Future NASA spaceborne SAR missions

Abstract

Two Earth-orbiting radar missions are planned for the near future by NASA-Shuttle Radar Topography Mission (SRTM) and Lig,htSAR. The SRTM will fly aboard the Shuttle using interferometric synthetic aperture radar (IFSAR) to provide a global digital elevation map. SRTM is jointly sponsored by NASA and the National Imagery and Mapping Agency (NIMA). The LightSAR will utilize emerging technology to reduce mass and life-cycle costs for a mission to acquire SAR data for Earth science and civilian applications and to establish commercial utility. LightSAR is sponsored by NASA and industry partners. The use of IFSAR to measure elevation is one of the most powerful and practical applications of radar. A properly equipped spaceborne IFSAR system can produce a highly accurate global digital elevation map, including cloud-covered areas, in significantly less time and at significantly lower cost than other systems. For accurate topography over a large area, the interferomehic measurements can be performed sitnultaneously in physically separate receive systems. The Spaceborne Imaging Radar C (SIR-C), successfully flown twice in 1994 aboard the Space Shuttle Endeavour, offers a unique opportunity for global multifrequency elevation mapping by the year 2000. The addition of a C-band receive antenna of approximately 60 m length, extended from the Shuttle bay on a mast, and operating in concert with the existing SIR-C antenn~produces an interferometric pair. It is estimated that the 90 percent linear absolute elevation error achievable is less that 16 meters for elevation postings of 30 meters. The SRTM will be the first single-pass spaceborne IFSAR instrument and will produce a near-global high-resolution digital topography data set. Since LightSAR offers important benefits to both the science community and U.S. industry, an innovative government-industry teaming approach is being explored, with industry sharing the cost of developing LightSAR in return for commercial rights to its data and operational responsibility. LightSAR will enable mapping of surface change. The instrument's high-resolution mapping, along with its quad pohuization, dual polarization, interfkrometric and ScanSAR modes will enable continuous monitoring of natural hazards, Earth's surface deformation, surface vegetation change, and ocean mesoscale features to provide commercially viable and scientifically valuable data products. Advanced microelectronics and lightweight materials will increase LightSAR's functionality without increasing the mass. Dual frequency L/X-band designs have been examined.

Quantitative analysis of InSAR digital elevation models for identification of areas with different tectonic activities in southern Italy

“…The use of InSAR for topographic mapping has been one of the major issues since the introduction of this technique by Graham in 1974. Since then several works have demonstrated the accuracy and limitations of this technique (Gens and Van Genderen, 1996;Rosen et al, 2000). A specific 11-day spaceborne mission, the Shuttle Radar Topography Mission (SRTM), was realized in 2000, with the aim of producing a global high resolution DEM of the Earth's surface, covering 80% of the whole land between 60°N and 56°S (Hilland et al, 1998) (further information is …”

“…This DEM has been obtained by means of the radar interferometry technique using data acquired by the SRTM space mission, which in 2001 covered about 80% of the earth surface (Hilland et al, 1998;Farr and Kobrick, 2000;Rabus et al, 2003). The advantage of the SRTMderived DEM is the homogeneous quality of topographic information due to consistency in data collection and analysis.…”

On the application of SAR interferometry to geomorphological studies: estimation of landform attributes and mass movements

“…Since then, several workers have demonstrated the accuracy and limitations of this technique (Rosen et al, 2000). A specific 11-day spaceborne mission, the Shuttle Radar Topography Mission (SRTM), flew in 2000, with the objective of producing a global high resolution Digital Elevation Model (DEM) covering 80% of the Earth's surface between 608 N and 568 S (Hilland et al, 1998; further information is available at the URL http:// www-radar.jpl.nasa.gov/srtm/). 1 The basic relationship used to derive the topographic height z from the interferometric phase u is the following…”

Updating DEMs using RADARSAT-1 data

“…We expect that better results could be achieved with better quality InSAR and DEM data. In particular, the public domain DEMs available from the successful Shuttle Radar Topography Mission (SRTM; Hilland et al, 1998) could be improved by taking advantage of the large amount of archived two-pass satellite SAR data, which have a finer grid spacing than the SRTM DEM data.…”