ICSO 2012 / Imagers and Radiometers First inflight results of Pleiades-1A innovative methods for optical calibration Philippe KUBIK Octobre 9 th, 2012 philippe.kubik@cnes.fr Titre du document + date Arial 8 à modifier dans le masque (Affichage/Masque/Masque des diapositives)
The PLEIADES mission and system PLEIADES commissioning goals Scope The agile revolution : a new era of calibration In-flight results of innovative methods Conclusion 2
from SPOT to PLEIADES SPOT4 SPOT5 PLEIADES SPOT2 SPOT1 swath 60 km, 2 instruments East/West tilt +/- 27 SPOT 1-4 : 10m PA, 20m XS SPOT 5 : 2.5m PA, 10m XS swath 20 km, 1 instrument agile Satellite 70 cm PA, 2.80 XS 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 SPOT1 SPOT2 SPOT3 SPOT4 SPOT5 2010 2012 PLEIADES 3
Pleiades Main Mission Requirements Image characteristics 0.7 m Pan resolution at nadir four XS bands (blue, green, red, near IR) with 2.8 m resolution at nadir 20 km swath at nadir data coded on 12 bits Revisit Capability Daily accessibility to any point on the globe (with 2 satellites) Improved access image delay Better than 24 hours between image request and image delivery in nominal mode and even better, 1 hour, with Direct Tasking Large coverage capability In average 350 segments per satellite and per day with only Kiruna and Toulouse ground stations and even better with Regional Image Receiving Stations Normalized spectral sensivity Pleiades spectral bands Wavelength 4
Instrument exploded view Korsch type telescope focal length = 13 m input diameter = 65 cm 5
Arrays on PLEIADES 5 x TDI PA: 6000 columns x 20 lines, 13 µm 8 cm 20 lines 13 cm 5 x 4-color XS detector: 1500 columns, 52 µm Blue Green Red NIR 6 Distance inter-xs: 936 µm ~18 lines ~ 50 metres
MAIN COMMISSIONING GOALS Viewing frame Stability SNR Detectors normalization Focus MTF Viewing directions Absolute calibration 7
Viewing directions Ref Pleiades UNTIL RECENTLY inst _ roll inst _ pitch Viewing frame Detectors Normalization, SNR Correlation GCP model measures MTF Thousands of images! Expensive operational cost Weather/season dependent Landscape dependent 8
Agility suited to demanding mission needs up to 6 bands at 30 up to 6 bands at 30 120 120 km km x x 110 110 km km Automatically Automatically orthorectified and orthorectified and mosaicked mosaicked In a single pass, In a single pass, stereo stereo tri-stereo tri-stereo To follow To follow linear linear targets targets such as coasts, borders, such as coasts, borders, roads, pipelines, rivers roads, pipelines, rivers AGILE for the mission? AGILE for CALIBRATION 9
How agile? Steady-mode 10
STEADY-MODE Calibration results t 0 t dc (t 0, t) dc (t) Radiometric Noise assessment SNR(L2) ~ 150 Stability in roll direction 11
Agility for detectors normalization 90 yaw AMETHIST Each detector views the same landscape 12
Agility for detectors normalization Amethist image acquisition Dedicated satellite guidance: 90 yaw 13
AMETHIST Method and Results Column shift Histograms Digital counts Histogram matching process Inter-detector sensitivities Excellent normalization results Far less operational cost 14
Agility for viewing directions calibration Autocalibration Static/Dynamic separability of push-broom acquisition In red : classical method In blue : autocalibration : 0.03 pixel 15
Agility for viewing frame estimation Auto-reverse DEM geometry correlation dc 2 inst _ roll Disparities maps dr 2 inst _ pitch 16
Agility for stability assessment Without µvib With µvib 17
Agility for stability assessment Accuracy : a few nrad! 18
Agility for MTF and focus assessment XS PSF PA PSF Few image acquisition Best accuracy 19
MTF assessment MTF(Nyq) MTF_X MTF_Y PAN 0.15 0.155 B0 0.33 0.28 B1 0.33 0.27 B2 0.33 0.25 B3 0.33 0.26 20
Absolute focus assessment compared to focus monitoring 21
Ghosts assessment with Sirius Magnitude = -1.5 Equivalent signal = 400,000 LSB A Ghost w.r.t position within the field E B D C 22
CONCLUSION A big step forward for in-flight calibration : Improvement of calibration accuracy Less constraints for the operational mission Simplification of the commissioning Certainly many others new methods to invent and tune : Next challenge is active optics in-flight calibration! 23
24 Thank you for your attention!