I have updated the satpy scripts for polar satellites. Using an option '-histtle' the date of the tle is compared to the date of used data; if needed the right tle is downloaded from spacetrack. This tle is saved so it can be reused without downloading again. The max. allowed age can be specified (now set to 0); for this purpose it is not necessary to have exact tle's. (They are only used to select files covering the area of interest).

The functions taken care for this are in the file with common functions: satpy_ecast_rts.py; you can easily extract them to use them with other scripts, if you want.

Description how tle's are used and saved are in:

http://www.alblas.demon.nl/wsat/software/satpy.html#tle

For spacetrack you need a login which you can easy get from https://www.space-track.org/

Rob.