GMI Status

This viewgraph presentation is concerned with the status of the Global Precipitation Measurement-Microwave Imager (GMI). Included in the presentation is an overview that shows a diagram of the craft, the improvements over other precipitation measurement satellites, and information about the calibration approach

GPM Microwave Imager Engineering Model Results

The Global Precipitation Measurement (GPM) Microwave Imager (GMI) Instrument is being developed by Ball Aerospace and Technology Corporation (BATC) for the GPM program at NASA Goddard. The Global Precipitation Measurement (GPM) mission is an international effort managed by the National Aeronautics and Space Administration (NASA) to improve climate, weather, and hydro-meteorological predictions through more accurate and more frequent precipitation measurements. The GPM Microwave Imager (GMI) will be used to make calibrated, radiometric measurements from space at multiple microwave frequencies and polarizations. GMI will be placed on the GPM Core Spacecraft together with the Dualfrequency Precipitation Radar (DPR). The DPR is two-frequency precipitation measurement radar, which will operate in the Ku-band and Ka-band of the microwave spectrum. The Core Spacecraft will make radiometric and radar measurements of clouds and precipitation and will be the central element ofGPM's space segment. The data products from GPM will provide information concerning global precipitation on a frequent, near-global basis to meteorologists and scientists making weather forecasts and performing research on the global energy and water cycle, precipitation, hydrology, and related disciplines. In addition, radiometric measurements from GMI and radar measurements from the DPR will be used together to develop a retrieval transfer standard for the purpose of calibrating precipitation retrieval algorithms. This calibration standard will establish a reference against which other retrieval algorithms using only microwave radiometers (and without the benefit of the DPR) on other satellites in the GPM constellation will be compared

GPM Microwave Imager Design, Predicted Performance and Status

The Global Precipitation Measurement (GPM) Microwave Imager (GMI) Instrument is being developed by Ball Aerospace and Technology Corporation (BATC) for the GPM program at NASA Goddard. The Global Precipitation Measurement (GPM) mission is an international effort managed by the National Aeronautics and Space Administration (t.JASA) to improve climate, weather, and hydro-meteorological predictions through more accurate and more frequent precipitation measurements. The GPM Microwave Imager (GMI) will be used to make calibrated, radiometric measurements from space at multiple microwave frequencies and polarizations. GMI will be placed on the GPM Core Spacecraft together with the Dual-frequency Precipitation Radar (DPR). The DPR is two-frequency precipitation measurement radar, which will operate in the Ku-band and Ka-band of the microwave spectrum. The Core Spacecraft will make radiometric and radar measurements of clouds and precipitation and will be the central element of GPM's space segment. The data products from GPM will provide information concerning global precipitation on a frequent, near-global basis to meteorologists and scientists making weather forecasts and performing research on the global energy and water cycle, precipitation, hydrology, and related disciplines. In addition, radiometric measurements from GMI and radar measurements from the DPR will be used together to develop a retrieval transfer standard for the purpose of calibrating precipitation retrieval algorithms. This calibration standard will establish a reference against which other retrieval algorithms using only microwave radiometers (and without the benefit of the DPR) on other satellites in the GPM constellation will be compared

The Global Precipitation Measurement (GPM) Microwave Imager (GMI): Instrument Overview and Early On-Orbit Performance

The Global Precipitation Measurement (GPM) mission is an international satellite mission that uses measurements from an advanced radar/radiometer system on a core observatory as reference standards to unify and advance precipitation estimates made by a constellation of research and operational microwave sensors. The GPM core observatory was launched on February 27, 2014 at 18:37 UT in a 65 inclination nonsun-synchronous orbit. GPM focuses on precipitation as a key component of the Earth's water and energy cycle, and has the capability to provide near-real-time observations for tracking severe weather events, monitoring freshwater resources, and other societal applications. The GPM microwave imager (GMI) on the core observatory provides the direct link to the constellation radiometer sensors, which fly mainly in polar orbits. The GMI sensitivity, accuracy, and stability play a crucial role in unifying the measurements from the GPM constellation of satellites. The instrument has exhibited highly stable operations through the duration of the calibration/validation period. This paper provides an overview of the GMI instrument and a report of early on-orbit commissioning activities. It discusses the on-orbit radiometric sensitivity, absolute calibration accuracy, and stability for each radiometric channel. Index Terms-Calibration accuracy, passive microwave remote sensing, radiometric sensitivity

GPM Microwave Imager Key Technologies, Performance and Calibration Results

The Global Precipitation Measurement (GPM) Microwave Imager (GMI) Instrument was built and tested by Ball Aerospace and Technologies Corporation (Ball) under a contract with the GPM program at the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center. The GMI instrument was delivered to Goddard in February 2012 and launched onboard the GPM spacecraft in late February 2014. This paper presents an overview of the GMI instrument, examines pre-flight radiometric accuracy and evaluates early on-orbit data versus pre-flight performance. The GPM Mission is an international effort managed by NASA to improve climate, weather, and hydro-meteorological predictions through more accurate and more frequent precipitation measurements [1]. The GPM Microwave Imager (GMI) infers precipitation by making calibrated passive radiometric measurements at multiple microwave frequencies. Also onboard the GPM spacecraft, the Dual-frequency Precipitation Radar (DPR) provides high resolution precipitation profiles by measuring the radar backscatter from the rain column. The data products from GPM afford frequent, near-global precipitation information for meteorologists and scientists making weather forecasts and performing research on the global energy and water cycle, precipitation, hydrology, and related disciplines. The GMI and DPR will be used together to develop a transfer standard for the purpose of calibrating precipitation retrieval algorithms and will establish a reference against which other satellites in the GPM constellation will be compared. The GMI instrument consists of 13 radiometric channels from 10.65 GHz to 183.31 GHz [2], providing accurate measurement of precipitation and multiple other environmental parameters. The GMI has a deployable antenna making it relatively compact for the 1.2 meter aperture size. For the GPM orbit, the GMI antenna provides 25 km native resolution at the lowest frequency and up to 5 km resolution at the higher frequencies. Multiple enhancements have been incorporated into the GMI to improve calibration accuracy over heritage systems. The calibration enhancements include tight shrouding around the hot load to keep out the sun, noise diodes on the 7 low frequency channels to provide a dual calibration system, and a proven robust reflective coating for the antenna [3]. The state-of-the-art receiver subsystem built by ITT Exelis provides low noise figures and very good stability for excellent radiometric performance. The GMI was extensively tested at Ball and Goddard over all on-orbit and launch environments. The key results of the ground performance and environmental testing are reported as well as projections for on-orbit performance based on the ground measurements. We describe the on-orbit performance. The areas discussed include the NEDT performance for each channel, the number of counts from each channel when viewing the warm target, the stability of each channel, the temperature stability of the instrument and the resulting stability of each channel, spin rate stability, and early indicators of absolute calibration performance. [1] Hou, A and Kirshbaum, D, “At the core, Global Precipitation Measurement (GPM) Mission,” Meteorological Technology International, pp. 6-10, Nov 2010. [2] Draper, D. and Newell, D, “Global Precipitation Measurement (GPM) Microwave Imager (GMI) calibration features and predicted performance,” MicroRad Conference Publication, pp. 236-240, March 2010. [3] D. W. Draper, D.A. Newell, D.A. Teusch, P.K. Yoho, “Global Precipitation Measurement Microwave Imager (GMI) hot load calibration,” IEEE Trans. Geosci. Rem. Sens., vol. 51, no. 9, Sep. 2013