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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

●

●

●

●

●

●

○

○