-- Company Thanks Customers and Employees for Their Contributions
                         Over Last 25 Years --

   -- Orbital Tallies Over 770 Rockets and Satellites Built or Under
                        Contract Since 1982 --

DULLES, Va.April 2, 2007--Orbital Sciences Corporation (NYSE:ORB) celebrated the company's first quarter-century in the space business today as it completed 25 years of operations since the enterprise's founding on April 2, 1982. At anniversary events starting at the company's Dulles, Virginia headquarters and continuing later this week at other sites, Orbital executives thanked its employees and customers for making possible the company's successes to date, and for providing exciting opportunities for future achievements.

"Reflecting on our first 25 years in business, Orbital's Board of Directors and senior management team are deeply grateful to our customers for their willingness to trust a new enterprise to carry out many of their critical space projects. We also want to offer our heartfelt thanks to the company's employees and their families, whose creativity, dedication and sacrifices allowed us to fulfill our customer commitments while also building a strong foundation for future growth," said Mr. David W. Thompson, Orbital's Chairman and Chief Executive Officer.

From three cofounders and no revenues in 1982, Orbital has grown to over 3,000 people and almost $900 million in annual revenues expected in 2007. During the last 25 years, the company has generated cumulative revenues of approximately $8.7 billion, providing over 45,000 person-years of high-technology employment for its workforce.

Since its founding in 1982, the company has been among the space industry's most active developers and manufacturers of launch vehicles and space systems. Its operational accomplishments during the past quarter-century have involved selling, designing and building 772 rockets and space systems. This total includes 583 launch vehicles, missiles, satellites and other space systems completed and delivered to date, plus 189 satellites, rockets and related systems currently under firm contracts with customer deliveries scheduled from 2007 to 2012.

Technology Advances and Product Innovations

Orbital pioneered several significant space industry innovations during the last 25 years, including these important milestones:

    --  Development of the world's first privately-funded space launch
        vehicle, culminating in the Pegasus rocket's inaugural flight
        in 1990;

    --  Creation of the industry's first modern microsatellites,
        involving the design, manufacturing and operation of more than
        20 100-kilogram (or smaller) spacecraft for various customers
        and applications in the 1985-1993 period;

    --  Design, production and launch of the first commercial
        low-orbit communications satellites in 1995, leading to full
        deployment of a 35-satellite global network during 1997-1999;

    --  Modification of the first U.S. solid fuel ICBM's to be used as
        space launch vehicles and special-purpose R&D platforms, with
        launches beginning in 2000;

    --  Introduction of the industry's leading small geosynchronous
        communications and broadcasting satellites in the late 1990's
        and early 2000's; and

    --  Substantial contributions to the advancements of critical
        technologies over the last five years, in areas such as
        missile defense programs, ramjet and scramjet propulsion,
        autonomous space rendezvous, responsive space operations, and
        satellite communications and imaging systems.

    Satellite and Launch Vehicle Manufacturing Activity

Orbital's experience over its first quarter-century includes design, development and manufacturing of 122 satellites and 43 major space systems for commercial, scientific and national defense customers, with details as follows:

    --  64 commercial communications, broadcasting and imaging
        satellites for operators in North America, South America,
        Europe, Asia and Australia;

    --  24 space and Earth science spacecraft for government agencies,
        universities and research laboratories;

    --  34 R&D, technology demonstration and operational satellites
        for national defense and civil government users; and

    --  43 satellite subsystems and attached space payloads for
        government and commercial customers.

During that same 25-year period, the company also designed and built, or now has under development and production, 607 launch vehicles and missile systems, comprising four general categories of rockets:

    --  78 space launch vehicles and related systems for unmanned and
        manned space missions, including the Pegasus, Taurus and
        Minotaur space launchers and NASA's new Orion crew exploration
        vehicle launch escape system;

    --  75 interceptor launch vehicles for missile defense systems,
        consisting of boost vehicles for both the Missile Defense
        Agency's (MDA) Ground-based Midcourse Defense and Kinetic
        Energy Interceptor programs;

    --  118 major target vehicles for missile defense testing and
        related experimental applications, covering a wide array of
        short-, medium- and long-range targets and countermeasure
        systems; and

    --  336 smaller missile systems and scientific sounding rockets,
        including low-altitude supersonic ramjet-powered targets and
        various high-altitude research vehicles.

Orbital's constant focus on product safety and dependability has resulted in a 96.6% reliability record on the 320 major space missions (those with total value in excess of $5 million) it has conducted over the last 25 years, increasing to 98.7% on 153 major missions carried out in the last 10 years and 100% on 65 major missions in the last five years.

Looking Ahead

Today, the company's space systems and launch vehicles are used by our customers in many mission-critical governmental and commercial applications, including the following:

    --  Over a dozen company-supplied MDA long-range missile
        interceptor boosters are currently on alert status -
        increasing to 24 interceptors by this fall -- in Alaska and
        California, vital elements of the United States' first-ever
        national defense system protecting 300 million Americans from
        missile attack;

    --  55 company-built satellites are currently in operation,
        including 40 commercial communications spacecraft providing
        broadcast, voice and data services to millions of customers
        around the globe;

    --  During the 2007-2009 interval, more than a dozen Pegasus,
        Taurus and Minotaur rockets are scheduled to launch NASA, U.S.
        Air Force, MDA and Defense Advanced Research Projects Agency
        satellites and other payloads into space, in support of
        important scientific and defense missions;

    --  By mid-2007, the Orbital-developed Dawn deep-space exploration
        spacecraft will be on its way to explore two of the solar
        system's largest main-belt asteroids, beginning an eight-year,
        multi-billion mile mission of scientific discovery;

    --  Some 50 "Coyote" supersonic ramjet targets, already delivered
        or now being built by the company, are helping the U.S. Navy
        test and perfect defense systems for aircraft carriers and
        other naval vessels from sea-skimming anti-ship missiles; and

    --  Beginning next year, launch escape systems under development
        by the company for NASA's Orion human space exploration
        vehicle will begin test flights, contributing to enhanced
        safety for our astronauts for decades to come.

"As proud as I am of what Orbital's people have achieved so far, I am convinced that the company's greatest accomplishments are still to come. With the continued confidence of our customers and commitment of our employees, our adventure is just beginning," Mr. Thompson concluded.

About Orbital

Orbital develops and manufactures small space and missile systems for commercial, civil government and military customers. Orbital's primary products are satellites and launch vehicles, including low-orbit, geosynchronous-orbit and planetary spacecraft for communications, remote sensing, scientific and defense missions; ground- and air-launched rockets that deliver satellites into orbit; and missile defense boosters that are used as interceptor and target vehicles. Orbital also offers space-related technical services to government agencies and develops and builds satellite-based transportation management systems for public transit agencies and private vehicle fleet operators.

    CONTACT: Orbital Sciences Corporation
             Public and Investor Relations
             Barron Beneski, 703-406-5528

    SOURCE: Orbital Sciences Corporation