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Advanced Synthetic Aperture Radar (ASAR)

Source: http://darc.nerc.ac.uk, access on 28th, Apr. 2010 Source: http://mtp.jpl.nasa.gov, access on 28th, Apr. 2010 (modified)

The ASAR instrument is operating at C-band and provides both continuity to the ERS-1 and ERS-2 mission SARs and next generation capabilities in terms of coverage, range of incidence angles, polarisation, and modes of operation. The resulting improvements in image and wave mode beam elevation steerage allow the selection of different swaths, providing a swath coverage more than 400km wide using ScanSAR techniques. ScanSAR is a Synthetic Aperture Radar (SAR) technique that combines large-area coverage and short revisit periods with a degraded spatial resolution compared to conventional SAR imaging modes. ASAR can provide a range of incidence angles ranging from 15° to 45° and can operate in alternating polarisation mode, providing two polarisation combinations (VV and HH, HH and HV, or VV and VH). The ASAR is onboard the EnviSat satellite, which was launched into a sun-synchronous orbit in March 2002. The exact repeat cycle for a specific scene and sensor configuration is 35 days. ASAR coverage for the Murrumbidgee Catchment is summarised in the table below. ASAR data can be downloaded from ESA.

Mission ASAR
Sensor Advanced Synthetic Aperture Radar (ASAR)
Spacecraft Envisat
Launch date 1st, Mar. 2002
Design life 3 years with a goal of 5 years
Orbit Sun-synchronous polar orbit (SSO): Nominal reference orbit of mean altitude 800km, 35 days repeat cycle, 10:00am mean local solar time (MLST) descending node, 98.55°. inclination. [envisat.esa.int]
Spacecraft operations control centre ESA
Frequency (GHz) 5.331 (C-Band)
Mode Image mode Alternating polarisation Wide swath Global monitoring Wave mode
Polarisation HH or VV HH/VV or HH/HV or VV/VH HH or VV HH or VV HH or VV
Incidence angle (°) 15 ~ 45
Swath (km) <= 100 <= 100 >= 400 >= 400 5×5 (vignette)
Spatial resolution (m) 30 ~30 150 1000 30
Temporal resolution 35 days repeat cycle

ASAR overpass time

ASAR coverage for the Murrumbidgee Catchment during the AACES-2 campaign has been calculated by a Fortran program based on NORAD data for 29th, Aug. 2010, and is summarized in the table below. Date and time are in UTC. Aircraft flights were assumed to be conducted at 7:45 for descending overpass and 20:35 for ascending overpass.

  : Transect flight within 6 hours   : Patch flight within 6 hours
: Fully covered : Partially covered

UTC Date Start UTC Time Duration (s) Flight Patch
1 2 3 4 5 6 7 8 9 10
2010/09/08 12:42:41 83        
2010/09/08 23:56:14 76        
2010/09/11 12:48:29 78            
2010/09/12 0:01:55 76              
2010/09/12 23:30:51 55 P04                
2010/09/14 12:54:17 63                  
2010/09/15 0:07:44 54                  
2010/09/15 12:22:32 71                
2010/09/15 23:36:18 76              
2010/09/18 12:28:10 81            
2010/09/18 23:41:57 77 P06      
2010/09/21 12:33:56 82      
2010/09/21 23:47:40 76 P08  
2010/09/24 12:39:44 83      
2010/09/24 23:53:21 76      
Created: September 2010
Last Modified: September 2010
Maintainer: YE Nan, Ye.Nan@monash.edu