Document:

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                                                                    EXHIBIT 10.2

August 22, 2001

Dr. Michael D. Griffin
12325 Myterra Way
Oak Hill, VA  20171

Dear Mike:

This letter of agreement ("Agreement") serves to acknowledge that your last day
of employment at Orbital Sciences Corporation is August 24, 2001. You will be
eligible for severance benefits, conditional upon your signing this Agreement.
The following information relates to your pay, benefits, and other
employment-related issues:

FINAL PAYMENTS

1.   You are eligible to receive six (6) months of severance pay, paid in a lump
     sum. Should you not obtain other full time employment by February 24, 2002,
     you will be eligible to continue to receive severance, paid on a bi-weekly
     basis, for up to an additional three (3) months. You will also be paid all
     unused composite leave on record as of your separation date. Your severance
     and composite leave payments will reflect deductions of all applicable
     taxes and withholdings.

2.   You will to receive a bonus for calendar year 2001 (less deductions for all
     applicable taxes and withholdings) when Orbital pays bonuses to employees
     in early 2002. The percentage of your target bonus that you will receive
     will reflect the percentage granted to Corporate employees.

OTHER

3.   You will be given the opportunity to utilize career counseling and
     placement services through Lee Hecht Harrison for three months. A
     representative from Lee Hecht Harrison will contact you to establish an
     initial meeting.

4.   Effective August 24, 2001, a consulting contract for a period of one year
     will be offered. During this period, Orbital will cooperate with you in an
     effort to maintain your current Security Clearance.

5.   Office space and limited administrative support will be provided at Orbital
     for a period of six months.

BENEFITS

6.   Through COBRA, Orbital will pay the full cost of your medical/dental group
     insurance, based upon your current level of elections, for a period of one
     year. After that date, you may elect to continue your medical and/or dental
     insurance benefits at your own expense for up to an additional six months
     through COBRA. You are also eligible to convert your health coverage to an
     individual policy.

7.   Subject to your signing the Consulting Agreement dated August 24, 2001
     between you and Orbital Sciences Corporation, your stock options granted
     under the Orbital Sciences Corporation 1997 Stock Option and Incentive Plan
     (the "1997 Plan") will remain in effect during the term of the Consulting
     Agreement in accordance with the terms of the 1997 Plan and on the same
     vesting schedule which would have been in effect had your services as an
     employee not ceased on August 24, 2001. When your Consulting Agreement
     terminates, this will constitute a "termination of employment" under the
     Plan and you will have a period of six months in which to exercise your
     vested stock options. Your options granted under the Orbital Imaging
     Corporation 1996 Stock Option Plan (the "ORBIMAGE Plan") will also remain
     in effect during the term of your Consulting Agreement. When your
     Consulting Agreement terminates, you will have a period of three months in
     which to exercise your vested ORBIMAGE Plan options. With respect to
     options granted to you under the Orbital Sciences Corporation 1990 Stock
     Option Plan (the "1990 Plan"), your change in status from employee to
     consultant is a termination of employment pursuant to the terms of the 1990
     Plan. You have a period of three months from your August 24, 2001
     termination date in which to exercise your 1990 Plan vested stock options.

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8.   Your group life and accidental death and dismemberment (AD&D) insurance
     terminates at midnight on your separation date. You will have the
     opportunity to convert this coverage to an individual policy. Your
     supplemental life insurance policy is considered an individually-owned
     policy, so there is no conversion involved. Your request for conversion of
     group life, AD&D and/or portability of supplemental life insurance must be
     submitted to Reliance Standard Life Insurance Company within 31 days from
     your termination of employment. Reliance will provide you with payment
     rates, which may vary from your current rates. Please contact Sherry Smith
     at (703) 406-5993 to request the necessary forms.

9.   Your short-term and long-term disability coverage terminates at midnight on
     your separation date.

10.  You may continue your ARAG group legal insurance for the remainder of the
     plan year. Please call ARAG's representative, Laura Lanigan, at (800)
     888-4184 for further details and rates.

