1. OMEGA GROUND CALIBRATION B. Gondet,Saint Louis, 21/05/2008

2. Optical test bench OMEGA was mounted on a two axis platform 0.1 mrad in both site and azimuth (0.1 IFOV) Cold sink for regulating the operating temperatures light sources: - monochromator (spectraPro 275) the grating can be set as a mirror - tungsten ribbon lamp (Russia) brightness temperature from 2500 K to 2850 K five filters with different transmission profiles pinhole point source (steps of 0.05 IFOV) sample holder - black body, from 325 K to 1400 K (Galaï – 1200 BB) circular aperture covering 4 IFOV’s - grid of 4 x 4 IFOV-sized black bodies (Galileo) - cold plate, from 150 K to 293 K OMEGA calibration plan spectral calibration photometric calibration influence of detector temperature and spectrometer temperature linearity geometric calibration co-alignment, registration stray light reference targets

3. OMEGA IN THE CALIBRATION TANK

4. THE OPTICAL BENCH

5. 1.Spectral calibration (lambda.dat)

6. TspectroT det (IR)Position in the FOV -90°C 20°C 5 -90°C 20°C 1 (center) -80°C -195°C 5 -80°C -195°C 1 (center) -70°C -195°C 3 -95°C 20°C 3 VNIR (100 &200) ms TspectroTdet (IR)Position in the FOV -90°C-195°C3 -80°C-195°Ccenter -70°C-195°C3 -90°C-191°Ccenter -90°C-198°Ccenter -90°C-200°Ccenter -90°C-197°Ccenter -90°C-193°Ccenter -90°C-188°Ccenter SWIR (2,5 ms & 5ms) List of spectral calibration performed using the monochromator

7. Procedure and examples of results for SWIR Tspectro = -90°C Tdet = -195°C Tspectro = -70°C Tdet = -195°C

8. Spectel number Nanometers SWIR-L spectral calibration as a function of position in the FOV right of FOV left of FOV

9. Spectral match between OMEGA Earth spectrum, and "MODTRAN" simulated SWIR-C SWIR-L

10. 2. radiometric calibration mtfYYMM_25.dat (2.5 msec, release of year YY, month MM) mtfYYMM_50.dat ( 50 msec, release of year YY, month MM)

11. Operational parameters Hot Black body source temperature, varying from 9°C to 1175°C Cold BB temperature from 10°C down -120°C IR detector temperature from –201°C to –188°C (-195°C nominal) Integration time = 2,5 ms, 5 ms & 10ms for SWIR = 100 ms & 200 ms for VNIR Test at several positions in the FOV

12. 197°C 295°C 368°C 523°C saturation low S/N Signal in DN divided by the corresponding black body flux DETERMINATION OF THE PHOTOMETRIC FUNCTION (C CHANNEL)

13. Photometric response of OMEGA VIS SWIR C SWIR L Bright region Dark region S/N ratio for observations of Mars Phase = 0°, surface temperature = 250 K Wavelength (µm)

14. INFLUENCE OF THE TEMPERATURE OF THE SPECTROMETER For OMEGA, photons remove electrons from pre-charged wells The available dynamics decreases rapidly with the temperature of the spectrometer beyond 4.5 µm, in particular for long integration times (5 msec) This is essential for the detection of sulfates 200 K 190 K 175 K Solid line: 5 msec Dashed lines: 2.5 msec Wavelength (µm)

15. 3. geometric calibration

16. "AZIMUTH" = pitch: spacecraft motion "SITE" = yaw: SCANNING MIRROR motion SLIT Point Source (ribbon lamp, grid Officine Galileo) Geometric calibration

17. "Site", scanning mirror Azimuth, spacecraft motion

18. 1.IFOV for each spectel, for each of the 128 spatial directions 2.perpendicular to the slit ("azimuth") direction - for each channel, relative variation of the viewing direction along the spectrum, for each IFOV within the entire 128 px FOV - spectral registration for the 3 channels, and each of the 128 positions 3.along the slit ("site") direction - relation between the IR swath position and the VNIR column number - spectral registration for the 3 channels, and each of the 128 directions Geometric calibration files

19. IFOV = f(wavelength), at the center of the FOV

20. 12 pixels l l l l.45 µm 1. µm 2.5 µm 5 µm (Y,λ) maps of a point source scanned in azimuth VNIR SWIR-L SWIR-C

21. IRCIRLVIS (i,j) (i,j-/+n)(i-/+m,j-/+n)

22. REGISTRATION : creation of false feature in case the viewing direction of # spectels would be as follows…  …we would end up with a misinterpretated spectral feature

23. REGISTRATION EFFECTS along the azimuth

25. 4. Stray light

26. Measurements made: ± 30° ("site") ± 40° ("azimuth") Source: ribbon lamp, full power No stray light detected

27. 5. Reference samples

28. Samples used: "ISM " samples "NASA" samples "Lecce" samples Source: Ribbon lamp Integration times: 2.5 ms, 5 ms, 10 ms (SWIR) 100 ms, 200 ms (VNIR) Number of files acquired : 140

30. Calcite Montmorillonite Gypsum Diopsite Fayelite Labradorite Magnetite wavelength (micrometers)