In 1997, the Japan Aerospace Exploration Agency (JAXA) and NASA launched a satellite designed to monitor the distribution and variability of precipitation in the tropics. More than 16 years later, that satellite—the Tropical Rainfall Measuring Mission (TRMM)—has some new company. On February 28, 2014, at 3:37 a.m. Japan Standard Time, an H-IIA rocket successfully carried the Global Precipitation Measurement (GPM) Core Observatory into orbit from the Tanegashima Space Center in southern Japan.
The nosecone fairing (protecting GPM from the drag of the atmosphere) was jettisoned four minutes after launch, and the spacecraft began transmitting telemetry to mission operators at Goddard Space Flight Center five minutes later. GPM separated from the rocket 15 minutes after launch and successfully deployed its solar arrays within 40 minutes. The satellite will assume a non-Sun-synchronous orbit 253 miles (407 kilometers) above Earth.
The new satellite has two main sensors: the Global Precipitation Imager (GPI) and the Dual-Frequency Precipitation Radar (DPR). GMI is a microwave radiometer that will observe precipitation with 13 different microwave channels ranging in frequency from 10 GHz to 183 GHz. The DPR consists of a Ku-band precipitation radar (KuPR) and a Ka-band precipitation radar (KaPR) that will provide three-dimensional observations of rain and also will provide an accurate estimate of rainfall rates.
Together these instruments should provide a database of measurements against which microwave observations made by a constellation of existing and future satellites can be compared and combined to make a global precipitation dataset. Collectively, GPM and its partner satellites will quantify when, where, and how much it rains and snows around the world.
Ball Aerospace and Technology Corporation built the GMI under contract with NASA Goddard Space Flight Center. The Japan Aerospace and Exploration Agency (JAXA) and Japan’s National Institute of Information and Communications Technology (NICT) built the DPR. The GPM Core Observatory was developed and tested at NASA Goddard Space Flight Center.
Photo by Bill Ingalls/NASA. YouTube video by JAXA. Caption by Adam Voiland, based on information from NASA news releases.