the terms of the Lease and the terms of these
Rules and Regulations, the terms of the Lease shall take precedence.

     Landlord may, upon request by any tenant, waive the compliance by such
tenant of any of the foregoing rules and regulations, provided that (i) no
waiver shall be effective unless signed by Landlord or Landlord's authorized
agent, (ii) any such waiver shall not relieve such tenant from the obligation to
comply with such rule or regulation in the future unless expressly consented to
by Landlord, and (iii) no waiver granted to any tenant shall relieve any other
tenant from the obligation of complying with the foregoing rules and regulations
unless such other tenant has received a similar written waiver from Landlord.

1.  The sidewalks, entrances, passages, courts, elevators, vestibules,
stairways, corridors or halls or other parts of the Building not occupied by any
tenant shall not be obstructed or encumbered by any tenant or used for any
purpose other than normal ingress and egress to and from the demised premises.
Landlord shall have the right to control and operate the public portions of the
Building and the grounds, and the facilities furnished for the common use of the
tenants, in such manner as Landlord deems best for the benefit of the tenants
generally.  No tenant shall permit the visit to the demised premises of persons
in such numbers or under such conditions as to interfere with the use and
enjoyment by other tenants of the entrances, corridors, elevators and other
public portions or facilities of the Building or of the grounds.

2.  Access to the building will be via recognised entrances only and tenants,
their employees, agents and guests will refrain from using emergency exits -
except in emergency situations.

3.  Employees of each tenant shall be provided by Landlord with a photo ID
access card which will facilitate entry to the common areas in the building.
Each tenant shall be responsible for returning all such cards to the Landlord on
termination of employment of any such person - or all cards upon termination of
the lease.  In the event of the loss, or failure to return any such card or
cards on termination of contract or lease, or for any other reason, tenant shall
pay Landlord all replacement costs involved.

4.  No signs, pictures, awnings or other projections shall be attached to the
outside walls of the Building without the prior written consent of Landlord.  No
drapes, blinds, shades or screens shall be attached to or hung in, or used in
connection with, any window or door of the
<PAGE>

demised premises, without the prior written consent of the Landlord, which
consent will not be unreasonably withheld.

5.  The lavatories and other plumbing fixtures shall not be used for any
purposes other than those for which they were constructed, and no sweepings,
rubbish, rags, or other substances shall be thrown therein.  All damages
resulting from any misuse of the fixtures shall be borne by the tenant who, or
whose employees, agents or guests, shall have caused the same.

6.  There shall be no marking, painting, drilling into or other form of
defacement or damage of any part of Building or grounds.  No boring, cutting or
stringing of wires shall be permitted without the prior written consent of
Landlord, which consent shall not be unreasonably withheld.  No tenant shall
construct, install, maintain, use or operate within, or on the outside of, the
Building or on the grounds, any electrical device, wiring or apparatus in
connection with a loudspeaker or other sound system.

7.  No animals, birds or pets of any kind shall be brought into or kept in or
about the Building or grounds.  Automobiles, motorcycles and bicycles may be
parked in the Building garage only in designated areas and only with the
specific prior approval of Landlord.  Automobiles, motorcycles and bicycles
parked without Landlord's approval, or not parked in designated areas, are
subject to removal without notice.

8.  No cooking shall be done or permitted by Tenant in the Building or on the
grounds, provided, however, that Tenant may install and maintain a microwave
oven, hot plate, coffee station, beverage and/or candy vending machines in the
demised premises for the convenience and exclusive use of Tenant's employees.
No tenant shall cause or permit any unusual or objectionable odors to originate
from the demised premises.

9.  No space in the Building shall be used for manufacturing.

10.  No tenant shall make, or permit to be made, any disturbing noises or
disturb or interfere with occupants of this Building or neighboring buildings or
premises or those having business with them, whether by the use of any musical
instrument, radio, talking machine or in any other way.  No tenant shall discard
anything into the public or common areas.

11.  No firearms or controlled substances shall be brought into or kept upon the
Building or grounds.
12.  No flammable, combustible or explosive fluid, chemical or substance shall
be brought or kept within the Building or upon the grounds.

13.  No additional locks or bolts of any kind shall be placed upon any of the
doors or other parts of the demised premises by any tenant, nor shall any
changes be made in existing locks or the machanisms thereof, without the prior
written consent of Landlord, which consent shall not be unreasonably withheld.
The doors leading to the corridors or main halls shall be kept closed during
business hours except as they may be used for normal ingress or egress.  Each
tenant shall, upon the termination of his tenancy, return to Landlord all keys
either furnished to, or otherwise procured by, such tenant, and in the event of
the loss of any such keys, such tenant shall pay to Landlord the cost of
replacing the locks.
<PAGE>

14.  All removals, or the carrying in or out of any safes, freight, furniture,
box, container or bulky matter of any description must take place during the
hours which Landlord or its agent may determine from time to time.  Landlord
reserves the right to inspect all materials to be brought into or out of the
Building or grounds, and to exclude from the Building and grounds all materials
which violates any of these Rules and Regulations or the Lease of which these
Rules and Regulations are a part.

15.  Any person employed by any tenant to perform janitorial services within the
demised premises must obtain Landlord's consent prior to commencing such work,
and such persons shall, while in or outside the Building, comply with all
instructions issued by Landlord or its representatives.  No tenant shall pay any
employees of Landlord or Landlord's agents to perform any work or services in or
outside the Building.

