A 1m Resolution Camera For Small Satellites

Transcription

1 A 1m Resolution Camera For Small Satellites Paper SSC06-X-5 Presenter: Jeremy Curtis 1

2 Introduction TopSat launched October 2005 carrying RAL s 2.5m GSD camera into a 686km orbit Built and operated by consortium: SSTL, RAL, QinetiQ and InfoTerra Over 500 usable images, operating continuously for 9 months Success has encouraged RAL to set-up a commercial business to exploit this technology New company (Orbital Optics Ltd) has initiated development of 1m GSD camera 2

3 Typical mission for 1m camera Mission Altitude Orbit Lifetime ~ 600km Sun-synchronous ~ 10:30 LTAN 5 years Spacecraft per launcher 3 Camera GSD Swath width Target mass Imaging method Channels 1m >10km <40kg (excluding on-board storage) Bushbroom, no pitch compensation Panchromatic R,G,B & NIR (desirable) 3

4 Optics Design Short trade-study of optical designs undertaken Scaling the TopSat optical design (a TMA) would not lead to a particularly compact camera design Build spacecraft around the camera - on-axis cylindrical design best 4

5 Optics Design Ritchey-Chrétien design with a three lens corrector group selected Focal plane sized for four identical CCDs R, G, B and NIR (pan can be achieved by combining the RGB channels) Lightweight Zerodur mirrors for primary and secondary mirrors 4 Detectors & filters -NIR -RED - GREEN -BLUE ~0.5m ~1.1m 5

6 Detector Electronics TDI CCDs needed to get sufficient exposure without pitching spacecraft Commercial CCD with 12,228 pixels (8µm), and 96 selectable TDI stages At 600km altitude it takes 145µs to traverse 1m - readout rate >10.6Mpixels/s through each of eight output amplifiers Pixel data contained within 2 bytes, so data rate for each output amplifier is 21.2 Mbytes/s Overall data rate for all four CCDs will be Mbytes/sec (a CD per second!) 6

7 Detector Electronics Packaging Enclosure ADC board CCDs 8 Spacewire connections per board 7

8 Structure Design Primary structural components made from low CTE composite material (graphite epoxy), based on TopSat heritage Stability requirements relaxed through the use of adjustable (on-orbit) M2 mirror assembly Actuators located outside of the aperture preventing any further obscuration of the system Two options for mounting the spacecraft possible: one inside a central cylinder, and the other to a flat panel Breadboard model of primary structure and mirror adjustment mechanism under design. Plan is to build and test these items early to de-risk the flight model programme 8

9 Structure Design M2 adjusters Baffle Metering Tube Focal Plane Assembly M2 Mirror Cell M1 Support Plate 9

10 Section View 10

11 Primary Mirror Design Machining of Zerodur has advanced considerably and it is now possible to achieve a high degree of light-weighting at relatively low cost Ø480mm Method Mass (kg) % Lightweight Honeycomb Pocketing Double arch Primary mirror with pockets 11

12 Spacecraft Layout Two cameras plus spacecraft under a Kosmos-3M fairing. Could possibly accommodate a third spacecraft on an upper platform. 12

13 Mass Budget Item Mass (kg) M1 assembly 13.7 Bulkhead assy. 4.2 Lens barrel assy. 4.2 FPA & Ebox. 2.9 M2+spider assy. 3.7 Tube assy. 4.3 Camera mounts 2.7 Actuators + harness 1.5 Thermal subsystem 2.0 Total

14 Technology Transfer 2.5m imagery from a small satellite has been demonstrated Technology and IPR has been spun out of CCLRC-RAL into a commercial company CCLRC retains majority shareholding (~ 40% is held by investors and TopSat inventors) Investment into the new company has enabled a 1m GSD breadboard programme to be started, with the majority of work subcontracted back to CCLRC- RAL Orbital Optics Ltd will develop and market a range of low cost camera solutions, and will eventually become less dependent on CCLRC-RAL for development support Washington, USA 31 st Mar 06 14

15 The future Low cost cameras and platforms will make constellations affordable, allowing greater global coverage than is currently possible with a single platform The 1m camera design will be complete by the end of August, with the hardware expected to take about 6 months to procure. A test programme will start early next year, to confirm the primary structure stability and the effectiveness of the M2 adjustment system Dartford, London 7 th Dec 05 15

16 Contacts Jeremy Curtis Rutherford Appleton Laboratory John Ellis Orbital Optics Limited 16