Tuesday, October 23, 2007

New World of SAR - A round-up of SAR Systems

Recently I wrote an article with the same topic for a magazine that shall not be named, and received claims from editor that it was too biased. Since I can't make the deadline for a new article and the editors left it too late to pass on their opinion, I am going to use this soap box to stand and narrate my perspective on the current state-of-art in SAR Systems, commercial and research based, the rest (presumably a lot of them military) are not common knowledge.

  • Air-Borne Systems
    • Commercial - Very few commercial players exist in this field
      1. Intermap IFSAR - Operational X-Band single pass Interferometric System with proven track record and very large archive of proven quality data. The P-Band system feature foliage penetration but is repeat-pass based.
      2. Fugro-EarthData GeoSAR - Newly operational for X and P band single pass interferometry. Available data archive is limited and data validation is not wide-spread. Theoretically should produce good quality DEM's using P-Band but this may conflict with the X-Band results, needing reconciliation. The system is ex-NASA. The accuracy in the system is achieved by redundancy/repeat flights. A good set of samples can be obtained at the NOAA site.
      3. Orbisat InSAR - A Brazilian system with InSAR capability in X and P bands.
    • Research - A fair few research systems exist operated by space agencies and educational institutions, the data from these systems has limited availability is based on pre-planned campaigns. A suitable summary is on the POLSARPRO site. In addition to these a lot of institution have the aspiration to operate a SAR system, it is a highly prestigious club to belong to.
      1. AIRSAR(NASA/JPL) - The elder statesman of air-borne systems, last known campaign was in 2004. The last time I accessed the AirSAR site was offline.
      2. EMISAR(DCRS) - Technical University of Denmark dual-band(L/C) fully polarimetric system.
      3. ESAR(DLR) - Quad-Band(X/C/L/P) fully polarimetric system with very high quality data used for Insar, Polsar and Polinsar research. This system served as a template for the TerraSAR-X sensor.
      4. Pi-SAR(NASDA-CRL) - JAXA Airborne L-Band system, the inspiration behind JERS and ALOS-PALSAR.
      5. RAMESES/SETHI(ONERA) - Someone in France must be obsessed with Egyptian history and pharaohs, or may be it is related to the sand penetration experiments with these systems.
      6. SAR-Convair(CCRS) - Polarimetic X/C-Band system used as a test-bed for Radardat 1 and 2 sensors by the Canadians. Mainly used for research in ice-monitoring, because that's all Canadians are interested in.
  • Space-Borne Systems -Recent years have seen the launch of numerous SAR sensors, both civilian and military. I have started to lose track of the military ones, here are a few: SARLupe-1 and 2(Germany) , YaoGan(Chinese), Cosmo-Skymed 1 and 2(Italy) and many more. The systems of interest to me are those that have readily accessible data, are currently operational or will be near future(which can mean anytime in the next 5 years given the nature of the space industry - you can really feel the relativistic time dilation, we must be near a black hole).
    • Currently In-Orbit Systems - These are either old die-hard systems, long past their scheduled expiry date or recently launched top-of-the-line sensors.
      1. RADARSAT-1 - The long lived Canadian SAR system operating in C-Band HH.
      2. ENVISAT-ASAR - SAR sensor on the multi-sensor Envisat bus. The data from this sensor is accessible for research from a rolling archive over the last 15days. The sensor can operate in alternate polarization mode.
      3. ALOS-PALSAR - The first fully polarimetric L-Band space borne sensor. The data from this sensor is heavily consumed by the Kyoto and Carbon project for global forest monitoring. It collects on a fixed schedule over all land-mass. The data is highly affordable and of good quality.
      4. TerraSAR-X - Newly launched poster child of the SAR world, first commercial SAR sensor to provide upto 1m resolution. Alternate polarization mode is operational, full-polarimetry and along track interferometry are some of the research modes available.
    • Planned/To-be-launched-soon systems - These are the bad boys, getting to school late or the toddlers which show great promise. Not yet in orbit but will be nice to have data from them.
      1. RADARSAT-2 - The naughtiest of the bad boys, showing a lot of promise but not sitting for the exam. Long planned, but delayed in launch, it will be the first fully polarimetric C-band spaceborne system.
      2. Sentinel-1 - Follow on to the aging ENVISAT system mentioned above, with upgrades with new technology in C-band. Unlike its predecessor, it will be a smaller and dedicated SAR bus, other optical sensors will have to find their own rides on Sentinel 2 and 3. It is due for launch in 2011.
      3. TerraSAR-L(Cartwheel) and Tandem-X - The novel concept in SAR systems is a constellation, this will allow single pass along-track and cross-track interferometry.
      4. MAPSAR - An L-band joint program between INPE(Brazil) and DLR, due some time the next decade.
      5. RADARSAT Constellation - Another program due next decade or after that(if RS-2 is anything to go by) designed to provide daily global coverage using SAR.
That is my summary for today. Those that have attended more conferences than I have may have encountered a lot more exotic ideas and sensors. I hope this will attract comments on those sensors not mentioned here and their capabilities.
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