-- Mission Marks 15th Consecutive Success for Minotaur Launch
                              Vehicles --

DULLES, Va.Sept. 25, 2008--Orbital Sciences Corporation (NYSE:ORB) announced today that its Minotaur II+ rocket was successfully launched for the U.S. Air Force Space and Missile Systems Center (SMC) in support of the Missile Defense Agency (MDA) Near-Field Infrared Experiment (NFIRE). The mission was conducted on Tuesday, September 23, 2008, from Vandenberg Air Force Base (VAFB), California. The program office responsible for Minotaur launch vehicles is the Launch Test Squadron of the Space Development and Test Wing (SDTW) at Kirtland Air Force Base, New Mexico. This mission was the eighth for the Minotaur II Target Launch Vehicle (TLV) and the 15th for the Minotaur family, all of which have been successful.

The launch originated from VAFB at approximately 11:57 p.m. (PDT) on September 23. Final targeting for the mission was uploaded to the rocket approximately one and a half hours prior to launch. The vehicle was successfully launched within a one-second launch window, which was required to meet the mission's precise targeting requirements. The vehicle's first two solid rocket motors burned for approximately two minutes, at which time the vehicle entered into a coast phase lasting over one minute. After its coast period, the third and final stage ignited, placing the vehicle on course to burn through a precise aim point at an exact time nearly 250 km above the Pacific Ocean. The vehicle was being observed by the NFIRE satellite and a variety of Missile Defense Agency sensors deployed across the Pacific region. At the point of closest approach, the Minotaur target vehicle and NFIRE satellite were within several kilometers of each other. In addition to conducting this Minotaur II+ TLV mission, Orbital also launched the NFIRE satellite in April 2007 aboard a Minotaur I space launch vehicle in a mission conducted from NASA's Wallops Flight Facility in Eastern Virginia. Orbital also conducted an earlier Minotaur II+ TLV launch that was observed by the NFIRE satellite last year.

Minotaur II+ is an upgraded version of the reliable and proven Minotaur II vehicle, yielding a more capable vehicle for future applications. The major upgrades include a higher performing third stage and larger structures. The new stage and structures enable the launch of larger and heavier payloads or reentry vehicles. The previous Minotaur II+ mission was launched in August 2007 and met all customer requirements, also demonstrating precise timing and targeting accuracy. The flight involved a number of first flight items, including a new Pierce Point Guidance algorithm and demonstration of a launch minus 90-minute target point upload to the flight computer, capabilities that have Operationally Responsive Space (ORS) applications.

Orbital is one of the country's leading suppliers of launch vehicles used in missile defense and other military applications. In addition to numerous configurations of target vehicles, Orbital is also designing and building the interceptor boosters for two major missile defense programs, including the Ground-based Midcourse Defense (GMD) system, which uses the company's three-stage Orbital Boost Vehicle (OBV), and the Kinetic Energy Interceptors (KEI) program, which is designed to intercept and destroy enemy missiles in the early boost phase of flight. These interceptors are part of a layered missile defense system for defending the nation, our armed forces and our allies against ballistic missile attacks.

About Orbital's Minotaur Product Line

The Minotaur product line consists of the only proven launch vehicles currently capable of supporting the U.S. Department of Defense's evolving ORS space launch requirements, as well as long-range target delivery for missile defense and technology demonstration missions. They are specifically designed to be capable of launching from all major U.S. spaceports, including government and commercial launch sites in Alaska, California, Florida and Virginia. In addition, the minimal amount of specialized ground infrastructure that is required to support Minotaur launches enable them to be employed at other U.S. launch sites. Orbital's use of standardized avionics and subsystems, mature processes and experienced personnel make Minotaur rockets both reliable and cost-effective for U.S. government customers.

Orbital's Minotaur product line currently consists of the following configurations:

    --  Minotaur I - The initial member of the Minotaur family, the
        Minotaur I is a four-stage space launch configuration that can
        place up to 1,300 lbs. into low-Earth orbit. It was originally
        launched in January 2000 and carries a perfect seven-for-seven
        mission success record. The next planned Minotaur I mission is
        the launch of the TacSat-3 spacecraft currently scheduled for
        the fourth quarter of 2008.

    --  Minotaur II - A three-stage suborbital rocket, the Minotaur II
        is used as a target vehicle for testing U.S. missile defense
        systems and related missions. This configuration carries a
        perfect eight-for-eight mission success record since its first
        flight in June 2000.

    --  Minotaur III - A three-stage suborbital rocket, Minotaur III
        can deliver suborbital technology demonstration payloads of up
        to 6,500 lbs. or serve as a target vehicle for testing U.S.
        missile defense systems and similar missions.

    --  Minotaur IV - A heavier-lift four-stage space launch vehicle
        using retired Peacekeeper rocket motors, the Minotaur IV is
        capable of launching satellites weighing up to 3,800 lbs. into
        low-Earth orbit. The first Minotaur IV mission is currently in
        final production to launch a satellite for the U.S. Air Force
        in early 2009. A configuration with increased performance,
        Minotaur IV+, is also under contract for an initial launch in
        late 2009.

    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 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; and missile defense systems that are used as interceptor and target vehicles. Orbital also provides satellite subsystems and space-related technical services to government agencies and laboratories.


    Notes to Editors:

    --  More information about the Minotaur II launch vehicle is
        available on Orbital's web site at:
        http://www.orbital.com/MissileDefense/MissileDefenseTargets/

    --  High-resolution photos of a Minotaur II rocket are also
        available on Orbital's web site at:
        http://www.orbital.com/NewsInfo/Images/MissileDefense/



    CONTACT: Orbital Sciences Corporation
             Barron Beneski, 703-406-5528
             Public and Investor Relations
             Beneski.barron@orbital.com

    SOURCE: Orbital Sciences Corporation