Don't have all the answers, but last night, on the webcast, they were explaining that the spacecraft uses the stars for navigation [1].
In addition, instead of wasting valuable power for radio transmission, they send a simple tone back to Earth [2]. With that, they can determine if various events were successful (tones are sent at specific event times), also calculate the changes in speed/rotation using doppler shifts from the "tones" [3] (validating the engine fired, current spin, etc)
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Don't have all the answers, but last night, on the webcast, they were explaining that the spacecraft uses the stars for navigation [1].
In addition, instead of wasting valuable power for radio transmission, they send a simple tone back to Earth [2]. With that, they can determine if various events were successful (tones are sent at specific event times), also calculate the changes in speed/rotation using doppler shifts from the "tones" [3] (validating the engine fired, current spin, etc)
[1] https://solarsystem.nasa.gov/basics/bsf13-1.php
[2] https://spaceflightnow.com/2016/06/30/juno-switched-to-autop...
[3] https://solarsystem.nasa.gov/basics/bsf6-4.php