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                                                                   EXHIBIT 4.1.5

                                  DATUM INC.
                               FIFTH AMENDMENT
                                      TO
                          1994 STOCK INCENTIVE PLAN

        As approved by the stockholders of Datum Inc. (the "Company") at the
Company's duly called, noticed and held annual meeting of stockholders of June
8, 2000, the Company's 1994 Stock Incentive Plan (the "Plan") is amended as of
such date such that the second and third sentences of Section 2 of the Plan are
amended and restated in their entirety as follows:

        The total number of shares of Common Stock of the Company which may be
        issued under the Plan shall not exceed, in the aggregate, 1,477,217
        shares which amount shall increase by 2% of the number of shares of
        common stock outstanding as of the Company's fiscal year-end. The
        aggregate maximum number of shares represented by options or rights to
        purchase under this Plan that may be granted or offered under stock
        options or rights to purchase to any one person may not exceed one
        hundred fifty thousand (150,000) shares per calendar year.<PAGE>   1

                                                                   EXHIBIT 10.23

                                     LEASE

        Lease made this 28th day of June, 1999 by and between NAGOG DEVELOPMENT
COMPANY, a Massachusetts limited partnership, with a principal place of business
at One Nagog Park, Acton, Massachusetts, hereinafter referred to as "Landlord",
which expression shall include its successors and assigns where the context so
admits of the one part, and VIASAT, INC., a California corporation, with a
principal place of business at 2290 Cosmos Court, Carlsbad, California 92009,
hereinafter referred to as "Tenant", which expression shall include its
successors and assigns where the context so admits of the other part.

                                   WITNESSETH

        1. PREMISES. Landlord hereby leases and demises to the Tenant and the
Tenant does hereby hire and take from the Landlord those premises consisting of
2,240 square feet, more or less, of rentable area on the third floor of the
building at 125 Nagog Park, Acton, Massachusetts, 01720, shown outlined in red
on a sketch attached hereto and marked Exhibit A, together with all rights and
appurtenances thereto belonging, herein "Demised Premises". This lease is made
subject to all rights, easements, restrictions and agreements of record, if any,
insofar as now in force and applicable, and local zoning and building laws.

        Tenant shall have the right to use in common with Landlord and others
lawfully entitled thereto, the lobby, rest rooms, loading areas, stairways,
sidewalks, parking areas and access ways to the building, herein referred to as
"Common Areas". Included within Tenant's rights to use the Common Areas shall be
its right to use its pro rata share of parking spaces. Landlord reserves the
right to assign particular spaces in the parking areas to particular tenants.

        2. TERM. To have and to hold the Demised Premises for a term of three
(3) years. Said term shall commence on July 1, 1999 and terminate on June 30,
2002.

        3. RENT. Yielding and paying therefor as rent the sum of Forty-One
Thousand, Four Hundred Forty and 00/100 ($41,440.00) Dollars per annum payable
in equal monthly installments of Three Thousand, Four Hundred Fifty-Three and
33/100 ($3,453.33) Dollars due in each case on the first day of each month in
advance, the first such payment to be made herewith. If the

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said term commences or terminates on a day other than the first day of any
month, said rent shall be equitably apportioned.

        The Landlord may collect a "late charge" not to exceed three percent
(3%) of any installment unpaid for ten (10) days after the due date. This right
is in addition to and not in lieu of any other remedies the Landlord may have by
law or as provided in this Lease.

        4. TAXES AND COMMON AREA CHARGES. Tenant agrees to pay as additional
rent its pro rata share of any and all increases over the Base Real Estate Taxes
of such taxes, including any charges hereafter levied in lieu of, in
substitution for or in addition to such real estate taxes as now constituted and
all assessments, including betterments, levied or assessed against the property
of which the Demised Premises are a part. Said tax payments shall be equitably
apportioned for any portion of a year at the beginning or end of the term
hereof. The same shall be additional rent. Tenant shall make equal monthly
payments on account of such taxes to be held by Landlord equal to one-twelfth of
the taxes imposed upon the property of which the Demised Premises are a part for
the prior tax year. Upon determination of the actual taxes, Tenant shall within
ten (10) days after presentation of a bill therefor from Landlord pay its pro
rata share of any excess required and conversely if Tenant shall have paid on
account in monthly installments more than its share such excess shall be
credited against tax payments then or thereafter accruing.

