Farewell, Cassini - and we thank you

[GordonD]

The Cassini probe, which for the last twelve years has been sending back data about Saturn and its moons, is now almost out of propellant so will be put on a trajectory that will take it between the planet's upper atmosphere and its ring system, which means it will enter the atmosphere and burn up in September.

 

http://www.bbc.co.uk/news/science-environment-39672263

[SleeperService]

Rest easy little probe, you done good.

 

[Eric Mc]

It's not finished yet. It has another five months or so to go before it meets its end.

[GordonD]

Those unmanned probes do so well, don't they? (When they're not going to Mars, that is!)

 

Larry Niven wrote an excellent short story called Like Banquo's Ghost, narrated by a reporter in the control centre when data from the first interstellar probe starts to come in. The probe reached the Alpha Centauri system four years earlier (having been launched thirty years before that) but due to the time-lag the signals are only now being received. Throughout the story the narrator is talking to someone called Butch, who is extremely interested in what the probe is doing. Then the probe drops behind the planet it's mapping and the signal is cut off.

 

And Butch says

Spoiler

"It will not reappear." Turns out Butch is an alien from Alpha Centauri and when the probe appeared in their sky they thought it was hostile and shot it down; only when they examined the wreckage did they find out the truth and Butch came to Earth in a faster-than-light starship to make contact. If the probe can make accurate maps of the planet then they will trade their FTL drive for the probe's technology, which they are very impressed with.

 

[Robert]

Why not just use the gravitational pull from Saturn and send it off into deep space like Voyager which is in its 40th year.

[Eric Mc]

32 minutes ago, Robert said:

Why not just use the gravitational pull from Saturn and send it off into deep space like Voyager which is in its 40th year.

Voyager was not in orbit around Saturn. It was barrelling in towards the planet at a high rate of knots and used Saturn's gravity to alter its trajectory and set it on course for Uranus. I don't think it picked up much in the way of additional speed relative to the sun from its Saturn flyby.

 

Cassini is firmly in orbit around Saturn. It would need a massive addition to its speed relative to Saturn (and the sun) to allow it to escape Saturn's gravity and head off further into the outer Solar System. To get the required delta V, it would need a big push from an on board rocket motor and the expenditure of a lot of fuel. Although Cassini does have a rocket motor, it doesn't have sufficient fuel to give it that delta V..

[Richard E]

44 minutes ago, Robert said:

Why not just use the gravitational pull from Saturn and send it off into deep space like Voyager which is in its 40th year.

 

As Saturn's gravity is holding the probe on orbit it probably hasn't got the "oomph" ^** to fling it out into deep space and, sadly, there's probably more scientific benefit to be gained from the data it would gather about Saturn's atmosphere before it burned up than from the comparative emptiness of outer space.

 

^** "oomph" is the less technical term for delta V

Edited April 23, 2017 by Richard E

[Doug Rogers]

'Better to burn out than fade away'. 

 

Was down at Winchester Science Centre last week and the scientific community is getting quite excited about Enceladus, they've certainly got a lot of information from Cassini

[Richard E]

Farewell Cassini and thank you for the insights you have given us

[GordonD]

I'd actually forgotten I started this topic - I was going to do a new one (with the same title!  ) but didn't get round to it.

Footage here of Mission Control at the moment Cassini went silent, followed by a press announcement.