16.  No tenant shall purchase spring water, ice, coffee, soft drinks, towels, or
other products or services from any company or persons who violate the Building
regulations or disturb occupants of the Building.

17.  Landlord reserves the right to exclude from the Building and grounds at all
times any person who is not known or does not properly identify himself to the
Building management, receptionist or security guard on duty.  Landlord may, at
his option, require all persons admitted to or leaving the Building or grounds
to register with Building security guards.  Each tenant shall be responsible for
all persons for whom such tenant authorizes entry into the Building or upon the
grounds, and shall be liable to Landlord for all acts and omissions of such
persons.

18.  The premises shall not be used for lodging or sleeping or any immoral or
illegal purpose.

19.  The requirements of tenants will be acted upon only by the Landlord or
Landlord's designated representative.  Landlord's employees shall not be
requested to perform any work or do anything outside of their regular duties
unless authorized by the management of the Landlord.

20.  Canvassing, soliciting and peddling in the Building or upon the grounds is
prohibited and each tenant shall cooperate to prevent same.

21.  No water cooler or plumbing fixture may be installed by any tenant without
the prior written consent of the Landlord.

22.  There shall not be used in any space, or in the public or common halls of
the Building, either by any tenant or by others, any hand trucks, except those
equipped with rubber tires and side guards.

23.  Mats, trash or other objects shall not be placed in the public or common
corridors.

24.  There shall be no parking of vehicles or other obstructions placed in the
loading dock area.
<PAGE>

25.  Landlord reserves the right at any time, upon written notice to Tenant, to
make, eliminate, or modify these Rules and Regulations as in Landlord's sole
judgement may be necessary or desirable.

26.  Smoking is prohibited anywhere on INTELSAT property, including but not
limited to all offices, hallways, stairwells, garages," common areas, entrances,
parks and all surrounding grounds.  This regulation applies to all building
occupants, visitors and guests.
<PAGE>

                                                                       Exhibit D

                                    Diagram
<PAGE>

                       INTERNATIONAL TELECOMMUNICATIONS
                             SATELLITE ORGANIZATION

                       CERTIFICATE BY LANDLORD AND TENANT
                    AS TO DATE OF DELIVERY AND ACCEPTANCE OF
                         POSSESSION OF LEASED PREMISES

     Attached to and made a part of the Agreement of Lease, dated 18 June 1993,
as amended by Lease Amendment No. 2 dated 28 April 1995, entered into by and
between International Telecommunications Satellite Organization as Landlord, and
MIL 3, Inc. as Tenant.

     Landlord and Tenant do hereby declare that possession of the Additional
Office Space, 378 square feet located on the second level of Pod L of Phase II
of the INTELSAT Building, all as more fully described in Lease Amendment No. 2,
was accepted by Tenant on the 28th day of April, 1995.  The commencement date
for the term of lease for this Additional Office Space is hereby established as
1 May 1995, and the termination date shall be in accordance with Article 50,
Paragraph B of Lease Amendment No. 2.

<TABLE>
<CAPTION>
<S>                                          <C>
                                             LANDLORD

Attest:                                      INTELSAT


[sig]                                        /s/ Robert A. Lambert
-------------------------------------------  --------------------------------------------

                                             By:     Robert A. Lambert
                                                 ----------------------------------------
                                             Date:     15/5/95
                                                  ---------------------------------------
                                             TENANT

Attest:                                      MIL 3, Inc.


/s/ Marc A. Cohen                            /s/ Alain Cohen
-------------------------------------------  --------------------------------------------

                                             By:    Alain Cohen, President
                                                 ----------------------------------------
                                             Date:     5/14/95
                                                  ---------------------------------------
</TABLE>
<PAGE>

                             LEASE AMENDMENT NO. 3
                             ---------------------

     THIS LEASE AMENDMENT NO. 3 is made and entered into this 8th day of
September 1995, by and between the International Telecommunications Satellite
Organization ("Landlord") and MIL 3, Inc., a corporation organized and existing
under the laws of the State of Maryland ("Tenant") for the purpose of amending
the LEASE dated 18 June 1993 between said parties.

     WHEREAS, Landlord and Tenant entered into an Agreement of Lease on 18 June
1993 (the "Lease") for certain office space (the "demised premises") located on
the second and fourth levels of Pods L of Phase II of the office building
situated at 3400 International Drive, N.W., Washington, D.C. 20008-3098;

     WHEREAS, Landlord and Tenant entered into Lease Amendment No. 1 on 26
October 1994 to provide for the temporary lease by Landlord to Tenant of 1,580
rentable square feet on the second level of Pod L of Phase II;

     WHEREAS, Landlord and Tenant entered into Lease Amendment No. 2 on 28 April
1994 to provide for the temporary lease by Landlord to Tenant of 378 rentable
square feet on the second level of Pod L of Phase II;

     WHEREAS, Tenant desires to lease from Landlord, in addition to other leased
space described in the Lease, 1,958 rentable square feet located in the second
level of Pod L of Phase II, 7,768 rentable square feet located in the third
level of Pod L of Phase II and 105 rentable square feet located in the fourth
level of Pod L in Phase II (the "Additional office Space");

     WHEREAS, Landlord and Tenant are agreed upon the terms and conditions for
such lease of Additional Office Space; and

                                      -2-
<PAGE>

     WHEREAS, Landlord and Tenant are agreeable to amending the Lease to address
this matter;

     NOW THEREFORE, in consideration of the mutual promises of Landlord and
Tenant contained herein and for other good and valuable consideration, receipt
of which is hereby acknowledged, the parties hereto, intending to be legally
bound, agree to amend the Lease as follows:

1.  The following is ADDED to the end of Article 1:

          Effective 17 June 1998, the square footage measurements for Pod 2L
     shall be changed to 4,745 square feet of rentable area (2,260 + 2,485) and
     for Pod 4L shall be changed to 2,652 square feet of rentable area (1,432 +
     1,220).  In the event that there are any changes to the designation of fire
     corridors prior to 17 June 1998, the parties agree that the above changes
     in the square footage measurements may require further adjustments.

