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Ulysses Spacecraft on its Last Legs
doconnor writes "JPL announced that Ulysses' mission will be ending after 17 years. The power generated by the decay of a radioactive isotope has been slowly decreasing. To conserve power its main transmitter was shut off. Unfortunately due to a fault in its power supply it cannot be turned back on. The team plans to continue operating the spacecraft in its reduced capacity, using the alternate S-band transmitter, for as long as they can over the next few weeks." Congratulations to all the geniuses involved in this one.
If you had read the article you would know that this originally was intended to be a five year mission, and the spacecraft has been sending us useful data for seventeen years. Yes, they got plenty of of it before transmission was cut off - more than they bargained for.
I know reading articles goes against everything slashdot stands for, but doing it from time to time can make you smarter.
Seven puppies were harmed during the making of this post.
'Every story, if continued long enough, ends in death.' --Ernest Hemingway
...so three times, not four, but still, a spacecraft tripling its expected useful life is a strong testament to the skill of its engineers. Our Martian Robotic Geologists' (Spirit and Opportunity) primary mission was only supposed to last 90 days. And they landed in 2004. So that makes them somewhere in the neighborhood of 12 times older than they're supposed to be.This kinda makes me wonder if NASA and other space agencies purposely over-estimate the useful lives of their spacecraft.
The game.
This kinda makes me wonder if NASA and other space agencies purposely over-estimate the useful lives of their spacecraft.
It's easy to make such a statement if you didn't know the history of rovers & other landers.
Before the Rovers Spirit & Opportunity, there were NO rovers that lasted 90 days on another planet before dying. The predecessor, Sojourner, lasted 83 days. Before that, I think the record was 56 days. 90 days was a good goal. They thought the solar panels would just get covered with dust. They could have put on dust cleaners, but that has a weight penalty, and they decided to use the weight for science payload. They got lucky when they found they can get cleaned from the wind storms.
Hey genius, don't you mean, under estimate?
That aside, lets take the problem straight on and consider the mars rovers. You are the engineer. You don't have anything remotely resembling a clue as the abrasive qualities or the dirt and dust on Mars. You have an inkling of a clue about wind and such, but Martian surface weather is still a pretty big mystery. You have to build a device that is mobile, must supply power to all kinds of instruments, it has to communicate to a orbiting platform that is not in constant communication range, it has to deal with wild temperature variations, it has to survive the violence of being shot into orbit, then survive the cold of interplanetary space on its way to Mars, then survive being bounced across the surface of Mars in what is essentially a huge beach ball, then be able to warm up, unfold and start driving around...
And you suspect the engineers might be hedging their bets just a teeny bit? Ya think!
Hey KID! Yeah you, get the fuck off my lawn!
In space, even solar power is far from perminant. Over time, solar cells are destroyed by particle radiation. A solar sail will gradually be filled with pinholes degrading it's performance until it finally falls apart.
Their site is amazing! It shows all of the instruments and links to the data they've provided directly. For instance, the DUST instrument measures dust impact events (imagine that). You can use the heliocentric latitude and longitude for these thousands of events to track the spacecraft position throughout it's 17 year journey. A nice readme file explains the structure of the data file. That's just one of the 12 scientific instruments. Very cool stuff...
On another note, why are people saying four times as long as they expected? 17 years is closer to three times the original five years than four. You can't really say it's lasted four times as long as expected until after it has lasted 20 years.