GEOS 657 - Lecture 10 GEOS 657 – MICROWAVE REMOTE SENSING SPRING 2019 Lecturer: F.J. Meyer, Geophysical Institute, University of Alaska Fairbanks; [email protected] Lecture 10: SAR Image Acquisition Modes; Past, Current, & Future SAR Sensors; Basics of InSAR Image: DLR, CC-BY 3.0 UAF Class GEOS 657 AVAILABLE SAR SENSORS Franz J Meyer, UAF GEOS 657: Microwave RS - 2 Current and Future SAR Satellites TerraSAR-X & TanDEM-X PAZ SAR X-band Cosmo-SkyMed 1st and 2nd generation ERS-1/2 Envisat Sentinel RADARSAT-2 RCM C-band RADARSAT-1 JERS-1 ALOS-1 ALOS-2 SAOCOM L-band Seasat NISAR BIOMASS P-band 1978 1990 2000 2010 Present Day Future Franz J Meyer, UAF GEOS 657: Microwave RS - 3 1 GEOS 657 - Lecture 10 Current and Future SAR Satellites Accessible Through ASF TerraSAR-X & TanDEM-X PAZ SAR X-band Cosmo-SkyMed 1st and 2nd generation ERS-1/2 Envisat Sentinel-1 RADARSAT-1 RADARSAT-2 RCM C-band JERS-1 ALOS-1 ALOS-2 SAOCOM L-band Seasat NISAR BIOMASS P-band 1978 1990 2000 2010 Present Day Future Franz J Meyer, UAF GEOS 657: Microwave RS - 4 Resolution vs. Spatial Coverage • Medium (10m-class) resolution large-coverage systems: – Sensors: Current: ALOS-2; Sentinel-1; RADARSAT-2 Most of the medium-res Future: SAOCOM; NISAR; RCM; BIOMASS data are free or low cost (not ALOS-2 and R-2) – These sensors are suitable for applications such as: • Monitoring medium to large scale surface deformation (e.g., subsidence; slopes) • Assessing impacts of hazards (flooding; earthquakes) • General mapping and change detection • High (1m-class) limited-coverage resolution systems: – Sensors: Current: TerraSAR-X; TanDEM-X; COSMO-SkyMed constellation nd Future: PAZ SAR; COSMO-SkyMed 2 Gen High-res data is typically – These sensors are suitable for applications such as: more expensive • Mapping and analysis of urbanized environments (buildings, bridges) • Detecting localized hazards (sinkholes; small landslides) • As most high-res systems have higher repeat frequency tracking of things that change quickly Franz J Meyer, UAF GEOS 657: Microwave RS - 5 Free of Charge vs. Commercial • Free of charge data: – Current: Sentinel-1 – Future: SAOCOM (partly); NISAR; BIOMASS; RCM • Commercial data: – Current: TerraSAR-X; TanDEM-X; COSMO-SkyMed Constellation – Future: COSMO-SkyMed 2nd Gen; PAZ SAR Franz J Meyer, UAF GEOS 657: Microwave RS - 6 2 GEOS 657 - Lecture 10 MEANS OF DATA ACCESS (1) THE ALASKA SATELLITE FACILITY (ASF) Franz J Meyer, UAF GEOS 657: Microwave RS - 7 A Short Intro to the Alaska Satellite Facility (ASF) • ASF is NASA Distributed Active Archive Center (DAAC) for SAR Data – Established in 1991 as the prime U.S. downlink and processing center for SAR data – Operates three antennas for command uplink and data downlink of a series of NASA and non-NASA remote sensing satellite systems • Currently, ASF is housing about 7PB of SAR data in its archives all data available on spinning disks for immediate download Visit ASF @ www.asf.alaska.edu Franz J Meyer, UAF GEOS 657: Microwave RS - 8 Recent ASF Milestones MAY 2015: ASF’S ALOS PALSAR DATA HOLDINGS BECOME UNRESTRICTED MAY 2015: CORRECTED FOR GEOMETRIC AND RADIOMETRIC DISTORTIONS & RELEASE OF PALSAR RTC DATA AVAILABLE AS FULLY