2.  In the penultimate line of Article 1, DELETE "or decrease".

3.  DELETE Article 2.A in its entirety and SUBSTITUTE the following therefor:

          The term of this Lease (hereinafter referred to as the "term") shall
     commence on 17 June 1993 ("Lease Commencement Date") and shall expire on 31
     December 1999 ("Lease Expiration Date").

                                      -3-
<PAGE>

4.  AMEND Article 2.B. by ADDING the words "(l January 2000 through 31 December
    2004)" after the words "additional period of five (5) years" which appear
    in the first sentence.

5.  AMEND Article 4.A. by ADDING the following after the second paragraph:

    Effective 17 June 1998, Tenant shall pay to Landlord a fixed monthly rental
    of Five Thousand Seven Hundred Thirty-three and 54/100 ($5,733.54) for the
    office spaces located in Pod 2L and Four Thousand Nine Hundred Fifty and
    40/100 ($4,950.40) for the office spaces located in Pod 4L due and payable
    in advance on the first (1st) day of each and every calendar month during
    the term of this Lease and any renewals of such term pursuant to Article 2.

6.  Article 8.B as follows:

    On lines 4 and 8, SUBSTITUTE "thirty (30) days" for "sixty (60) days".

    On line 9, SUBSTITUTE "one hundred eighty (180) days" for "ninety (90)
    days".

    DELETE subparagraph (d) and SUBSTITUTE "(d)" for "(e)".

    At the end of Paragraph B, ADD, "Within thirty (30) days of execution of
    any sublease or assignment made pursuant to this Article 8, Tenant shall
    submit to Landlord a copy of such sublease or assignment agreement."

                                      -4-
<PAGE>

7.  AMEND Article 8.C as follows:

    On line 4, DELETE "the notice from Tenant set forth in paragraph B above"
    and SUBSTITUTE "Tenant's Notice of Availability of Space (which need only
    describe the office space available)".

    On line 6, REPLACE the phrase "or portion thereof" with the parenthetical,
    (or portion thereof in floor-by-floor increments)".

    On Line 13, SUBSTITUTE "one hundred eighty (180) days" for "ninety (90)
    days".

8.  Reverse the order of Articles 8.B and 8.C such that "Recapture" becomes
    Paragraph B and "Tenant's Application (Assignment and Sublease)" becomes
    Paragraph C.

9.  DELETE Article 45 in its entirety and substitute the following therefor:

         In the event space in addition to the demised premises becomes
    available for commercial use at any time during the Term (including any
    extensions thereof) in Pod 7L, and Landlord does not require such
    additional space for its own use, Landlord shall provide written notice to
    Tenant of the availability of such additional space and Tenant shall have
    an option, exercisable by providing written notice to Landlord no later
    than ten (10) days from the date of receipt of Landlord's notice, to lease
    from Landlord, in addition to the demised premises, the additional space
    referenced in Landlord's notice; provided, however, that based upon
    Landlord's own need for office space Landlord may make its offering of

                                      -5-
<PAGE>

    space in Pod 7L conditional upon Tenant vacating office space within its
    leased premises located in Pods 2L, 3L and 4L.

10. A new Article 51 shall be ADDED as follows:

    51.  ADDITIONAL OFFICE SPACE

         The Additional Office Space described in paragraph A of this Article
    51 shall be governed by the terms and conditions of this Lease unless
    otherwise provided in this Article 51.

    A.  Demised Premises
        ----------------

         In addition to other leased space described herein, Landlord leases to
    Tenant, and Tenant hereby leases from Landlord, certain space outlined on
    Exhibit H attached hereto, and located on the second level of Pod L of
    Phase II of the INTELSAT Building, certain space outlined on Exhibit I
    attached hereto, and located on the third level of Pod L of Phase II of the
    INTELSAT Building, and certain space outlined in Exhibit J attached hereto,
    and located on the fourth level of Pod L of Phase II of the INTELSAT
    Building.  The parties hereto agree that the Additional Office Space
    constitutes 1,958 square feet of rentable area in Pod 2L, 7,768 square feet
    of rentable area in Pod 3L, and 105 square feet of rentable area in Pod 4L.
    This Additional Office Space shall be considered to be a portion of the
    "demised premises" as used throughout this Lease, during the term specified
    in Paragraph B of this Article 51, unless such meaning would be
    inconsistent with the provisions of this Article 51.  Tenant, at Tenant's
    sole expense, shall have the right to verify Landlord's measurement of the

                                      -6-
<PAGE>

    Additional Office Space, and shall also have the right to verify the
    necessity for, and location of, the additional fire corridor in Pod 3M.
    Adjustments to Tenant's square footage will be made if deemed appropriate
    by both parties.  Tenant hereby agrees that Landlord shall have the right,
    for the purposes of accommodating other tenants of Pod L or otherwise, to
    increase or decrease the dimensions, change the configuration, or to
    otherwise alter the common corridors; however, such alteration of the
    common areas shall not materially impair Tenant's use of the demised
    premises, and shall not increase the amount of common area attributable to
    Tenant as specified in this Article.

