WASHINGTON — With development work on most of its weather and climate sensors complete, the majority of the risk associated with the National Polar-orbiting Operational Environmental Satellite System (NPOESS) has been eliminated, prime contractor Northrop Grumman says.

Los Angeles-based Northrop Grumman Aerospace Systems believes sticking with the program of record, despite its delays and cost overruns, is the most certain way to successfully field the civil-military weather satellite system, said Ron Birk, the company’s director of mission integration for civil space systems.

“Progress on the program continues to be on track,” he said in a Jan. 13 interview. “A majority of the development risk on the program has been retired at this point.”

The NPOESS program is jointly managed by the U.S. Defense Department, the National Oceanic and Atmospheric Administration and NASA. Once planned for launch in 2009, the first NPOESS satellite is now scheduled to fly in 2014. A precursor satellite dubbed the NPOESS Preparatory Project (NPP), now scheduled for launch in late 2011, was supposed to launch in 2006 and serve as a test bed for the primary NPOESS sensors, but will now be thrust into an operational role because of the delays. The current life-cycle cost of NPOESS is $14 billion.

NASA Earth Science Division Director Michael Freilich indulged in a bit of gallows humor in mid-December when he told an American Geophysics Union audience that “pretty much all the issues have been taken care of with the exception of capabilities and requirements, implementation approach, the governance and the budget. But the rest of the stuff is pretty well in hand.”

Freilich was more or less echoing the conclusion of an independent review panel led by former Martin Marietta Chief Executive A. Thomas Young that reported  last spring that the NPOESS  program is hobbled by an ineffective management structure and needs a near-term infusion of cash to succeed. The White House Office of Science and Technology Policy assembled a task force in the summer to make changes to get the program back on track, but no decisions have been announced. Congress has fenced off half of the funding appropriated for NPOESS in 2010 until Defense Secretary Robert Gates certifies the program will meet schedule and performance requirements.

The instrument that has taken much of the blame for the program’s problems, the Visible Infrared Imaging Radiometer Suite (VIIRS), built by Raytheon Space and Airborne Systems of El Segundo, Calif., now appears to be on track. The first version of the instrument that will fly on NPP completed environmental testing in November and was shipped Jan. 14 to Ball Aerospace & Technologies Corp. of Boulder, Colo., which is building NPP, Birk said.

The first VIIRS sensor will meet 21 of the 22 environmental data record measurements it was originally required to meet, falling short of its intended capability to record ocean-color measurements. Engineering changes for the second unit that will fly on the first NPOESS satellite are expected to correct the deficiency, Birk said.

Now the long pole in the tent appears to be the Cross-track Infrared Sounder, being built by ITT Geospatial Systems of Rochester, N.Y. NASA’s Freilich said Dec. 17 that the instrument “is now on the critical path to NPP and is causing a substantial delay.”

The company was supposed to deliver the instrument in early 2009, but thermal vacuum tests revealed problems with some of the sensor’s computer chips. Then late in 2009 a circuit card assembly was found to be not durable enough to withstand the rigors of the space environment. The result of these problems is a six- to nine-month delay to the NPP launch. Birk said the component issues have been addressed, and the Cross-track Infrared Sounder completed performance testing the week of Jan. 4 that showed it will meet or exceed all of its requirements once on orbit.

Young’s review panel recommended program management responsibility be transferred from the National Oceanic and Atmospheric Administration to an established space acquisition center, either NASA’s Goddard Space Flight Center in Greenbelt, Md., or the Air Force’s Space and Missile Systems Center in Los Angeles.

Northrop Grumman is under contract to deliver two NPOESS satellites, and electing to go with another company for any potential follow-on satellites would introduce technical and schedule risk, Birk said. “It was a well-thought-out program that a lot of highly qualified people put a lot of time and energy into defining the configuration so that all of the components of the program would work together to deliver the environmental data needed by the nation for both civil and military purposes,” he said.