        Tenant shall pay as additional rent its pro rata share of increases in
any and all reasonable charges incurred by the Landlord over the Base Common
Area Maintenance Cost in connection with the maintenance, management, repair and
operation of the Common Areas, including, but without limitation, maintenance
and repairs, landscaping, snow removal and plowing, cleaning, lighting and
rubbish removal to which shall be added fifteen percent (15%) for Landlord's
supervision, record keeping and related overhead (the "Common Area Maintenance
Costs"). Tenant shall pay all Common Area Maintenance Costs solely attributable
to it. Tenant shall make equal monthly payments on account of Common Area
charges based upon Landlord's good faith estimate of such amount and at the
expiration of each calendar year during the term hereof Landlord shall advise
Tenant of any deficiency or overpayment and an accounting between the parties
shall be had.

        Tenant's pro rata share for all purposes during the term of this Lease
will be determined by the following formula:

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                    Tenant's share =     2,240
                                        ------
                                        73,538

        Base Real Estate Taxes are $1.01 per square foot and Base Common Area
Maintenance Costs are $1.30 per square foot.

        5. RULES AND REGULATIONS. The Tenant shall, at its own cost and expense,
promptly comply with all laws, ordinances, orders, regulations and rules of any
duly constituted governmental authority and/or Board of Fire Underwriters or
similar organization having jurisdiction thereof relating to the Demised
Premises or their use, provided, however, that Tenant shall not be required to
make structural alterations to the Demised Premises unless the same are due
specifically to its use.

        6. TENANT IMPROVEMENTS. Landlord and Tenant shall do that work set forth
on the Work Letter, attached hereto as Exhibit B, attributable to them in a good
and workmanlike manner in full compliance with all applicable laws and in
compliance with plans and specifications therefor. Upon completion of Landlord's
work, Tenant shall cause the same to be inspected and any item of defective
workmanship or material observed by Tenant shall be reported to Landlord within
thirty (30) days after the Commencement Date.

        Except for the work to be done by Landlord contained in the Work Letter,
if any, Tenant accepts the Demised Premises in their present condition and
acknowledges that no representations or warranties have been made by or on
behalf of the Landlord with respect to the Demised Premises, their fitness or
availability for any particular purpose or otherwise.

        7. ASSIGNMENT AND SUBLETTING. Tenant shall have no right to assign this
Lease, or sublet or license the whole or any part of the Demised Premises
without the express written consent of the Landlord having been obtained in each
instance, which consent shall not be unreasonably withheld. A transfer of any
controlling share of the capital stock of a corporate tenant, alone, or on the
aggregate shall be deemed to be an assignment of this Lease. In the event the
Landlord consents to an assignment or sublet, the Tenant shall not be released
from its obligations under this Lease and shall remain primarily liable
hereunder. Consent by Landlord to any assignment or sublet does not relieve
Tenant from obtaining Landlord's consent to any further assignment or sublet.

        8. REPAIRS. Except as provided in the next paragraph, during the term of
this Lease, the Tenant shall keep and maintain the Demised Premises and the
appurtenances thereto in good order and repair in all

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respects, reasonable wear and use, based upon good maintenance practices, damage
by fire or other unavoidable casualty only excepted.

        It is understood and agreed that the Landlord is not responsible for
making any repairs whatsoever to the Demised Premises, except that Landlord
shall make necessary repairs to the roof, foundation, building systems
(including the heating, ventilating and air conditioning systems) and exterior
walls (but not glass, doors or windows), unless such repairs are required
because of any act, neglect or default of Tenant, or anyone claiming by, through
or under Tenant or for whom Tenant is responsible.

        Tenant shall pay its pro rata share of Landlord's cost to make such
repairs which cost is included in Common Area Maintenance Costs, provided that
if any such repair shall be due wholly to Tenant's act, omission, default or
neglect, then Tenant shall pay the entire cost of such repair. Any such capital
costs will be amortized over the useful life of the repair based on generally
accepted accounting principles.

