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Description
The Advanced Microwave Precipitation Radiometer (AMPR) remotely senses passive microwave signatures of geophysical parameters from an airborne platform. The instrument is a low noise system which can provide multi-frequency microwave imagery with high spatial and temporal resolution. AMPR data are collected at a combination of four microwave frequencies (10.7, 19.35, 37.1, and 85.5 GHz) which are complimentary to current aircraft and satellite instrumentation. These frequencies are best suited to the study of rain systems, but are also useful to studies of other atmospheric, oceanic, and land surface processes.
Principles of Operation
The AMPR is a cross-track scanning total power microwave radiometer with four channels centered at 10.7, 19.35, 37.1 and 85.5 GHz. It has a dual-lens antenna to accommodate two separate feed horns. The horn that feeds the three higher frequency channels is a copy of the Special Sensor Microwave/Imager (SSM/I) space borne multi-frequency feed horn currently flying aboard the Defense Meteorological Satellite Program (DMSP) satellites. A separate AMPR feed horn, which was built by the Georgia Technology Research Institute (GTRI), accommodates the 10.7 GHz frequency.
AMPR performance characteristics
Characteristic |
85.5GHz |
37.1GHz |
19.35GHz |
10.7GHz |
Bandwidth (MHz) |
1400 |
900 |
240 |
100 |
Integration Time (ms) |
50 |
50 |
50 |
50 |
Horn Type |
SSM/I |
SSM/I |
SSM/I |
GTRI |
Lens Diameter (inches) |
5.3 |
5.3 |
5.3 |
9.7 |
Beam width (degrees) |
1.8 |
4.2 |
8.0 |
8.0 |
Footprint (km) [@20 km ER-2 alt. 500kts] |
0.64 |
1.48 |
2.78 |
2.78 |
Beam Efficiency (%) |
N/A |
98.8 |
98.7 |
97.8 |
Cross Polarization (%) |
N/A |
0.4 |
1.6 |
0.2 |
Instrument Geometry
The AMPR radiometer has flown on the NASA ER-2 and DC-8 aircraft. The instrument has a 90 degree total scan centered at nadir. The data footprints are designed to be contiguous at 85.5 GHz and coincident at all four channels leading to over-sampling at the lower frequencies. The polarization varies from vertical at 45 degrees to the left of nadir, an equal mixture of vertical and horizontal polarization at nadir, and horizontal 45 degrees to the right of nadir.
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