Antares Conducts Flawless Maiden Launch

Press release from Orbital Sciences following today’s successful launch of the Antares booster

ORBITAL SUCCESSFULLY LAUNCHES FIRST ANTARES ROCKET

— Company Introduces America’s Newest Medium-Class Space Launch Vehicle —

— Orbital Now Poised to Conduct Cargo Resupply Demonstrations Mission to
International Space Station in Mid 2013 —

(Dulles, VA 21 April 2013) – Orbital Sciences Corporation (NYSE: ORB), one
of the world’s leading space technology companies, today completed a
successful test launch of its new Antares™ rocket from the Mid-Atlantic
Regional Spaceport (MARS) located at NASA’s Wallops Flight Facility in
eastern Virginia. Lift-off took place at 5:00 p.m. (EDT) followed by
payload separation approximately 10 minutes later and mission completion at
about 18 minutes after launch, once the rocket’s upper stage completed
planned maneuvers to distance itself from the payload. The test flight
demonstrated all operational aspects of the new Antares launcher, including
the ascent to space and accurate delivery of a simulated payload to a
target orbit of approximately 150 by 160 miles, with an inclination of 51.6
degrees, the same launch profile it will use for Orbital’s upcoming cargo
supply missions to the International Space Station (ISS) for NASA.

“Today marked a giant step forward for the Antares program, with a fully
successful inaugural flight of the largest and most complex rocket the
company has ever developed and flown, said Mr. David W. Thompson, Orbital’s
Chairman and Chief Executive Officer. “With its successful test flight
from the MARS pad at Wallops Island, we will now move forward toward
completing the full demonstration mission of our system to resupply the
International Space Station with essential cargo in just a couple of
months.”

Today’s test launch, dubbed the Antares A-ONE mission, was conducted under
the Commercial Orbital Transportation Services (COTS) Space Act Agreement
Orbital entered into with NASA in 2008. Following a successful
demonstration mission to the ISS of Orbital’s complete system in mid-2013,
including the launch of the first Cygnus cargo logistics spacecraft,
Orbital will begin regular operational cargo delivery missions to the Space
Station under its Commercial Resupply Services (CRS) contract with NASA.
The $1.9 billion CRS contract calls for the delivery of up to 20,000
kilograms of essential supplies to the ISS over eight separate missions
from 2013 to 2016.

In addition to supporting cargo missions to the ISS, the new Antares rocket
will offer other commercial, civil government, and defense and intelligence
customers affordable and reliable medium-class launch services for
medium-class satellites that do not require the industry’s larger, more
expensive launch vehicles. Moving upward from its traditional focus on
small-class rockets, Orbital’s Antares medium-class launcher will provide a
major increase in the payload launch capability that the company can
provide to NASA, the U.S. Air Force and other potential customers. It is
designed to launch spacecraft weighing up to 14,000 lbs. into low-Earth
orbit, as well as lighter-weight payloads into higher-energy orbits.

Orbital’s newest launcher is currently on-ramped to both the NASA Launch
Services-2 and the U.S. Air Force’s Orbital/Suborbital Program-3 contracts,
enabling the two largest U.S. government space launch customers to order
Antares for “right-size and right-price” launch services for medium-class
spacecraft. For more information on Antares, visit
http://www.orbital.com/Antares-Cygnus/.