1 Thursday 04-Jun ASAR WORKSHOP 2011 Canadian Government Calibration Operations within the RADARSAT Program Assessment of Distributed Target Sites S. Cote, S. Srivastava Canadian Space Agency S. Muir Calian Technologies Ltd T. Lukowski Defence R&D Canada

2 Thursday 04-Jun ASAR WORKSHOP 2011 Outline Amazon Canadian Boreal Forest Congo Antarctica

3 Thursday 04-Jun ASAR WORKSHOP 2011 Introduction Exploitation of naturally distributed targets for calibration-validation of space-based radars and scatterometers 1978 Seasat (L-band) 1985 SIR-B (L) 1991 ERS-1 (C-band) 1992 ERS-2 (C) 1994 SIR-C (X-band) 1992 JERS-1 (L) 1996 RADARSAT-1 (C) 2002 ENVISAT (C) 2006 ALOS PALSAR (L) 2007 TerraSAR-X (X) 2007 RADARSAT-2 (C) Cal-val measurements Measurements aimed at validating elevation beam patterns and radiometric levels Polarimetry: imbalance, cross-channel leakage (Luscombe, CEOS SAR WGCV 2008)

4 Thursday 04-Jun ASAR WORKSHOP 2011 Introduction Cal-val measurements …are made relative to a reference elevation beam pattern used for pattern compensation in processing Elevation Angle Two-Way Gain In-orbit measurements of elevation beam pattern (range line averaging ) Pattern difference Relative Radiometric accuracy Reference pattern Radiometric Offset Elevation Angle Use of uncompensated imagery Routine measurements and update of reference patterns when needed Absolute Radiometric Accuracy (worst-case) = Rad. Offset * Rel. Rad. Accuracy

5 Thursday 04-Jun ASAR WORKSHOP 2011 Introduction Sought properties of naturally distributed targets: Temporal stability Spatial uniformity Isotropy, or simple backscatter dependence with range Increasing quantity of SAR imaging modes entails a more intensive use of a restricted set of distributed target sites for cal-val Diversification of sites is desirable Would add planning flexibility Cal-val robustness RADARSAT-2 Data and Products © MacDONALD, DETTWILER AND ASSOCIATES LTD All Rights Reserved RADARSAT is an official mark of the Canadian Space Agency Amazon RADARSAT-2 F22 HH+HV (R+G)

6 Thursday 04-Jun ASAR WORKSHOP 2011 The Amazon in the RADARSAT Program CEOS SAR WGCV 2004 LL: 7°53', 68°20' UR: 6°06', 66° 34' RADARSAT : acq. / cycle Hundreds of acquisitions spanning 11 years All acquired within a well circumscribed area Very few issues utilizing the data Data records suggested that the potential of the area could be exploited more fully Area was exploited for R1 until termination of On-Board Recorder operations in early 2009 Normalized Gamma Levels: (Luscombe, CEOS SAR WGCV 2003) ©2011 Google – © Imagery 2011 TerraMetrics © Canadian Space Agency

7 Thursday 04-Jun ASAR WORKSHOP 2011 In , RADARSAT-1 was utilized to find and test alternate areas of the Amazon basin in search of extra validation sites for RADARSAT-2. Sets of ascending and descending scenes were acquired over a year-long period, using calibrated R-1 beams. Beam pattern measurements were compared against corresponding ones from the prime area. During the test, average radiometric deviations obtained demonstrated good potential for all areas: Prime Area: 0.55 dB Area 1-E: 0.45 dB Area 1-W: 0.59 dB Area 2-E: 0.33 dB Area 2-W: 0.42 dB 1-W 2-E 1-E 2-W P The Amazon in the RADARSAT Program

8 Thursday 04-Jun ASAR WORKSHOP 2011 Recorded acquisitions at the Amazon have long been known to potential be at risk for the R1 Calibration Plan due On-Board Recorder reliability. The Canadian Boreal Forest Site 2002: Following an Extended Mission Review, OBR was addressed as a concern and the R1 IQWG began investigating alternate distributed target sites within Canadian receiving masks (Gatineau, Prince Albert). 2003: Radiometric assessments were made of Tundra, Taiga and boreal forest areas A boreal forest area in the Hudson Bay basin, Ontario, was selected for further experiments. Northwestern Ontario landmass (Hudson Bay basin) Boreal spruce, balsam fir, jack pine, poplar, birch, tamarack, cedar © Canadian Space Agency

9 Thursday 04-Jun ASAR WORKSHOP 2011 Elevation beam pattern deviations are routinely monitored for EL1, S and W beams The beam pattern deviation measurements performed at the boreal forest site are considered as a worst-case performance indicator. In summer, this upper bound to the radiometric deviation is as follows: EL1: <1.4 dB S beams: <0.6 dB W beams: <0.7 dB The Canadian Boreal Forest Site

10 Thursday 04-Jun ASAR WORKSHOP 2011 Antarctica: Dome-C Potential calibration site for microwave sensors (CEOS WGCV Plenary, 2008). R-1 data were first acquired in 2008 to survey the site at various spatial resolutions. R-2 acquisitions commenced later in Locate a suitable area for longer-term data collection; 2.Characterize, in like and cross pol, the backscatter range profile – monitor backscatter variations with pass orientation; 3.Derive a backscatter range model of the area and perform elevation beam pattern measurements. Dome C High-latitude offers frequent revisits; Light wind and stable wind patterns: temporal stability of possible surface patterns, smoothness; Acquisition campaigns were undertaken by the CSA to examine the site at C-band and report to the CEOS.

11 Thursday 04-Jun ASAR WORKSHOP 2011 Antarctica – Dome-C area 300 km Dome- C Concordia Station R-2 SCWA HH data - Backscatter profiles Featureless terrain: N, NW and SW of Concordia station RADARSAT-2 Data and Products © MacDONALD, DETTWILER AND ASSOCIATES LTD All Rights Reserved RADARSAT is an official mark of the Canadian Space Agency

12 Thursday 04-Jun ASAR WORKSHOP 2011 Antarctica – Dome-C area Fine data acquisitions around Concordia Station (50 x 50 km) HH+HV Ascending Various incidence angles Descending Various incidence angles

13 Thursday 04-Jun ASAR WORKSHOP 2011 Antarctica – Dome-C area  (dB) Incidence Angle (deg.) Backscatter profiles from R-2 Fine beams, HH AmazonDome-C Incidence Angle (deg.)  (dB) A backscatter model was derived for elevation beam pattern measurement tests Fine beam datasets were acquired over a one year period, around Concordia station: Measurements give an average radiometric deviation of 0.41 dB, Amazon measurements on similar beams give 0.39 dB; Standard deviation at both areas is around 0.25 dB.