A demonstration of L2C tracking from space for atmospheric occultation

The new GPS L2C modulation is important for scientific GPS data users who require high-precision ionosphere-free phase measurements when access to the decrypted L2P modulation is not available. The IGOR GPS receiver, built by Broad Reach Engineering, has software radio features that allow re-programming of some signal processing functions. Engineers at JPL working with scientists at JPL and UCAR remotely modified the IGOR payload on one of the COSMIC weather satellites. The COSMIC satellite constellation, operated by the Taiwanese space agency, NSPO, comprises six small satellites, each operating an IGOR GPS receiver built by Broad Reach Engineering. The main purpose of the IGOR is to produce 50 Hz L1 and L2 phase and amplitude science observations as GPS signals rise and set through the Earth's atmosphere. These signals are greatly attenuated by de-focusing due to strong refraction in the lower atmosphere, so SNR can be very weak. Initial processing of the L2C data from the COSMIC mission shows much significant improvement in the depth of penetration of the L2C signal allows compared to L2P observations with a code enhanced technique. We will show early on-orbit tracking results and discuss scientific implications for use of this data on the COSMIC Radio Occultation Mission.