        Landlord furthermore shall make all necessary repairs to the Common
Areas and shall maintain all landscaping in a reasonably neat and attractive
manner, plow snow and generally keep the improved portion of the land upon which
the Demised Premises are located in a reasonably neat condition, and provide
lighting as and when required, all of which costs are included in Common Area
Maintenance Costs.

        9. UTILITIES. Included in the Base Rent are Base Utilities of $2.00 per
annum per square foot. Base Utilities consist of separately metered electricity
for lighting and wall outlets in the Demised Premises, Tenant's pro rata share
of water and sewer charges and Tenant's pro rata share of the electricity for
Heating, Ventilation and Air Conditioning, not separately metered for the
Demised Premises.

        Tenant agrees to pay as additional rent its pro rata share of all
increases over the Base Utilities. Tenant shall make equal monthly payments on
account of Base Utilities charges based upon Landlord's good faith estimate of
such amount and at the expiration of each calendar year during the term hereof
Landlord shall advise Tenant of the actual Utilities costs. Upon determination
of the actual costs, Tenant shall within ten (10) days after presentation of a
bill therefor from Landlord pay its pro rata share of any excess required and
conversely if Tenant shall have paid on account in monthly installments more
than its share such excess shall be credited against rent payments then or
thereafter accruing.

        In the event of an interruption of any or all such services, this lease
shall not become void or voidable unless such failure continues for thirty (30)

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days, in which case Tenant may terminate this Lease upon five (5) days written
notice to the Landlord. Landlord shall not be liable to Tenant for the
interruption of any such services, unless the interruption is a result of
Landlord's negligence.

        10. ALTERATIONS, ADDITIONS AND SIGNS. The Tenant shall have the right to
make non-structural alterations, additions and improvements to the Demised
Premises as it may deem necessary or desirable for its business, but shall have
no right to make structural alterations, additions and improvements to the
Demised Premises (with the exception of the satellite dish) without prior
written consent of the Landlord in each instance, which consent shall not be
unreasonably withheld. Any such improvements (with the exception of the
satellite dish) shall remain upon and be surrendered with the Demised Premises
upon the expiration or other termination of the Lease, unless Landlord elects
otherwise. Should Landlord elect to relinquish Landlord's right to the
improvements, Tenant shall remove such improvements, including the satellite
dish, and repair any damage caused by said removal.

        All structural alterations, additions and improvements to the Demised
Premises made by the Tenant and all signs erected by Tenant shall be made or
erected only after plans and specifications therefor have been submitted to the
Landlord and approved by the Landlord, and provided further that all such
alterations, additions and improvements and all such signs shall be made in a
good and workmanlike manner in all respects and in full compliance with all
laws, rules, regulations and ordinances of any duly constituted governmental
authority and in compliance with the recommendations of any Board of Fire
Underwriters or any similar organization having jurisdiction of the premises.

        All additions, improvements and signs shall be at the sole cost and
expense of the Tenant and no part thereof shall be borne by the Landlord.

        11. INDEMNIFICATION. The Tenant shall hold harmless and indemnify the
Landlord of and from any and all claims for injury to person and damage to
property by reason of any accident or happening on or about the Demised
Premises. The Tenant shall carry public liability insurance in limits of at
least $1,000,000 for injury or death to person and $100,000 for damage to
property. Tenant shall furnish Landlord with certificates showing the existence
of said insurance prior to possession by Tenant. Landlord shall be named as an
insured on such insurance policies. Each policy must furthermore provide that
insurance may not be canceled without 15 days written notice to Landlord.

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        12. EXPIRATION OF TERM. Upon the expiration of the term hereof, or at
any prior termination hereof as herein provided, the Tenant shall peaceably
yield up the Demised Premises and all additions, improvements and alterations
made thereto or thereupon broom clean, free of all rubbish, debris and personal
property and in good order, condition and repair in all respects, reasonable
wear and use, based upon good maintenance practices, and damage by fire and
unavoidable casualty only excepted.

        The Tenant shall have the right at the expiration of the term hereof, if
it shall not be in default hereunder, to remove its trade fixtures from the
Demised Premises, provided that such removal may be accomplished without any
damage to the Demised Premises or that any damage is repaired and the premises
restored to its original condition and provided further that Tenant shall pay
rent at the minimum rate for the period ending five (5) days after said property
shall have been removed. Any such property not removed within thirty (30) days
after the expiration or termination of this lease shall, at the express written
election of Landlord, be deemed to have become Landlord's property.

