<SUBMISSION>
<ACCESSION-NUMBER>0000938166-10-000002
<TYPE>4
<PUBLIC-DOCUMENT-COUNT>1
<PERIOD>20090505
<FILING-DATE>20100106
<DATE-OF-FILING-DATE-CHANGE>20100106
<REPORTING-OWNER>
<OWNER-DATA>
<CONFORMED-NAME>Little Pamela A
<CIK>0001337465
</OWNER-DATA>
<FILING-VALUES>
<FORM-TYPE>4
<ACT>34
<FILE-NUMBER>001-34595
<FILM-NUMBER>10511760
</FILING-VALUES>
<MAIL-ADDRESS>
<STREET1>SANDY SPRING BANK
<STREET2>17801 GEORGIA AVENUE
<CITY>OLNEY
<STATE>MD
<ZIP>20832
</MAIL-ADDRESS>
</REPORTING-OWNER>
<ISSUER>
<COMPANY-DATA>
<CONFORMED-NAME>ATS CORP
<CIK>0001325460
<ASSIGNED-SIC>8742
<IRS-NUMBER>113747950
<STATE-OF-INCORPORATION>DE
<FISCAL-YEAR-END>1231
</COMPANY-DATA>
<BUSINESS-ADDRESS>
<STREET1>7925 JONES BRANCH DRIVE
<CITY>MCLEAN
<STATE>VA
<ZIP>22102
<PHONE>571-766-2400
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>7925 JONES BRANCH DRIVE
<CITY>MCLEAN
<STATE>VA
<ZIP>22102
</MAIL-ADDRESS>
<FORMER-COMPANY>
<FORMER-CONFORMED-NAME>Federal Services Acquisition CORP
<DATE-CHANGED>20050429
</FORMER-COMPANY>
</ISSUER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2009-05-05</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001325460</issuerCik>
        <issuerName>ATS CORP</issuerName>
        <issuerTradingSymbol>ATSC</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001337465</rptOwnerCik>
            <rptOwnerName>Little Pamela A</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>ATS CORPORATION</rptOwnerStreet1>
            <rptOwnerStreet2>7925 JONES BRANCH DRIVE</rptOwnerStreet2>
            <rptOwnerCity>MCLEAN</rptOwnerCity>
            <rptOwnerState>VA</rptOwnerState>
            <rptOwnerZipCode>22102</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>EVP and CFO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2010-01-04</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>75000</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>264254</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Options</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>1.5</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2009-05-05</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>100000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2010-05-05</value>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <value>2019-05-05</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>100000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>100000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Represents 75,000 restricted shares under the terms of the Company's Omnibus Incentive Compensation Plan, of which 10,000 shares vest on 1/4/11, 15,000 shares vest on 1/4/12, and 50,000 shares vest on 1/3/13.</footnote>
        <footnote id="F2">The total amount of securites includes 27,254 shares purchased per the terms of the Company's 2007 Employee Stock Purchase Plan.</footnote>
        <footnote id="F3">The options vest over a four year period, in 25,000 increments on each May 5, beginning on May 5, 2010.  This transaction was indadvertantly filed late.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Pamela A. Little</signatureName>
        <signatureDate>2010-01-06</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SUBMISSION>
