AN ADVANCED HIGH RESOLUTION OPTICAL SENSOR FOR SMALL SATELLITE MAPPING MISSIONS David Purl, Mike Cutter Alex da Silva Curiel Dr Wei Sun Sir Martin Sweeting ©SSTL Contents • Overview of Beijing-1 project – Mission –Instrument – Next generation instrument • Mission status –Applications ©SSTL 2 Advancing smallsat capability • World-leading performance in small satellites – Best GSD achieved for the size spacecraft – Lowest cost spacecraft to achieve this GSD • Beijing-1 <US$15m (all incl.) • TOPSAT <US$23m (all incl.) High resolution EO mission GSD achieved for a spacecraft mass Mission Launch GSD Mass 6 QuickBird-2 2002 0.61 980 IKONOS-1 2000 1 726 ORBVIEW-4 2002 1 368 5 IGS-1a 2003 1 850 ORBVIEW-3 2004 1 300 KOMPSAT-2 2005 1 470 4 Beijing-1 EROS-A 2001 1.8 280 EROS-B 2006 1.8 280 ) TOPSAT m Formosat-2 2004 2 764 ( D 3 SPOT-5 2002 2.5 3030 IRS-P5 (Cartosat) 2004 2.5 1500 GS TOPSAT - SSTL 2006 2.85 112 ALOS 2006 2.5 4000 2 RazakSat-1 2007 2.5 200 Earlybird 1998 3 310 OFEQ-5 2002 3 300 1 Beijing-1 - SSTL 2006 4 168 Lewis 1998 5 288 PROBA-1 2002 5 120 0 0 500 1000 1500 Mass (kg) ©SSTL 3 Constellations for EO • Existing EO satellites provide100 – High spatial resolution s) ay d – Good spectral discrimination ( Traditional Earth d Resources Missions •But… 10 – Poor temporal resolution Revisit perio – Very high cost Constellations Commercial Remote sensing 1 • Small Satellites SSTL Constellations – Very low unit cost of small satellites – Constellations of EO satellites become affordable – Capable of medium spatial 0.1 resolution and spectral 0.1 1 10 100 discrimination Spatial resolution (metres) ©SSTL 4 Beijing-1 project • Procurement by Beijing Land View Imaging Information Technology Company Ltd, and the Chinese Ministry of Science and Technology – US$18m contract (Development, Space segment, Ground segment, Launch and LEOP) • Mission – Systematic mapping of China over a 5 year period • Including Olympics preparation – Participate in Disaster Monitoring Constellation (DMC) ©SSTL Jul03 – contract start Launch - Oct055 Beijing-1 mission • Specifications – Up to 15 minute of continuous mapping operations per orbit • 4m Panchromatic data acquisition •Data downlinking – Operate as part of Disaster Monitoring Constellation • 32m multispectral ©SSTL 6 Beijing-1 Platform • 166kg, Enhanced SSTL microsatellite • Dual redundant avionics • 5 year design life • S-band TM/TC •Power – Body mounted arrays, triple junction GaAs – 50W OAP generated •Data Handling – Flexible Control and Updating of On-Board Software from the Ground Station • High performance ADCS – Stable and Flexible Attitude Control for Off-Pointing Imaging – Off-nadir pointing • ±30º Roll – Control 0.1 º (3-σ), stability 2.5mdeg/s • Orbit control and determination –GPS navigation – Xenon electro-thermal propulsion, 17m/s – Maintenance in constellation with DMC ©SSTL 7 Payload • High resolution payload – 4-metre GSD pan (SIRA Ltd) – 24km swath width 3,000km swath length – 40Mbps X-band downlink – On-board data compression – 3 Gbytes solid-state storage – 240 Gbytes hard disk storage system • DMC payload – 32-metre GSD multi-spectral (3-bands) – >600km swath width – 8Mbps S-band downlink – 1.5Gbytes Solid State Storage ©SSTL 8 Payload block diagram SSDR Solid State Data Recorder NV-DR Non-Volatile Data Recorder MS IMGR PAN DSP RTR Digital Signal Processor / Router PAN Panchromatic imager MS IMGR Multispectral imager OBC386 On Board Computer NV-DR DSP RTR DSP RTR NV-DR RF Receivers 2x CAN OBC386 OBC386 SSDR SSDR SSDR SSDR 512Mb 512Mb 1Gb 2Gb RF Transmitters RF Transmitters S-band X-band D/L D/L 20, 40Mbps ©SSTL 8Mbps 9 Payload Support • Image processor and compressor –DSP based – Software defined JPEG compression • Solid State Data Recorders – PowerPC based with SRAM technology • Hard drive data recorders – Flexible Use of Hard Disk for On Board Data Storage, to Get More Storage Space with Lower Cost and Lower Power Consumption – 240GByte • X-band downlink – 20+40Mbps – Flexible Downlink Mode for the Ground Station: •Real Time Mode • Store and Forward Mode ©SSTL 10 Mapping instrument • Panchromatic imager – Supplied by SIRA (acquired by SSTL in March 2006) – Sensor CCD Pushbroom, 8 micro pixels – Focal length 1.37m – Band 500-800nm – GSD 4m (@686km) – Swath 24km – Aperture 310mm ©SSTL 11 Mapping instrument • Compact, on-axis telescope, scalable design –GSD – Area on focal plane –No requirement for satellite motion compensation – Unlimited “on-time” • Low coefficient of thermal expansion providing good stability – Pseudo-Isostatic mount – Carbon fibre composite structure – Zerodur and fused silica optics – Invar optical mounts • Robust optical design – In-orbit adjustable focusing – Compatible with high vibration levels – Thermally isolated