        13. CARE OF PREMISES. Tenant shall keep the Demised Premises clean and
regularly remove its waste and debris from the Demised Premises and not allow
the same to accumulate thereon, Tenant agrees that it will not permit any
caustic or corrosive or otherwise detrimental or hazardous fluids or materials
to be disposed of into the drainage or sewer systems serving the building of
which the Demised Premises are a part, nor shall Tenant store any hazardous
materials or chemicals on site without having first obtained all necessary
licenses, permits and approvals.

        14. TENANT'S RISK. The Landlord shall not be responsible for any damage
to property in the Demised Premises, all of which shall be at the sole risk of
Tenant, nor for injury to person, whether caused by water, steam, gas or
electricity, or by any breakage, leakage or obstruction of oil pipes, conduits
or plumbing, nor from any other source, nor for loss of property by theft or
otherwise, unless caused by Landlord's negligence.

        15. LANDLORD'S ACCESS. A. Tenant agrees that Landlord may come upon the
Demised Premises at reasonable hours upon reasonable notice, for the purpose of
inspecting the same; making repairs, without any obligation to do so; and for
any other purpose necessary or desirable to enforce the Landlord's rights
hereunder or to protect the Landlord's interest hereunder and during the last
six (6) months of the term hereof to show the same to prospective purchasers and
tenants.

        B. Landlord shall have the right during the last three (3) months of the
term hereof to place the usual "For Rent" or "For sale" signs upon the

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Demised Premises, provided, however, that it shall not have the right to place
them in any display windows or upon any doors of the Demised Premises.

        C. Landlord may from time to time introduce, maintain, locate and
relocate conduits, pipes, wires and other matters necessary or desirable in
connection with the operation of the building and/or any other tenant therein,
provided that Landlord shall not thereby unreasonably interfere with the use of
the Demised Premises by Tenant.

        D. For each of the aforesaid purposes, Landlord shall provide Tenant
with a twenty-four hours notice prior to entering premises at which time an
escort may be required in designated areas. Landlord has the right to use any
and all means which Landlord may deem proper to come upon the Demised Premises
in an emergency.

        16. HOLDING OVER. In the event that the Tenant or anyone claiming by,
through or under the Tenant shall remain on the Demised Premises after the
termination of this Lease, or any renewals, extensions or modifications thereof,
it shall be deemed to be a tenancy from month to month, subject to all the terms
and conditions hereof as may be applicable, except that the rent shall be at one
and one-half times the rate herein stipulated.

        17. MECHANIC'S LIEN. Notice is hereby given that the Landlord shall not
be liable for any labor or materials furnished to the Tenant upon credit and
that no mechanic's lien or other lien for any such labor or materials shall
attach to or affect the reversionary or other estate or interest of the Landlord
in and to the Demised Premises. The Tenant further agrees to indemnify the
Landlord against any and all costs, damages and expenses it may suffer on
account of the same. Tenant shall cause the same to be removed or dissolved by
bond.

        18. INSURANCE RATE. Tenant agrees that it will bring nothing upon the
Demised Premises, nor use the Demised Premises in such a way as to cause to be
void or voidable any policy of insurance affecting the Demised Premises, and
further agrees that it will pay to the Landlord the increased cost of any of
Landlord's insurance which may be due to the use of the Demised Premises other
than for the purpose herein demised.

        19. FIRE, DAMAGE AND TAKING. If the Demised Premises or the building of
which they are a part, shall be destroyed or damaged by fire or other casualty,
or taken by eminent domain, Landlord shall have the right to terminate this
Lease by notice to that effect to the Tenant within thirty (30) days after such
damage, destruction or taking.

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        If all or substantially all of the Demised Premises shall be destroyed
or damaged by fire or other casualty such that in the Landlord's opinion the
building cannot be restored within 90 days, Tenant shall have the right to
terminate this lease by notice to that effect to the Landlord within 30 days of
notice from Landlord of such damage or destruction.

        If this Lease be not so terminated, Landlord shall restore the said
building and the Demised Premises as soon as reasonably possible, taking into
account the time necessary to settle and obtain insurance proceeds, to the same
condition as the Demised Premises, or what may remain thereof, were in
immediately prior to such damage, destruction or taking.

