Let down by solar panels

Let down by solar panels
<http://washingtonpost.com/news/speaking-of-science/wp/2014/11/14/the-rosetta-lander-is-dead
Should have had nuclear instead :-P
<http://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generator>
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Actually its not dead. it had batteries for the prime mission, which are now exhausted, but there is still data in flash and a clock powered from a normal battery. The system is, according to the bod I heard, designed to hibernate and wait till there is sufficient charge before it is brought to life again, so one assumes its some kind of very low power mode. They always said that any landing site might be shaded and they expected it to not always be so as it headed in toward the sun, so it could well spring back to life when its got the correct charge. apparently embeded in the data is a signal from the charging system suggesting that there had been some charging but at a very low level. So I guess its a waiting game and anything else they get will be a bonus. If it had actually stayed where it first set down it would have been good they reckon, but trying to land on a body which has a the consistancy of something between rubbar and candy floss is never going to be easy. Brian
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"Andy Burns" < snipped-for-privacy@adslpipe.co.uk> wrote in message
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On 15/11/2014 08:16, Andy Burns wrote:

Should have used grab adhesive on the lander's legs. Or a can of polyurethane foam. :-)
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On 15/11/2014 08:53, polygonum wrote:

That WAS the problem - the No More Nails on the end of the legs failed.
The solar power is working exactly as it does on your average domestic roof in the UK - it doesn't work when you actually need the most power.
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On 15/11/2014 08:16, Andy Burns wrote:

Did I really hear an interviewer on Radio 4's Today program refer to it as "putting their probe where the sun doesn't shine" ?
:-)
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On Saturday, November 15, 2014 9:55:34 AM UTC, nemo wrote:

yes I heard that as well. It was not clear to me if the interviewer realised what he had said. The interviewee clearly grasped the full double meaning and said something like "well, that's an interesting way of putting it".
Robert
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wrote:

You certainly heard John Humphries mentioning it being on Mars, and someone else talking about "charging the solar cells".
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On Sat, 15 Nov 2014 08:42:17 -0000, Brian Gaff wrote:

Especially when you have a mass of ~100kg but sod all gravity. I think it was on BBC WS Discovery a while back that Philae weighs the same as a sheet of paper, so very little force on quite a large mass.
I've not looked all that hard about the go/no go decisions but wasn't there a problem with the thruster on the top designed to hold Philae down?
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On Sat, 15 Nov 2014 11:02:21 +0000, Tim Streater wrote:

to it

I always thought Mr Humpries was reasonably on the ball for journo/presenter, oh well...

Then I didn't miss hear that one on BBC News 24 either. B-( It's not difficult for crying out loud.
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On Saturday, November 15, 2014 1:28:05 PM UTC, Dave Liquorice wrote:

It's John HUMPHRYS
- Just so that I'm not missed ...
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On Saturday, November 15, 2014 1:28:05 PM UTC, Dave Liquorice wrote:

You're not the only one, Pallab's ill-considered dialogue was heavily edited to remove that by lunchtime when I heard it next....
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True but you need to be in the vicinity of the Sun. No good for the outer reaches of the Solar System.
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On Sat, 15 Nov 2014 15:03:28 +0000, Tim Streater wrote:

By next summer it will be "in the vicinity of the sun" and hopefully start working again a good deal before then. Ridiculously over ambitious project, though, if it's for real. Landing on a comet! Bonkers!
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On Sat, 15 Nov 2014 15:03:28 +0000, Tim Streater wrote:

Have they lost any primary science? I haven't heard they have. Philea was only built to run off battery for a couple of days then go into a repeated sleep & charge / operate mode.

into

Er, It's somewhere between the distance of Earth and Mars from the sun hardly "the outer reaches of the solar system". Perihelion is 1.29 AU, an AU is the sun-earth distance.
It will be interesting to see what happens as the coment moves around the sun, it may well start to illuminate Philae for longer and it'll wake up more and more. Also I'd expect the flight crew to have worked out the crafts attitude and surroundings and come up with some means of either making it "hop" away from the cliff or orientate itself to get maximum benefit of sunlight.
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Dave Liquorice wrote:

Maybe the media has been harsh on them (or badly briefed on what to expect?) the initial reports were "It's bounced off and they admit they've lost contact with it" when it was expected to only have periodic contact in any case.
<http://www.esa.int/Our_Activities/Space_Science/Rosetta/Frequently_asked_questions
"How long will the lander operate on the comet nucleus? The Rosetta lander, called Philae, will touch down on the comet's surface on 12 November 2014. The science observations will start immediately. During the first 2.5 days the first series of scientific measurements will be completed. During this phase the lander will operate on primary battery power. In a second phase that may last up to three months, a secondary set of observations will be conducted, using backup batteries that will be recharged by the energy from the solar cells on the lander. However, no one knows precisely how long the lander will survive on the comet."
I presume they expected to get more drilling done than they have been able to so far ...
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I'm surprised that the rotation of the comet is apparently so stable. On that basis, the Sun will rise as the comet approaches.

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It was originally projected to last until next March, after which it would be destroyed by the summer heat and the increasing attack by debris. It may be that the shadow will delay the death by overheating, whilst the approching summer will allow more power to it before it's killed by heat.
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On Sat, 15 Nov 2014 18:55:50 +0000, Tim Lamb wrote:

Why? There is an awful lot of nothing out there, with nothing close by there are no significant forces acting on it so it just carries on as it is.

The comet has a rotational period of around 12 hours so the sun rises about every 12 hours, trouble is it sets about 1.5 hours later. B-( Which isn't long enough to put enough charge into the battery.
What may happen as the comet swings around is the "season" will change and just maybe the amount of sunlilght Philae sees will increase. Think of sitting in a chair a few feet from a tall wall to your south. In winter you may only sit in sun shine for an hour or two around midday. Come mid-summer you'll be in sunlight for much much longer. Of course Philae could be in "mid-summer" now...
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Oddly enough I know all that. I was referring to the notion that solar panels might be considered the answer for all probes.
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Yes. Objects that shape tend to undergo chaotic tumbling.
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those who insist on a perfect world, freedom will have to do." -- Bigby Wolf
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