InSAR Access — API
Among ASF’s many collaborations, University NAVSTAR Consortium (UNAVCO)/Western North American InSAR (WInSAR), the Alaska Satellite Facility (ASF), and the Jet Propulsion Laboratory (JPL) worked on an information technology and data-management development project to design and implement a seamless distributed access system for synthetic aperture radar (SAR) data and derived interferometric data products. The seamless SAR archive increases the accessibility and the utility of SAR science data to solid Earth and cryospheric science researchers.
An example of the Vertex baseline plot. Users are provided with the capability to observe the perpendicular and temporal baseline distribution of an InSAR stack based on the selection of a desired master, filter granules, and select granules to download.
Specifically, the project will provide simple web services tools to more seamlessly and effectively exchange and share SAR metadata, data and archived and on-demand derived products between the distributed archives, individual users, and key information technology development systems such as the NASA/JPL Advanced Rapid Imaging and Analysis (ARIA) projects that provide higher level resources for geodetic data processing, data assimilation and modeling, and integrative analysis for scientific research and hazards applications. The proposed seamless SAR archive will significantly enhance mature IT capabilities at ASF’s NASA-supported DAAC, the Group on Earth Observations (GEO) Supersites archive, supported operationally by UNAVCO, and UNAVCO’s WInSAR and EarthScope archives that are supported by NASA, the National Science Foundation (NSF), and the United States Geological Survey (USGS) in close collaboration with the European Space Agency (ESA)/European Space Research Institute (ESRIN).
ALOS-PALSAR amplitude image, coherence image, interferogram, and interferogram overlaid on the amplitude of the master image (left to right). Master image: acquired 2006-11-05. Paired image acquired 2008- 11-10 over Baja, California, Mexico. The copyright for the scenes used to create this image (and those below) is held by the Japan Aerospace Exploration Agency/Ministry of Economy, Trade and Industry.
As part of the proposed effort, data/product standard formats and new QC/QA definitions will be developed and implemented to streamline data usage and enable advanced query capability. The seamless SAR archive will provide users with simple browser and web service API access tools to view and retrieve SAR data from multiple archives, to place their tasking requests, to order data, and to report results back to data providers; to make a larger pool of data available to scientific data users; and to encourage broader national and international use of SAR data. The new Advancing Collaborative Connections for Earth System Science (ACCESS)-developed tools will help overcome current obstacles including heterogeneous archive access protocols and data/product formats, data provider access policy constraints, and an increasingly broad and diverse selection of SAR data that now includes ESA/European Remote Sensing Satellite (ERS)/Environmental Satellite (ENVISAT) (and upcoming Sentinel mission), the Canadian Space Agency (CSA)/Radarsat, the Japan Aerospace Exploration Agency (JAXA)/Advanced Land Observation Satellite Phased Array type L-band Synthetic Aperture Radar (ALOS-PALSAR), German Aero-Space Research Establishment (DLR)/TerraSAR-X satellite data and NASA/Uninhabited Aerial Vehicle SAR (UAVSAR) data. The list will continue to expand with NASA/Deformation, Ecosystem Structure and Dynamics of Ice (DESDynI) further increasing the need to efficiently discover, access, retrieve, distribute, and process huge quantities of new and diverse data.
To facilitate terrain corrections, the proposed NASA SAR (NSAR) project will provide InSAR-ready topographic data through OpenTopography. Shown in (a) above is the terrain correction (EGM96 removed) via Generic Mapping Tools (GMT) SAR (GMTSAR) from NASA SRTM data. The terrain-corrected differential interferogram unwrapped phase in (b) from the same ALOS PALSAR pair was processed using ROI_PAC. Red star shows epicenter of April 2010 Mw 7.2 earthquake. The apparent range change variation is 30 cm. (c) shows the zenith path delay difference from Online Services for Correcting Atmosphere in Radar (OSCAR) Modeling, Data and Information Systems (MODIS) zenith path delay maps. The path delay difference map shows no large gradient due to the troposphere in this case. The NSAR project will standardize product and corrections/QC formats and facilitate this type of product quality evaluation and access to products critical to the interpretation of interferograms for earth surface motions and deformation.
- Develop and implement a federated metadata query and product-download capability from distributed airborne (NASA UAVSAR) and spaceborne SAR archives at ASF and UNAVCO/WInSAR.
- Define and make available new QC parameters and products that will enhance the usability of data and data products from these existing NASA-funded collections.
- Implement a web services enabled terrain correction service for interferometry (InSAR) using NASA Shuttle Radar Topography Mission (SRTM) data at the San Diego Supercomputer Center (SDSC).
- Enhance ASF InSAR processing service to access distributed data collections, utilize terrain correction service, and generate enhanced QC products.
- Establish processed data products archive.