11.  You have the option to make after-tax contributions on your Flexible
     Spending Health Care Account (HCA) on a monthly basis until the end of the
     current plan year (December 31, 2001). If you make no further
     contributions, you may only submit valid HCA claims for reimbursement that
     were incurred between your HCA effective date in 2001 and your last date of
     contribution. Please contact Sherry Smith at (703) 406-5993 if you wish to
     make after-tax contributions to your HCA.

12.  Distribution of vested 401(k) plan contributions will be handled directly
     through CIGNA's AnswerLine. By calling the telephone number in the enclosed
     brochure, you can discuss your ditribution options with a CIGNA
     Distribution Specialist. A summary of the most frequently asked questions
     and answers regarding the 401(k) plan is also enclosed.

13.  You may choose from among three options for receiving funds from your
     Orbital Sciences Deferred Compensation Plan account. You may elect 1) an
     immediate lump sum cash distribution, 2) a lump sum cash distribution paid
     within one year of your termination, or 3) monthly installment payments
     (not to exceed 120 payments). A Payment of Benefit Election Form is
     attached.

COMPANY PROPERTY

14.  You are expected to release and return all records and property in your
     possession that belong to or relate in any manner to the affairs of
     Orbital, including: computer(s), keys, files and credit cards, Sprint
     FONCARD, employee handbook and employee identification badge.

NON-DISCLOSURE AGREEMENT

15.  You are reminded of your legal obligations regarding proprietary rights and
     information of Orbital Sciences Corporation, which you assumed when you
     joined Orbital. As you may be aware, these obligations survive the
     termination of your employment with Orbital and may therefore have a
     bearing on your future activities. A copy of the agreement is attached.

RELEASE

16. The benefits you are being offered are more than what Orbital Sciences
Corporation (Orbital) is required to provide under its normal policies and
procedures upon the termination of your employment. If you wish to receive these
benefits, you must sign this letter stating that you are releasing and waiving
any claims you may have against Orbital.

You understand that, except for the applicable benefits described above, you
will receive no other wages, benefits, or other payments from Orbital.

In return, you promise and agree to release Orbital, all current and former
parents, subsidiaries, related companies, partnerships, or joint ventures, their
predecessors and successors; as well as all past, present, and future employees,
officers, directors, stockholders, owners, representatives, assigns, attorneys,
agents, insurers, employee benefit programs (and the trustees, administrators,
fiduciaries, and insurers of such programs), and any

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other persons acting by, through, under, or in concert with any of the persons
or entities listed, and their successors, from all claims you may have based on
your employment or the termination of employment with Orbital. You understand
that this includes rights or claims under federal, state or local
anti-discrimination laws, including the Age Discrimination in Employment Act of
1967, Title VII of the Civil Rights Act of 1964, as amended, the Fair Labor
Standards Act, the Equal Pay Act, the Americans With Disabilities Act, common
law or statutory claims for breach of contract, wrongful termination or tort
claims, and legal claims of any sort, whether you know about them at this point
in time or not. You are not releasing any claims under the Age Discrimination in
Employment Act that arise after you sign this Agreement and Release. Except to
the extent governed by federal law, the statutes and common law of the
Commonwealth of Virginia shall govern this Release.

You represent that you have not filed any complaints or charges against Orbital
with any governmental agency or any court, and that you will not do so
hereafter. You agree to keep the fact of this Agreement, as well as the terms,
conditions, benefits and payments of this Agreement confidential and not to
disclose the terms, conditions, benefits and payments of this Agreement to any
person or entity which is not a party to this Agreement.

You understand that this Agreement represents no implication of admission of
liability or wrongdoing by Orbital, and that the existence and execution of this
Agreement shall not be considered, and shall not be admissible, in any
proceeding as an admission by Orbital of any liability, error or violation of
law.

You agree that you shall hold in confidence and not directly or indirectly
disclose any confidential or proprietary information of Orbital, its
subsidiaries or affiliates to any person or entity, or use any such confidential
and proprietary information for any purpose, except as authorized by Orbital,
provided that the forgoing restrictions shall not apply to information that
becomes known to and available for use by the public other than as a result of
your unauthorized acts or failures to act. You acknowledge that all materials
that in any way contain, incorporate or reflect confidential or proprietary
information of Orbital, its subsidiaries or affiliates, including but not
limited to documents, reports, plans, notes, memoranda, sketches, drawings,
discs and records (including electronic records), belongs exclusively to
Orbital. You agree to promptly deliver to Orbital all copies of such materials
that you may possess or have under your control.