from platform ©SSTL 12 Imaging Payload Description • Overview – Digitisation 10 bits – SNR 140 (35º latitude and albedo of 0.3) – Mass 25kg – Power 12W – Volume 780x380x380mm ©SSTL 13 Performance achieved Parameter Required Achieved System MTF (Ground) GSD (m) 4 4 MTF, cross-track, 1° field Nyquist Swath (km) 24 24 1 0.8 Band (nm) 500-800 500-800 0.6 Band edge accuracy across FoV ±30 2 F (nm) MT 0.4 0.2 Energy in pass-band ≥ 90% 98% 0 MTF at Nyquist: Centre ≥ 15% ≥ 19.6% 0 102030405060 Edge ≥ 10% ≥ 13.6% Cycles/mm Signal-to-noise ratio ≥ 140 210 MTF, along-track, 1° field 1 Power (W) at 28V ≤ 25 24 0.8 Mass (kg) ≤ 12 11.9 0.6 3 Volume (mm ) except mounting 790x400x400 790x380x378 MTF 0.4 feet 0.2 0 0 102030405060 Cycles/mm Parameter Conditions Spectral response Orbit 686 km, sun synchronous,11:00 1.8E+05 LTAN, nadir pointing 1 1.6E+05 sr^- . Signal 0.3 albedo at 35° latitudeat 11:00 on 2 1.4E+05 ^- m 1.2E+05 March 21st c . W 1.0E+05 Temperatures at imager mounting panel:10°C ± 10° 8.0E+04 DU / ± 10° uncertainty-25°C to +60°C- A , 6.0E+04 e 50°C to +88°C s n o 4.0E+04 s p Vibration (qual) 21 grms random vibration 2.0E+04 Re 1 g2/Hz peak 0.0E+00 450 500 550 600 650 700 750 800 850 ©SSTL Wavelength, nm 14 Next generation payload Parameter Performance Bands Panchromatic Multi-spectral: 4-5 bands (R,[RE],G,B,NIR) Panchromatic GSD 2.5m Multi-spectral GSD 5.0m Imaging ground swath widths 20km PAN and 20km MS (700km) Modulation transfer function (MTF) Centre: >= 13% Nyquist, >=26% half Nyquist, Edge: >= 9% Nyquist, >=18% half Nyquist Signal to Noise Ratio (SNR) Panchromatic: 103 (2.5m GSD) Signal to Noise Ratio (SNR) Blue: 64 Green: 90 (5m GSD) Red: 70 Near Infra-Red: 100 ©SSTL 15 Launch •Oct’05 ©SSTL 16 Results from an operational mission Products and applications ©SSTL Data Products of Beijing-1 Level Descriptions File Format L1 Radiometric Correction RAW L2 Systematic Geometric Correction GeoTIFF L3 Precision Geometric Correction using GCPs GeoTIFF L4 Ortho-Rectification using DEM Data GeoTIFF L5 3D View Image Product using DEM data - L6 Fusion Image Product using 32m Multi- GeoTIFF Spectral Image and 4m Panchromatic Image ©SSTL 18 Examples of data products (L1 product: Radiometric correction of PAN data) Image Data before De-stripping Image Data after De-stripping Strip Noise is Removed using Statistical Method and Wavelet Method ©SSTL 19 Examples of data products (L1 product: Radiometric correction for MSI) Image Data before Image Data after Radiometric Correction Radiometric Correction Radiometric Correction of MSI includes Automatic Band Registration and ©SSTL MTF Restoration using Wiener Filter 20 Examples of data products (L2product: Systematic Geometric correction for MSI) L1: Radiometric Correction Product L2: Systematical Geometric Correction Product (1) Imaging in Ascend (2) Average Accuracy of Systematical Geometric Correction is 600 meters. ©SSTL 21 Examples of data products (L4 product: Ortho-rectivication for MSI) L3 Product + DEM Data L4: Ortho-Rectification Product (1) Average Accuracy is within 1 Pixel in Plain Areas (2) Average Accuracy is between 1 and 2 Pixels in Mountain Areas ©SSTL 22 Examples of data products (L3 product: Precision geometric correction for MSI) L2 Product＋GCPs L3: Precision Geometric Correction Product (1) Average Geometric Accuracy is within 1 pixel in Plain Areas (2) Average Geometric Accuracy is between 2 and 3 pixels in Mountain Areas ©SSTL 23 Examples of data products (L5 product: 3D View product using DEM data) ©SSTL 24 Examples of data products 32m multi-spectral image of Qinghai provice, China ©SSTL 25 Examples of data products 32m multi-spectral image of Tianjin Harbor ©SSTL 26 Examples of data products 4m panchromtic image of Beijing city ©SSTL 27 Examples of data products (L6: Fusion Product using 32m MSI and 4m PAN) ©SSTL 28 Examples of data products 4m panchromatic image of Tehran airport, Iran (Feb 06) ©SSTL 29 Examples of data products 4m panchromatic image of Cairo airport (Dec05) ©SSTL 30 Examples of data products Pan sharpened product of He Fei City, Anhi province, China) ©SSTL 31 Applications of Beijing-1 Image Products • Land Use / Land Cover Analysis • Environmental Monitoring • Precision Agriculture • Urban Dynamic Monitoring • Disaster Monitoring • Comprehensive Regional Management System ©SSTL 32 Example of data products China Map using Beijing-1 32m Multi-Spectral Images (Dec05-May06) ©SSTL 33 Conclusions • Small satellite EO capability now includes high resolution imaging • Beijing-1 operational – Commercial service provider – Excellent results, products and applications • Scalable, Robust Instrument design – Matched to microsat environment – 1-5m GSD (Pan) – 2-20m GSD (MS) ©SSTL 34 Beijing-1 – pan sharpened product ©SSTL 35.