Dual-frequency Precipitation Radar (DPR)
One of the prime instruments onboard the GPM Core Observatory is 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, which operates at 13.6 GHz, is an updated version of the highly successful unit flown on the Tropical Rainfall Measuring Mission (TRMM). The KuPR and the KaPR are co-aligned on the GPM spacecraft bus such that the 5-km footprint location on the earth is the same.
Data collected from the KuPR and KaPR units provide 3-dimensional observations of rain and also provide an accurate estimation of rainfall rate to the scientific community.
Measuring Precipitation in 3D
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 mid 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 instantaneous field of view (IFOV) to realize a 0.2 mm/h sensitivity. The KuPR and KaPR instruments provide rain sensing over both land and ocean, day and night.
Top-level general design specifications are as follows:
|Swath Width||245 kilometers (km)||245 kilometers (km) as of May 2018 (previously 120km)|
|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)|