You agree not to solicit for employment (or to assist with such solicitation),
or to hire (including employment as a full-time or part-time employee or
consultant) any employee or contractor of Orbital for a one-year period after
your termination from Orbital. The restrictions set forth in this paragraph
apply to the solicitation or hiring of any person who is an employee or
consultant of Orbital as of the date of your termination from Orbital.

You agree to refrain from making untruthful oral or written statements to the
public, or any third party, about Orbital, your employment with Orbital, or any
general matter concerning Orbital's reputation, standing in the business
community, or business practices, or the reputation, standing in the business
community, or business practices of any present of former officers, directors,
employees, consultants or independent contractors of Orbital.

You hereby acknowledge that you first received a copy of the original of this
Separation Agreement and Release on August 22, 2001; that you were given a
period of 21 days to review and consider it; that you understand you could use
as much of the 21-day period as you wish; that you were strongly encouraged to
consult with a lawyer or advisor, and did so, if and to the extent you saw fit;
you understand the language of this agreement and its effect; and that you are
signing it voluntarily and of your own free will.

You understand and agree that this Separation Agreement and Release is final and
binding if you do not revoke it. You understand that you may revoke it within
seven days of signing it by delivering a written notice of revocation to Emily
Bender, 21839 Atlantic Blvd., Dulles, VA 20166, no later than the close of
business on the seventh day after the Agreement is signed. If you revoke the
Separation Agreement and Release in a timely manner, it will not be effective or
enforceable and you will not receive the severance benefits described above.

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You understand that this letter sets forth the entire agreement between you and
Orbital; you acknowledge that you are not relying on any other representation or
statement; you acknowledge this Agreement shall be binding on your successors,
heirs or representatives, and will enure to the benefit of all released parties
and their successors, heirs, or representatives. You acknowledge that the
Agreement may not be modified or canceled in any manner except by a written
statement signed by both you and an authorized Orbital official.

------------------------------      ------------------------
Emily Bender                        Date
Sr. Director, Human Resources
Orbital Sciences Corporation

I hereby agree to and accept the terms of this Separation Agreement and Release.
I understand that this Agreement contains a full and final release of all
claims, known and unknown, that I have against Orbital.

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Michael D. Griffin                  Date<PAGE>

                                                                     EXHIBIT 4.1

                                 PROMISSORY NOTE

$25,000.00                                                      October 12, 2001

For value received, INTEGRATED SECURITY SYSTEMS, INC., a Delaware corporation
(hereinafter referred to as "Maker"), promises to pay to the order OF FROST
NATIONAL BANK, CUSTODIAN, FBO RENAISSANCE CAPITAL GROWTH & INCOME FUND III,
INC., a Texas corporation (hereinafter referred to as "Payee"), the principal
sum of Twenty-Five Thousand Dollars ($25,000.00). The principal of and interest
on this Note shall be due and payable in lawful money of the United States of
America, c/o Security Processing T-8, P. O. Box 2479, San Antonio, Texas
78298-2479. All correspondence and notices should be mailed to the above address
with a copy to the offices of Payee at 8080 N. Central Expressway, Suite 210,
Dallas, Texas 75206, or at such other place as the holder hereof may from time
to time designate by written notice to Maker.

         1. Interest. Interest shall accrue on the unpaid principal balance due
under this Note at an annual rate equal to eight percent (8%). Interest shall
accrue from and including the date of this Note until, but not including, the
day on which it is paid in full. In no event shall the interest charged
hereunder exceed the maximum rate of interest allowed from time to time by law.
Interest shall be due and payable monthly on the first (1st) day of each month,
commencing November 1, 2001.

         2. Payment of Note. The principal balance of, and all accrued unpaid
interest on, this Note shall be due and payable one hundred twenty (120) days
from the date hereof, except as otherwise provided herein. ("Maturity Date").

