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Dual-frequency Precipitation Radar (DPR)
One of the prime instruments for the GPM Core Observatory and 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. (shown below) The KuPR and the KaPR will be co-aligned on the GPM spacecraft bus such that that the 5 km footprint location on the earth will be the same.
Data collected from the KuPR and KaPR units will provide the 3-dimensional observation of rain and will also provide an accurate estimation of rainfall rate to the scientific community. The DPR instrument will be allocated 190 Kbps bandwidth over the 1553B spacecraft data bus. The collection of the DPR data will be transmitted to the ground using the TDRSS multiple access (MA) and single access (SA) services.
DPR Instrument Details
The DPR is a spaceborne precipitation radar capable of making accurate rainfall measurements. The DPR is expected to be more sensitive than its TRMM predecessor especially in the measurement of light rainfall and snowfall in the high latitude regions. Rain/snow determination is expected to be accomplished by using the differential attenuation between the Ku-band and the Ka-band frequencies. The variable pulse repetition frequency (VPRF) technique is also expected to increase 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 will provide rain sensing over both land and ocean, both day and night. Expanded views of the KuPR and KaPR instruments are shown in Figures 3.1-1 and 3.1-2. Top-level general design specifications are as follows:
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Item | KuPR | KaPR | |
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 | 1000 Watts (W) | 140 Watts (W) | |
Pulse Repetition Freq. (In nominal operations mode) | 4100 to 4400 Hertz (TBD) | 4100 to 4400 Hertz (TBD) | |
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) |
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The ground processing of the Dual-frequency Precipitation Radar (DPR) data will result in being able to provide detailed 3-dimensional measurements of cloud structure, rainfall, and rain rates. As a result, the community will benefit in getting accurate 3-hourly global rain maps to help in areas such as, but not limited to, improved weather forecasts, flood forecasting, climate change assessments, and water resource management.
GPM Swath Measurements (view large)
Partners
The DPR instrument is being developed by Japan Aerospace Exploration Agency (JAXA) and the National Institute of Information and Communications Technology (NICT) for a flight on the GPM Core Observatory. NEC Toshiba Space Systems, Ltd. (NTSpace) is designing and testing the radars under the direction of JAXA and NICT.
Related Links
+ GMI Instrument
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