One of the prime instruments onboard the GPM Core Observatory is called the Dual-frequency Precipitation Radar (DPR). The DPR consists of a Ku-band precipitation radar (KuPR) and a Ka-band precipitation radar (KaPR). The KuPR (13.6 GHz) is an updated version of the highly successful unit flown on the TRMM mission. The KuPR and the KaPR are co-aligned on the GPM spacecraft bus such that that the 5 km footprint location on the earth is the same.
Data collected from the KuPR and KaPR units provides 3-dimensional observations of rain and also provides an accurate estimation of rainfall rate to the scientific community. The DPR instrument is allocated 190 Kbps bandwidth over the 1553B spacecraft data bus.
DPR Instrument Details
The DPR is a spaceborne precipitation radar capable of making accurate rainfall measurements. The DPR is more sensitive than its TRMM predecessor especially in the measurement of light rainfall and snowfall in high latitude regions. Rain/snow determination is accomplished by using the differential attenuation between the Ku-band and the Ka-band frequencies. The variable pulse repetition frequency (VPRF) technique increases the number of samples at each IFOV to realize a 0.2 mm/h sensitivity.
The KuPR and KaPR, together with GMI, are the primary instruments on the GPM spacecraft. These Earth-pointing KuPR and KaPR instruments provide rain sensing over both land and ocean, both day and night.
Top-level general design specifications are as follows:
|Swath Width||245 kilometers (km)||120 kilometers (km)|
|Range Resolution||250 meters (m)||250/500 meters (m)|
|Spatial Resolution||5 km (Nadir)||5 km (Nadir)|
|Beam Width||0.71 degrees||0.71 degrees|
|Transmitter||128 Solid State Amplifiers||128 Solid State Amplifiers|
|Peak Transmit Power||1013 Watts (W)||146 Watts (W)|
|Pulse Repetition Freq. (In nominal operations mode)||4100 to 4400 Hertz||4100 to 4400 Hertz|
|Pulse Width||two 1.667 microseconds (µs) pulses||two 1.667 microseconds (µs) pulses in matched beams two 3.234 microseconds (µs) pulses in interlaced scans|
|Beam Number||49||49 (25 in matched beams and 24 in interlaced scans)|
The DPR instrument was developed by Japan Aerospace Exploration Agency (JAXA) and the National Institute of Information and Communications Technology (NICT) for flight on the GPM Core Observatory. NEC Toshiba Space Systems, Ltd. (NTSpace) designed and tested the radars under the direction of JAXA and NICT.