The Synthetic Aperture Radar (SAR) data available from the GAGE Facility includes satellite-transmitted and received radar scans of the Earth’s surface. SAR data, analyzed using Interferometric SAR (InSAR) techniques, can be used to model millimeter-to-centimeter scale deformation of the Earth’s surface over regions tens to hundreds of kilometers across. These displacement fields are essential guides for studies of tectonics, earthquake focal mechanisms, volcano behavior, hydrology, and public safety related to Earth hazards.
See our video about Open Access SAR Data at the GAGE Facility for a general overview of available SAR Data:
SAR Data Levels
Current satellites produce different levels of SAR data products that can be utilized for different purposes.
- Level 0 SAR data consists of the raw and unfocused data taken by satellites.
- Level 1 SAR data comes from a satellite’s processing facility taking the raw Level 0 data and running it through different algorithms to produce SLC’s and GRD’s
- Single Look Complex (SLC) images preserve phase information from raw acquisitions and retain original pixel spacing
- Ground Range Detected (GRD) images preserve amplitude information from raw acquisitions
- Level 2 SAR data are products derived from Level 1 data and are typically geolocated with a specific application in mind (surface radial velocity, ocean wind fields, etc.)
Note: different satellites will have different naming conventions for the various levels of data, so it is important to check on what each satellite and its corresponding space agency list as different products. Here are a few examples below:
Sentinel-1: https://sentinels.copernicus.eu/web/sentinel/user-guides/sentinel-1-sar/product-types-processing-levels
ALOS-1: https://earth.esa.int/eogateway/catalog/alos-palsar-products
SAR Data Collections
WInSAR
The GAGE Facility archives SAR data for WInSAR. WInSAR is a consortium of universities and research laboratories established by a group of scientists and engineers to facilitate collaboration in, and advancement of, Earth science research using radar remote sensing. WInSAR helps coordinate requests for data acquisition and for data purchase, aiding individual investigators by simplifying interactions with data providers and with government agencies funding science, including NASA, NSF, and the USGS. The WInSAR ESA collection is made of SAR scenes acquired by WInSAR from the European Space Agency (ESA) missions, e.g. ERS-1, ERS-2, and Envisat. ESA has also generously contributed to the WInSAR holdings by providing data and tasking at low or no cost. WInSAR Full Members are eligible to request that additional data from ESA be added to this collection.
Access the WInSAR Collection: To download SAR data from the WInSAR ESA collection in the GAGE Facility SAR archive, you must be affiliated with a WInSAR Full or Adjunct I Member Institution and apply to become an authorized WInSAR data user. Institutions engaged in SAR research may apply for WInSAR Institutional Membership.
2003-2018 EarthScope program ESA/CSA
A goal of the 2003-2018 EarthScope program was the improved understanding of the tectonic evolution of the North American continent. Identifying and understanding deformation rates in all tectonic regimes is critical to reaching that goal. The GeoEarthScope component of the 2003-2018 EarthScope program included the acquisition of SAR data, aerial and satellite imagery, and geochronology data, to examine the strain field beyond the time scales available from the Plate Boundary Observatory geodetic instrumentation. Consequently, UNAVCO (now EarthScope Consortium) acquired SAR data from the ESA (ERS1, ERS2, and Envisat missions) and from the Alaska Satellite Facility (ERS1, ERS2 and RADARSAT-1). Data from ESA missions make up the EarthScope ESA collection and data from the Canadian Space Agency (CSA) RADARSAT-1 mission make up the EarthScope CSA collection. These two 2003-2018 EarthScope program collections are currently static with no new SAR scenes being added to them.
Access the EarthScope ESA/CSA Collection: If you are an authorized WInSAR data user, you have access to the EarthScope ESA and CSA collections.
PI Specific Data
In some cases, data from various SAR satellite platforms (e.g., DLR TSX, JAXA ALOS-2, and ASI CSK) are available to a group of principal investigators (PIs) via a proposal process. The GAGE Facility provides WInSAR PIs the ability to host these data in the GAGE Facility SAR archive and handles the role-based authentication necessary to control access to the data. See the WInSAR site for more information about management of PI SAR datasets.
Obtain SAR Data
The primary tool for discovering and accessing SAR data from the GAGE Facility is the Seamless SAR Archive (SSARA). This tool is available as a command line utility (API) and web-based interface (GUI) that allows for the search and download of data from WInSAR’s collection as well as data from the Alaska Satellite Facility (ASF) and some PI specific collections:
GUI: https://web-services.unavco.org/brokered/ssara/gui
API: https://www.unavco.org/gitlab/unavco_public/ssara_client
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- Last updated: 22 August 2023