Point of Contact:

Steve Durden
NASA Jet Propulsion Laboratory
Office Telephone: (818) 354-4719
ARMAR Homepage:

Brief Instrument Description of the
Airborne Rain Mapping Radar (ARMAR)

The NASA/JPL Airborne Rain MApping Radar (ARMAR) was developed for the purpose of supporting future spaceborne rain radar systems, including the TRMM PR. ARMAR flies on the NASA DC-8 aircraft and operates at 13.8 GHz (Ku-band); it has Doppler and multi-polarization capabilities. It normally scans its antenna across track +/- 20 degrees but can also operate with its antenna pointing at a fixed angle. In addition to acquisition of radar parameters, it also spends a small fraction of its time operating as a radiometer, providing the 13.8 GHz brightness temperature. ARMAR is a pulse compression radar, meaning that it transmits an FM chirp signal of relatively long duration. The raw data is recorded directly to a high speed tape recorder. Post-processing occurs in two steps; first, the raw data is compressed by correlating it with the transmitted chirp, giving data comparable to a conventional short pulse radar. These data are used to form various second-order statistics, which are averaged over at least 100 (often several hundred) pulses. The second processing step takes the pulse-compressed and averaged data and performs calibration. This step uses data acquired by the system calibration loop during flight to convert the measured power to the equivalent radar reflectivity factor Ze. It also produces Doppler velocity and polarization observables, depending on the mode of operation during data collection.

Operating Frequency 13.8 GHz
Surface Horizontal Resolution 800 m
Vertical 6 dB Resolution 80 m
Polarization HH,VV,HV
Antenna Beamwidth 3.8 deg.
Antenna Scan Angle +/- 20 deg.
Transmitter Power 200 W
Transmit Chirp Duration 5-45 microsec
Pulse Repetition Frequency 1-8 kHz
Chirp Bandwidth 4 MHz
A/D Sampling Rate 10 MHz
A/D Resolution 12 bits
Number Independent Samples < 100
Radiometer Delta K 1K

Table 1. ARMAR Instrument Characteristics

Have you used our data? Register for updates