SIR-B Subsurface Imaging of a Sand-Buried Landscape: Al Labbah Plateau, Saudi Arabia

Abstract

Despite a diminution in the transmit and receive power of the SIR-B system, a striking L-band radar image was produced for a portion of the southern Al Labbah Plateau, Saudi Arabia, a landscape dominated by eolian sand features. Distinct tonal and digital number (DN) signatures uniquely define 1) areas where the SIR-B beam penetrated a relatively thin sand sheet to be diffusely reflected from the buried carbonate rocks of the Aruma Formation and 2) a thick sand hill and associative sand shadow where SIR-B subsurface imaging did not occur. Computer analysis of the digital SIR-B image data indicates there is about a 26-DN difference between the sand-buried Aruma Formation and the unpenetrated sand hill and shadow. Depth measurements from more than 80 test holes show that subsurface imaging occurred through a sand layer whose maximum measured thickness is 1.24 m. The penetrated medium is a fine-to medium-grained low-density quartz sand that had a very low moisture content (average of about 0.2 weight percent) on the day of the Space Shuttle overpass. The minimum thickness of sand features where subsurface imaging did not occur is thought to be about 3.1 m.