| Paper: | TH-P1.1 |
| Session: | Radio-Frequency Interference II |
| Time: | Thursday, March 29, 13:20 - 13:40 |
| Presentation: |
Oral
|
| Topic: |
RFI and spectrum management: |
| Title: |
ANALYSIS OF RESIDUAL RFI SOURCES IN SMAP RADIOMETER MEASUREMENTS |
| Authors: |
Alexandra Bringer; The Ohio State University | | |
| | Joel Johnson; The Ohio State University | | |
| Abstract: |
NASA’s Soil Moisture Active and Passive (SMAP) satellite was launched in January 2015 to provide global measurements of soil moisture and freeze/thaw state. Soil moisture products are derived from SMAP radiometer measurements acquired at L Band (1.4 GHz). Even though this is a protected band, unauthorized transmitters emitting either within the band or in adjacent bands cause radio frequency interference (RFI). Because RFI contributions corrupt the radiometer measurements and therefore can lead to biases in retrieved soil moisture, the SMAP radiometer includes special hardware to enable RFI detection and filtering using multiple detection algorithms.
Nine algorithms have been implemented to detect and mitigate various types of RFI based on their nature (pulse or continuous, narrowband or wideband) and level (low, moderate and high). Their good overall performance has been previously established in most cases. However, persistent residual RFI sources are still noticeable in the filtered data. They are a challenging issue as those RFI are usually low or moderate wideband sources that makes them hard to detect by the algorithms.
The first part of the study will focus on trying to characterize these sources by making an extensive statistical analysis of SMAP data in areas where the residual RFI sources are present most of the time (in Europe for example). We will also investigate another method to detect those RFI by combining the current algorithms or defining new criteria that will help to identify and to mitigate the moderate residual RFI.
An additional method for investigating residual RFI contributions is taking advantages of the SMAP scanning antenna. Indeed, as the SMAP antenna scans over a continuous RFI source of moderate to large amplitude, the source is observed at varying RFI levels. The RFI level encountered at its maximum amplitude can be used as “truth” value for other antenna scan positions having lower level RFI contributions. The performance of SMAP detection and mitigation algorithms can then be examined as a function of a “known” RFI level at low amplitudes, with the results used to refine detector performance for lower amplitude sources. Results from this study will also be reported in the presentation.
|
