Effective mitigation of radio frequency interference by AMSR-2 instrument performance improvement

With the development of microwave remote sensing technology, the measurements of spaceborne microwave radiometer have been widely used in atmospheric research. However, data from these sensors are often contamined by Radio Frequency Interference(RFI), which reduce the utilization of microwave measurements, especially for the low frequency observations. In order to mitigate the RFI in spaceborne microwave measurements at 6.9 GHz channel, two new channels centered at 7.3 GHz are added in Advanced Microwave Scanning Radiometer-2(AMSR-2) based on AMSR-E. Moreover, AMSR-2 also has a larger diameter antenna reflector(2.0 m compared to 1.6 m for AMSR-E) and narrower beam width than AMSR-E. To make an evaluation about whether AMSR-2's hardware improvements and two new channels mitigate the RFI in microwave measurements, AMSR-2 and AMSR-E observations at 6.9 GHz and 7.3 GHz from August 2012 to July 2013, August 2016 to July 2017 and October 2010 to September 2011 over global land are analyzed using the means and standard deviation method in this paper. Research results show that the number of RFI-contaminated pixels in AMSR-2 at 7.3 GHz observations is much less than that in AMSR-E at 6.9 GHz observations, especially in the United States and Japan. At the same time, AMSR-2 hardware improvement increases the main beam efficiency and improves the spatial resolution. Comparing with AMSR-E the field of view number of RFI in AMSR-2 at 6.9 GHz observations has a decrease both in range and intensity. It can be concluded that the hardware improvement and two new added channels indeed mitigate AMSR-2 RFI contamination in C band, especially in the United States and Japan. Moreover, the distribution of RFI at 6.9 GHz is quite different from that at 7.3 GHz. Therefore, observations of the two channels can effectively be complemented each other when inverting the geophysical parameters.