        Landlord shall in no event be obligated to restore any improvements made
to the Demised Premises by Tenant. Upon notification from Landlord to Tenant
that Landlord has restored the Demised Premises to the condition aforesaid,
Tenant shall promptly undertake to resume occupancy and use the Demised Premises
if the same shall have been interrupted. Tenant shall make such restorations of
its own improvements as Tenant may elect to do.

        Any and all awards made for any taking or any injury resulting in direct
or consequential damages are the sole and exclusive property of Landlord and no
part thereof shall be paid to Tenant. Tenant may, however, apply for and retain
any award made especially for moving expenses or personal property.

        In the event of any such damage, destruction or taking there shall be an
abatement of rent according to the nature and extent of the injury suffered
until the premises shall have been restored.

        20. DEFAULT. If the Tenant shall neglect or fail to perform or observe
any of the covenants, conditions or obligations on the part of the Tenant herein
contained or observed; or if any petition shall be filed by or against Tenant
under any Bankruptcy or Insolvency Law, now or hereinafter enacted, State or
Federal; or if the estate hereby created shall be attached or taken by legal
process; or if the Tenant shall make an assignment for the benefit of its
creditors by way of trust mortgage, judicial proceedings, or otherwise; or if a
receiver, trustee or similar officer shall be appointed to take charge of any
part of the Tenant's property; then and in any of such events notwithstanding
any waiver or license of any former breach and without prejudice to any other
remedy which the Landlord may have for arrears of rent or otherwise, Landlord
may, without demand or notice, enter into and upon the Demised Premises, or any
part thereof, in the name of the whole, and repossess the same as of its former
estate, and expel the Tenant and those claiming by, through or under it, and
remove its or their goods and

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effects, forcibly if necessary, and may store the same in the name and at the
expense of the Tenant, and upon entry as aforesaid this Lease shall terminate.
Such entry may be effected by written notice to Tenant to the same effect as
actual entry for breach of condition. In the event of such termination, the
Tenant covenants and agrees to indemnify and hold harmless the Landlord from and
against any and all loss of rent, damages and other expenses, including
reasonable attorneys' fees, brokerage, and costs of reletting incurred by the
Landlord by reason of such termination, from time to time, upon demand of the
Landlord. The Tenant further agrees that it will, upon demand, pay to the
Landlord in the event of such termination a sum equal to the amount by which the
rent and other charges herein reserved for the balance of the term hereinabove
specified exceeds the fair market rental value of the Demised Premises for the
balance of said term. Credit shall be given to the liability of Tenant to
indemnify Landlord under this paragraph 20 for any payments made under the
preceding sentence.

        Prior to termination of this Lease by Landlord by reason of Tenant's
default, Landlord shall give Tenant ten (10) days written notice with respect to
any payment of money and fifteen (15) days written notice in all other events,
provided that if by reason of the nature of the default the same cannot be
reasonably cured within said fifteen (15) day period, Tenant shall not be deemed
in default, if Tenant shall commence the cure within said fifteen (15) day
period and proceed diligently thereafter to completion.

        21. FIRE INSURANCE. The Landlord shall throughout the term of this Lease
provide and maintain fire insurance in an amount of not less than the full
replacement value of the building of which the Demised Premises are a part. Said
policies shall contain a so-called rent insurance endorsement providing Landlord
with not less than twelve (12) months rent in the event of damage, destruction
or taking. Tenant shall pay its pro rata share of the cost of all insurance
carried by Landlord with respect to the premises of which the Demised Premises
are a part which cost is included in the Common Area Maintenance Costs.

        22. USE. The Demised Premises are to be used and occupied only for
conduct therein of Tenant's business, which consists of corporate offices and
related facilities, and for no other purpose or purposes whatsoever.

