Introduction

The project CHRIS/Proba Toolbox for BEAM (CHRIS-Box) has been brought into life in order to support users of data of the CHRIS sensor onboard of the ESA Proba platform. BEAM and the CHRIS-Box are user tools which ESA/ESRIN are providing free of charge to the Earth Observation Community. The CHRIS-Box software provides extensions for BEAM, which allow accomplishing the following tasks:

1. Noise reduction: Removes the vertical striping in CHRIS response-corrected images caused by the slit effect and a superposition of high-frequency noise
2. Cloud screening: Marks cloudy pixels in CHRIS noise-corrected images; the cloud screening algorithm provides cloud probability and abundances for each pixel
3. Atmospheric correction: Provides a surface reflectance retrieval algorithm. The method applies to noise-corrected radiance images with (or without) a probabilistic cloud mask as generated by the cloud screening algorithm
4. Geometric correction: Provides a CHRIS/Proba atmosphere-corrected product with information on latitude/longitude and viewing geometry for each pixel
5. TOA reflectance computation: Computes top-of-atmosphere apparent reflectance from the top of atmosphere radiance (radiometrically calibrated data) as provided by the CHRIS noise-corrected images
6. Feature extraction: Computes certain surface and atmospheric features which are used by the CHRIS-Box cloud screening algorithm; the feature extraction is applicable to TOA reflectance images only

The CHRIS-Box software has been developed by

• Brockmann Consult (BEAM Team)
• Universidad de Valencia (L. Alonso, L. Gomez-Chova, L. Guanter, J. Moreno)
• Swansea University (P. North, W. Grey)

under ESA contract initiated and coordinated by Peter Regner (ESRIN).

License

The CHRIS-Box is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation. This program is distributed in the hope it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

Source Code

The source code for the CHRIS-Box software is available via the git repository at http://github.com/bcdev/chris-box.

Reporting

You can submit CHRIS-Box bug reports and feature request to the CHRIS-Box issue tracker.

Download

Please choose an installer appropriate for your platform. Note that the CHRIS-Box is an add-on to BEAM and thus all installers require an existing installation of BEAM (download here).

Telemetry Data: An archive of CHRIS/Proba telemetry data, which is needed by the geometric correction module, can be downloaded here. The archive provides the telemetry for CHRIS/Proba heritage data until January 2008. The telemetry for more recent data must be downloaded from the CHRIS/Proba Payload Additional Data site (see below).

CHRIS-Box for BEAM 4.8

CHRIS-Box for BEAM 4.7.1

CHRIS-Box for BEAM 4.7

Usage

The CHRIS-Box tools can be invoked through the BEAM/VISAT tools menu, as illustrated in the screenshot shown below. Note that the geometric correction is not included in CHRIS-Box Version 1.0.2, but will be included in Version 1.1 scheduled for release in July 2009.

Finding telemetry files

As of now CHRIS images are not distributed with their corresponding telemetry files. Telemetry files have been recently made publicly available at an ESA/REDU archive server: http://194.78.233.110/products/data/CHRIS_Additional_data/. The archive provides individual files for the most recent acquisitions, older files are bundled in compressed files.

To find the corresponding telemetry files for a given acquisition follow these steps: Get [Target Name] and [Date] from image meta data; the dashes '-' in the date must be removed (e.g. for image CHRIS_MB_080501_9BE1_41 meta data [Target Name]=Manly-Beach and [Date]=20080501 removing the '-' from the meta data date value '2008-05-01') Connect to the telemetry archive Use a filter *.[Target Name]_?????_CHRIS_center_times_[Date]_* to locate the Image Center Times file (e.g. it would find: Pass9301.Manly-Beach_39905_CHRIS_center_times_20080501_65534) ????? should match a five-digit string to be used as reference [Ref] (e.g. in this case it would be [Ref]=39905) Use a filter CHRIS_[Ref]_*.tar.gz to locate the compressed GPS file (e.g. it would find: CHRIS_39905_39909.tar.gz) Extract from the gzip archive the file: CHRIS_[Ref]_*_PROBA1_GPS_Data, where PROBA's GPS position and velocity data are recorded. There also is a second file PPU_UPLOAD_*, which can be ignored (e.g. extract CHRIS_39905_39909_PROBA1_GPS_Data)