News From Above: SMAP Update in IEEExplore

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After over a year collecting data from space, The Ohio State University's contributions to a NASA climate sensing satellite were published in the IEEE Transactions on Geoscience and Remote Sensing.

On Jan. 31, 2015 the Soil Moisture Active and Passive (SMAP) satellite launched into space, with the goal of producing global maps of soil moisture. The data is used to help improve the understanding of Earth’s water and carbon cycles, as well as the ability to manage water resources worldwide.

Students and university faculty involved in the project published an update on the mission in the recent IEEEXplore Transactions on Geoscience and Remote Sensing publication, titled “SMAP L-band Microwave Radiometer: RFI Mitigation Prelaunch Analysis and First Year on-Orbit Observations.”

The lead author of the paper, Priscilla Mohammed of the Goddard Earth Sciences Technology and Research, Universities Space Research Association, collaborated with electrical engineering researchers from Ohio State, including Mustafa Aksoy, Joel Johnson, and Alexandra Bringer of the ElectroScience Laboratory, as well as Jeffrey Piepmeier, Chief Engineer for passive microwave instruments with the Instrument Systems and Technology Division, NASA Goddard Space Flight Center.

Overall, Johnson said, the technology the team included on board the satellite is working well for addressing one of the key challenges of the mission: radio frequency interference (RFI) to SMAP's microwave radiometer. 

“The SMAP radiometer RFI processor seems to be doing a good job of detecting and filtering radio frequency interference from SMAP’s L-band microwave radiometer measurements,” he said. “The processor appears to be making soil moisture science measurements possible in regions where RFI would have previously prevented success. However, some regions of the globe still remain problematic due to an excess of RFI.”

While this technology helps to remove man-made RFI emanating from most of the world, the paper reports some areas (including most of Japan) remain shrouded in heavy interference.

“On-orbit results indicate that sources which are wideband and occupy much of SMAP’s bandwidth at all times cannot be corrected by any of SMAP’s RFI filtering procedures, resulting in the exclusion of extended spatial regions from soil moisture retrievals,” the research states. “These results highlight the need for continued vigilance in the protection of spectrum for microwave radiometry and the need for active enforcement of these protections.”

NASA reported the team has entered the next phase of the work: turning raw data collected by instruments on a spacecraft orbiting 426 miles above Earth into more than a dozen data products, and then coordinating the information to users through NASA’s Alaska Satellite Facility and National Snow and Ice Data Center Distributed Active Archive Centers.

“For the SMAP team, the release of public soil moisture and freeze/thaw data marks not only the end of more than a half-decade of work, but the start of a challenging period of making sure these data and data products are delivered on time and provide the quality expected by data users around the world,” NASA reported.

Meanwhile, SMAP's radiometer continues to return valuable data for scientific research and analysis.