Radio-frequency interference (RFI) mitigation for the soil moisture active/passive (SMAP) radiometer

Abstract

The presence of anthropogenic RFI is expected to adversely impact soil moisture measurement by NASA's Soil Moisture Active Passive mission. The digital signal processing approach and preliminary design for detecting and mitigating this RFI is presented in this paper. This approach is largely based upon the work of Johnson [1] and Ruf [2].Index Terms-SMAP, Soil Moisture Active Passive, Digital Radiometer, Filterbank, Kurtosis done for the Hydros mission [7] as its basis, the SMAP digital backend will provide both time and frequency diversity data at each footprint to enable the ground processing algorithms to detect and remove RFI. To do so, it will use digital signal processing (DSP) techniques to measure 1200 samples in time and frequency for each SMAP footprint. This paper summarizes the DSP algorithms and electronics implementation using field-programmable gate arrays (FPGAs) in the SMAP preliminary design.

Digital processor breadboard for RFI detection and mitigation in spaceborne radiometers

“…This has been done in sub-orbital systems using high conversion rate Analogue-to-Digital Converters (ADCs) and fast Field Programmable Gate Arrays (FPGAs) [5,6]. With the development of suitable space qualified ADCs and FPGAs, it has become feasible to perform spaceborne RFI detection and mitigation [7]. This paper describes an on-board configurable RFI detection and mitigation system being developed from concept demonstration breadboard [8] to complete functional performance breadboard based on the long heritage of both DTU Space and Harp Technologies Ltd experience with suborbital systems [9].…”

Preliminary results from the soil moisture active/passive (SMAP) radiometer digital electronics engineering test unit (ETU)

“…In particular, the SMAP radiometer employs the first spaceborne digital back-end processor subsystem called the RDE. The RDE is a field-programmable gate array (FPGA)-based digital signal processing system that uses time, frequency, statistical and polarization diversity to detect and flag RFI during its mission lifetime [4]. The completed RDE-ETU is shown in Figure 1.…”

Wideband digital signal processing test-BED for radiometric RFI mitigation

“…When F S < F M AX , the ADC can provide the digitized signal directly to the FPGA pins and subsequent digital logic. The digital logic can then implement the RFI signal processing stages serially, as in [10], for example. Conversely, if F S > F M AX , the digitized signal must first be split into two or more parallel processing paths so that the effective clock switching rate of each path is less than F M AX .…”