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CHRIS PROBA instrument
Wout VerhoefITC, The Netherlands
verhoef @itc.nl
29 June 2009, D1L5
Contents
• Satellite and instrument• Images• Multi-angular analysis• Toolbox
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.
CHRIS-PROBA
PROBA satellite
Satellite
CHRIS (Compact High Resolution Imaging Spectrometer)
Instrument
China's Three Gorges dam -CHRIS image, 30 July 2003
Images
Proba image of the Gobi Desert in China
Images
Georeferenced nadir acquisitions
25 March 2003 02 June 2003 18 July 2003 03 August 2003
675, 713, 781 nm
Upper Rhine Valley test-site 2003
Source: Heike Bach, 2005
Spectral signatures, Upper Rhine ValleyMeasured nadir spectra of different land covers (Aug 03):
0
10
20
30
40
50
60
450 550 650 750wavelength [nm]
refle
ctan
ce[%
]maizetobaccopotatomiscanthusforest
Development of maize in 2003 (nadir spectra):
850 950 1050
0
10
20
30
40
50
450 550 650 750 850 950 1050
wavelength [nm]
refle
ctan
ce[%
]
25.03.
02.06
18.07.03.08.
Source: Heike Bach, 2005
Maize, Aug 03 (1 pixel, no smoothing)
0
10
20
30
40
50
470 570 670 770 870 970
Wavelength [nm]
Ref
lect
ance
[%]
-55°-36°0°+36°+55°
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
Maize, Aug 03 (simulated)
0
10
20
30
40
50
470 570 670 770 870 970
Wavelength [nm]R
efle
ctan
ce [%
]
-55°
-36°0°
+36°+55°
Comparison with SLC simulation results
Maize; Upper Rhine Valley, Aug 2003
Source: Heike Bach, 2005
Measured and Simulated BRDF for Maize
BRDF, Maize, 18.07.2003
0.6
0.8
1
1.2
1.4
1.6
-60 -40 -20 0 20 40 60
angle [°]
BR
DF
fact
or re
late
d to
nad
ir
0.5300.5520.5520.5700.6310.6740.6850.6970.7060.7120.7180.7250.7310.7380.7440.7510.7580.7650.7730.7840.7950.8030.8660.8840.8980.9080.9170.9270.9580.9680.9780.9891.0001.021
BRDF, Maize, 18.07., simulated, LAI = 5, Cab = 50
0.6
0.8
1
1.2
1.4
1.6
-60 -40 -20 0 20 40 60
angle [°]
BR
DF
fact
or re
late
d to
nad
ir
0.5300.5520.5700.6310.6610.6740.6850.6970.7060.7120.7180.7240.7310.7380.7440.7510.7580.7650.7720.7830.7950.8030.8660.8840.8980.9080.9170.9270.9420.9570.9680.9780.9890.9991.021
18.7.2003
LIDF a = -0.10 b = -0.40 Source: Heike Bach, 2005
Anisotropy plots
CHRIS/Proba Toolbox
• Status Quo
Toolbox
Module Implementation
CancelledCompletedAOD retrieval (per pixel) for landAerosol Retrieval
Pending the ATBD, going to be completed by end of Nov
Going to be completed by 2nd week of Oct
Geographic coregistration of different looks
Geometric Correction
CompletedCompletedAOD retrieval (per scene) for land and water, surface reflectance and water vapour column calculation
Atmospheric Correction
Completed - GUI improvements in progress
CompletedTOA reflectance calculation, feature extraction, unsupervised cluster analysis, manual cluster labelling, probabilistic cloud mask calculation
Cloud Screening
CompletedCompletedSlit correction, removal of vertical striping, dropout correction
Noise Reduction
CompletedCompletedRCI data and metadata import, mask refinement, cosmetic dropout correction
Reader
ImplementationSpecification / ATBDFeaturesModule
Toolbox
Module Characteristics1. 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 ScreenshotsToolbox
Thanks for your attention!