Lockheed Martin Space Systems has been given the go-ahead by the US Air Force to begin modifying a production GPS Block IIR-M navigation satellite to transmit a third civil signal designed to boost accuracy for civil aviation applications while reducing intentional or unintentional signal corruption.

The work is part of a $6 million contract the air force awarded to Lockheed, the prime contractor for the GPS IIR-M program, in April. The modified spacecraft, one of five GPS IIR-M satellites remaining under Lockheed's 21-satellite contract for the air force's Global Positioning Wing, is slated to be launched next year.

The test payload will temporarily transmit a new GPS civil frequency known as L5 that, when combined with the existing L1 civil frequency and the Wide Area Augmentation System (WAAS), will allow for precision instrument approach capabilities without ground navigation aids.

The additional civil frequency will increase positioning accuracy from 10m (33ft)to 1m, regardless of whether WAAS is available, while higher signal power and multiple frequencies will decrease the possibility of interference.

The military plans have a full constellation of 30-32 next-generation multi-frequency satellites, known as GPS III, in the 2015 timeframe.

Source: Flight International