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Why We Do Need to Place Multi-band Single and Multiple Pass POLinSAR Monitoring Platforms into Space

Professor Wolfgang-Martin Boerner (1)

(1) University of Illinois at Chicago, 900 W Taylor, SEL-4210, Chicago, IL 60607-7018, United States


The ESA POLinSAR Workshop on "Applications of SAR Polarimetry and Polarimetric SAR Interferometry" is arranged at the ideal time for developing this urgently required technology for environmental stress-change and local-to-global conflict monitoring in air and specifically in space. In this overview, reasons are provided on why we do need to place multi-modal, multi-band single and multiple pass POLinSAR monitoring platforms into space. The questions "on what POLinSAR monitoring can provide that POL-SAR and IN-SAR by themselves cannot accomplish" is assessed; whereupon facts and justifications on placing POL-IN-BISAR satellite clusters into space are presented. Reasons for this technology becoming a basic requirement for current, near-future and much more so for future all-day & night year-round monitoring of the terrestrial covers are analyzed in view of the un-abating and uncontrollable terrestrial population explosion. The pertinent questions on how to reduce the exorbitant cost for initiating this "home-globe security protection" technology are also broached, and the expected benefits are laid out in detail. The pertinent National and International airborne and space borne multi-modal, multi-band SAR remote sensing and security conflict surveillance support agencies are herewith invited for co-sponsoring our proposal, which is timely and POLinSAR platforms are urgently required to be placed into space.


I. Background with developmental technology history

1.1. POLinSAR theory and algorithm development has been accomplished and is verified.

1.2. POLinSAR image data takes were acquired with space borne SIR-C/X-SAR and with several POLinSAR airborne platforms like the DLR-OP-IHR E-SAR, the DCRS EMI-SAR, the CRL PiSAR, the ONERA RAMSES-SAR and the NASA-JPL AIRSAR.

1.3. POLinSAR image feature sorting and identification algorithms have been tested and are available as was demonsrated by Cloude and Papathanassiou beyond doubt.

1.4. Cost reduction with the aid of bistatic cartwheel POL-SAR imaging platforms in air and space have been and/or are being demonstrated currently in North America and Europe.

II. From airborne to space borne POLinSAR platform deployment

2.1 Not withstanding space borne applications, airborne multi-modal, multi-band POLinSAR test platform development is essential, must go on for years to come in order to support basic technology advancement and algorithms verification

2.2 Airborne POL-inSAR platform deployment, while truly imperative for technology development, is too expensive for wide area conflict monitoring, and need be replaced by "Unmanned Automated Vehicle: UAV" POLinSAR platforms at the same time during which the entire air and space borne technology is being developed

2.3 While both airborne and UAV multi-modal, multi-band POLinSAR platform deployment is very essential for localized, regional and mission-oriented flight-path imaging; global terrestrial and future planetary remote sensing and surveillance require the urgent and rapid development of space borne multi-modal, multi-band single and multiple pass POLinSAR monitoring platforms

2.4 Global worldwide monitoring of the terrestrial hydro-sphere and biosphere together with a more accurate acquisition of more precise biomass estimation require single and distributed multi-modal, multi-band POLinSAR monitoring platform deployment. This technology will become all the more relevant for effective global conflict surveillance

III. Applications and improvement on terrestrial biomass estimation

3.1 POL-SAR imaging platform deployment enabled the development of highly improved supervised and unsupervised image feature sorting and interpretation algorithms including soil moisture and roughness parameter estimation, which are far superior to those of mono/multiple-polarization-amplitude SAR and/or passive lidar sensing.

3.2 IN-SAR can provide only average-in-altitude "Digital Elevation Maps: DEM" and it is not able to discern canopy cover versus under-store, versus vegetated ground and/or multilayered under burden returns.

3.3 Although for rather specific limited cases multiple complex amplitude-only (HH, HH + VV, HH + HV, VV + VH) quasi-polarimetric SAR may provide may provide improved "specific scenario-dependent" information on vegetation cover above that of amplitude- only SAR, it is not sufficient for precise biomass estimation of densely vegetated and especially forested regions; whereas INSAR does not help at all to acquire 3-D forest canopy versus forest under-store, versus vegetated ground und multi-layered under-burden differentiation, which only and only multi-band single and multiple pass POLinSAR and POL-TOMO-SAR can accomplish. This applies especially to soil moisture and roughness estimation as well as to the mapping of flooded regions.

IV. Cost reduction via POLin BISAR cart-wheel clusters in space

4.1 It is a well known fact that any novel advanced forefront imaging technique whether in non-destructive testing, medical radiology, sub-aquatic sonar imaging, and/or Radar/SAR remote sensing and conflict surveillance - is exorbitantly costly during its infant stages; and these relatively high cost factors cannot and must not be considered a deterrent factor, hampering the steady and urgent advancement of POLinSAR technology.

4.2 Multi-modal multi-band polarimetric SAR deployment was proven a viable novel imaging technology hitherto not surpassed or even closely competing with existing SAR imaging technology. In fact, it was demonstrated beyond doubt that fully polarimetric POL-SAR outperforms conventional mono/multiple-polarization-amplitude- only SAR by a factor of 12 15 dB in general.

4.3 Airborne and space borne POLinSAR imaging & sensing platform deployment was successfully demonstrated with the SIR-C/X-SAR missions 1 & 2, which were complemented more recently by the DLR-OP-IHR multi-pass E-SAR POL-TOMO-SAR experiments, providing the first true 3-D image-reconstructions of volumetric vegetation scatter, which when extended to the multi-band microwave POLinSAR image data take acquisition will enable the isolation of compact (point) targets in a 3-D forest and vegetated or urban environment being of essential relevance to `National home-land' and even more so to `International home-globe' security conflict surveillance missions

4.4 The first steps in developing airborne and space borne clusters of partially and fully polarimetric bistatic cartwheel SAR imaging deployment are well under way both in Europe and North-America and, a fully polarimetric Cartwheel SAR Cluster deployment was proven to be feasible - at least on the drawing boards. The costs are only slightly above those of purely amplitude-only systems, and the truly impressive improvements obtained in deploying bistatic POLinSAR cart-wheel clusters for a highly more accurate and close-to-reality biomass estimation justify the costs.

V. Benefits for highly improved and more accurate biomass estimation, and for the ` homeland' plus `home-globe' security conflict mitigation missions

5.1 Near future and future environmental stress-change remote sensing and localized to wide area security conflict surveillance requires monitoring technologies which are being advanced towards the limits of physical realizability like POLinSAR is

5.2 The entire field of local to global biomass estimation of multi-modal, multi-band microwave POLinSAR imaging in concert with advanced passive and active polarimetric EO sensing will be advanced most actively and will become quantitatively accessible.

5.3 The initial exorbitant cost factors are being addressed and shown to be not as drastic - with the introduction of multi-static cartwheel clusters of multi-band POL-SAR, i.e., POL-IN-BISAR systems - as previously estimated, which will pave the way to "all-day & night year-round" 3-D monitoring of the terrestrial covers.

5.4 Similar to placing the equidistantly spaced fleet of orbiting GPS satellites into space, we are herewith developing the complementary set of equidistantly spaced orbiting clusters of multi-modal, multi-band microwave POL-IN-BISAR monitoring satellites for space deployment, which will provide day and night, hourly stress-change and security conflict indicators. These all-important indicators are required already now, and much more so are in desperate need in the nearer and distant future for protecting "Mother Earth = our home-globe" suffering from an un-abating population explosion and therewith an ever increasing number of future environmental stress-change and political security conflicts.


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