I think you've very much missed the point -
The neural net was trained on outputs from both sensors on the craft when they were working, to identify potentially complex correlations between them (if a million parameters are involved) that could not have been guessed without the ground truth of 2 years of concurrent data.
In other words they can only guess at the sensors outputs now because the really had the sensor working before. It wasn't a waste to send it up in the first place.
