-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
Originator-Key-Asymmetric:
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 QEHvIA2nOC0xS29V0Sp2qzdo4GcF+J9tRPkBMEYWXHeNzks9VOU+iQeSGxd3xOpl
 +S3cuureIOiJ+MSl/i3LEg==

<SEC-DOCUMENT>0001181431-05-022733.txt : 20050420
<SEC-HEADER>0001181431-05-022733.hdr.sgml : 20050420
<ACCEPTANCE-DATETIME>20050420144724
ACCESSION NUMBER:		0001181431-05-022733
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20050419
FILED AS OF DATE:		20050420
DATE AS OF CHANGE:		20050420

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			ISENSTEIN BARRY S
		CENTRAL INDEX KEY:			0001211773

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-23599
		FILM NUMBER:		05761730

	MAIL ADDRESS:	
		STREET 1:		199 RIVERNECK ROAD
		CITY:			CHEISFORD
		STATE:			MA
		ZIP:			01824

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			MERCURY COMPUTER SYSTEMS INC
		CENTRAL INDEX KEY:			0001049521
		STANDARD INDUSTRIAL CLASSIFICATION:	ELECTRONIC COMPONENTS & ACCESSORIES [3670]
		IRS NUMBER:				042741391
		STATE OF INCORPORATION:			MA
		FISCAL YEAR END:			0630

	BUSINESS ADDRESS:	
		STREET 1:		199 RIVERNECK RD
		CITY:			CHELMSFORD
		STATE:			MA
		ZIP:			01824
		BUSINESS PHONE:		9782561300

	MAIL ADDRESS:	
		STREET 1:		199 RIVERNECK ROAD
		CITY:			CHELMSFORD
		STATE:			MA
		ZIP:			01824
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>rrd76079.xml
<DESCRIPTION>OPEN MARKET SALE
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2005-04-19</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001049521</issuerCik>
        <issuerName>MERCURY COMPUTER SYSTEMS INC</issuerName>
        <issuerTradingSymbol>MRCY</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001211773</rptOwnerCik>
            <rptOwnerName>ISENSTEIN BARRY S</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>93 WOODBINE ROAD</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>CARLISLE</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>01741</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>VP Defense Electronics Group</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2005-04-19</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>1000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>25.00</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>33804</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By The Isenstein Family Investment Trust</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">The sale reported on this Form 4 was effected pursuant to a Rule 10b5-1 trading plan adopted by Mr. Isenstein on December 15, 2004.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Joseph M. Hartnett, Attorney-in-fact</signatureName>
        <signatureDate>2005-04-20</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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