Northrop Grumman is lobbying Congress and the Air Force for money to overhaul the company’s current fleet of long-range surveillance aircraft, rather than grounding the planes by 2015 because of obsolete parts.

The defense contractor is eyeing all moving defense bills, including the emergency war spending measure, to pay for a new radar system that would upgrade its E-8C Joint STARS planes — short for Joint Surveillance Target Attack Radar System.

Another $3 billion would allow the company to finish and install the new radar on Joint STARS before a dearth of replacement parts makes the aircraft’s existing system obsolete in the next decade, Northrop officials say.

The lobbying effort comes as the Air Force considers what wide-area surveillance capabilities to invest in for the future. There is no consensus yet in the Air Force as to whether Northrop’s E-8C Joint STARS will carry the new radar.

Currently, Joint STARS is the only wide-area ground surveillance capability in the Air Force to detect moving targets. The plane has been a workhorse in the Iraq and Afghanistan wars.

But Northrop Grumman is facing hurdles with the plane’s radar — the centerpiece of the system. By 2012, the company will no longer be able to replace parts because the technology is now two decades old. It would have been very costly to keep the manufacturing line open for the older technology that outfits a total of 17 aircraft, according to Northrop officials.

Without a stock of new parts, Northrop would have to ground the fleet by 2015 and use parts from the existing aircraft. The plane, a Boeing 707, could still fly for another 50 years, but without working radar would have limited use, company officials argue.

The Air Force is juggling several other high-cost priorities, including the F-22 Raptor, the Joint Strike Fighter and a new refueling tanker, and did not include any funding for the radar or E-8C upgrades necessary to house the radar in its fiscal 2009 budget request.

Instead, the service asked Congress for $285 million to continue the development of MP-RTIP in its unfunded priorities list. Every year, the services submit the list to the defense committees in hopes that more money is included in the budget.

Oftentimes, projects on those lists are of high congressional interest, translating into job creation or security in districts across the country.

Joint STARS and MP-RTIP has some strong congressional support from the Florida, Connecticut and Georgia delegations. Northrop employs about 540 people in Melbourne, Fla., for the E-8C program. About 130 work with the Air Force in support of the 17 aircraft based at Robins Air Force Base, Ga. About 90 work in Norwalk, Conn., on developing the radar technology.

Northrop Grumman and Raytheon are the two contractors working on MP-RTIP. The companies are under contract to develop a smaller version of the radar for the Global Hawk unmanned aerial vehicle.

However, the government has invested in the development of the large radar that would not only enhance air-to-ground surveillance and targeting but also provide cruise-missile defense.

Without more money to finish the development, the nearly $1 billion spent would essentially go to waste, Dave Nagy, vice president for intelligence, surveillance and reconnaissance for Northrop Grumman, said in an interview. He added that the company can begin upgrading the Joint STARS by 2015 and quickly have the rest of the fleet ready.

“There is no capability on the battlefield that is remotely like this,” Nagy said. Without a last investment effort, “the war fighters won’t have this revolutionary capability on the battlefield.”

The radar had been envisioned for an aircraft wider than Boeing’s 707 and therefore would need some adjustments, but Northrop officials say they are not major. The Air Force has contemplated installing the radar on the new KC-45 tanker, also a Northrop Grumman program.

Already, Sen. Joe Lieberman (I-Conn.), the chairman of the Senate Armed Services Air and Land subcommittee, added $98 million in the 2009 defense authorization bill for the development of the large MP-RTIP radar. Most of the work for the radar is done at Northrop Grumman is Norwalk, Conn.

The committee recommended that the Air Force pursue a stronger option than the Global Hawk drone alone. The committee recommended the $98 million increase for MP-RTIP to be included either on Joint STARS or some other plane.

Meanwhile, the House Armed Services Committee is marking up its version of the defense bill on Wednesday.

Apart from the 2009 unfunded priority list, the Air Force also included funding requests in the 2008 war supplemental. The Air Force requested $178 million for the radar and $85 million for Joint STARS to address the diminishing manufacturing sources for the radar. Both the House and the Senate are working on the supplemental bill this week.

Northrop’s fight will likely continue for several months as the defense appropriators take up the Pentagon spending bill for 2009. There’s some uncertainty as to whether Congress will pass the defense appropriations bill in an election year or resort to a continuing resolution funding the Pentagon at 2008 levels.