An Atlas 5 rocket launched spaceward late Thursday, hauling a clutch of six military research satellites into orbit for the U.S. Air Force.

The United Launch Alliance (ULA) booster shot into the night sky above Florida's Cape Canaveral Air Force Station at 10:10 p.m. EST (0310 March 9 GMT) carrying two Orbital Express spacecraft refueling demonstrators and four experimental microsatellites under the Air Force's Space Test Program-1 (STP-1) mission.

"This is a proud moment in our company's history and a significant step forward in providing our nation assured access to space using the most cost-effective means possible," Michael Gass, ULA president and CEO, said in a post-launch statement, adding that the space shot marked the first launch of an expendable Atlas booster for the U.S. Air Force.

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Thursday's space shot occurred about a half hour later than planned due to launch-range radio interference and booster-vent valve issues, though both proved only short delays.

Orbital Express, microsatellites reach orbit

The flagship of the STP-1 mission is Orbital Express, a two-spacecraft mission to demonstrate the feasibility of autonomously servicing a satellite in space.

Built for the Defense Advanced Research Projects Agency (DARPA), the $300 million vehicles include the 2,100-pound (952-kilogram) ASTRO servicing satellite and its 500-pound (226-kilogram) target NextSat.

The spacecraft are expected to spend about three months testing autonomous satellite rendezvous, refueling and component replacement in Earth orbit.

"We're very proud to be at this point," USAF Lt. Col. Fred Kennedy, project manager for Orbital Express, said in a telephone interview before launch. "We've been working a long time to be at this stage."

Shortly after the Orbital Express spacecraft were deployed at 10:28 p.m. EST (0328 March 9 GMT), the MidStar-1 microsatellite — built by midshipmen at the U.S. Naval Academy — successfully reached orbit.

The 265-pound (116-kilogram) satellite carries a series of experiments, including a pair of space computer payloads, the Eclipse experiment to examine electrochemical membranes in space for NASA and Eclipse Energy Systems, and a prototype microdosimeter sponsored by the National Space Biological Research Institute.

The ULA Atlas 5 rocket also orbited three other small spacecraft:

— STPsat-1: A 343-pound (156-kilogram) satellite carrying two experiments to collect atmospheric data and demonstrate spacecraft technologies for the U.S. Air Force's Space Test Program.

— Cibola Flight Experiment (CFEsat): A 350-pound (159-kilogram) satellite built for the Los Alamos National Laboratory to test a series of new technologies, including inflatable boom antennas, a new power supply and a prototype supercomputer designed to process data onboard rather than sending raw information directly to Earth.

— FalconSat-3: Built by cadets at the U.S. Air Force Academy, the small, 119-pound (54-kilogram) satellite carries five experiments to study the near-Earth space plasma environment, test new hardware and demonstrate a Micropropulsion Attitude Control System.

"STP-1 required an extraordinary level of coordination and innovation to achieve the mission requirements," Jim Sponnick, ULA vice president of Atlas programs, said in a statement. "One of those innovations was the mission design to achieve the two mission orbits, which was enabled by the development of a very flexible new guidance design."

Thursday's launch marked the 80th consecutive successful space shot for an Atlas rocket and the ninth flight of the booster family's Atlas 5 variant.

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