This story was updated Sept. 28 at 4:22 p.m. EST

WASHINGTON — Orbital Sciences Corp., one of two companies under contract to fly cargo to the international space station for NASA, has been cleared by the U.S. space agency to begin launch pad operations at the Mid-Atlantic Regional Spaceport (MARS) on Wallops Island, Va.

MARS is located on NASA’s Wallops Island Flight Facility, so NASA is responsible for certifying that Pad 0-A, from which Orbital plans to launch all of its space station cargo missions, is safe. That certification, which Orbital needed before it could begin a series of Antares rocket tests and demonstration flights that would pave the way for the company to start regular space station cargo runs, has been slow in coming. The company blamed the state of Virginia, which operates MARS through the Virginia Commercial Spaceflight Authority, for the delay.

Orbital spokesman Barron Beneski said Sept. 27 that the company had been cleared to proceed with critical tests at the pad, beginning with a long-awaited hold-down test scheduled to take place sometime during the next several weeks.

“We were authorized to begin our on-pad operations,” Beneski said. “Once the rocket is hooked up, it will be four to six weeks before we do the hot-fire test.”

In the hold-down test, an Antares first stage powered by two kerosene-fueled AJ-26 engines will be hooked up to Pad 0-A and fired for 30 seconds, Beneski said.

Orbital had planned to move the Antares first stage out to the pad Sept. 27 but had delayed the rollout because of a “battery issue” with one of the transport vehicles used to haul Antares from its hangar to the pad, Beneski said.

“We determined the issue was a fuse,” Beneski said Sept. 28. “We had a bad fuse, but it’s a specialized fuse and the nearest supplier is in Raleigh, N.C. So we need to get one from down there, and then there’s supposed to be bad weather over the weekend at Wallops so we’re just going to push it to Monday [Oct. 1].”

The Antares first-stage hold-down test is one of the last remaining milestones under Orbital’s Commercial Orbital Transportation Services (COTS) agreement with NASA. If the hold-down test is successful, it will clear the way for Antares’ maiden launch — a test flight carrying a dummy payload instead of Orbital’s Cygnus cargo tug — followed by a full-up demonstration flight to the space station by the end of this year, Beneski said.

Orbital plans to use Antares and Cygnus to fulfill its $1.9 billion Commercial Resupply Services contract with NASA. The 2008 agreement calls for Orbital to make eight cargo delivery runs to the space station.

Dan Leone is a SpaceNews staff writer, covering NASA, NOAA and a growing number of entrepreneurial space companies. He earned a bachelor’s degree in public communications from the American University in Washington.