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MODIS Airborne Simulator (MAS)


June 5, 2002 - Error in MAS and MASTER HDF data

It has come to our attention that two of the solar geometry and one of the sensor geometry scientific data sets in the level-1b format of the MODIS Airborne Simulator (MAS) and the MODIS / ASTER Airborne Simulator (MASTER) are in error.

The calibrated video and navigation data sets are NOT affected in any way.

The data sets titled "SolarZenithAngle" and "SolarAzimuthAngle" incorrectly represent the sun's position at the given data point, resulting from the use of GMT rather than local sun-time. The third scientific data set with errors is the "SensorAzimuthAngle". This has an incorrect value for pixels 2-358.

Only data processed with Version #10 of the level-1b software is affected. This can be determined by the global attribute of the HDF files titled "SoftwareVersion". All the data collected in 2001 is affected. Specifically MAS flights 00-137 through 01-143 and MASTER flights 01-003-02 through 02-920-00. The effected flights may also be identified by the new longer file name associated with the V.10 software.

The MAS and MASTER data will be reprocessed and distributed with these errors corrected. We are sensitive to the inconvenience that this may have caused and would like to prioritize the reprocessing effort. It you have a project underway and would like the Airborne Sensor Facility to expedite the processing please contact us as soon as possible.

We deeply regret any hardship that this has caused with the processing of the MAS or MASTER data. I will keep people informed about any further issues. Please do not hesitate to contact us if you have any questions.

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April 16, 2001 - Level-1b processing software rewritten

Greetings everyone,

It is my pleasure to announce the completion and impending implementation of version #10 of the Level-1b software for the MAS (MODIS Airborne Simulator) and MASTER (MODIS/ASTER Airborne Simulator) data. This effort is the result of a proposal brought forth at the October 1999 instrument status meeting at GSFC. This new level-1b processing code is written entirely in C and is fully integrated into the suite of data processing routines at the Airborne Sensor Facility.

Version 10 of the level1b processing code offers the operator a more efficient and simplified procedure for generating the archive data product. Calibration and navigational parameters are better incorporated into the processing flow. Flight and line specific information is inputted much easier. The result will be a higher quality data product with a faster delivery time.

The code maintains all of the fundamental calibration algorithms and HDF file format present in the past version of the MAS and MASTER data product. Revisions to the data format are a result of discussion with the instrument and science support staff, data users and representatives from the NASA DAAC's. Global attributes in the HDF file have been modified to eliminate unnecessary information and new information has been added. Scientific data sets in the HDF file have been streamlined, redundancies eliminated and accuracy has been increased. A new file naming convention has been proposed that embeds flight parameters into the name and follows the model of the TERRA data sets.

All data flown in FY2001 will be distributed and archived in this new format with version 10 of the processing code. Data collected in FY2000 will be reprocessed with version 10 of the level-1b as time permits. Effectively all MAS and MASTER data flown from FY2000 on will be processed with version 10.

-- Mike Fitzgerald


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