        23. RELEASE OF SUBROGATION. Each of Landlord and Tenant hereby releases
the other from any and all liability or responsibility to the other (or anyone
claiming through or under them by way of subrogation or otherwise) for any loss
or damage to property caused by fire or any of the extended coverage of
supplementary contract casualty or casualties insured against by said party,
even if such fire or other casualty shall have been

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caused by default or negligence of the other party, or anyone for whom such
party shall be responsible, provided, however, that this release shall be
applicable and in force and effect only with respect to loss or damage occurring
during such time as the releasor's policies shall contain a clause or
endorsement to the effect that any such release shall not adversely affect or
impair said policies or prejudice the right of the releasor to recover
thereunder. Each of Landlord and Tenant agree that their policies shall include
such a clause or endorsement so long as the same shall be obtainable without
extra cost, and if extra cost shall be charged therefor, so long as the other
party pays such extra cost. If extra cost shall be chargeable therefor, each
party shall advise the other thereof of the amount of the extra cost and the
other party, at its election, shall pay the same but shall not be obligated so
to do.

        24. NOTICE CLAUSE. Any notices required to be given under the terms
hereof shall be given by 1) mailing said notice by certified mail, return
receipt requested, postage paid, 2) hand delivery or 3) if sent by electronic
mail or facsimile transmission (with receipt confirmed), and shall be deemed
given on the date of mailing if mailed or if delivered or faxed on date of
delivery or transmission. Notices to the Landlord, at the last address at which
rent was paid, and if to the Tenant, at the principal office of the Tenant, or
such other place as either may designate from time to time in writing.

        25. WAIVER. One or more waivers of the breach of any covenant or
condition by either party shall not be construed as a waiver of a further breach
of the same covenant or condition.

        26. ENTIRE AGREEMENT. This instrument contains the entire and only
agreement between the parties, and no oral statements or representations or
prior written matter not contained in this instrument shall have any force and
effect.

        27. PARAGRAPH HEADINGS. The paragraph headings used herein are used only
as a matter of convenience for reference and are not to be considered part of
this Lease, or to be used in determining the intent of the parties of this
Lease.

        28. STATUS OF LANDLORD. The Landlord shall be liable hereunder only so
long as it shall be seized of the property hereby demised. No fiduciary or
beneficiary or Partner, general or limited, of the Landlord named herein shall
ever be personally or individually liable for the obligations of the Landlord.
Tenant agrees to look solely to the real estate of which the Demised Premises
are a part for satisfaction of any claim; provided

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that the Landlord named herein may be named as a defendant in order to obtain
jurisdiction.

        29. NO BROKER. The Tenant warrants and represents that no broker or
agent was instrumental in connection with this lease transaction and covenants
to hold the Landlord harmless and indemnified from and against any claim made by
any broker in connection herewith.

        30. SUBORDINATION. At the election of Landlord, which election may be
changed from time to time, this Lease shall be subject and subordinate, or prior
and superior to any mortgage now or hereafter placed upon the real estate of
which the Demised Premises are a part; provided that with respect to each
subsequent mortgage to which this Lease shall be made subject and subordinate,
the mortgage must agree that, in the event of foreclosure, Tenant shall not be
disturbed in its possession except in accordance with the terms of this Lease.
Tenant agrees at the request of such mortgagee or any purchaser at foreclosure
sale, to attorn.

        31. SELF HELP. If Tenant shall fail to perform or observe any of its
obligations under this Lease after written notice of the requirement therefor by
Landlord, Landlord may, at its election, without any obligation to do so perform
such obligation for the account of the Tenant, and Tenant shall forthwith upon
demand reimburse Landlord for the cost of such performance, together with
interest at the rate of 12% per annum until paid. In the event of emergency,
Landlord may undertake such action without written notice but after using
reasonable efforts to notify Tenant by telephone or otherwise.

        32. SECURITY DEPOSIT. Tenant shall deposit with Landlord upon the
execution of this Lease, the sum of Three Thousand, Four Hundred Fifty-Three and
33/100 ($3,453.33) Dollars as security deposit hereunder. Landlord shall not be
obligated to pay interest on said sum or to segregate the same, nor shall
Landlord be obligated to use said sum, or any part thereof, to cure any default
of Tenant. At the expiration or prior termination of this Lease upon Tenant
vacating the Demised Premises in the condition required under this Lease, and
fully performing its obligations herein, Landlord shall, within thirty (30) days
thereafter, return said security deposit, or such part thereof as may remain, to
Tenant. In the event that during the term of this Lease Landlord shall use all
or any part of said security deposit to cure any default on the part of Tenant,
Tenant shall forthwith, upon demand, replenish said security deposit so that the
same is always kept at the required amount.