GEOCODED GEOTIFF DEC 2015: ASF PROVIDES ACCESS TO GLOBAL SENTINEL-1A ARCHIVE SPRING 2016: SELECTED AS DATA CENTER FOR UPCOMING NASA-ISRO SAR (NISAR) MISSION 9 3 GEOS 657 - Lecture 10 VERTEX – ASF’s Search and Download Interface https://vertex.daac.asf.alaska.edu/# • Let’s look at the Vertex Search Engine in more detail: Franz J Meyer, UAF GEOS 657: Microwave RS - 10 MEANS OF DATA ACCESS (2) THE EUROPEAN SPACE AGENCY Franz J Meyer, UAF GEOS 657: Microwave RS - 11 All of ESA’s SAR data ESA’s Past and Current SAR Sensors are freely available ERS-1 & -2 (European State Envisat ASAR (European Sentinel-1 A/B (European Agency ESA) State Agency ESA) State Agency ESA) • Sentinel-1A: Since 2014 • Identical twin satellites • Sentinel-1B: Since 2016 • ERS-1: 1991 – 3/2000 • Same orbit as ERS-1/2 • 흀: 5.6cm (C-band) • ERS-2: 1995 – 7/2011 • Lifetime: 2002 – 8/2012 • Stripmap, TOPS Mode • 흀: 5.6cm (C-band) • 흀: 5.6cm (C-band) • Resolution: 5m – 100m • Stripmap mode only • Stripmap, ScanSAR • Swath: 80 - 400km • Resolution: ~ 25m • Resolution: 25m – 150m • 12 days repeat cycle (6 • Swath: 100km • Swath: 100 - 400km days in the constellation) • 35 day repeat cycle • 35 day repeat cycle • Polarization: HH, VV, • 1996-2000: tandem phase • Polarization: HH, HV, HH/HV, VV/VH (acquisitions 1 day apart) VV/HH, HH/HV, VV/HV • Some Level-2 ocean • Polarization: VV products Franz J Meyer, UAF GEOS 657: Microwave RS - 1212 4 GEOS 657 - Lecture 10 ESA’s Copernicus Space Program Holistic Earth Observation with a Multi-Sensor Constellation S1A/B: Radar Mission Launched in ‘14 & ‘16 S2A/B: High Resolution Optical Mission S2A launched in ‘16 S3A/B: Medium Resolution Imaging and Altimetry Mission S4A/B: Geostationary Atmospheric Chemistry Mission S5P: Low Earth Orbit Atmospheric Chemistry Precursor Mission S5A/B/C: Low Earth Orbit Atmospheric Chemistry Mission Jason-CS A/B: Altimetry Mission Franz J Meyer, UAF GEOS 657: Microwave RS - 13 ESA’s Science Hub Search and Download Interface https://scihub.copernicus.eu/dhus/#/home • Let’s look at the SciHub interface: Franz J Meyer, UAF GEOS 657: Microwave RS - 14 SAR IMAGE ACQUISITION MODES Franz J Meyer, UAF GEOS 657: Microwave RS - 15 5 GEOS 657 - Lecture 10 Different SAR Modes for different Applications Mode 1: Stripmap Mode SAR • Stripmap Mode Observation radar Geometry: – Radar images a strip-like swath V parallel to satellite orbit H – Standard operational mode V Franz J Meyer, UAF GEOS 657: Microwave RS - 16 Different SAR Modes for different Applications Mode 1: Stripmap Mode SAR • Stripmap Mode Observation radar Geometry: – Radar images a strip-like swath V parallel to satellite orbit H – Standard operational mode • Properties: – Range resolution 100% dependent on transmitted bandwidth 푊 – Azimuth resolution defined by length of synthetic aperture which is defined by length of physical antenna V Franz J Meyer, UAF GEOS 657: Microwave RS - 17 Different SAR Modes for different Applications Mode 2: Spotlight Mode SAR • To increase azimuth resolution, synthetic aperture length is increased by beam steering to selected area • Non-continuous imaging (areas before and after the selected area cannot be imaged!) • Properties: – Range resolution 100% dependent on transmitted bandwidth 푊 – Azimuth resolution defined by length of synthetic aperture which is now independent of length of physical antenna area to be imaged Summary: higher resolution at the expense of spatial coverage Franz J Meyer, UAF GEOS 657: Microwave RS - 18 6 GEOS 657 - Lecture 10 Different SAR Modes for different Applications Mode 3: ScanSAR Mode • To achieve wider swaths, synthetic aperture is divided into short pieces (bursts) Length of Synthetic Aperture per burst 퐿 successive illumination of several parallel swaths for increased swath width (100 to 500km) • Properties: – Range resolution 100% dependent on transmitted bandwidth 푊 – Azimuth resolution defined by length of synthetic aperture dedicated to one #1 sub-swath (퐿) (shorter than 퐿, #2 hence, lower resolution than stripmap #3 mode) Franz J Meyer, UAF GEOS 657: Microwave RS - 19 Examples of SAR Image Acquisition Modes • Available Image Modes: – ScanSAR Mode: • Lowest resolution – largest coverage – Stripmap Mode (standard mode) • Intermediate resolution – Spotlight Mode • Highest resolution – limited coverage Franz J Meyer, UAF GEOS 657: Microwave RS - 20 Coverage of Standard Beam and ScanSAR • Comparison of RADARSAT SWB and RADARSAT ST-6 Franz J Meyer, UAF GEOS 657: Microwave RS - 21 7 GEOS 657 - Lecture 10 First Envisat/ASAR ScanSAR Image – Antarctic Peninsula Franz J Meyer, UAF GEOS 657: Microwave RS - 22 Recently Developed SAR Modes Toward Full Resolution and Wide Swath SARs Terrain Observation by Progressive Scan (TOPS) Scan on Receive SAR (SweepSAR) Scan beam forward in azimuth during burst • Time-share synthetic aperture among elevation • Time-share pulse returns on receive with beams to increase swath multiple receive beams to increase swath • Scan beam forward in azimuth within burst to • Track receive echoes as they propagate improve radiometry across the swath • Degraded azimuth resolution • Narrow receive beam controls ambiguities Franz J Meyer, UAF GEOS 657: Microwave RS - 23 THE SENTINEL-1 AND NISAR SENSORS Franz J Meyer, UAF GEOS 657: Microwave RS - 24 8 GEOS 657 - Lecture 10 Sentine-1: First SAR Sensor with Operational Character • Sentinel-1 (2014 - 2021): First SAR satellite system with operational mission – Regular reliable observation according to operational requirements – Imaging all landmasses, coastal zones and shipping routes every six days – Specifically designed for InSAR 25 ASF’s Sentinel-1 SAR Archive • Rapidly growing global S-1A archive multitude of new SAR users / applications (complex) images (complex) SLC Sentinel-1 SAR Archive SAR Sentinel-1 Franz J Meyer, UAF GEOS 657: Microwave RS - 26 ASF’s Sentinel-1 SAR Archive • Rapidly growing global S-1A archive multitude of new SAR users / applications (only amplitude)(only images GRD Sentinel-1 SAR Archive SAR Sentinel-1 Franz J Meyer, UAF GEOS 657: Microwave RS - 27 9 GEOS 657 - Lecture 10 NISAR: NASA L-/S-Band SAR for Global Deformation Mapping Jet Propulsion Laboratory California Institute of Technology NISAR (2020): • Full global coverage with every cycle • Rapid commanding & rapid data delivery for hazard monitoring • Specifically designed for InSAR 28 The