WASHINGTON — Boeing and Iridium Communications next year hope to begin selling a service to the U.S. government that uses low-orbiting communications satellites to enhance GPS navigation and timing signals and nullify the effects of jamming.

Boeing Defense, Space & Security of St. Louis has been working for about three years on a program called High Integrity GPS, or iGPS, that will culminate in 2011 with a series of operational demonstrations of the full capability, David Whelan, Boeing’s chief scientist, said in an April 7 interview.

The U.S. military has become extremely reliant over the past decade on GPS for navigation and targeting, so much so that U.S. Air Force Chief of Staff Gen. Norton Schwartz recently suggested the services must reduce their dependency on the system. In a January speech, Schwartz said GPS is a vulnerable capability and an alternative system should be developed.

Iridium operates a constellation of 66 low Earth orbiting communications satellites that were built and launched by a Motorola-led consortium at a cost of about $5 billion. The original Iridium company went bankrupt in 1999, and the fleet was bought for pennies on the dollar by a group now called Iridium Communications that operates out of Bethesda, Md. Boeing has been operating the constellation since the transfer of ownership.

The Iridium satellites were designed to be reprogrammable on orbit, and many of the Motorola engineers that developed the system now work for Boeing, Whelan said. In 2005, Boeing went to the U.S. government with the idea to reprogram Iridium satellites to augment the GPS constellation’s navigation and timing signals, and about a year later the company was issued a study contract. In 2008, the Naval Research Laboratory awarded a three-year, $153 million contract to Boeing to develop the software upgrades and ground infrastructure needed for iGPS.

The GPS satellites currently on orbit were designed with a relatively low-power signal that can be interfered with using simple jamming devices on the ground. The idea behind iGPS is to create a package of navigation signals that is so robust that jamming is not practical, Whelan said. The Iridium signal is about 10,000 times more powerful than a GPS signal, and jamming iGPS would require a large radio transmitter that could be easily identified, located and targeted, he said.

The Boeing-developed iGPS software allows the Iridium satellites to send a position and timing signal, followed by another message to correct for errors, to specially designed GPS receivers. This extra information enables the GPS receiver to acquire a signal more quickly and operate in areas where other receivers are rendered useless by intentional or unintentional radio frequency interference, Whelan said.

Boeing and Iridium have completed three increasingly difficult demonstrations so far, including one in August that they claim was the first GPS signal acquisition and geolocation determination in a jammed environment. Now they are working to shrink the receiver technology so that small units can be fielded by the end of the year for testing and evaluation.

If the field trials are successful, the military could begin buying the service in 2011 from Boeing and Iridium “by the pound,” Whelan said. The iGPS capability can be turned on and off like a light switch, and it can be tailored to only work in a specific region for a specific amount of time, he said.

As for the military’s current GPS capability, it will be improved starting this year with the first launch of the GPS 2F satellites that feature a new military signal called M-Code. The iGPS capability is designed to work with and improve the M-Code signal, Whelan said. The first block of GPS 3 satellites that are expected to begin launching in 2014 also will have this new signal, but the military does not plan to incorporate certain anti-jamming technologies into the constellation until the third and final block of satellites begins launching near the end of the decade, Whelan said.

“The potential value here really does bridge a gap until GPS 3C comes along and addresses those gaps around 2020,” Whelan said. “There is a vulnerability and a potential for exploitation by our adversaries.”

In addition to military applications, Boeing and Iridium also see potential for iGPS use in commercial and civil government applications, such as the next-generation air traffic control system planned for implementation by the Federal Aviation Administration, he said.