NASA commercial partner Orbital Sciences Corporation launched its Cygnus cargo spacecraft aboard the Antares rocket at 1:07 p.m. EST Thursday from the Mid-Atlantic Regional Spaceport Pad 0A at NASA's Wallops Flight Facility in Virginia for the Orbital-1 cargo resupply mission to the International Space Station.

At the time of launch the station was flying about 260 miles over the Atlantic Ocean just off the coast of Brazil.

Over the next two and a half days, Cygnus will perform a series of engine firings to put it on track for a Sunday morning rendezvous with the station. When the vehicle reaches the capture point about 30 feet from the complex, Expedition 38 Flight Engineers Mike Hopkins and Koichi Wakata will use Canadarm2, the station's 57-foot robotic arm, to reach out and grapple Cygnus at 6:02 a.m. The crew then will use the robotic arm to guide Cygnus to its berthing port on the Earth-facing side of the Harmony node for installation beginning around 6:20 a.m.

NASA television coverage of the rendezvous and berthing begins at 5 a.m. Sunday, followed at 7 a.m. with coverage of the installation.

For its first official commercial resupply mission, designated Orbital-1, Cygnus is delivering 2,780 pounds of supplies to the space station, including vital science experiments for the Expedition 38 crew members aboard the orbiting laboratory. Orbital Sciences successfully proved the capability of the Cygnus spacecraft during its first and only demonstration flight to the station back in September 2013.

Cygnus will remain at the station until mid-February when it will be unberthed from the station for a destructive re-entry over the Pacific Ocean. That departure will clear the way for the arrival of Space Exploration Technologies' SpaceX-3 commercial cargo mission aboard the Dragon spacecraft. These two back-to-back resupply missions by U.S. companies will mark a milestone in NASA's ability to deliver critical new science payloads to the only laboratory in space.

The launch of Antares was scheduled for Thursday after a launch attempt on Wednesday was scrubbed due to an unusually high level of space radiation that exceeded constraints imposed on Antares.

Orbital conducted a comprehensive review of data related to the radiation environment in space, further reviews and modeling of the rocket's avionics systems, and the forecast for favorable terrestrial weather conditions at Wallops. Upon a deeper examination of the space weather environment, Orbital's engineering team, in consultation with NASA, determined that the risk to launch success was within acceptable limits established at the outset of the Antares program.

With a busy weekend of Cygnus capture activities ahead of them, Hopkins, Wakata and Flight Engineer Rick Mastracchio enjoyed a mostly off-duty day Thursday aboard the station to relax and recharge.

Hopkins and Wakata began their day with a series of eye exams for the Ocular Health study. Vision changes have been observed in some astronauts returning from long-duration spaceflight, and researchers want to learn more about its root causes and develop countermeasures to minimize this risk.

Wakata also downloaded data from sensors he wore for a 36-hour data collection period of the Circadian Rhythms study. The knowledge gleaned from this experiment will not only provide important insights into the adaptations of the human autonomic nervous system in space over time, but also has significant practical implications by helping to improve physical exercise, rest- and work shifts as well as fostering adequate workplace illumination.

In the afternoon, Hopkins, Mastracchio and Wakata participated in a debrief with support personnel on the ground to review the two U.S. spacewalks conducted in late December to remove and replace a faulty ammonia pump module. That pair of spacewalks conducted by Hopkins and Mastracchio with robotic assistance from Wakata at the controls of Canadarm2 successfully restored an external cooling loop that uses ammonia to prevent station systems from overheating.

Commander Oleg Kotov and Flight Engineer Sergey Ryazanskiy spent much of their day replacing lights in the Russian segment of the station.

Ryazanskiy also performed the Uragan Earth-observation experiment, which seeks to document and predict the development of natural and man-made disasters on Earth.

Flight Engineer Mikhail Tyurin began the day conducting routine daily maintenance on the life-support system in the Zvezda service module. Afterward he joined Kotov for a familiarization session for the KAPLYA-2 experiment, which is studying the hydrodynamics and heat transfer of monodisperse drop flows in space.