MEX VMC Reduced Data Record (RDR)

RDR – Reduced Data Record

Instrument:Visual Monitoring Camera

PDS Data Set ID (Nominal Mission): MEX-M-VMC-3-RDR-V1

PDS Data Set ID (Extended Mission 1): MEX-M-VMC-3-RDR-EXT1-V1

PDS Data Set ID (Extended Mission 2): MEX-M-VMC-3-RDR-EXT2-V1

PDS Data Set ID (Extended Mission 3): MEX-M-VMC-3-RDR-EXT3-V1

PDS Data Set ID (Extended Mission 4): MEX-M-VMC-3-RDR-EXT4-V1

PDS Data Set ID (Extended Mission 5): MEX-M-VMC-3-RDR-EXT5-V1

PDS Data Set ID (Extended Mission 6): MEX-M-VMC-3-RDR-EXT6-V1

PDS Data Set ID (Extended Mission 7): MEX-M-VMC-3-RDR-EXT7-V1

DOI: Mars Express DOI Overview Page

For more information about VMC EDR products, see the VMC Product EAICD.

No on-ground calibration exists for the VMC camera and so in-flight calibration has been performed.

The master dark current file is made from images of dark sky. The dark has a mean value of 2.4 DN, and only 0.1% of pixels have values >4 DN. Currently, the same dark current file is used for all exposures and temperatures.

The flat-field file was created using dark-corrected images of flat portions of Mars that were well and uniformly illuminated, as free as possible from large structures, and as flat as possible (e.g. taken at pericentre, in the northern plains of Mars). Sigma-clipping was performed that rejected pixels two standard deviations away from the mean value of the pixels across all the images for darker images, and 4 standard deviations away for higher pixel value images, so that images with poorer illumination had less influence on the final master flat. Once this sigma-clipping was performed, the remaining pixels were averaged across all the images and then normalized to create the master flat-field file. This was done by averaging the counts of the central portion of the images (typically the most well illuminated) to 1 and then dividing all the pixels of the master flat by that number. This flat-field calibration may be improved in future as we take more observations, but the current flat field has provided good results so far.

In the BROWSE calibrated products, the vignetting effect produced by the camera is not corrected (though such correction is done for the DATA products using the flat-field image), as these PNGs cannot save values above 255, but the BROWSE products are not intended to be used for scientific purposes.

The process of calibration in the processing pipeline for the Level 3 DATA products is as follows: first, all saturated (=255 and above) are converted to NAN (‘Not a Number’) so that they are removed from the calibration, then the dark current file is subtracted, and the result is divided by the flat. Both the flat-field and dark-current file used are provided in the CALIB directory.

VMC RDR products have the following file names:

VMC_TR_YYMMDD_hhmmss_ccc.FIT

where:

VMC – Visual Monitoring Camera

T – Purpose of data. S stands for Science.

R – Reduced Data Records (radiometrically calibrated)

YY – Year

MM – Month

DD – Day

hh – hours

mm – minutes

ss – seconds

ccc – counter of the image within an observation series

In ODE, RDR products have the following Product IDs:

VMC_TR_YYMMDD_HHMMSS_CCC.FIT