Large FOV Mobile E-O Telescope for Searching and Tracking Low-earth Orbit Micro-satellites and Space Debris

Transcription

1 Large FOV Mobile E-O Telescope for Searching and Tracking Low-earth Orbit Micro-satellites and Space Debris WANG Jian-li, ZHAO Jin-yu, ZHANG Shi-xue Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences

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3 Outline Introduction Large FOV mobile E-O telescope conceptual design Optical system Optical primary mirror Tracking mount and trailer Image processing Operation mode Detection capability analysis Conclusion 3

4 Introduction With the fast increment of space activities, more and more small satellites and debris appeared in low orbits. Debris larger than centimeter can severely damage the space satellite, so there is an urgent requirement for the detection and tracking of small space debris (1~30cm) in LEO. The main instruments for ground-based space objects detection and tracking are radar and E- O telescope. E-O telescope is more sensitive. 4

5 Introduction Determined orbit LEO objects tracking is easy. But Undetermined objects searching and tracking is a big challenge for E-O telescope because of narrow FOV. We propose a large field of view telescope that can search and then track undetermined objects. 5

6 Introduction The example of searching and tracking LEO objects. 6

7 Introduction We propose a large FOV mobile E-O telescope conceptual design for searching and tracking loworbit micro-satellites and space debris. When space objects are collided or broken, the telescope can be transported to the proper observing place immediately. 7

8 Large FOV mobile E-O telescope conceptual design We use primary focus optical system, and the effective aperture is 1.2m. The FOV is 2.8 (diagonal), and 80% of the energy concentration is within 24µm. Primary mirror uses lightweight SIC materials, and the 1.2m SIC mirror weighs only 100kg. Use a lightweight truss frame alt-azimuth tracking mount. Use the design ideas of trailer integration, and the rotating part of the telescope weighs not exceeding 2.5 tones. Use Hawes transform to improve the system detection capability and the automatic data processing. Trailer-based mobile telescope. 8

9 Optical system optic system diagram spot diagram 9

10 Optical system modulation transfer function (MTF) encircled energy 10

11 Optical system parameters Pupil diameter: 1200 mm Focal ratio: F = 1.17 Focal length: f = 1400 mm Detection FOV: FOV = 2.8 (diagonal) Focal Plane Size: mm MTF: 0.62 (@ 21lp/mm) RMS spot diffusion radius: <12 μm 80% of the energy concentration radius: <12.2 μm Optical tube length: mm Back focal distance: mm 11

12 Optical primary mirror The materials of optical primary mirror adopt lightweight RB-SIC developed by CIOMP. The 1.2m SIC primary mirror is only 100kg, and it greatly reduces the weight of the primary mirror supporting structure. 1.2mSiC light weighted primary mirror 12

13 Tracking mount and trailer The telescope s tracking mount uses truss structure. The enclosure is mounted on the trailer. Telescope and trailer 13

14 Image processing Use Hough transform to identify the object when blind search. Simulated result of target detection at 2:1 SNR Test with GEO objects 14

15 Operation mode Stare at the interested orbital plane and waits the objects flying into the FOV. Once the objects is detected, the telescope then changes to tracking mode to chase the objects. Moving along the interested orbital plane to search the objects. Tracking the objects with course forecast orbit and scanning to find the objects. 15

16 Detection capability analysis Total detection signal strength: SNR: NetSignal = Sky S + D C + S SNR 2 Rn SkyS DC S Relation equation between object signal strength and other factors: S S SNR SNR SNR Rn DC SkyS 2 4( ) 16

17 Detection capability analysis System parameters value System parameters value CCD 2Kx2K System obstruct 10% Pixel size 24μm Telescope focus primary focus CCD readout noise 15e -1 Spectral range 400nm~700nm Dark current can be ignored Optical coating standard aluminum Quantum efficiency 80% SNR 2:1 F number 1.2 Sky brightness 21 mag / arcsec 2 Telescope aperture 1.2m Observations angle zenith 17

18 Detection capability analysis Detection capability on different low orbits of our 1.2m large FOV telescope 300km: better than 13.5 magnitude 500km: better than 14.2 magnitude 1000km: better than 15.1 magnitude 18

19 Conclusion We propose the use of large FOV optical design, lightweight primary mirror material, and lightweight compact structure design, to meet the requirements of trailer-based mobile large FOV searching and tracking telescope. It can meet the practical requirement for searching and tracking low-orbit micro-satellite and small debris. This mobile large FOV searching telescope can be deployed in the proper place easily when burst thing happens such as collision or broken events. 19

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