Iridium Satellite LLC graphicThe Boeing Company has received a three-year, $153.5-million cost-plus-fixed-fee contract to continue its efforts to augment GPS for military applications by exploiting the Iridium low earth orbit (LEO) communications satellite system.
The Boeing Company has received a three-year, $153.5-million cost-plus-fixed-fee contract to continue its efforts to augment GPS for military applications by exploiting the Iridium low earth orbit (LEO) communications satellite system.
Awarded by the U.S. Navy’s Naval Research Laboratory (NRL), the funding will be used for research, development, and demonstration of the High Integrity GPS Technology Concept — known more commonly as iGPS. The program is developing techniques that enable faster acquisition (time to first fix or TTFF) of GPS satellite signals in adverse operating environments, including those with RF interference or urban settings.
The i-GPS architecture involves high-precision time transfer of GPS time and its rebroadcast over the higher powered Iridium communications channels. The High Integrity GPS team includes Boeing Advanced Systems and Phantom Works, Iridium LLC, Rockwell Collins, Coherent Navigation, and experts from academia. Phantom Works is the advanced research and development unit of Boeing.
Availability of the precise time allows GPS equipment to reduce the search volume of the receiver’s DSP correlators and accelerate TTFF, potentially including direct acquisition of the military P(Y)-code signals. The stronger Iridium signals also make GPS signal tracking more robust by increasing the antijamming capability of user equipment.
Field tests conducted in June 2007 at Cedar Rapids, Iowa, home of Rockwell Collins, which is providing user equipment modified for iGPS, demonstrated the capability of iGPS to provide time transfer to improve resistance to GPS jamming.
The contract will also support Boeing’s efforts to refine narrow-band ranging techniques using the Iridium satellite broadcasts directly, as well as broadband ranging in the future. This is made possible by the highly flexible design of the Iridium satellites, which allows on-orbit reprogramming of the spacecraft, according to David Whelan, chief scientist for Boeing Integrated Defense Systems (IDS) and general manager and deputy for IDS’s Advanced Systems group, an integrated innovation team that pursues new business opportunities.
This aspect of the iGPS draws on the experience of Transit, the Navy Navigation Satellite System that operated from the 1960s until 1996, when its navigation service was superseded by GPS. Also a LEO system, the five-satellite/five-spare Transit constellation provided ranging signals based on Doppler effects with much different dynamic parameters than GPS.
“In effect, we are remapping Iridium into a modern-day Transit system and integrating it with the GPS MEO [middle earth orbiting] system,” Whelan said in an interview with Inside GNSS.
Moreover, Boeing is investigating the use of real-time carrier phase differential GPS to improve positioning accuracy to the centimeter level, as well as integration of iGPS with microelectromechanical system (MEMS) inertial measurement units (IMUs), says Whelan, who along with the iGPS engineering team has received a number of Boeing innovation awards for their work.
The initial studies that evolved into the iGPS effort began in 2002. In addition to the military-oriented iGPS development now underway, Boeing is also investigating potential civil and commercial applications, including safety-of-life uses. “High integrity is the greatest value” of iGPS, Whelan said. Whether and when those civil applications come about depends on the DoD and NRL sponsors of iGPS, he added.
Under the NRL contract, work will be performed at Boeing facilities (or companies associated with the iGPS program) in Huntington Beach, California (34.3 percent); Philadelphia, Pennsylvania (17.3 percent); St. Louis, Missouri (1.5 percent); El Segundo, California (12.6 percent); Cedar Raids, Iowa (12.3 percent); Bethesda, Maryland (15.3 percent); Washington, D.C. (5.4 percent); Ithaca, New York (.5 percent); Chicago, Illinois (.3 percent); Burlingame, California (.5 percent), with completion expected by January 2011.
The largest commercial satellite system in the world, Iridium is a 66-satellite, cross-linked LEO constellation originally developed and launched by a consortium headed by Motorola, Inc.
Service was launched on November 1, 1998, but the company went into Chapter 11 bankruptcy within a year. A new group of investors operating as Iridium Satellite LLC acquired Iridium’s assets out of bankruptcy in December 2000 bolstered by a substantial Department of Defense (DoD) contract.
Aside from Boeing’s work on iGPS, Iridium already provides enhanced mobile satellite services (EMSS) as a DoD-supported augmentation to the company’s commercial service. Unique DoD features include end-to-end encryption, interface to secure telephone equipment, and protection of sensitive user information.
The DoD established a dedicated EMSS gateway in Wahiawa, Hawaii for government use through the Defense Information Systems Network (DISN), providing a direct connection to the Defense Switched Network (DSN), Federal Telecommunications System (FTS), or Public Switched Telephone Networks (PSTN). EMSS-authorized user handsets support secure communications.
