Calibration of the TRMM Precipitation Radar Using the Active Radar Calibrator (ARC)

Abstract

Active radar calibrator (ARC) are generally used for calibration of spaceborne or airborne SAR. The Japan Aerospace Exploration Agency (JAXA) and National Institute of Information and Communications Technology (NICT) developed the ARC for calibration of the first spaceborne Precipitation Radar (PR) onboard the Tropical Rainfall Measuring Mission (TRMM) satellite. The main characteristic of this ARC is three function of radar receiver, beacon-signal transmitter, and delayed-transponder function. On the development phase of TRMM-PR, it was confirmed that the ARC is useful for calibration of active array radar such as TRMM-PR. Since the TRMM launch in 1997, TRMM-PR has been calibrated with the ARC per a few months, and its calibration results have been reflected in the PR data processing system as calibration coefficients. At first, TRMM-PR used to be calibrated only by the radar receiver and beacon-signal transmitter function of the ARC, but we established a new calibration technique using delayed-transponder function which can calibrate radar cross section of TRMM-PR directly. Through the five year calibration period using the ARC, transmittion and receiption gains of TRMM-PR have been calibrated to an accuracy of ±0.5 dB or better, and the PR-measured radar cross section has been calibrated to an accuracy of within±1 dB.