I believe that the SGP4 model for orbit estimation for LEO satellites uses TLE data as initial condition. Some CubeSats chose to use up-link TLE data than installing GPS.
My question is for the case when just after launch and detumbling, there is no communication has been made between the CubeSat and Ground station and the satellite has no TLE data, then how the ADCS would work without position of satellite. As there is no GPS and SGP4 would not work until someone feed it TLE.
If somehow the communication is possible then by up-link the TLE the SGP4 would run, I understand but for having that communication the satellite has to be in proper orientation and for that ADCS (sun model and IGRF model) need position in orbit. Sort of chicken-egg problem.