CHRIS PROBA instrument Wout Verhoef ITC, The Netherlands verhoef @itc.nl 29 June 2009, D1L5
Contents Satellite and instrument Images Multi-angular analysis Toolbox
CHRIS-PROBA PROBA-CHRIS Project for On-Board Autonomy CHRIS (Compact High Resolution Imaging Spectrometer) is an AO hyperspectral instrument whose objective is the collection of BRDF (Bidirectional Reflectance Distribution Function) data for a better understanding of spectral reflectances. CHRIS is the prime instrument of the PROBA mission. The technology objective is to explore the capabilities of imaging spectrometers on agile small satellite platforms.
Satellite PROBA satellite
Instrument CHRIS (Compact High Resolution Imaging Spectrometer)
Images China's Three Gorges dam - CHRIS image, 30 July 2003
Images Proba image of the Gobi Desert in China
Georeferenced nadir acquisitions Upper Rhine Valley test-site 2003 25 March 2003 02 June 2003 18 July 2003 03 August 2003 675, 713, 781 nm Source: Heike Bach, 2005
Spectral signatures, Upper Rhine Valley Measured nadir spectra of different land covers (Aug 03): 60 reflectance [%] 50 40 30 20 maize tobacco potato miscanthus forest 50 Development of maize in 2003 (nadir spectra): 40 10 0 450 550 650 750 85020 950 1050 wavelength [nm] Source: Heike Bach, 2005 reflectance [%] 30 10 0 25.03. 02.06 18.07. 03.08. 450 550 650 750 850 950 1050 wavelength [nm]
Comparison with SLC simulation results Maize; Upper Rhine Valley, Aug 2003 Maize, Aug 03 (1 pixel, no smoothing) Maize, Aug 03 (simulated) 50 50 40 40 Reflectance [%] 30 20 10-55 -36 0 +36 +55 Reflectance [%] 30 20 10-55 -36 0 +36 +55 0 470 570 670 770 870 970 Wavelength [nm] 0 470 570 670 770 870 970 Wavelength [nm] Soil moisture: 5%; leaf chlorophyll: 40 µg/cm², LAI = 4.0, leaf water content: 0.02 g/cm², fraction brown: 35% optimised to nadir spectrum Source: Heike Bach, 2005
Measured and Simulated BRDF for Maize Anisotropy plots BRDF factor related to nadir BRDF, Maize, 18.07.2003 1.6 1.4 1.2 1 0.8 0.6-60 -40-20 0 20 40 60 angle [ ] 0.530 0.552 0.552 0.570 0.631 0.674 0.685 0.697 0.706 0.712 0.718 0.725 0.731 0.738 0.744 0.751 0.758 0.765 0.773 0.784 0.795 0.803 0.866 0.884 0.898 0.908 0.917 0.927 0.958 0.968 0.978 0.989 1.000 1.021 BRDF factor related to nadir BRDF, Maize, 18.07., simulated, LAI = 5, Cab = 50 1.6 1.4 1.2 1 0.8 0.6-60 -40-20 0 20 40 60 angle [ ] 0.530 0.552 0.570 0.631 0.661 0.674 0.685 0.697 0.706 0.712 0.718 0.724 0.731 0.738 0.744 0.751 0.758 0.765 0.772 0.783 0.795 0.803 0.866 0.884 0.898 0.908 0.917 0.927 0.942 0.957 0.968 0.978 0.989 0.999 1.021 18.7.2003 LIDF a = -0.10 b = -0.40 Source: Heike Bach, 2005
Toolbox CHRIS/Proba Toolbox Status Quo
Toolbox Module Implementation Module Features Specification / ATBD Implementation Reader RCI data and metadata import, mask refinement, cosmetic dropout correction Completed Completed Noise Reduction Slit correction, removal of vertical striping, dropout correction Completed Completed Cloud Screening TOA reflectance calculation, feature extraction, unsupervised cluster analysis, manual cluster labelling, probabilistic cloud mask calculation Completed Completed - GUI improvements in progress Atmospheric Correction AOD retrieval (per scene) for land and water, surface reflectance and water vapour column calculation Completed Completed Geometric Correction Geographic coregistration of different looks Going to be completed by 2nd week of Oct Pending the ATBD, going to be completed by end of Nov Aerosol Retrieval AOD retrieval (per pixel) for land Completed Cancelled
Toolbox Module Characteristics 1. Reader Reads all CHRIS/PROBA RCI data, quality mask data and metadata Performs on-the-fly mask refinement and cosmetic dropout correction Fully integrates CHRIS/PROBA products into the BEAM/VISAT environment 2. Noise Reduction Operates on either single scenes or acquisition set Removes noise and dropout artefacts almost completely Batch mode capable 3. Cloud Screening Operates on the noise-corrected product Interactive cloud labelling Produces either a binary mask (cluster analysis) or a probabilistic mask (spectral unmixing) 4. Atmospheric Correction Operates on the noise-corrected product, takes into account cloud mask Per scene AOD retrieval for land and water Smile correction for modes 1 and 5 Produces surface reflectance (and water vapour map for modes 1, 3, and 5) Optionally applies adjacency correction Optionally applies spectral polishing 5. Geometric Correction Requires CHRIS metadata, telemetry, ground control points Calculates latitude, longitude and viewing angles per pixel
Toolbox Some Screenshots
Toolbox More Screenshots
Thanks for your attention!