-----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,
 McfTDxP0dgHjLvnkgbyHxV+xN5s9oGb9XbhhrhpwAU6hITiTKIrRIrbLS15ABArN
 CHyajaM2tiB3exIIIFhazA==

<SEC-DOCUMENT>0001140361-10-031303.txt : 20100803
<SEC-HEADER>0001140361-10-031303.hdr.sgml : 20100803
<ACCEPTANCE-DATETIME>20100803163506
ACCESSION NUMBER:		0001140361-10-031303
CONFORMED SUBMISSION TYPE:	4/A
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20100730
FILED AS OF DATE:		20100803
DATE AS OF CHANGE:		20100803

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			ORBITAL SCIENCES CORP /DE/
		CENTRAL INDEX KEY:			0000820736
		STANDARD INDUSTRIAL CLASSIFICATION:	RADIO & TV BROADCASTING & COMMUNICATIONS EQUIPMENT [3663]
		IRS NUMBER:				061209561
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1204

	BUSINESS ADDRESS:	
		STREET 1:		21839 ATLANTIC BLVD
		CITY:			DULLES
		STATE:			VA
		ZIP:			20166
		BUSINESS PHONE:		703 406 5524

	MAIL ADDRESS:	
		STREET 1:		21839 ATLANTIC BLVD
		STREET 2:		21839 ATLANTIC BLVD
		CITY:			DULLES
		STATE:			VA
		ZIP:			20166

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	ORBITAL SCIENCES CORP II
		DATE OF NAME CHANGE:	19900212

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			THOMPSON DAVID W
		CENTRAL INDEX KEY:			0001045853

	FILING VALUES:
		FORM TYPE:		4/A
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-14279
		FILM NUMBER:		10988060

	MAIL ADDRESS:	
		STREET 1:		21700 ATLANTIC BLVD
		STREET 2:		ORBITAL SCIENCES CORP
		CITY:			DULLES
		STATE:			VA
		ZIP:			20166
</SEC-HEADER>
<DOCUMENT>
<TYPE>4/A
<SEQUENCE>1
<FILENAME>doc1.xml
<DESCRIPTION>FORM 4/A
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4/A</documentType>

    <periodOfReport>2010-07-30</periodOfReport>

    <dateOfOriginalSubmission>2010-08-03</dateOfOriginalSubmission>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000820736</issuerCik>
        <issuerName>ORBITAL SCIENCES CORP /DE/</issuerName>
        <issuerTradingSymbol>ORB</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001045853</rptOwnerCik>
            <rptOwnerName>THOMPSON DAVID W</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>21839 ATLANTIC BLVD</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>DULLES</rptOwnerCity>
            <rptOwnerState>VA</rptOwnerState>
            <rptOwnerZipCode>20166</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>COB and CEO</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>23000</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Spouse</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">This Form 4/A is being filed in order to the amend the reporting person's August 3, 2010 Form 4 which inadvertently omitted the indirect ownership of these shares.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ David W. Thompson by Vanessa T. Hoang, Attorney-in-Fact</signatureName>
        <signatureDate>2010-08-03</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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