X0303 4 2010-11-11 0 0000820736 ORBITAL SCIENCES CORP /DE/ ORB 0001045853 THOMPSON DAVID W 21839 ATLANTIC BLVD. C/O ORBITAL SCIENCES CORP DULLES VA 20166 1 1 0 0 COB and CEO Common Stock 2010-11-11 4 M 0 25000 4.00 A 176497 D Common Stock 2010-11-11 4 S 0 25000 17.0184 D 151497 D Common Stock 23000 I By Spouse Employee Stock Option (right to buy) 4.00 2010-11-11 4 M 0 25000 0 A 2011-04-24 Common Stock 25000 25000 D This transaction was executed in multiple trades at prices ranging from $17.00 to $17.081. The price reported above reflects the weighted average sale price. The reporting person hereby undertakes to provide upon request to the SEC staff, the issuer or a security holder of the issuer, full information regarding the number of shares and prices at which the transaction was effected. The option, representing a right to purchase a total of 100,000 shares, vested in three installments on April 24, 2001, February 6, 2002 and February 6, 2003. /s/ Susan Herlick, Attorney-in-Fact 2010-11-12