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Cassini's Saturn Mission Goes Out In A Blaze Of Glory (npr.org)
An anonymous reader shares a report: Controllers at NASA's Jet Propulsion Laboratory sent a final command Friday morning to the Cassini spacecraft orbiting Saturn. Not long after, accounting for the vast distance the message traveled, the order was received, putting the craft into a suicidal swan dive, plummeting into the ringed planet's atmosphere. Flight Director Julie Webster called "loss of signal" at about 7:55 a.m. ET, followed by Project Manager Earl Maize announcing "end of mission" as the spacecraft began to break up in Saturn's atmosphere. "Congratulations to you all," Maize announced to applause. "It's been an incredible mission, incredible spacecraft, and you're all an incredible team." With Cassini running on empty and no gas station for about a billion miles, NASA decided to go out Thelma & Louise-style. But rather than careen into a canyon, the plucky probe took a final plunge into the object of its obsession. Just how obsessed? Its 13-year mission to explore the strange world of Saturn went on nearly a decade longer than planned. It completed 293 orbits of the planet, snapped 400,000 photos, collected 600 gigabytes of data, discovered at least seven new moons, descending into the famed rings and sent its Huygens lander to a successful 2005 touchdown on the surface of yet another moon, Titan. Also read: Cassini's Best Discoveries of Saturn and Its Moons.
It was a worry over biological contamination. JPL (and NASA) have very specific protocols for planetary protection. Huygens went through some extreme decontamination prior to launch. Cassini, as an orbiting probe, not so much. Also, at launch we didn't know as much about the Saturn system and it's moons. The RTGs aren't really a concern, as they're not all that radioactive. Pu-238 is primarily an alpha emitter, and is mostly just toxic.
...si hoc legere nimium eruditionis habes...
It was a worry over biological contamination. JPL (and NASA) have very specific protocols for planetary protection. Huygens went through some extreme decontamination prior to launch. Cassini, as an orbiting probe, not so much. Also, at launch we didn't know as much about the Saturn system and it's moons.
Specifically, we learned that Enceladus has a large subsurface ocean, at the bottom of which may lie hydrothermal vents. Since those on Earth are often teeming with life, we didn't want to risk contamination of Enceladus' oceans.
my, your, his/her/its, our, your, their
I'm, you're, he's/she's/it's, we're, you're, they're
NASA-TV showed displays of the S-band and X-band carriers prior to loss of signal, sharp spikes above a noise background. The S-band signal faded out first, as the spacecraft began to lose pointing accuracy for its high gain antenna when the thrusters could no longer keep up with the atmospheric forces. The X-band signal persisted for a few more seconds (more antenna gain at the shorter wavelength, presumably) before it faded out, but then it reappeared briefly above the noise before going away forever. It was as if the spacecraft gave one last effort to stay in touch with home. A very sad moment.
Here you go: http://www.21stcentech.com/money-spent-nasa-not-waste/
And this: https://www.sciencefriday.com/articles/meet-the-researchers-behind-the-cassini-mission/
And from here: http://www.airspacemag.com/flight-today/team-cassini-180960062/
"one of more than 5,000 people who have worked on the project over the years"
Maybe next time do research on your own and get educated about the subject before you bitch about it.
TFA states that plowing the craft into Saturn was necessary to prevent contamination of the moons, but the mission began with dropping a Huygens Lander on Titan. Seems like nobody has make the distinction between bacterial contamination and radioactive contamination. I suspect that the latter is actually the concern as the probe used an RTG for power and thus it was safest to de-orbit it into Saturn.
It was a worry over biological contamination.
Exactly. Huygens was battery powered: after the battery died, it dropped to a temperature of about 90K, barely above liquid nitrogen. No terrestrial life will contaminate anything at that temperature.
Cassini, on the other hand, contained several RTGs. In the unlikely case that it did impace into Titan, the RTGs would keep a tiny fraction of the probe debris above the liquidus point of water, and hence in principle terrestrial contamination could survive and even multiply.
The scenario is absurdly unlikely, of course, but it can't be absolutely ruled out, and since it can't be ruled out, it triggers the planetary protection protocol.
You have it backwards. The upper display was x band. It faded first because the antenna has higer gain at the higher x band frequency, so the pointing is more critical. S band was on the bottom and faded a bit later because the dish has a wider beamwidth at 2 GHz than it does at 11 GHz.