Articles

The Global Precipitation Measurement (GPM) Microwave Imager (GMI) instrument is a multi-channel, conical- scanning, microwave radiometer serving an essential role in the near-global-coverage and frequent-revisit-time requirements of GPM. The instrumentation enables the Core spacecraft to serve as both a precipitation standard and as a radiometric standard for the other GPM constellation members. The GMI is characterized by thirteen microwave channels ranging in frequency from 10 GHz to 183 GHz. In addition to carrying channels similar to those on the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI), the GMI carries four high frequency, millimeter-wave, channels near 166 GHz and 183 GHz. With a 1.2 m diameter antenna, the GMI provides significantly improved spatial resolution over TMI.

The Global Precipitation Measurement (GPM) Core Observatory satellite operates in low Earth orbit, carrying two instruments for measuring Earth's precipitation and serving as a calibration standard for other members of the GPM satellite constellation. The satellite was developed and tested in-house at NASA Goddard Space Flight Center and launched from Tanegashima Space Center, Japan, on February 27th, 2014. The GPM Core Observatory orbits Earth at an inclination of 65 degrees, which enables it to cut across the orbits of other microwave radiometers and sample the latitudes where nearly all precipitation occurs. A non-sun-synchronous orbit that takes it around Earth roughly 16 times per day allows it to sample precipitation at different times of the day. Data is transmitted continuously to ground systems on Earth by the Tracking and Data Relay Satellite (TDRS) communications network.