B.T. Banik

RADARSAT image quality and calibration — Update

Abstract This paper reviews image quality and radiometric calibration aspects of the first two years of operation of RADARSAT. This includes the calibration of almost all beams (a total of more than 25 beams when considering shifted positions of each of the Fine beams), and the stability and calibration accuracies achieved during the mission to date. The measurements show that the SAR performance is better than the specifications. In September 1997, RADARSAT underwent a major configuration change to accommodate the Antarctic Mapping Mission for a period of about five weeks. To achieve this, the spacecraft was rotated to allow imaging from a left-looking geometry. The image quality and calibration results for the left-looking mode are also discussed.

RADARSAT-1 image quality and calibration — a continuing success

Abstract The Canadian earth observation satellite, RADARSAT-1 was launched on November 4, 1995 with the first image acquired on November 28 of that year. After commissioning it was put into routine operation on April 1, 1996. Since then more than four years of successful operation have been completed, utilizing data for their intended applications. Significant effort has been extended in the provision of radiometrically and geometrically calibrated products to users by the Canadian Data Processing Facility (CDPF). Particular emphasis has been on the maintenance of image quality and calibration as monitored using images of the Amazon Rainforest and of the RADARSAT-1 Precision Transponders (RPT). This first part of the paper will review the image quality and calibration evolution of RADARSAT-1, complementing previously presented reviews on this subject. Data will be given on various image quality parameters related to impulse response, location error, antenna pattern and noise equivalent measures, and on calibration accuracy as achieved to date. Recent work on calibration and image quality improvements for ScanSAR products are also presented. The latter part of the paper describes methodologies developed for maintenance of radiometric calibration performance of RADARSAT-1, including a statistical technique useful for early detection of radiometric problems associated with single calibrated beams.

RADARSAT elevation antenna pattern determination

The operations plan for RADARSAT is based on implicit calibration of the imagery products from this sensor system. The determination of the antenna gain patterns in elevation for RADARSAT is a critical step in the radiometric calibration of this imagery. The shapes of the antenna patterns in elevation were derived from imagery collected over the South American rain forests of Brazil and Colombia with a consistency on the order of /spl plusmn/0.2 dB. The absolute levels of the patterns have been determined by superposing the shapes on results from a set of precision radar ground targets known as the RADARSAT Precision Transponders. As pattern revisions are determined, they are included operationally in the determination of the corrections that are required in the Canadian Data Processing Facility to create radiometrically calibrated image products.

RADARSAT-1 image quality and calibration — Continuing success in extended mission

Abstract RADARSAT-1, the first Canadian SAR remote sensing satellite, was launched on November 4, 1995. After commissioning, it was put into routine operations on April 1, 1996. Since then, it has been operating successfully, even after completing its five and a quarter years of design lifetime, and providing data to users for their intended applications. Significant effort continues to be expended in the provision of high quality products to users generated by the Canadian Data Processing Facility (CDPF). After initial calibration, both single beams and ScanSAR are monitored routinely as part of the Maintenance Phase for image quality performance. Image quality is monitored through periodic measurements of impulse response function, location error and radiometry, using images of the Amazon Rainforest and RADARSAT-1 Precision Transponders (RPTs). ScanSAR radiometry is also monitored through periodic measurements of the Amazon Rainforest. A major upgrade of the ScanSAR processor completed recently in CDPF made significant improvements in image quality and radiometry. An experiment was conducted to determine if antenna pattern change was due to the heating or cooling of Variable Phase Shifters (VPS) forming antenna beams. It was concluded that changes in beam pattern are not due to temperature variations. New methods and software tools have been developed to improve operational efficiency. Also, a new methodology was implemented to assess spacecraft roll variation, using ocean images for improved characterization of spacecraft attitude performance. This methodology was used in several experiments that were conducted to gain a better understanding of image quality when operating the spacecraft in ADM3 mode.

Maintaining image quality and calibration of RADARSAT-1 CDPF products

RADARSAT-1 was launched in November 1995 with the first image acquired on November 28 of that year. After commissioning, it was put into routine operation on April 1, 1996. Significant effort has been expended in the provision of radiometrically and geometrically calibrated products to users by the Canadian Data Processing Facility (CDPF). Particular emphasis has been on the determination of the antenna gain patterns and on image quality as measured using images of the Amazon rainforest and of the RADARSAT-1 Precision Transponders (RPT). This paper reviews stability and calibration accuracy as achieved to date, image quality results and includes the latest developments for ScanSAR products.

RADARSAT image quality and calibration performance-update

This paper reviews image quality and radiometric calibration aspects of the first two years of operation of RADARSAT. This includes the initialization of almost all beams, stability and calibration accuracies achieved during the mission to date. In September 1997, RADARSAT underwent a major configuration change to accommodate the Antarctic Mapping Mission for a period of about five weeks. To achieve this, the spacecraft was rotated to allow imaging from a left-looking geometry. The image quality and calibration results for the left-looking mode are also discussed.

Statistical methodology for monitoring radiometric performance of RADARSAT-1

An important objective of RADARSAT-1 is to provide users with geometrically and radiometrically calibrated products. This has been achieved largely through continuous long term monitoring of both point target measures at Canadian transponder sites, and the elevation beam patterns using the Amazon rainforest. This paper describes a statistical method useful for monitoring the radiometric performance of calibrated single beams during the life of the mission. The method is useful for early detection of radiometric problems associated with changes in the beam pattern shape or pointing; this is important for initiating the process of re-calibration of the beam pattern used by the processor.

Calibration and image quality performance results of RADARSAT

Abstract The Canadian earth observation satellite, RADARSAT, was launched in late 1995. The aim of this space borne Synthetic Aperture Radar (SAR) program is to provide C-band HH polarized SAR data products for five years at varying incidence angles, resolutions and area coverages. The system has been designed to produce imagery using single beams in elevation and also to operate in the ScanSAR mode by combining different elevation beams. SAR images have been obtained and were used to measure system performance during the Beam Qualification Phase. The measured image quality parameters for single beam products dealing with all aspects of image quality except radiometric calibration have been found to meet and exceed the system specifications. Based on the system performance and on completion of the commissioning activities, the Initial Operational Capability for the system was declared in April 1996.

RADARSAT-1 image quality/continuing success in extended mission

RADARSAT-1, the first Canadian SAR remote sensing satellite has successfully completed its design lifetime of five and a quarter years. It is in an extended mission operation meeting customer demands. The Image Quality Control program is kept fully operational. Measured results indicate that image quality performance continues to be better than system specification. This paper briefly describes image quality and recalibration work and measured results.

RADARSAT-1 image quality/five years of achievement

RADARSAT-1, the first Canadian SAR remote sensing satellite, was launched on November 4, 1995. After commissioning, it was put into routine operations on April 1, 1996. In September 1997, RADARSAT-1 underwent a major configuration change to accommodate the Antarctic Mapping Mission (AMM - a joint mission by Canada and USA aimed at completing high-resolution mapping of Antarctica) for a period of about five weeks. Significant effort continues to be expended in the provision of high quality products to users generated by the Canadian Data Processing Facility (CDPF). The image quality measurement results indicate that the RADARSAT-1 system is meeting and exceeding its performance specification and that image quality is maintained. This paper will describe the overall process of data acquisition, data analysis and re calibration for image quality maintenance.