NASA L-SAR instrument for the NISAR (NASA-ISRO) Synthetic Aperture Radar mission

Abstract

The National Aeronautics and Space Administration (NASA) in the United States and the Indian Space Research Organization (ISRO) have partnered to develop an Earth-orbiting science and applications mission that exploits synthetic aperture radar to map Earth's surface every 12 days or less. To meet demanding coverage, sampling, and accuracy requirements, the system was designed to achieve over 240 km swath at fine resolution, and using full polarimetry where needed. To address the broad range of disciplines and scientific study areas of the mission, a dual-frequency system was conceived, at L-band (24 cm wavelength) and S-band (10 cm wavelength). To achieve these observational characteristics, a reflector-feed system is considered, whereby the feed aperture elements are individually sampled to allow a scan-on-receive ("SweepSAR") capability at both L-band and S-band. The instrument leverages the expanding capabilities of on-board digital processing to enable real-time calibration and digital beamforming. This paper describes the mission characteristics, current status of the L-band Synthetic Aperture Radar (L-SAR) portion of the instrument, and the technology development efforts in the United States that are reducing risk on the key radar technologies needed to ensure proper SweepSAR operations.

Improved forest height estimation by fusion of simulated GEDI Lidar data and TanDEM-X InSAR data

“…The fidelity of the GEDI-derived DTM had a significant impact on the efficacy of GEDI/TDX fusion. A key step to providing more accurate height products may be to enhance the GEDI DTM (below canopy topography) (Lee et al 2018) using, for example, DEM (surface elevation) products from TDX (Bräutigam et al 2014), SRTM (Rodriguez et al 2006), Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) (Abrams et al 2010), or data from future missions such as ICESat-2 (Abdalati et al 2010) and NASA-ISRO Synthetic Aperture Radar (NISAR) (Hoffman et al 2016). In particular, the combination of the transect sampling lidar observations from ICESat-2 and GEDI, when combined with continuous, but less accuracte surface elevation meausrements from other missions (Lee et al 2018), within an improved spatial interpolation/kriging framework is a promising avenue for future research.…”

HazMapper: A global open-source natural hazard mapping application in Google Earth Engine

“…The usefulness of satellite-observations in the scientific community are difficult to overstate and future developments (e.g. Hoffman et al, 2016) are increasing the need for enhanced processing methodologies and techniques. Some traditional uses for satelliteobservations include identifying landslides and debris flows (e.g.…”

“…MODIS, Sentinel) have improved capabilities and increasingly complex satellite networks continue to be developed (e.g. Hoffman et al, 2016;Langhorst et al, 2019). Analysis of remote-sensing data has traditionally been performed by trained analysts on highpowered computers, often creating a resource-barrier for fiscally strained communities or those without advanced training.…”

Multichannel Staggered SAR Azimuth Processing

“…where the normalization factor is given by 3 A similar strategy is adopted in [7], though in a different optimization context. 4 Numerically speaking only the ratio of the weights between the coefficients of the two cost functions in (28) matters for the solution, so that a single parameter would suffice.…”

“…Clearly, both high (spatial) image resolution and short revisit times (equivalent to a high temporal resolution) translate into a larger information content which is highly desirable for numerous applications. State-of-the-art and next-generation SAR systems [1], [2], [3] are in fact required to simultaneously provide high spatial and temporal resolutions in order to enable nearlycontinuous scientific observation of important dynamic Earth processes.…”