    B.  Term
        ----

         The term of lease for the Additional Office Space shall commence upon
    the date that Landlord notifies Tenant that Landlord's work (as set forth
    in Exhibits K and L of this Lease Amendment) is substantially complete;
    provided, however, that in the event that construction is substantially
    completed in either one of the new office spaces in 2L and 3L prior to
    substantial completion of construction in the other new office space,
    Landlord shall notify Tenant, and Tenant, at its sole option, shall be
    entitled to take occupancy of the substantially completed space.  If Tenant
    so elects to take occupancy, Tenant shall so inform Landlord in writing,
    and the Term for that office space shall commence upon the date that Tenant
    takes occupancy of the substantially completed space.  In such event,
    Tenant's total monthly rental shall not include rental for the location and
    square footage of the space which remains unfinished until such time as
    Landlord notifies Tenant that Landlord's work as set forth in Exhibits K

                                      -7-
<PAGE>

    and L of this Lease Amendment in the remaining new office space is
    substantially completed.  The term of the lease for the Additional office
    Space shall expire at midnight on 31 December 1999.

    C.  Rental
        ------

         (i)  Fixed Monthly Rental - In addition to the fixed monthly rental
    specified in Paragraph A of Article 4 of this Lease, Tenant shall pay to
    Landlord a sum of Two Thousand Two Hundred-two and 75/100 Dollars
    ($2,202.75) for the Additional Office Space in Pod 2L (1,958 rentable sq.
    ft.), Twelve Thousand Nine Hundred Forty-six and 67/100 Dollars ($12,946.67)
    for the Additional Office Space in Pod 3L (7,768 rentable sq. ft.), and One
    Hundred Ninety-six and 00/100 Dollars ($196.00) for the Additional Office
    Space in Pod 4L (105 rentable sq. ft.) due and payable in advance on the
    first day of each and every calendar month during the lease term specified
    in Paragraph B of this Article 51. Partial months shall be prorated.
    Landlord shall abate 50% of the fixed monthly rental for the Additional
    Office Space for each of the first twelve (12) months of the first lease
    year. Such abatement shall commence upon the date that Landlord notifies
    Tenant that all of Landlord's work as set forth in Exhibits K and L of this
    Lease Amendment is substantially complete.

         (ii) Operating Costs - In addition to the percentage of operating
    expenses specified in Article 4.B, Tenant shall pay to Landlord throughout
    the lease term specified in Paragraph B of this Article 51, as additional
    rental, 0.0331 (3.31%) (being the approximate and agreed upon proportion
    which the floor area of the Additional Office Space (9,831 rentable square

                                      -8-
<PAGE>

    feet) bears to the architectural and engineering (A&E) design figure for
    total area of the Building) (296,733 rentable square feet) of the Actual
    Operating Expenses.

         In the event Tenant obtains and exercises an option to take occupancy
    of the new office space in Pod 2L prior to taking occupancy of the new
    office space in Pod 3L, Tenant shall pay to Landlord until the date that
    Landlord notifies Tenant that all of Landlord's work as set forth in
    Exhibits K and L of this Lease Amendment is substantially complete, as
    additional rental, 0.0066 or (0.66%) (being the approximate and agreed upon
    proportion which the floor area of the new office space in Pod 2L (1,958
    rentable square feet) bears to the architectural and engineering (A&E)
    design figure for total area of the Building) (296,733 rentable square
    feet) of the Actual Operating Expenses.  once such notice is provided by
    Landlord to Tenant, Tenant shall begin paying to Landlord, as additional
    rental, 0.0331 (3.31%), in lieu of the 0.0066 (.66%) of the Actual
    operating Expenses.

          In the event Tenant obtains and exercises an option to take occupancy
    of the new office space in Pod 3L prior to taking occupancy of the new
    office space in Pod 2L, Tenant shall pay to Landlord until the date that
    Landlord notifies Tenant that all of Landlord's work as set forth in
    Exhibits K and L of this Lease Amendment is substantially complete, as
    additional rental, 0.0262 (2.62%) (being the approximate and agreed upon
    proportion which the floor area of the new office space in Pod 3L (7,768
    rentable square feet) bears to the architectural and engineering (A&E)
    design figure for total area of the Building) (296,733 rentable square
    feet) of the Actual Operating Expenses.  Once such notice is provided by

                                      -9-
<PAGE>

    Landlord to Tenant, Tenant shall begin paying to Landlord, as additional
    rental, 0.0331 (3.31%), in lieu of the 0.0262 (2.62%) of the Actual
    Operating Expenses.

         The projected Operating Expenses for 1995 are estimated to be Four
    Dollars and Forty Seven Cents ($4.47) per square foot of total area of the
    Building for 1995.

