WATCH LIVE | Cassini's last dance with Saturn
Cassini's 13-year tour of the Saturn system is about to end as the probe plunges into the planet in order to keep its moons pristine.
Saturn's moons may play host to alien life, so scientists would rather not contaminate them with any Earth-born microbes that may be on the probe.
A few months ago, Cassini scientists announced that a form of chemical energy on which life could feed appeared to exist on Saturn's moon Enceladus.
Cassini blasted off for Saturn in 1997, and entered the planet's orbit in 2004.
Its end will be the first time a spacecraft has entered that region of Saturn.
The dive will be the last of 22 weekly dives that began in late April. Cassini's end, with commentary, will be broadcast from mission control starting at 1pm Pretoria time.
"Because Saturn is so far from Earth, Cassini will have been gone for about 83 minutes by the time its final signal reaches the Deep Space Network's Canberra station in Australia," Nasa said in a statement.
Cassini's final diary
7:08: Cassini passes by Enceladus for the last time.
09:14: Cassini will begin a five-minute roll to point instrument to sample Saturn's atmosphere, and it will reconfigure its instruments for real-time date transmission at 27 kilobits per second.
09:22: Cassini will cross the distance of Saturn's F ring for the last time.
12:31: Cassini starts tumbling into the planet, and communication will start failing.
13:55: Nasa will lose all communication with Cassini.