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TMSAT Imaging changes.



To improved the time required to download images we are going to make a few
changes
to the image file processing.  Tomorrow morning during the Surrey passes we
will load
a version of ZIP to compress the images on the satellite.  This process
takes a little
time, but will reduce the size of the images by about 20% (depending on the
scene).
This has two effects -:
1) It reduces download time by 20%
2) It increases the lifetime of the files on the satellite by 20% which will
make
   the images easier to download before they are deleted.

The images will be compresses as ZIP files.  The filename will be the
original file
number with a ZIP extension.  Once this ZIP is extracted, you will be left
with the
original DL file, just as if you had downloaded it directly using MSPE etc.

The original uncomressed images will be deleted once they are compressed.

eg.
   Image file number  A77
   ZIP file number    AA8
   ZIP filename       AA8.ZIP
   Extracted filename A77.DL

(I hope that makes sense)

This afternoon we have taken an image over the southern tip of South
America.  To save 
wasting download time, it is not worth downloading these images since they
will shortly
be PKZIPed on the spacecraft and the uncompressed images will no longer be
available.

73
Chris G7UPN / ZL2TPO




Chris Jackson
Groundstation and Operations Manager
Surrey Satellite Technology Ltd
University of Surrey
Guildford, Surrey GU2 5HX,  UK 
Ph: +44 1483 259-141
Fax: +44 1483 259-503
http://www.ee.surrey.ac.uk/EE/CSER/UOSAT/
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