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Rosetta space mission - Philae probe due to land on comet on 12th Nov 2014

What I'm confused about is why they landed on it so far away: why not hop on when it was closer to the Sun/Earth? Would surely have taken much less time and therefore less chance to fuck things up (not that anything did fuck up on the way to the rock).
 
Fez909 said:
What I'm confused about is why they landed on it so far away: why not hop on when it was closer to the Sun/Earth? Would surely have taken much less time and therefore less chance to fuck things up (not that anything did fuck up on the way to the rock).
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The comet would have been far more active then. Much more hazardous to approach and try and land on - it probably wouldn't have been possible to image the nucleus and select a landing site (for example). Then on trying to land out gassing would have probably just pushed the lander away (and sandblasted the instruments, solar panels).
 
Fez909 said:
What I'm confused about is why they landed on it so far away: why not hop on when it was closer to the Sun/Earth? Would surely have taken much less time and therefore less chance to fuck things up (not that anything did fuck up on the way to the rock).
Click to expand...

They were likely constrained by the limited number of possible ways to slingshot Rosetta to match the comets orbit, and they'd need a solution where the comet wasn't outgassing everywhere at the time of arrival.
 
2hats said:
The comet would have been far more active then. Much more hazardous to approach and try and land on - it probably wouldn't have been possible to image the nucleus and select a landing site (for example). Then on trying to land out gassing would have probably just pushed the lander away (and sandblasted the instruments, solar panels).
Click to expand...
TheHoodedClaw said:
They were likely constrained by the limited number of possible ways to slingshot Rosetta to match the comets orbit, and they'd need a solution where the comet wasn't outgassing everywhere at the time of arrival.
Click to expand...
Thanks, that makes sense.

I thought the reasons were going to be travelling too fast at that point and/or too hot, but the gassing thing and not being able to assess it for safe landing spots seems like two pretty big reasons not to do it close to the Sun. The slingshot would be possible some other way I would have thought. The route they used was pretty insane anyway :cool:
 
Fez909 said:
The slingshot would be possible some other way I would have thought.
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Rosetta was initially designed to rendezvous with another comet, but an Ariane launch failure nixed that, so they had to improvise a bit to get to this one. I don't know what limitations and extra risks that imposed on them, but I'm sure someone here does :)
 
TheHoodedClaw said:
They were likely constrained by the limited number of possible ways to slingshot Rosetta to match the comets orbit, and they'd need a solution where the comet wasn't outgassing everywhere at the time of arrival.
Click to expand...

No. They could have reached it when closer to the sun as that would have required even less energy. The main driver was to observe the evolution of the comet as it approaches the sun - the development of the coma and tail, the processes on the surface.
 
TheHoodedClaw said:
Rosetta was initially designed to rendezvous with another comet, but an Ariane launch failure nixed that, so they had to improvise a bit to get to this one. I don't know what limitations and extra risks that imposed on them, but I'm sure someone here does :)
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The change of plan was committed to before they left Earth, though, so I imagine it didn't increase the risk a great deal.
 
TheHoodedClaw said:
Rosetta was initially designed to rendezvous with another comet, but an Ariane launch failure nixed that, so they had to improvise a bit to get to this one. I don't know what limitations and extra risks that imposed on them, but I'm sure someone here does :)
Click to expand...

They had to beef the lander up for the stronger gravity at this comet and improve thermal protection.
 
2hats said:
No. They could have reached it when closer to the sun as that would have required even less energy. The main driver was to observe the evolution of the comet as it approaches the sun - the development of the coma and tail, the processes on the surface.
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Ah right. So they had quite a range of options then?
 
TheHoodedClaw said:
Ah right. So they had quite a range of options then?
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The original mission design considered something like 4-6 comets.

e2a: correction - there were 7... 73P/Schwassmann-Wachmann, 46P/Wirtanen, 15P/Finlay, 25D/Neujmin, 79P/du Toit-Hartley, D/1978 R1 (Haneda-Campos), 16P/Brooks. In a combination of 11 mission possible profiles.
 
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More on the decision to activate the MUPUS drill:
the team has decided to operate another moving instrument, named Mupus, on Thursday evening. This could cause Philae to shift, but calculations show that it would be in a direction that could improve the amount of sunlight falling on the probe. A change in angle of only a few degrees could help. A new panoramic image will be taken after the Mupus deployment to see if there has been any movement.
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http://www.theguardian.com/science/...-tight-spot-comet-tough-decisions-esa-rosetta
 
We find out sometime shortly after the start of the next telemetry window at 0830UTC whether, if anything that perturbed the lander.
 
The SD2 surface drill package has been given a go-ahead to operate as well (will take sub-surface samples for gas analysis). Perhaps, having collected data from all the other instruments, they have decided to go for broke before the battery drains (at last report they were still on the primary battery, with the lower capacity secondary yet to play) and let the remaining teams try and get some data after waiting so long.
 
Currently they are radio range finding from orbiter to lander to locate it. Not sure yet if the drilling overnight has moved the lander. If they manage to get one further communication window with it this evening, and there is sufficient power left, they will try slewing the craft using the landing gear to orientate it into a more favourable charging position. Data from the lander should start flowing again around 0920UTC when the orbiter maneuvers for communications.

Someone has cooked up a nice little graphic of all the solar system bodies that have been landed upon:

B2U6IfqIUAEfK7K.jpg:large
 
ESOC report a change in the radio signal character from the lander (to the orbiter). One possibility is that the lander orientation/position has altered.
 
brogdale said:
wonder if its better or worse?
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The original signal was described as weak, coming and going (lowering the data rate as a result) before stabilising. This morning they waited for the signal. Heard nothing. Time elapsed. Then suddenly a very strong signal. One interpretation of this could be that the lander has moved and is in a better orientation for the antenna (at least).
 
2hats said:
The original signal was described as weak, coming and going (lowering the data rate as a result) before stabilising. This morning they waited for the signal. Heard nothing. Time elapsed. Then suddenly a very strong signal. One interpretation of this could be that the lander has moved and is in a better orientation for the antenna (at least).
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Sounds encouraging. Thanks.
 
Regarding locating the lander from orbit, Rosetta is now some 50km above the nucleus (optimal orbit for the radio science and data relay). Unfortunately this means that if they can image the lander at all it will be barely one pixel in extent so very hard to spot visually if at all. Triangulating it from the radio signals is the best bet.

e2a: the lead of the OSIRIS team says they are still waiting to download the higher resolution images taken during the descent and bounces. They hope to have a before and after of the lander at first touchdown ie an indication of the direction of the first bounce.
 
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