A new, highly sensitive GPS receiver will help detect subtle fluctuations in the signals from GPS satellites on the International Space Station (ISS). Developed by engineers at Cornell University in the USA, the FOTON (Fast Orbital TEC for Orbit and Navigation) GPS receiver arrived at the ISS last month on board the SpaceX Falcon 9 rocket. It will study space weather charged particles in the plasma of space that affect the performance of communications and navigation satellites. Steven Powell of Cornell University told the university newspaper, the Cornell Chronicle, These fluctuations are typically filtered out by standard GPS receivers, but they are the scientific gold nuggets in the data analysis process. FOTON is part of the GROUP-C (GPS Radio Occultation and Ultraviolet Photometry Colocated) project. Scott Budzien of the Naval Research Laboratory is project leader, with Powell heading the Cornell team. Consisting of a GPS receiver and three antennas, FOTON shares a mounting palette on the outside of the ISS, receives power from large solar arrays, and uses the data communications system on the station to send data back to Earth. The equipment has been configured to maximize GPS signals and minimize unwanted reflections from the large metal portions of the ISS, enabling it to focus on GPS satellites as they move across the sky. Powell said, This experiment will allow us to study different, but equally interesting, effects in the ionosphere closer to the equator, where most of the worlds population lives. The GROUP-C experiment will last up to two years, so the quantity of data and the potential for meaningful scientific discovery is huge.