WASHINGTON — A hold-down test of Orbital Sciences Corp.’s Antares rocket, a prerequisite for the launch vehicle’s maiden flight, likely will not be completed before April because of ongoing tests and certification work on the vehicle’s launch pad at Wallops Island, Va., a launch official said.

“It’s really an integrated form of testing that’s going on now, as we speak, and we’re looking at completing that, hopefully, by the first of April,” Billie Reed, director of the Mid-Atlantic Regional Spaceport, told Space News Jan. 16.

Antares, formerly known as Taurus 2, is the rocket Orbital will use to launch the cargo-carrying Cygnus tug to the international space station under its $1.9 billion Commercial Resupply Services (CRS) contract with NASA. Orbital is supposed to begin flights under that contract this year, but it must first complete two Antares demonstration flights which themselves cannot proceed until the hold-down test is completed. Orbital’s official launch schedule has the hold-down test slated to occur before the end of March.

But Reed said that the Virginia Commercial Spaceflight Authority, the state entity that manages operations at the spaceport from which Orbital will launch, is still completing certification of individual systems. These include more than 130 pressurized vessels needed to support the launch of the liquid-fueled Antares. The authority is also working on what Reed called “integrated system performance and functional testing,” the purpose of which is to ensure that the various launch support systems and software at Orbital’s pad are working harmoniously.

Orbital Sciences spokesman Barron Beneski said the company would update its launch schedule on Feb. 9, when the Dulles, Va.-based rocket and satellite manufacturer is due to report its 2011 earnings. Beneski confirmed that, per the terms of its Commercial Orbital Transportation Services (COTS) agreement with NASA, Orbital must perform a hold-down test before launching Antares. During the hold-down test, Antares will be anchored to its launch pad for a long-duration engine burn.

“Orbital continues to work toward a more finalized launch date, and once the work with the pad is wrapped up, they will have a better idea of where they are headed in terms of launch dates,” NASA spokesman Josh Byerly told Space News Jan. 17. “Orbital will provide NASA with an updated report in early February, which will give us a better idea of target dates.”

Orbital’s latest publicly released schedule, last updated in late October, shows Antares’ hold-down test and maiden launch both occurring during the first three months of 2012. The first of Orbital’s eight contracted CRS flights, according to this schedule, would occur before the end of September.

A more recently updated internal NASA launch manifest, however, shows the maiden launch occuring in February followed by an April or May COTS demo flight and Orbital’s first CRS cargo run to the international space station in early October.

Beneski said that most of the Antares components needed for the hold-down test are at Wallops awaiting integration.

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.