The files in this folder contain information on predicted overpasses of the
CHRIS sites.  The predictions are based on orbital elements (TLEs) from the
NORAD website.

They have names such as this:  xxx_mmm_tle_ddd

where xxx is one of: satzen, solarzen, alitudes, time;
mmm is a three letter abbreviation for a month, and
ddd is the day of the year on which the TLE set was made.

Each file is a tab-delimited table.  The tables for satellite altitude contain 
the altitude of the sateliite in kilometres on potential imaging days, and 
zeros for the days when the satellite cannot see the ground site.  The satzen
table contains, to the nearest degree, the zenith angle of the platform, as 
seen from the ground, at the time of closest approach.  That time of closest 
approach is contained in the "times" file. The format for this is a four digit 
number of the form hhmm (hours and minutes, UT).  The "solarzen" file contains 
the solar zenith angle at the time of the satellite's closest approach.  This 
should always be less than 70, as higher values are not considered for imaging. 
For the zenith angle tables, and the times table, the entries are blank when 
then is no possible image.

These tables are updated weekly.  Predictions are reasonably good for about six 
weeks, but after that the uncertainties of the orbit, principally caused by 
atmospheric drag, make them less reliable. 

To use these tables, the simplest approach may be to download the file to
your desktop, then open the file from inside Microsoft Excel or a similar
package.  It will open from inside Word, although this is messier.