    D.  Security Deposit
        ----------------

         Concurrently with Tenant's execution of this Lease Amendment No. 3,
     Tenant shall deposit with Landlord the sum of Thirty Thousand Six Hundred
     Ninety and 84/100 Dollars ($30,690.84), less amounts already deposited with
     Landlord under Amendment No. 1 ($1,580.00) and Amendment No. 2 ($378.00);
     $15,345.42 of which shall be used as payment of the first month's rent
     actually due Landlord and the remaining portion of which shall be used as
     security for the full and faithful performance by Tenant of each and every
     term, provision, covenant, and condition of this Lease.  Landlord shall
     grant to Tenant an annual rental credit equal to 2.30% interest on the
     security deposited with Landlord pursuant to this Article 51.D.  The
     security deposited with Landlord pursuant to this Article 51.D shall be in
     addition to the security deposit previously paid by Tenant pursuant to
     Article 6 of the Lease and shall be subject to the provisions of Article 6
     of this Lease.

     E.  Preoccupancy Work
         -----------------

          Landlord, at its own expense, will provide design services and
     construct the demised premises and Additional Office Space in accordance

                                     -10-
<PAGE>

     with the provisions set forth in Exhibits K and L attached hereto and made
     a part hereof.  Landlord shall have no obligation to make any alterations,
     additions, or improvements to the demised premises or the Additional office
     Space except as set forth in Exhibits K and L; provided, however, Tenant
     may, at its own expense, substitute a higher grade item for that of a
     building-standard item (e.g., door locks) in which case Tenant shall
     receive a credit from INTELSAT for the cost of the building-standard item
     being replaced.  Subject to the need to minimize remobilization costs,
     Tenant shall have the right to specify the scheduling of construction in
     the different office spaces, to minimize any disruption to Tenant's
     business.

     F.  Parking Option
         --------------

          Tenant shall have the right, on a one-time offer, to lease from
     Landlord six (6) parking permits in the Building garage in addition to
     those specified in Article 46.  This parking option may be exercised by
     Tenant only upon the date on which Tenant executes this Lease Amendment No.
     3.  The additional parking permits shall be leased by Tenant at prevailing
     market rates, currently $80 per space, per month.

11.  A new Exhibit H is attached hereto and incorporated herein.

12.  A new Exhibit I is attached hereto and incorporated herein.

13.  A new Exhibit J is attached hereto and incorporated herein.

14.  A new Exhibit K is attached hereto and incorporated herein.

15.  A new Exhibit L is attached hereto and incorporated herein.


                                     -11-
<PAGE>


     IN WITNESS WHEREOF, on the day and year first hereinabove written, the
undersigned have executed two copies of this Lease Amendment No. 3.
<TABLE>
<CAPTION>
                                              LANDLORD
                                              --------
<S>                                           <C>
                                              International Telecommunications Satellite
                                              Organization
                                              3400 International Drive, N.W.
                                              Washington, D.C.  20008-3098


Attest:     /s/ R. A. Lambert                 By:     /s/ David T. Tudge
       -----------------------------------       -----------------------------------------
                  Signed                                      Signed

                                                          David T. Tudge
                                              --------------------------------------------
                                              Title:  Vice President & Chief
                                                      Financial Officer

                                              TENANT
                                              ------

                                              MIL 3, Inc.
                                              3400 International Drive, N.W.
                                              Pod 4L
                                              Washington, D.C.  20008-3098


Attest:     [sig]                             By:     /s/ Alain Cohen
       -----------------------------------       -----------------------------------------
                     Signed                                Signed


                                              --------------------------------------------
                                                               Typed

                                              Title:
                                                    --------------------------------------
</TABLE>

                                     -12-
<PAGE>

                   A new Exhibit H shall be ADDED as follows:


                                                           EXHIBIT H

                       PLAN OF ADDITIONAL SPACE IN POD 2L

                                     -13-
<PAGE>

                   A new Exhibit I shall be ADDED as follows:

                                                           EXHIBIT I

                       PLAN OF ADDITIONAL SPACE IN POD 3L

                                     -14-
<PAGE>

                   A new Exhibit J shall be ADDED as follows:

                                                           EXHIBIT J

                       PLAN OF ADDITIONAL SPACE IN POD 4L

                                     -15-
<PAGE>

                  STANDARD WORK LETTER FOR TENANT IMPROVEMENTS

                                INTELSATBUELDING

                                    PHASE II

<TABLE>
<CAPTION>
<S>                  <C>
Partitioning:        .    Partitioning between suites and units to be slab to slab and sound insulated.

                     .    Partitioning to be constructed of 3 5/8" steel studs at 24 inches o.c. and 5/8' gypsum

Painting:            .    Three coats eggshell finish paint building standard color for all office partitioning.

                     .    Interior doors to be stained building standard red oak or equal.

Doors:               .    Interior doors of rift cut red oak veneer, or equal with glass sidelights, will be provided for each
                          office in the rentable space.

                     .    Doors to be 2'-8" x 7'10" solid core, metal frame equipped with building standard latch set.
                          One suite entrance door will be provided for each tenant with metal frame, equipped with building
                          standard lock set.

Floor                .    Building standard carpet tile 18" x 18", special grey, including 2% vinyl straight base will be
Covering:                 provided.

Ceiling:             .    Building standard suspended, acoustical tile ceiling system provided.

Electrical:          .    One 120 volt duplex wall electrical outlet will be provided for each 150 square feet of rentable
                          space.

Telephone:           .    One telephone outlet will be provided for each 200 square feet of rentable space.

Outlets:             .    Any special cable or amperage requirements are not included, but will be provided by the landlord at
                          tenant's expense.

Lighting:            .    One 2' x 4' recessed fluorescent lighting fixture with parabolic lens per 80 square feet of rentable
                          space.

Heating and Air      .    Building standard beating and cooling for normal office use and one thermostat for each 200 square
Conditioning:             feet of rentable space is provided.

