setting 'W0' parameter rather than letting it self-optimise produces unexpected results #8

In the params file, the W0 parameter is defined as the transmit beam radius, but it also modifies the pupil_mode variable. This effectively modifies the fibre size from its optimal value for the specified D_GROUND, used for the reciprocity calculations.

Example where I noticed this issue:
If I want to model the uplink of a bidirectional link configuration, I will have my downlink aperture size set to some large value e.g. 1m. I will then set W0 to be my uplink beam radius (e.g. 5cm). Now, when I want to compute received power at the satellite, pupil_mode will be a gaussian with waist W0 within the much larger aperture diameter, and so my atmospheric losses will be incorrect.