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!