Purists look away (and bearing in mind I know fook all about sat boxes) lol
All Linux boot in essentially the same way i.e. build a mini file system in RAM then drag all the rest into the hole. At some point the kernel is loaded and the application follows (your sat program). The loading is spread into run-levels (accessed at rc file level if you want to change stuff) i.e. rc.local (edit this file to make stuff happen before the interface appears).
If you want to know if something is mounted then do a 'mount' command at the command line to find out what and where then to check at any time you can do:
grep /media/Pictures /etc/mtab
Where /media/Pictures is where I expect to find my mounted SD card (in this case, change to suit your system). So, in a shell script I could do:
if grep /media/Pictures /etc/mtab != /dev/null; then
Bit crude but could easily be refined to check whether the USB stick was mounted correctly. Put this in a script at, say, rc2 and you could mount it if it wasn't already?