The open letter written by their colleagues/friends is also interesting:

http://itam.nsc.ru/about/news/2023-05-15.html

(Use Google Translate)

It's unfortunate that these guys are, in all probability, being thoroughly railroad.

However it's extremely difficult to have sympathy for anyone who continues to support the Russian military establishment after Feb 24, 2022. Especially in such a high-level capacity.

Looking at this briefly, it appears that three aerospace scientists have been charged with treasonous activity for having participated in international scientific conferences and journals.

This kind of erratic overreaction by the security apparatus is characteristic in Russia going back to Tsarist times. The only bright thought that comes to mind is that the victims seem to usually be rehabilitated after certain overeager apparatchiks are replaced.