On 12 September 2017 at 05:27 UT / 01:27 EDT the Cassini spacecraft reached apoapsis or the farthest point from Saturn it will reach. For Cassini apoapse was 1.3 million km / 800,000 miles.
Cassini is now headed right toward Saturn for the last time. The spacecraft will plunge into the Saturian atmosphere in just a few days, on 15 September 2017.
The signal from Cassini has to travel 83 minutes before reaching Earth. By the time we lose the signal from the spacecraft about 11:55 UT / 07:55 EDT on the 15th, the spacecraft will have already encountered Saturn. The time could change a little because of atmospheric drag during the final orbits.
If I calculated this correctly the “at Saturn” event time would be 10:32 UT / 06:32 EDT based on that original estimate.
The image above of the moon Titan is one of the very last we will see from the mission and was taken on 10 September 2017.
Image: NASA/JPL-Caltech/Space Science Institute