This instrument is an integrated GPS occultation receiver (IGOR) which has been developed by NASA/J PL in order to estimate the temperature and humidity with high quality and high vertical resolution from the phase delay due to refraction during occultation between GPS and LEO. The main characteristics of this receiver are (1) GNSS receiver exploiting at least two L-band frequencies around 1.18, 1.25 and 1.58 GHz.(or 19, 24 and 25.4 cm), (2) Earth's limb observation from surface to the satellite altitude during the occultation phase of satellites of the GNSS constellations (GPS, GLONASS, Galileo, Beidou), (3) Directional antennas looking aft- (for setting GNSS) and/or fore- (for rising GNSS), and toroidal antenna for navigation, (4) Spatial resolution around 300 km in the direction LEO-satellite to occulting GNSS-satellite, a few 10 km transverse, (5) Horizontal sampling limited by the daily number of occultation events, from 250 to 1500 depending on the number of tracked GNSS constellations and the aft- and/or fore- tracking capability, (6) Supported by a complex system of ground stations for clock error correction by double differentiation, and (7) Applicable only in LEO.