This paper will describe the TriG architecture, and how the new features will benefit the next-generation of global network instruments, as well as current test results.

TriG is the next generation NASA scalable space GNSS Science Receiver. It will track all GNSS and additional signals (i.e. GPS, GLONASS, Galileo, Compass and Doris). Scalable 3U architecture and fully software and firmware recofigurable, enabling optimization to meet specific mission requirements. TriG GNSS EM is currently undergoing testing and is expected to complete full performance testing later this year.

Remotely sensing the Earth's surface using GNSS signals as bi-static radar sources is one of the most challenging applications for radiometric instrument design. As part of NASA's Instrument Incubator Program, our group at JPL has built a prototype instrument, TOGA (Time-shifted, Orthometric, GNSS Array), to address a variety of GNSS science needs. Observing GNSS reflections is major focus of the design/development effort. The TOGA design features a steerable beam antenna array which can form a high-gain antenna pattern in multiple directions simultaneously. Multiple FPGAs provide flexible digital signal processing logic to process both GPS and Galileo reflections. A Linux OS based science processor serves as experiment scheduler and data post-processor. This paper outlines the TOGA design approach as well as preliminary results of reflection data collected from test flights over the Pacific ocean. This reflections data demonstrates observation of the GPS L1/L2C/L5 signals.

The new GPS L2C modulation is important for scientific GPS data users who require high-precision ionospherefree 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.

Remotely sensing the Earth's surface using GNSS (Global Navigation Satellite System) signals as bi-static radar sources is one of the most challenging applications for radiometric instrument design. As part of NASA's Instrument Incubator Program, our group at JPL is building a prototype instrument, TOGA (Time-shifted, Orthometric, GNSS Array), to address a variety of GNSS science needs. Observing GNSS reflections is major focus of the design/development effort. The TOGA design features an electronically steered antenna (ESA) array which forms simultaneous high-gain beams in multiple directions. Multiple FPGAs provide flexible digital signal processing logic to process both GPS and Galileo reflections. A Linux operating system based science processor serves as experiment scheduler and data post-processor. This paper outlines the TOGA design approach as it applies specifically to observing science quality GNSS-R signals from low Earth orbit.

The L2C signal is a great step forward for civil applications of GPS, enabling high-accuracy dual-frequency measurements. Engineers from the Jet Propulsion Laboratory and ITT teamed to reprogram FPGA firmware and add tracking software on an orbiting receiver to track the new GPS L2C signal from SAC-C. SAC-C is an Argentinean science satellite and was launched in November 2000 with a BlackJack GPS receiver. This is a dual-frequency digital receiver with 48 tracking channels and four antennas. On SAC-C, it provides precise orbits, atmospheric occultation data, tests of GPS surface reflections, and serves as an orbiting test bed for new GPS development such as the L2C tracking reported here.

ROCSat-3's primary instrument is the GPS Occultation Receiver (GOX) and is based on the Jet Propulsion Laboratory's (JPL) proven BlackJack GPS Receiver. The COSMIC GOX receivers will demonstrate an important new operational data type for near-real-time assimilation into weather models by providing over 2500 atmospheric profiles per day with a global distribution.