                     .    Excess capacity, special controls and exhaust requirements are not included, but will be provided by
                          landlord at tenant's expense.

Window Covering      .    No window covering provided by Landlord.

Floor Loads:         .    Floor loads am designed for 60 pounds per square foot of live load and an additional allowance of 20
                          pounds per square foot for partitioning.

Plumbing:            .    Landlord will provide rough plumbing from nearest plumbing stack to one location within space at
                          landlords option; 1,500 square feet of rentable space minimum.

Design Services:     .    Consultation with landlord's space designer is provided to prepare the documentation for tenant's
                          space plan and interior layout.

                     .    Two (2) two- (2) hour planning sessions are provided and one (1) major and two (2) minor revisions
                          in the space plans are allowed at no cost to tenant.

Allowance            .    Enumerated above are maximum allowance quantities to be provided by landlord at no cost to tenant.
                          There will be no credits for unused portions of allowance quantities.
</TABLE>

                                     -16-
<PAGE>

04 May 1999


Mr. Joseph Greeves
Chief Financial Officer
MIL-3, Inc.
3400 International Drive, N.W.
Suite 4L
Washington, D.C.  20008

                               VIA HAND DELIVERY
                               -----------------

Re:   Lease Amendment No. 4

Dear Mr. Greeves:

Enclosed for your files is one original, fully executed Amendment to Lease 4
INTEL-L-1433 (Lease Amendment No. 4), entered into by and between International
Telecommunications Satellite Organization as Landlord, and MIL-3, Inc. as
Tenant.  A copy of the Delivery & Acceptance Certificate is also enclosed.

If you have any questions, please call me at (202) 944-8235.

Sincerely,

CHARLES E. SMITH COMMERCIAL REALTY

/s/ Karen K. Wilson

Karen K. Wilson, RPA
Lease Administrator

/kkw
Enc. (2)

cc:  R. Lambert, INTELSAT
     C. Diehl, C.E. Smith
     Lease File

                                     -17-
<PAGE>

                             LEASE AMENDMENT NO. 4
                             ---------------------

     THIS LEASE AMENDMENT NO. 4 is made this 28th day of April, 1999, by and
between the International Telecommunications Satellite Organization
("Landlord"), an international organization, and MIL 3, Inc., a corporation
organized and existing under the laws of the State of Maryland ("Tenant") for
the purpose of amending the LEASE dated 18 June 1993 between said parties.

     WHEREAS, Landlord and Tenant entered into an Agreement of Lease on 18 June
1993 (the "Lease") for certain office space (the "demised premises") located on
the second and fourth levels of Pod L of Phase II of the office building
situated at 3400 International Drive, N.W., Washington, D.C. 20008-3098;

     WHEREAS, Landlord and Tenant entered into Lease Amendment No. 1 on 26
October 1994 to provide for the temporary lease by Landlord to Tenant of certain
office space on the second level of Pod L of Phase II;

     WHEREAS, Landlord and Tenant entered into Lease Amendment No. 2 on 28 April
1995 to provide for the temporary lease by Landlord to Tenant of certain office
space on the second level of Pod L of Phase II;

     WHEREAS, Landlord and Tenant entered into Lease Amendment No. 3 on 8
September 1995 to extend the term of the Lease, to provide for the lease by
Landlord to Tenant of certain office space on the second, third and fourth
levels of Pod L of Phase II, and to amend other provisions of the Lease;

     WHEREAS, Tenant desires to lease from Landlord, in addition to other leased
space described in the Lease, 3,987 rentable square feet located in the third
level of Pod M of Phase II (the "Additional office Space");

                                     -18-
<PAGE>

     WHEREAS, Landlord and Tenant are agreed upon the terms and conditions for
such lease of Additional Office Space; and

     WHEREAS, Landlord and Tenant are agreeable to amending the Lease to address
this matter;

     NOW THEREFORE, in consideration of the mutual promises of Landlord and
Tenant contained herein and for other good and valuable consideration, receipt
of which is hereby acknowledged, the parties hereto, intending to be legally
bound, agree to amend the Lease as follows:

1.  A new Article 52 shall be ADDED as follows:

    52.  ADDITIONAL OFFICE SPACE

         The Additional Office Space described in paragraph A of this Article
    52 shall be governed by the terms and conditions of this Lease unless
    otherwise provided in this Article 52.

          A.  Demised Premises
              ----------------

               In addition to other leased space described herein, Landlord
          leases to Tenant, and Tenant hereby leases from Landlord, certain
          space outlined on Exhibit M attached hereto, and located on the third
          level of Pod M of Phase II of the INTELSAT Building.  The parties
          hereto agree that the Additional office Space constitutes 3,987 square
          feet of rentable area.  This Additional Office Space shall be
          considered to be a portion of the "demised premises" as used
          throughout this Lease, during the term specified in Paragraph B of
          this Article 52, unless such meaning would be inconsistent with the
          provisions of this Article 52.  Tenant, at Tenant's sole expense,
          shall have the right to verify Landlord's measurement of the
          Additional Office Space.  Adjustments to Tenant's square footage will
          be made if deemed appropriate by both parties.  Tenant hereby agrees
          that Landlord shall have the right, for the purposes of accommodating
          other tenants of Pod M or otherwise, to increase or decrease the
          dimensions, change the configuration, or to otherwise alter the common
          corridors; however, such alteration of the common areas shall not
          materially impair Tenant's use of the demised premises, and shall not
          increase the amount of common area attributable to Tenant as specified
          in this Article.