         3. Prepayment. This Note may be prepaid in whole or in part at any
time, at the option of Maker, without premium or penalty.

         4. Default, Enforcement. Upon default in payment of this Note, Payee
may pursue any and all rights and remedies to which Payee may be entitled under
applicable law.

         5. Limitation of Interest. All agreements between Maker and Payee,
whether now existing or hereafter arising and whether written or oral, are
expressly limited so that in no contingency or event whatsoever, whether by
reason of advancement of the proceeds hereof, acceleration of the maturity of
the unpaid principal balance hereof, or otherwise, shall the amount contracted
for, charged, received, paid or agreed to be paid to the holder hereof for the
use, forbearance, or detention of the money evidenced by this Note or for the
payment or performance of any covenant or obligation contained herein or in any
other document pertaining to the indebtedness evidenced by this Note exceed the
maximum amount permissible under applicable usury laws. If, from any
circumstance whatsoever, fulfillment of any provision hereof or of any other
agreement shall, at the time fulfillment of such provision be due, involve
transcending the limit of validity prescribed by law which a court of competent
jurisdiction may deem applicable hereto, then, ipso facto, the obligation to be
fulfilled shall be reduced to the limit of such validity; and if from any
circumstance the holder hereof shall ever receive as interest an amount which
would exceed the

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maximum lawful rate, any amount equal to any excessive interest shall (a) be
applied to the reduction of the unpaid principal balance due hereunder and not
to the payment of interest, or (b) if such excess interest exceeds the unpaid
principal balance of this Note, such excess shall be refunded to Maker. All sums
contracted for, charged or received hereunder for the use, forbearance or
detention of the indebtedness evidenced hereby shall, to the extent permitted by
applicable law, be amortized, prorated, allocated and spread throughout the full
term of this Note until payment in full so that the rate of interest on account
of such indebtedness is uniform throughout the term hereof. The terms and
provisions of this paragraph shall control and supersede every other provision
of all agreements between Maker and the holder hereof.

         6. Waiver. Except as otherwise expressly provided herein, Maker waives
demand, presentment for payment, notice of intent to accelerate, notice of
acceleration, notice of nonpayment or dishonor, grace, protest, notice of
protest, all other notices, and any and all diligence or delay in collection or
the filing of suit hereon.

         7. Governing Law and Venue. This Note shall be construed according to
and governed by the laws of the State of Texas. The obligations of Maker under
this Note are performable in Dallas County, Texas.

         8. Security Agreement. This Note is secured by the Security Agreement,
dated September 27, 2001, among Maker, B&B Electromatic, Inc., Intelli-Site,
Inc., Payee and Renaissance US Growth & Income Trust PLC, and Payee is entitled
to the rights and benefits thereunder.

         9. Stock Pledge Agreement. This Note is secured by the Stock Pledge
Agreement, dated September 27, 2001, among Maker, Payee and Renaissance US
Growth & Income Trust PLC, and Payee is entitled to the rights and benefits
thereunder.

         10. Successors and Assign. This Note shall bind Maker's successors and
assigns.

         11. Collection Costs. If this Note is collected by legal proceeding or
through a probate or bankruptcy court, or is placed in the hands of an attorney
for collection after default (whether or not suit is filed), Maker agrees to pay
all costs of collection and/or suit, including but not limited to reasonable
attorneys' fees and expenses incurred by Payee.

         12. Unenforceability. The invalidity, or unenforceability in particular
circumstances, of any provision of this Note shall not extend beyond such
provision or such circumstances, and no other provision of this Note shall be
affected thereby.

         13. Headings. The paragraph headings of the sections of this Note are
inserted for convenience of reference only and shall not affect the meaning or
interpretation of this Note.

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IN WITNESS WHEREOF, Maker has duly executed this Note as of the day and year
first above written.

                                       INTEGRATED SECURITY SYSTEMS, INC.

                                       By: /s/ C.A. RUNDELL, JR.
                                           ------------------
                                           C. A. Rundell, Jr.
                                           Chairman and Chief Executive Officer

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