Peter Meadows

Dual-Polarization C-Band Radar Observations of Sea Ice in the Amundsen Gulf

Polarimetric observations of sea ice from synthetic aperture radar can, in principle, assist in sea-ice classification and ice-water discrimination. In this paper, we use dual-polarization ground-based scatterometer observations of sea ice to assess the potential value of spaceborne dual-polarization observations of sea ice for operational ice analysis, focusing on C-band and, in particular, the contribution of the HV backscatter coefficient and HH/VV polarization ratios. Results show that signature variability resulting from frost flowers, ice deformation, and snow cover can overwhelm systematic differences between younger ice types, up to first-year thin. As a result of this and noise floor limitations of spaceborne sensors, the HV backscatter coefficient makes visual ice type and open water discrimination easier only below about 30° incidence angle. The HH/VV ratio is less impacted by the noise floor of spaceborne sensors but retains similar ambiguities for sea-ice classification.

ALOS PALSAR products verification

ALOS, an enhanced successor of the Japanese Earth Resources Satellite 1 (JERS-1), was launched from JAXAs Tanegashima Space Center in January 2006. An important contribution to the ALOS mission is the verification of PALSAR products to be distributed by the European ADEN node using the PALSAR processor developed by JAXA. A total of 28 ALOS PALSAR products have been analysed with respect to radiometric, geometric and polarimetric quality (including effects of Faraday rotation caused by the ionosphere) and a summary of the results is shown in this paper.

“Flashing Fields” in Nearly Simultaneous ENVISAT and ERS-2 C-Band SAR Images

Large differences are observed between radar backscatter measurements made by the ENVISAT and ERS-2 satellite synthetic aperture radars, within 30 min of each other over certain agricultural fields in Flevoland, The Netherlands. The differences appear to be caused by the presence of highly directive scattering combined with very small variations in the azimuth illumination angle of the two sensors at the degree or subdegree level. There is relatively little awareness of such sensitivity to illumination direction, and it is not predicted by models for microwave interaction usually applied to soils and vegetation. It is, however, to be expected if there are significant contributions from coherent scattering extending over patches of the agricultural fields in question. We present analysis that supports such a conclusion.

Evaluation of RISAT-1 compact polarization data for calibration

Synchronous with RISAT-1 and RADARSAT-2 passes, corner reflectors (CR) were mounted for the evaluation of radiometric calibration of RISAT-1 compact polarimetric SAR data. Based on the CRs response on SLC images, RISAT-1 calibration constant, PSLR/ISLR, resolution, channel imbalance and cross-talk were analyzed and compared with that of product specifications. A difference of 0.5 to 1.5 dB is observed between product and estimated calibration constant K. The resolution and PSLR/ISLR are better than the specification of the product. Backscattering coefficient and compact polarimetric parameters of RISAT-1 were compared with RADARSAT-2 simulated compact polarization. The large difference in sigma-0 is observed for water and sand features due to high value of noise-equivalent-sigma-zero of RISAT-1. Similarly, some differences are observed between RISAT-1 estimated compact polarimetric parameters (m, mc, δ, χ, axial ratio, CPR) and that of RADARSAT-2 simulated compact data.

The Sentinel-1A instrument and operational product performance status

This paper addresses the results of the instrument and product performance verification, radiometric and geometric calibration achieved during the since commissioning and routine phase.

ASAR instrument performance and product quality evolution

ENVISAT ASAR is successfully operating since March 2002 and resulting ASAR products are operationally distributed to the user community since December 2002. This paper provides an update of the ASAR performance, from the instrument status to the product quality assessment.

Hybrid and dual linear polarimetric RISAT-1 SAR data for classification assessment

This paper compares the classification capability of data acquired in hybrid and dual linear polarization mode over the Chelmsford area, United Kingdom, from RISAT-1 C-band satellite. Support vector machine based supervised classification is used in the study and accuracy is assessed over the validation pixels. The hybrid-pol RH/RV combination shows better classification accuracy over linear pol HH/HV combination by 2.5 %. Overall classification accuracy is increased to 90% over the given area when Stokes parameter are added to the polarization combination.

The Sentinel-1 constellation mission performance

This paper addresses the results of the instrument and product performance verification, radiometric and geometric calibration achieved since the end of the respective Sentinel-1 A and B commissioning phases.