                                     -19-
<PAGE>

          B.  Term
              ----

               The term of lease for the Additional Office Space shall commence
          upon 23 January 1999 and shall expire at midnight on 31 December 1999.

          C.  Rental
              ------

               (i) Fixed Monthly Rental - In addition to the fixed monthly
          rental specified in Paragraph A of Article 4 of this Lease, Tenant
          shall pay to Landlord

                    (a) for the period 23 January 1999 to 8 April 1999, a sum of
               Five Thousand Nine Hundred Eighty and 50/100 ($5,980.50) per
               month, and

                    (b) for the period 9 April 1999 until expiration of this
               Lease, a sum of Six Thousand Twenty Three and 69/100 Dollars
               ($6,023.69) per month, due and payable in advance on the first
               day of each and every calendar month during the lease term
               specified in Paragraph B of this Article 52.  Payment for the
               first month under this Lease Amendment No. 4 shall be paid
               concurrently with Tenant's execution thereof.  Partial months
               shall be prorated.

               (ii) Operating Costs - In addition to the percentage of operating
          expenses specified in Article 4.B, Tenant shall pay to Landlord, for
          the period 9 April 1999 until expiration of this Lease, as additional
          rental, 0.0134 (1.34%) (being the approximate and agreed upon
          proportion which the floor area of the Additional Office Space (3,987
          rentable square feet) bears to the architectural and engineering (A&E)
          design figure for total area of the Building) (296,733 rentable square
          feet) of the Actual Operating Expenses.

          D.  Security Deposit
              ----------------

               Concurrently with Tenant's execution of this Lease Amendment No.
          4, Tenant shall deposit with Landlord the sum of Six Thousand Twenty
          Three and 69/100 Dollars ($6,023.69), which shall be used as security
          for the full and faithful performance by Tenant of each and every
          term, provision, covenant, and condition of this Lease.  The security
          deposited with Landlord pursuant to this Article 52.D shall be in
          addition to the security deposit previously paid by Tenant pursuant to
          the Lease and shall be subject to the provisions of Article 6 of this
          Lease.

          E.  Preoccupancy Work
              -----------------

               Notwithstanding any other provision of this Lease, the Additional
          Office Space shall be provided by Landlord to Tenant in "AS IS"
          condition.

                                     -20-
<PAGE>

          F.  Parking Option
              --------------

               Tenant shall have the right, on a one-time offer, to lease from
          Landlord three (3) parking permits in the Building garage in addition
          to those specified in Article 46 and Article 51.F.  This parking
          option may be exercised by Tenant only upon the date on which Tenant
          executes this Lease Amendment No. 4.  The additional parking permits
          shall be leased by Tenant at prevailing market rates, currently $80
          per space, per month.

2.  A new Exhibit M is attached hereto and incorporated herein.

          IN WITNESS WHEREOF, on the day and year first hereinabove written, the
undersigned have executed two copies of this Lease Amendment No. 4.

<TABLE>
<CAPTION>
<S>                                          <C>
                                             LANDLORD
                                             --------

                                             International Telecommunications Satellite
                                             Organization

                                             3400 International Drive, N.W.
                                             Washington, D.C.20008-3098


Attest:     /s/ R. Lambert                   By:     /s/ Joseph Corbett
       ----------------------------------       -----------------------------------------
                Signed                                       Signed

                                                            Joseph Corbett
                                             --------------------------------------------
                                             Title:  Vice President &
                                                     Chief Financial Officer

                                             TENANT
                                             ------

                                             MIL 3, Inc.
                                             3400 International Drive, N.W.
                                             Pod 4L
                                             Washington, D.C.20008-3098

Attest:     /s/ A. Dalton                    By:     /s/ Joseph F. Greeves
       ----------------------------------       -----------------------------------------
                                                             Signed

                                                          Joseph F. Greeves
                                             --------------------------------------------
                                                                Typed
                                             Title:  Chief Financial Officer
</TABLE>

                                     -21-
<PAGE>

                                                EXHIBIT M

                                  Mil 3 POD-3M

                                   3,987 s.f.


                                     -22-
<PAGE>

                        INTERNATIONAL TELECOMMUNICATIONS

                             SATELLITE ORGANIZATION

                       CERTIFICATE BY LANDLORD AND TENANT

                    AS TO DATE OF DELIVERY AND ACCEPTANCE OF

                         POSSESSION OF LEASED PREMISES

     Attached to and made a part of the Agreement of Lease, dated 18 June 1993,
as amended by Lease Amendment No. 4, dated 08 April 1999, entered into by and
between International Telecommunications Satellite Organization as Landlord, and
MIL 3, Inc. as Tenant.

     Landlord and Tenant do hereby declare that possession of the Additional
Office Space, 3,987 square feet located on the third level of Pod M of Phase If
of the INTELSAT Building, all as more fully described in Lease Amendment No. 4,
was accepted by Tenant on the 23rd day of January 1999.  The commencement date
for the term of lease for this Additional Office Space is hereby established as
23 January 1999, and the termination date shall be in accordance with Article
52, Paragraph B of Lease Amendment No. 4.

     In addition, Tenant acknowledges the exercising of their right to lease
three (3) additional parking spaces within Phase II of the INTELSAT Building
Parking Garage.

