The Air Force is developing an on-orbit reprogrammable digital waveform generator for GPS satellites.
"There is a need to develop a digital waveform generator that can be reprogrammed only from the GPS Ground Control Segment with new waveform generation routines while the satellite is in orbit," according to the Phase I small business innovation research solicitation.
GPS waveforms use selective availability to induce errors for civilian receivers attempting to use the data, as well as anti-spoofing to prevent false GPS signals. These waveforms contain two methods for denial of accuracy to civilian receivers: Selective Availability and Anti-Spoofing. S/A is the injection of intentional errors into the waveform to decrease precision, while A/S uses an encryption method to decrease the likelihood of false signals.
Waveform generation is becoming more complex as the GPS system matures, according to the solicitation. Currently, there is no practical way to modify the waveform generation routine on-board the satellite.
The ORDWG will be capable of modifying all current L1 pseudo-random noise codes, produce up to 10 different code signals, change the navigation message data rates, combine PRN codes and navigation messages with no losses or interference, and meet or exceed current applicable GPS specification requirements.