Calibration Concepts for Future Low Frequency SAR Systems Jens Reimann, Marco Schwerdt, Sravan Kumar Aitha and Manfred Zink
DLR.de Chart 2 Low Frequency SAR Missions OHB
DLR.de Chart 3 BIOMASS - Facts ESA Living Planet Program Frequency: P-band (435 MHz) Antenna: 12 m Offset-Reflector Polarization: Quad-Pol Abs. Radiometric Bias: 0.3 db (1σ) Spatial Resolution: about 60m
Parameter Value Comments No. Satellites 2 Bistatic operation Orbit Height 745km 231 cycles /16 days Frequency L-band Available Frequency band 1215 1300 MHz Bandwidth Up to 80 MHz Split Frequency Modes for Ionospheric corrections Look direction right & left Reflector Diameter 15 m Deployable Reflector with 10m Boom Polarization single/dual/quad Optionally compact pol
DLR.de Chart 5 Tandem-L: Antenna Concept Digital Feed-Array
DLR.de Chart 6 Tandem-L: Scan-On-Receive
First Calibration Approach for Tandem-L Internal Calibration Absolute Calibration Bistatic Calibration Target Development Analogue HW Characterization Digital Compensation Antenna Model Physical Antenna Model 64 Beams (H & V) Polarimetric Calibration DBF Antenna Model some thousands of Beams Geometric Calibration SAR Processor Antenna Pointing
DLR.de Chart 8 Low Frequency SAR Calibration Challenges Huge Target Size Large Reflector Antenna Ionosphere
DLR.de Chart 9 > Calibration Concepts for Future Low Frequency SAR Missions > Jens Reimann 08. September 2016 Calibration Targets: P-band BIOMASS Cal-Targets Corner Reflectors are impractical (60 dbm² = leg length 18 m ) BIOMASS Transponder with large and heavy 4 m x 4 m Planar Antenna High costs especially due to complicate Positioner
12.31cm DLR.de Chart 10 > Calibration Concepts for Future Low Frequency SAR Missions > Jens Reimann 08. September 2016 Alternative Calibration Target for P-band 12.7 cm DLR developed compact & light Horn Antenna Prototype at C & L-band Manufactured using 3D Printing Dispersible, but Reproducible Construction C-Band Prototype of printed Horn Antenna Gain: 14.9 dbi at C-band Cross-Polar Isolation: > -40 db
DLR.de Chart 11 > Calibration Concepts for Future Low Frequency SAR Missions > Jens Reimann 08. September 2016 Performance of Printed C-Band Horn Antenna
80 cm DLR.de Chart 12 > Calibration Concepts for Future Low Frequency SAR Systems > Jens Reimann > 09. June 2016 Printed Corrugated Horn at L-Band 70 cm
1.58 m DLR.de Chart 13 > Calibration Concepts for Future Low Frequency SAR Missions > Jens Reimann 08. September 2016 Printed Horn Antenna: Comparison conventional printed Antenna 12.4 kg 1 kg 64 cm 20 cm > 10x lighter > 3x shorter Comparison C-Band Antennas 2.03 m P-Band
DLR.de Chart 14 Low Frequency SAR Calibration Challenges Huge Target Size Large Reflector Antenna Ionosphere
DLR.de Chart 15 Large Reflector Antenna Issues Large Reflector Antenna Mechanical Stability Pointing & Antenna Pattern Knowledge
DLR.de Chart 16 Pattern Simulation: Tandem-L Performed using TICRA s GRASP Simulation of Tx Beam and 32 Physical Rx Beams Simulation of Disturbances Comparison of Disturbed and Non-Disturbed Configuration
DLR.de Chart 17 Pattern Simulation Results: Reflector Roll Offset of 0.033 Phase Difference Cross-Pol Power Difference Power Difference Nominal Pattern of Rx Beam No. 32 db caused by Disturbance deg db db
DLR.de Chart 18 Tandem-L Hardware Facts 5 Simultaneously Recorded Receive Channels in HW Arbitrary Combination & Weighting of Feed Elements No. of Required HW Channels dependents on PRF Swath Width Pol-Mode Topography Sometimes HW Channels are unused
DLR.de Chart 19 Permanent Pointing Monitoring - Theory Used as Notch Beam Receive Beam Blind Range Receive Beam outside the swath Range
DLR.de Chart 20 > Calibration Concepts for Future Low Frequency SAR Systems > Jens Reimann > 09. June 2016
DLR.de Chart 21 Permanent Pointing Monitoring - Example Question: Pointing Determination outside Amazon Rainforest feasible? Experimental Acquisition using TerraSAR-X/TanDEM-X Satellite Pulse-to-Pulse Switching between Nominal & Notch Beam (Aperture Switching) Two Images of the same Scene with different Antenna Pattern Mitigate Influence of underlying Scene
Average along Azimuth DLR.de Chart 22 Permanent Pointing Monitoring Preliminary Results I Nominal Beam Notch Beam Thanks to DLR IMF for Processing!
Average along Azimuth DLR.de Chart 23 > Calibration Concepts for Future Low Frequency SAR Systems > Jens Reimann > 09. June 2016 Permanent Pointing Monitoring Preliminary Results II Difference Image
DLR.de Chart 24 Challenges in Calibrating Low Frequency SAR Mission Investigation & Development of Suitable Antenna Cal-Targets in P- & L-Band First Calibration Approach for Tandem-L Antenna Pattern Simulations Novel Technique for Permanent Notch Beam Acquisitions First Assessment of Pointing Determination with Mitigated Scene Influence Dr.-Ing. Jens Reimann Wissenschaftlicher Mitarbeiter Kalibrierung Telefon +49 8153-28-3595 Telefax: +49 8153-28-1449 jens.reimann@dlr.de Deutsches Zentrum für Luft- und Raumfahrt e.v. (DLR) Institut für Hochfrequenztechnik und Radarsysteme Oberpfaffenhofen Münchener Straße 20 82234 Weßling Abteilung: Satelliten-SAR-Systeme
DLR.de Chart 25 Tandem-L: Staggered SAR Blind Range