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                     U.S. SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                     FORM 3

            INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES

    Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934,
       Section 17(a) of the Public Utility Holding Company Act of 1935 or
               Section 30(f) of the Investment Company Act of 1940


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1. Name and Address of Reporting Person

     Bertelli, James R.
- --------------------------------------------------------------------------------
   (Last)               (First)                 (Middle)

     51 Green Heron Lane
- --------------------------------------------------------------------------------
                                    (Street)

     Nashua, NH   03062
- --------------------------------------------------------------------------------
   (City)               (State)                 (Zip)


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2. Date of Event Requiring Statement (Month/Day/Year)

     1/29/98

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3. IRS or Social Security Number of Reporting Person (Voluntary)


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4. Issuer Name and Ticker or Trading Symbol

     Mercury Computer Systems, Inc.   MRCY
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5 Relationship of Reporting Person to Issuer
   (Check all applicable)

   [   ]   Director                             [   ]   10% Owner
   [ X ]   Officer (give title below)           [   ]   Other (specify below)


         President
      --------------------------------------------------------------------

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6. If Amendment, Date of Original (Month/Year)


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             Table I -- Non-Derivative Securities Beneficially Owned
================================================================================



                                                                 3. Ownership Form:
                                      2. Amount of Securities       Direct (D) or  
1. Title of Security                     Beneficially Owned         Indirect (I)       4. Nature of Indirect Beneficial Ownership
   (Instr. 4)                            (Instr. 4)                 (Instr. 5)            (Instr.5)                              
- ------------------------------------------------------------------------------------------------------------------------------------
                                                                                 

   Common Stock                          419,800                     D
- ------------------------------------------------------------------------------------------------------------------------------------
   

====================================================================================================================================

Reminder: Report on a separate line for each class of securities beneficially
owned directly or indirectly.

                           (Print or Type Responses)





FORM 3 (continued)

              Table II -- Derivative Securities Beneficially Owned
         (e.g., puts, calls, warrants, options, convertible securities)

================================================================================


                                                                                                        5. Owner-
                                                    3. Title and Amount of Securities                      ship
                                                       Underlying Derivative Security                      Form of
                         2. Date Exercisable           (Instr. 4)                                          Derivative
                            and Expiration Date     ---------------------------------    4. Conver-        Security:
                            (Month/Day/Year)                               Amount           sion or        Direct      7. Nature of
                         ----------------------                            or               Exercise       (D) or         Indirect
                         Date       Expira-                                Number           Price of       Indirect       Beneficial
1. Title of Security     Exer-      tion                                   of               Derivative     (I)            Ownership
   (Instr. 4)            cisable    Date            Title                  Shares           Security       (Instr.5)      (Instr. 5)
- ------------------------------------------------------------------------------------------------------------------------------------
                                                                                                  
Stock Option             (1)        7/30/06         Common                 10,000        4.00           D
(right to buy)  
- ------------------------------------------------------------------------------------------------------------------------------------
Stock Option             (2)        7/30/06         Common                  2,264        4.00           D
(right to buy)  
- ------------------------------------------------------------------------------------------------------------------------------------
Stock Option             (2)        7/30/06         Common                  4,865        4.00           D
(right to buy)  
- ------------------------------------------------------------------------------------------------------------------------------------
Stock Option             (3)        12/2/06         Common                  5,161        4.00           D
(right to buy)  
- ------------------------------------------------------------------------------------------------------------------------------------
Stock Option             (4)        9/8/07          Common                  8,601        4.00           D
(right to buy)  
- ------------------------------------------------------------------------------------------------------------------------------------
Stock Option             (5)        10/20/08        Common                 45,000        8.00           D
(right to buy)  
====================================================================================================================================

Explanation of Responses:
(1)  The option to purchase 6,000 shares is exercisable.  The remainder will 
     vest in equal increments on July 30 of each of 1998, 1999.
(2)  50% of the option is exercisable; 50% will vest on July 31, 1998.
(3)  50% of the option is exercisable; 50% will vest on December 2, 1998.
(4)  The option to purchase 4,301 shares will vest on September 8, 1998.
(5)  The option to purchase 11,250 shares will vest on October 20, 1998.
     The remaining options will vest in equal increments on October 20 of
     each of 1999, 2000 and 2001.



   /s/James R. Bertelli                                          1/29/98
- ---------------------------------------------            -----------------------
      **Signature of Reporting Person                             Date

**   Intentional misstatements or omissions of facts constitute Federal Criminal
     Violations.

     See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

Note:  File three copies of this Form, one of which must be manually signed.
       If space provided is insufficient. See Instruction 6 for procedure.