Orbital Sets December 9 as Date of Special Stockholder Meeting to Vote on Merger with ATK

Orbital Sciences Corporation (NYSE: ORB) today announced that it has set December 9, 2014 as the date for a special meeting of its stockholders at which stockholders will be asked, among other things, to adopt the previously announced transaction agreement with Alliant Techsystems Inc. (“ATK”) (NYSE: ATK), whereby Orbital and ATK’s Aerospace and Defense Groups will merge immediately following the spin-off of ATK’s Sporting Group business to ATK stockholders as a newly formed company called Vista Outdoor Inc. Orbital stockholders of record as of the close of business on October 29, 2014 are entitled to receive notice of, and to vote at, the special meeting. The special meeting will be held on December 9, 2014, at 9:00 a.m. local time, at Orbital’s corporate headquarters at 45101 Warp Drive, Dulles, Virginia 20166.

The transaction is expected to close by the end of 2014 or in January 2015, and is subject to customary closing conditions including regulatory approvals and the approval of each of Orbital’s and ATK’s stockholders. Additional information concerning the special meeting and the transaction will be included in an amendment to the ATK registration statement on Form S-4, which includes a joint proxy statement of Orbital and ATK and also constitutes a prospectus of ATK. This registration statement will be filed with the Securities and Exchange Commission and, once declared effective, the joint proxy statement/prospectus will be mailed to Orbital stockholders who are entitled to vote at the special meeting.

About Orbital

Orbital develops and manufactures small- and medium-class rockets and space systems for commercial, military and civil government customers. The company’s primary products are satellites and launch vehicles, including low-Earth orbit, geosynchronous-Earth orbit and planetary exploration spacecraft for communications, remote sensing, scientific and defense missions; human-rated space systems for Earth-orbit, lunar and other missions; ground- and air-launched rockets that deliver satellites into orbit; missile defense systems that are used as interceptor and target vehicles; and advanced flight systems for atmospheric and space missions. Orbital also provides satellite subsystems and space-related technical services to U.S. Government agencies and laboratories. More information about Orbital can be found at http://www.orbital.com.