Some considerations about the in-orbit calibration of spaceborne rotating fan beam radar scatterometer

Calibration and Estimation of Attitude Errors for a Rotating Fan-Beam Scatterometer Using Calibration Ground Stations

“…The PRF is much higher than that in normal mode (150 Hz). An alternative progress is to make the antenna stop spinning and operate at a fixed azimuth position; this requires a PRF of no less than 15 Hz, which is decided by the ground speed of the satellite [3]. The latter is employed in the method proposed in this paper to avoid modification of the hardware system, since PRF in this calibration mode can be kept the same as that of normal mode, and CGS receives 75 pulses per second from each antenna beam.…”

“…There are a number of factors affecting the RFSCAT measurement accuracy: 1) in-orbit antenna gain pattern, especially the gain pattern in the elevation direction; 2) antenna gain fluctuation due to the rotary joint; and 3) satellite attitude errors [3]. In this paper, we mainly consider issues 1) and 3), while issue 2) can be removed using, e.g., tropical rain forest backscattering.…”

“…Rotating fan-beam scatterometer (RFSCAT) is a new type that has more flexible views and larger observing swaths than fixed fan-beam ones, thus have more advantages in removing ambiguous solutions for wind retrieving [1], [2]. Moreover, it is not necessary to consider its beam balance for RFSCAT, which is an important issue for multiple fixed fanbeam scatterometers [3], [4]. Compared with rotating pencilbeam scatterometer, RFSCAT can also give more diverse observing views, since the spinning rate of RFSCAT antenna is much lower than rotating pencil-beam type, which also shows a potential improvement for the retrieval performance of wind direction [2], [5].…”

“…In-orbit calibration is one of the most essential parts to achieve such accuracy. For RFSCAT, this is realized by calibrations of in-orbit antenna gain pattern, especially the elevation parts, and satellite attitude errors estimation as well [3].…”

Pre-processing algorithm and airborne campaign result analysis of a rotating fan-beam scatterometer

“…measured in signal calibration process when the transmitted power is received directly after going through a loop with known loss[5]. With all loss values determined, ' cal X can be estimated and signal calibration is achieved, and signal channel loss and power amplifier output fluctuation is compensated.…”