<TABLE>
<CAPTION>
<S>                                          <C>
                                             LANDLORD

                                             INTELSAT


Attest:                                      By:     /s/ Robert A. Lambert
                                                -----------------------------------------
                                                         Robert A. Lambert, RPA, FMA
/s/ Karen K. Wilson
-------------------------------------------  Date:     13 April 1999
                                                  ---------------------------------------

                                             TENANT

                                             MIL 3, Inc.



Attest:                                      By:    /s/ Joseph F. Greeves
                                                -----------------------------------------
                                                       Joseph F. Greeves
/s/ A. Dalton
-----------------------------------------    Date:     4/12/99
                                                  ---------------------------------------
</TABLE>
                                     -23-
<PAGE>

12 October 1999


Mr. Joseph Greeves
Chief Financial Officer
MIL-3, Inc.
3400 International Drive, N.W.
Suite 4L
Washington, D.C.  20008                                 VIA HAND DELIVERY
                                                        -----------------

Re:   Lease Amendment No. 5

Dear Mr. Greeves:

Enclosed for your files is one original, fully executed Amendment to Lease
#INTEL-L- 1433 (Lease Amendment No. 5), entered into by and between
International Telecommunications Satellite Organization as Landlord, and MIL-3,
Inc. as Tenant.

If you have any questions, please call me at (202) 944-8235.

Sincerely,

CHARLES E. SMITH COMPANIES

/s/ Karen K. Wilson

Karen K. Wilson, RPA
Lease Administrator

/kkw
Enc.

cc:  Robert Lambert, INTELSAT
     John Navolio, C.E. Smith
     CES Lease File

                                     -24-
<PAGE>

                             LEASE AMENDMENT NO. 5
                             ---------------------

     THIS LEASE'AMENDMENT NO. 5 is made this 7th day of September, 1999, by and
                                             ---        ---------------
between the International Telecommunications Satellite Organization
("Landlord"), an international organization, and MIL 3, Inc., a corporation
organized and existing under the laws of the State of Maryland ("Tenant") for
the purpose of amending the LEASE dated 18 June 1993 between said parties.

     WHEREAS, Landlord and Tenant entered into an Agreement of Lease on 18 June
1993 (the "Lease") for certain office space (the "demised premises") located on
the second and fourth levels of Pod L of Phase II of the office building
situated at 3400 international Drive, N.W., Washington, D.C.  20008-3098;

     WHEREAS, Landlord and Tenant entered into Lease Amendment No. 1 on 26
October 1994 to provide for the temporary lease by Landlord to Tenant of certain
office space on the second level of Pod L of Phase II;

     WHEREAS, Landlord and Tenant entered into Lease Amendment No. 2 on 28 April
1995 to provide for the temporary lease by Landlord to Tenant of certain office
space on the second level of Pod L of Phase II;

     WHEREAS, Landlord and Tenant entered into Lease Amendment No. 3 on 8
September 1995 to extend the term of the Lease, to provide for the lease by
Landlord to Tenant of certain office space on the second, third and fourth
levels of Pod L of Phase II, and to amend other provisions of the Lease;

     WHEREAS, Landlord and Tenant entered into Lease Amendment No. 4 on 28 April
1999 to provide for the lease by Landlord to Tenant of certain office space on
the third level of Pod M of Phase II;

     WHEREAS, Tenant desires to extend the initial term of the Lease for one
year beyond the Lease Expiration Date of 31 December 1999, and Landlord is
agreeable to that extension.

     NOW THEREFORE, in consideration of the mutual promises of Landlord and
Tenant contained herein and for other good and valuable consideration, receipt
of which is hereby acknowledged, the parties hereto, intending to be legally
bound, agree to amend the Lease as follows:

1.  A new Article 53 shall be ADDED as follows:

    53.  ONE YEAR EXTENSION
         ------------------

         Notwithstanding Paragraph A of Article 2 and Paragraph B of Article 52
    to this Lease, and without prejudice to Paragraph B of Article 2 ("Option
    to Renew") to this Lease, the initial-term of this Lease shall be extended
    for one year and shall expire at midnight on 31 December 2000.  The fixed
    monthly rental shall be adjusted for the calendar year commencing on

                                     -25-
<PAGE>

     January 1, 2000 and on January 1 for each succeeding calendar year in
     accordance with Article 5 to this Lease.

     IN WITNESS WHEREOF, on the day and year first hereinabove written, the
undersigned have executed two copies of this Lease Amendment No. 5.

<TABLE>
<CAPTION>
<S>                                          <C>
                                             LANDLORD
                                             --------
                                             International Telecommunications Satellite
                                             Organization

                                             3400 International Drive, N.W.
                                             Washington, D.C.  20008-3098

Attest:

/s/ R. A. Lambert                            By:   /s/ Joseph Corbett
-------------------------------------------     ----------------------------------------
      Signed                                             Signed

                                                            Joseph Corbett
                                             --------------------------------------------
                                             Title:  Vice President &
                                                     Chief Financial Officer

                                             TENANT
                                             ------

                                             MIL 3, Inc.
                                             3400 International Drive, N.W.
                                             Pod 4L
                                             Washington, D.C.  20008-3098
Attest:

/s/ A. Dalton                                By:      /s/  Joseph F. Greeves
-------------------------------------------     ------------------------------------------
     Signed                                                   Signed

                                                          Joseph F. Greeves
                                              --------------------------------------------
                                                                Typed

                                              Title:  Chief Financial Officer
</TABLE>
                                     -26-