WASHINGTON — A fter spending several months revising its procurement approach to a new land-imaging satellite to please a key U.S. lawmaker, NASA is finally ready to get started on the project, known as the Landsat Data Continuity Mission.

NASA announced Oct. 24 that it intends to award separate contracts for the Landsat spacecraft bus and instrument next year and put one of its field centers in charge of assembling the components into a mission-ready satellite that would launch around 2011.

NASA previously planned to pick one company to do the entire Landsat Data Continuity Mission under a single fixed-price contract.

But objections raised over the summer by U.S. Sen. Barbara Mikulski (D-Md.) prompted NASA to alter its acquisition approach and put Goddard Space Flight Center in Greenbelt, Md., more firmly in charge of the project.

Mikulski, the ranking Democrat on the Senate Appropriations subcommittee that funds NASA , said she was pleased with the agency’s new direction on Landsat, which is expected to produce 28-32 jobs at Goddard.

“I welcome NASA’s decision to move forward with the next Landsat mission through a full and open competition,” she told Space News in an Oct. 26 statement. “This is the best approach for NASA and the taxpayer.”

NASA is under pressure to develop and launch a satellite to replace the old and ailing Landsats 5 and 7 before they cease operating. Landsat 7, the younger of the two by 15 years, is expected to run out of fuel in October 2010 if a hardware failure does not put it out of service sooner. The U.S. Geological Survey, which manages Landsat flight operations, is looking into ways to conserve fuel and extend Landsat 7’s service beyond October 2010.

Ted Hammer, acting associate flight program director for NASA’s Earth Science division, said Oct. 24 that the agency hopes to get the Landsat Data Continuity Mission on orbit before Landsat 7 runs out of fuel, but does not want to jeopardize the replacement system’s performance by pushing too hard on schedule.

Hammer declined to say what NASA expects to spend on the Landsat Data Continuity Mission. But other NASA officials said the project could cost $700 million, or about twice what the agency budgeted for last year when it still assumed it would be building a pair of Landsat instruments and handing them off to the U.S. Air Force and Commerce Department for inclusion on the nation’s next generation of polar-orbiting weather satellites.

When it became increasingly clear just how tricky it would be to include the Landsat sensors on the already over-budget and behind-schedule National Polar-orbiting Operational Environmental Satellite System , the White House brokered an interagency agreement finalized last December that put NASA in charge of fielding a dedicated satellite to continue the collection of Landsat imagery.

Landsat spacecraft have been collecting moderate-resolution multispectral imagery of the world’s land masses for more than three decades. Landsat users are worried that the existing satellites will cease working before their replacement arrives, introducing a potentially lengthy gap in what has been a continuous data record.

“We are going to try to minimize, if not eliminate, the potential data gap with Landsat 7,” Hammer said. “We don’t want to put the performance of the instrument at risk. It’s going to be a fine balancing act in order to have the instrument developed as fast as possible without jeopardizing its performance.”

Hammer said NASA intends to solicit bids for a Landsat-type multispectral sensor in late November or early December with a goal of selecting a provider and awarding a cost-reimbursable contract in early 2007.

Among the companies likely to bid on the instrument work, according to industry officials, are Ball Aerospace and Technologies Corp. of Boulder, Colo.; Rochester, N.Y.-based ITT Space Systems; and El Segundo, Calif.-based Raytheon Space and Airborne Systems.

Once NASA has picked an instrument builder, Hammer said, the agency will solicit bids for the spacecraft platform, or bus. He said NASA intends to limit the bus competition to companies listed in Goddard’s so-called Rapid Spacecraft Acquisition Catalog of pre-qualified spacecraft vendors and make a selection sometime next year.

NASA periodically opens the Rapid catalog to new vendors and buses, and now is one of those times. Hammer said NASA would wait for the process of evaluating prospective new catalog entrants to be completed before requesting bids for the Landsat bus.

The Rapid catalog was established to speed up the procurement process for missions that do not require highly specialized spacecraft . It currently includes 15 pre-negotiated bus offerings from five vendors: Ball Aerospace ; EADS Astrium of Europe; Dulles, Va.-based Orbital Sciences Corp.; General Dynamics’ Gilbert, Ariz.-based Spectrum Astro division; and the United Kingdom’s Surrey Satellite Technology Ltd.

Greg Smith, chief of the Rapid Spacecraft Development Office at Goddard , said a so-called on-ramp for new catalog entrants opened Oct. 25 and would remain open through Dec. 15.