Scanning L-Band Active Passive (SLAP)

The Scanning L-band Active Passive (SLAP) is a new airborne simulator for NASA’s SMAP soil moisture satellite that launched in early 2015. 

SLAP has both passive (radiometer) and active (radar) microwave L-band imaging capabilities, just as SMAP does.   The radiometer observes at 1.4 GHz using duplicate front end hardware from the SMAP satellite radiometer. It also includes a duplicate of the digital backend development unit for SMAP, thus the novel Radio Frequency Interference (RFI) detection and mitigation features and algorithms for SMAP are duplicated with very high fidelity in SLAP. The digital backend provides 4-Stokes polarization capability. The real-aperture radar operates in the 1215-1300 MHz band with quad-pol capability. Radar and radiometer share one antenna via diplexers that are spare units from the Aquarius satellite instrument. 

SLAP’s initial flights were conducted in Dec 2013 over the eastern shore of Maryland and successfully demonstrated radiometer imaging over 2 full SMAP 36x36 km grid cells at 1.3 km resolution within 3 hrs. A second flight on the same day also demonstrated SLAP’s quick-turn abilities and high-resolution/wide-swath capabilities with 200m resolution across a 1500m swath. 

Additional flights were conducted as part of the GPM iPHEX campaign in May, 2014. SLAP is currently preparing for the SLAPex series of campaigns to various locations in North America during 2015.

SLAP Data Imagery

 Figure Caption: Passive microwave image from SLAP. A 50x80 km region was mapped at 1.3 km resolution in <3 hrs, including two SMAP 36 X 36 km grid cells shown by the black squares. The yellows & oranges indicate slight variations in temperature and moisture across this portion of eastern Maryland and Delaware. Dark blue on the far right (Delaware Bay) corresponds to the low brightness temperatures typical of open water. Light blue is seen along land-water boundaries, including some rivers.