CaSSIS. Colour and Stereo Surface Imaging System. L. Gambicorti & CaSSIS team

Transcription

1 CaSSIS Colour and Stereo Surface Imaging System & CaSSIS team

2 CaSSIS on Exomars TGO l l Introduction CaSSIS: stereo-colour camera Telescope and Optical configuration Best focus on ground CaSSIS integration Best focus on flight Conclusion 1

3 CaSSIS on Exomars TGO CaSSIS: push-frame mode images on the same detector Four colour filter bands are oriented with their longer dimension perpendicular to the ground-track direction Framelets with repetition rate synchronized to the ground track velocity overlap between successive framelets to permit accurate mosaicking 2

4 CaSSIS Stereo Approach 3

5 CaSSIS stereo camera Focal length 880 (+/-50) mm Entrance Pupil Diameter 135 mm Nominal F# 6.52 Pixel size (square) Angular scale Rotation axis-boresight angle Stereo angle from 400 km altitude Rotation time (180 rotation) Nominal slant distance to surface Scale at slant angle 10 μm μrad /px 10.0 (+/- 0.2) s km 4.62 m/px 4

6 CaSSIS Focal Plane Assembly Detector CMOS spare Simbio-Sys detector (Bepi- Colombo mission) of the Italian Space Agency (ASI), developed by Raytheon Vision Systems 2kx2k hybrid Si-PIN array, 10 μm pixel pitch Filters in monolithic Filter Strip Assembly (FSA) selects 4 colour bands produced by Balzers Optics Jena and integrated on the detector by Selex ES (under TAS-I responsibility) [SPIE ] 1.33 cross track 0.88 along track 5

7 SNR for Typical Exposure 6

8 CaSSIS Telescope TMA TMA (Three Mirror Anastigmatic) corrected for the 3 optical aberration: Spherical, Coma and Astigmatism Intermediate focal plane (a) and two intermediate walls (f and g) which subdivide the telescope into an upper compartment with M1 and M2 and a lower compartment with M3 and M4 separated with baffles to avoid direct light in to the detector through the field stop Ray tracing of CaSSIS 135 EPD optical system The powered folding mirror M4 allows maintaining compact design and telecentric system 7

9 1 fo E E E E91.1 noitarugifnoc pam dleif sevaw SMR = = Y mµ xam = X = SMR nim dleif Telescope focal plane: WFE Requirement MTF>0.3 on FoV 1.33 cross track 0.88 along track corresponding to a mm x mm area on the image plane of the detector The wavefront error (WFE) at 632 nm is measured at 12 different detector positions with EPD 100 mm interferometer SISSaC 4102/40/90 :ecafrus ezis :htgnelevaw, egami , )rotceted( SMR tnorfevaw seerged 200-E E E E E E E21.9 x m z. 2 _ v o f _ 4 1 _ 2 0 _ 4 1 _ 4 I S - X Z - L M - L E T - S I S S a C PSF diameter wrt wavelength (Diffr limited ) 400 nm 6.35 micron (0.6 pixel) 650 nm 10.3 microns (1 pixel) 1000 nm 15.9 microns (1.6 pixel) 9

10 OGSE OGSE to integrate detector and to test the optical performances of CaSSIS (10 um) The collimated beam of 147 mm-diameter Off Axis Parabola (OAP) and a 10 µm pinhole is illuminated with either white (Quartz Tungsten Halogen) or monochromatic (10 nm FWHM bandpass) light. On vertical config to minimize the gravity effect 10

11 The CaSSIS Telescope CaSSIS telescope CFRP structure with baffles and the optical cube alignment before the detector integration 11

12 Best Focus procedure l l l l l l The pre-alignment of CaSSIS with the OAP optical axis was achieved using a theodolite alignment technique Through-focus along axis Z (20 C and under gravity)oap-pinhole axis and acquired images For each position of pinhole the PSF FWHM is fitted with 2D Gaussian function Best focus to be set to where PSF has the same dimensions contemporary on x and y of detector (spot circular) [in pixel] Residual astigmatism is collimator induced due to mounting tensions Double check with Zygo interferometer used as a collimator with Hartman mask (sub pupil 50 mm) curves fits 2 rd degree polynomials PSF ~ 1.6 px (FWHM) 12

13 FPA positioning on Best Focus PSF FWHM and best focus on the corresponding 12 different positions on detector A magnification factor, ratio of the respective focal lengths of the OAP and CaSSIS telescope was then applied to calculate the defocus distance of the CaSSIS detector 13

14 Environmental testing 14

15 CaSSIS in TGO Cassis in TGO encapsulated into the rocket (8 March 2016) Launched 14 March

16 Best Focus on ground Best focus acquired during the on ground calibration PSF FWHM 1.75 px Best focus for the first light acquired during the pointing commissioning PSF FWHM 1.2 px 17

17 Evolution of the PSF as CaSSIS thermal control stabilizes the telescope 18

18 What will do CaSSIS The second highest resolution imager flying to Mars (after HiRISE). The most capable high resolution colour imager combining 4 bands (HiRISE = 3) >9.4 km colour swath (HiRISE = 1.2 km) 4.6 m/px (HRSC > 12 m/px) The highest resolution imager designed for stereo It will complement previous imagers and the other TGO payloads perfectly 19

19 What CaSSIS shows First image of Mars during Mid cruise (13 June 2016) 41 million km 467 km/px 15 px across NIR filter 1.9 ms exp. time 13 deg phase angle 20

20 Roughly right.. 21

21 Schedule 16 October. Release of Schiaparelli. Done! 19 October. Mars Orbit Insertion Schiaparelli landing on surface. s/watch_exomars_arrival_and_landing November. First images in orbit. (1-2 December. ESA Ministers Conference) March Start of aerobraking. ~December Start prime mission. ~February End prime mission. 22

22 UniBern team Thanks to the spacecraft and instrument engineering teams for the successful completion of the instrument 23

23 Acknowledgement ESA European Space Agency CaSSIS is a project of the University of Bern and funded through the Swiss Space Office via ESA's PRODEX program. Italian Space Agency (ASI) (ASI-INAF agreement no. I/018/12/0), Leonardo-Selex ES, INAF/Astronomical Observatory of Padova, and the Space Research Center (CBK) in Warsaw

24 THANKS