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A New SAR Sensor designed for µ-Satellites
Prof. Dr. Hans Martin Braun
RST Radar Systemtechnik GmbH, Germany
1© RST, [email protected]'10, Honolulu
Content
Introduction
Image Quality Desires
Limits for µSAR
Available Frequency Bands
µ-SAR Sensor Trade Off
µSAR Design
SAR Parameters & Performance
Outlook
© RST, [email protected] 2IGARSS'10, Honolulu
Introduction
Space-borne SAR started with SEASAT in the 70th
Manny Countries followed with mostly 3 intensions Scientific Applications (e.g. SIR-C / X-SAR, SRTM, JERS, …..)
High Resolution Security Applications (SAR-Lupe, COSMO Skymed, TECSAR)
Environmental Monitoring (ENVISAT, RADARSAT, ….)
Space-borne SAR Sensors for medium resolution need large antennas big countries & organizations
Space-borne SAR Sensors with small antennas realize high resolution and need high sophisticated platforms and complex SAR Processors big countries & organizations
SAR Sensors for µSATs made by Small Countries and Universities ?
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Image Quality Desires
Parameter Value
Spatial Resolution ≥ 30 x 30 m2
Swath Width ≥ 30 km
Swath Length Continuous(limited only by battery or storage capacity)
NESZ at Swath Edge ≤ mean grass
Center Frequency t.b.d. (vegetation penetration desired)
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Limits for a µSAR
Dimensions of launch package ≤ 1 m3
Antenna dimensions ≤ 3 m x 1 m Power to payload ≤ 100 W average Total mass ≤ 100 kg
Mass for payload 40 – 50 kg
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µSAR Design Procedure
Use maximum antenna dimensions allowed
Select frequency as low as possible for desired swathwidth
Select range of incidence angles
Analyze required Doppler Bandwidth for desired resolution
Check / optimize ambiguity levels in Azimuth & Range
Select required RF-Bandwidth for Resolution & 4 Multi Looks
Analyze required power for NESZ desires
Check compliance of the design with µSAT capabilities
Trade / optimize parameters for best suitability
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SAR Processing Solution for reduced PRF
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Filtering Doppler Bandwidth allows operation with reduced PRF Keeping high Ambiguity Suppression For Required Spatial Azimuth Resolution
SAR Parameters (1)
Parameter Value
Center Frequency: S-Band 3.2 GHz
Bandwidth 15 MHz
Bandwidth for 4 Range-Multilooks 60 MHz (option)
Antenna Dimensions (LxW) 3.0 x 1.0 m2
Satellite dimensions (LxWxD) 1.0 x 1.0 x 0.4 m3
Pulse Repetition Frequency 4 kHz
Doppler Bandwidth after filtering 500 Hz
Peak Output Power 1 kW
Pulse Length 10 µs
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SAR Parameters (2)
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Parameter Value
Duty Cycle 4 %
Average Output Power 40 W
DC Power < 200 W
Ambiguity Level in Azimuth < - 20 dB
Ambiguity Level in Range < - 20 dB
Flight altitude over equator 460 km
Range of Incidence Angles 20 deg – 40 deg
Outlook
A Design of this kind will allow young teams of satellite engineers to start working with SAR Payloads on µSATs
Scientists in Universities of small countries will get their own satellites for contributing to the international SAR community
World-wide knowledge on spaceborne Radar Techniques will significantly increase with these capabilities
Small countries will be able to significantly contribute to international environmental monitoring and to disaster monitoring with their own satellites
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