WASHINGTON — Northrop Grumman Aerospace Systems expects to finalize its contract with the U.S. Air Force soon to develop a pair of polar-orbiting satellites that will provide weather information for military users, government and industry officials said.

The omnibus 2011 spending bill signed into law in April provided $175 million for the service’s Defense Weather Satellite System (DWSS), which will allow the program to complete a system requirements review for the scaled-back constellation by the end of the year, Linnie Haynesworth, Northrop’s DWSS vice president and program manager, said May 3.

The DWSS program was created after the White House dismantled the joint military-civilian National Polar-orbiting Operational Environmental Satellite System (NPOESS) in February 2010. The Air Force was directed to develop its own military weather satellites, while NASA and the National Oceanic and Atmospheric Administration pursue satellites for civil weather prediction and climate research observations.

Los Angeles-based Northrop Grumman was the NPOESS prime contractor, responsible for developing the satellite platforms, managing subcontractor development of instruments and the ground system, and integrating the entire system. Contracts for several of the instruments and the ground system were transferred to NASA to manage. Northrop Grumman remains under contract with the Air Force to build the satellite platforms and oversee the Visible Infrared Imaging Radiometer Suite instruments being developed by Raytheon Space and Airborne Systems of El Segundo, Calif., for DWSS and its NASA-managed civilian counterpart, the Joint Polar Satellite System.

Northrop Grumman and the Air Force Space and Missile Systems Center are “days or weeks” from finalizing a contract action that will allow the company to work to meet DWSS requirements, which are somewhat different from NPOESS requirements, Haynesworth said in an interview.

“The authorization that we would expect here soon would be one that would allow us to pursue DWSS-specific requirements, separate and apart from what is in the NPOESS program of record,” Haynesworth said.

Northrop Grumman expects it will retain responsibility for development of the satellite platforms and Visible Infrared Imaging Radiometer Suite, while the government will provide the microwave imagers and space environmental monitoring sensors for the DWSS satellites, which are planned for launch in 2018 and 2021.

One programmatic decision that remains for DWSS is which microwave imager the satellites will fly. The Naval Research Laboratory has been developing the Microwave Imager Sounder for the NPOESS program, but the Air Force last year reviewed other options for the capability. Lt. Gen. Tom Sheridan, commander of the Space and Missile Systems Center, made an instrument recommendation that must still be approved by the Pentagon’s acquisition chief; neither the recommendation nor the options under consideration have been publicly revealed.

Since the Pentagon signed off on the DWSS acquisition plan in August 2010, the program has had stable requirements, said Steven Leonard, the Air Force’s DWSS program manager. Because the first DWSS does not need to be ready for launch until 2018, a decision on the microwave instrument can wait until the fall or later, Leonard said in a May 5 interview.

Since the breakup of the NPOESS program, Northrop Grumman has worked with the government to develop a detailed transition plan that includes a new set of baseline requirements and a new cost estimate for development of the first two DWSS satellites, Haynesworth said. Because many of the requirements for DWSS are the same as those for NPOESS, the company has been able to continue making progress on the program in some areas.

“We certainly are leveraging the actions that we can take with the current contract, those things that are common from the NPOESS program of record and the DWSS program of record,” she said. “The bus activity … has continued to make strong progress.”