How hard would it be for access to be granted to the DSN? The challenge to build the transmission equipment does not seem insurmountable nor even particularly hard.
It's the logistics and red tape to make it happen.
I'd also like to point out, that this satilite will be doing a near earth flyby - you could probably get away with something smaller, maybe even a 3.5m dish versus a you know, 70m dish.
The engineers at GSFC say you will need the DSN. The smallest DSN antenna is 26m and that is used only for LEO (a couple thousand km).
You talk about "red tape" like moving a huge radio telescope is some kind of formality, and you quoted a figure of 3.5m with no apparent engineering basis. I find this ridiculous.
It's the logistics and red tape to make it happen.
I'd also like to point out, that this satilite will be doing a near earth flyby - you could probably get away with something smaller, maybe even a 3.5m dish versus a you know, 70m dish.