        33. SATELLITE DISH. For additional rent of $100.00 per month, Tenant
shall have the right to install and maintain a five meter satellite dish on the
loading dock roof.

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        Tenant shall be entitled to maintain such satellite dish, contingent
upon the following terms:

        -Tenant will secure adequate liability insurance;

        -Tenant will enter into agreements necessary with Landlord or Landlord's
         roofer to protect Landlord's roof warranty;

        -Tenant shall assume all liability in connection with the satellite dish
         and assume all costs of maintaining said satellite dish;

        -Landlord shall not withhold access to the satellite dish unreasonably.

        At the expiration of the Lease, Tenant shall have the right to remove
said satellite dish and shall return the roof of the loading dock as close to
its original condition as reasonably possible.

        34. AUDIT RIGHTS. Landlord shall at all times keep proper books of
record and accounts in accordance with generally accepted accounting principles
and practices, applied on a consistent basis, in which full, true and accurate
entries shall be made of all Operating Costs for each base year. Landlord shall
permit Tenant and Tenant's agent, at Tenant's expense, by appointment and during
normal business hours, to review Landlord's records, books and accounts of the
Building and any audited statements thereof relating to the Operating Costs for
such base year for the purpose of verifying Operating Costs and any accounting
which Landlord is required to provide hereunder. Any such audit by Tenant shall
occur no more frequently than one time per year, shall be limited to a review of
the then pertinent base year and shall be requested within thirty (30) days of
the Tenant's receipt of an invoice requesting payment of Tenant's pro rata share
of Operating Costs.

        Audit rights raised after such thirty (30) day period shall be deemed
waived. Books of record shall be retained by Landlord for one year after
Landlord delivers the accounting for the applicable base year, If the result of
such audit demonstrates that the Tenant has been unfairly charged in accordance
with generally accepted accounting principles, then Landlord shall make the
appropriate credit adjustment.

        36. HAZARDOUS MATERIALS. Neither Landlord nor Tenant shall at any time
use, generate, store or dispose of, on, under or about the Demised Premises, the
Building or parking areas or transport to or from the same any hazardous wastes,
toxic substances or related material ("Hazardous Materials") or permit or allow
any third party to do so, without compliance with all Regulations. Hazardous
Materials shall include but shall not be limited to, substances defined as
"hazardous substances" or "toxic substances" in the Comprehensive Environmental
Response, Compensation and Liability Act of 1980, as amended, 42 U.S.C.A.
Section 1802; the Resource

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Conservation Recovery Act, 42 U.S.C.A. Section 6901, et. Seq.; or those
substances defined as "hazardous wastes" in applicable codes in the Commonwealth
of Massachusetts and in the regulations adopted and publications promulgated to
such codes.

        36. OPTION TO EXTEND. Tenant at its option may extend the term of this
Lease for an additional two year period upon the same terms and conditions as
herein contained except as hereinafter provided by serving notice thereof upon
the Landlord at least 180 days before the expiration of the term and upon the
notice of said service, this Lease shall be extended upon all its terms and
conditions for the extended term without the necessity of the execution of any
further instrument or documents; provided however, that if at either the date of
expiration of the original term of this Lease, or the date upon which Tenant
exercises such option of renewal, Tenant is in default beyond any grace period
herein provided in the performance of any of the terms or provisions of this
Lease, the extension of the term shall become null and void at the election of
the Landlord. Said extended term shall be upon the same terms, provisions and
conditions herein contained, except that there shall be no further right of
extension, and the annual rent during the extended term shall be at fair market
rental.

        IN WITNESS WHEREOF, the parties have hereunto set their hands and seals
this 28th day of June, 1999.

                                            NAGOG DEVELOPMENT COMPANY

                                            BY: /s/ KIRK WARE
                                               ---------------------------------
                                               Kirk Ware
                                               Managing General Partner

                                            VIASAT, INC.

                                            BY: /s/ GREGORY MONAHAN
                                               ---------------------------------
                                               Gregory Monahan
                                               Chief Financial Officer

                                               Hereunto Duly Authorized

                                       13
<PAGE>   14

                                   EXHIBIT A

                                  [FLOOR PLAN]

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