smei_sgp4_orbits.txt is created/updated by smei_sgp4_orbits.pro.
Currently (March 2011) this procedure is called as part of
smei_pipeline.sh (executed hourly as cronjob on smeidb).

The file is used in IDL only by the procedure smei_coriolis.pro.
In Fortran the only function calling it is smei_orbit_info2.f.

Content of file:

1.	SMEI orbit number
2.	Orbit start time in format YYYY_DOY_hhmmssmss
	The orbital start time in format hh:mm:ss.mss
	Defined as the time Coriolis crosses a fixed geographic
	latitude (~ -31.1 degrees; close to the latitude of the
	SAA) going north.
3.	Orbital period, defined as time difference between two
	successive orbital start times
4.	Orbital period used in sgp4 software
	I think this is some sort of Keplerian orbital period;
	not particulary useful.
5.	Precision of geographic latitude calculation

The remaining columns are related to the normal of the SMEI orbital
plane (pointing towards the Sun).

6.	Solar elongation (in degrees) of the normal
7.	RA (in degrees) of the fictitious Sun
	This progresses strictly linear with UT going through
	360 degrees in 365.25 days (one Julian year).
	This is approximate, but good enough for government work)
8.	RA difference (J2000, in degrees) of the normal with the RA of
	the fictitious Sun.
9.	Declination of the normal (J2000, in degrees)