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

[wayward bob]

ah okay - good job you're on the case 2hats : thumbs :

 

[2hats]

My reading of it is it could be in that shadowed area or it might have bounced past it. I think that's what they are trying to convey.

 

[TopCat]

Bye bye plucky little probe.

 

[ferrelhadley]

 

[StoneRoad]

If the solar calls are getting less than 1.5 hrs of light instead of 12.4 hrs - I wonder how long it will take the back-up battery to re-charge with enough power to be useful, or will it discharge again trying to contact the orbiter ?
I suppose we may have to wait until Comet67P gets closer to the sun to find out if the lift and shuffle move has improved the situation. ........ Although anything more from Philae is a massive bonus over the FSS.

 

[2hats]

The (initial) problem is that the battery needs to be warmed first before it can be charged up and then there is a 'boot up' overhead (a certain number of watts will be needed to just get Philae in to a state where it can transmit). It will probably need substantially more sunlight than it is getting right now to do that. As the comet heads towards perihelion and the comet precesses this will happen and it will also warm. Quite possibly where it is will be an advantage as it was thought it would fail due to the higher temperatures after a few months. The current location may however shield the (main body of the) lander from this heat whilst (just) gradually providing enough sunlight to the solar arrays to get the battery up to a useful level. Only time will tell, of course. Rosetta will be listening... (and in the meantime gathering lots of data about the comet as it becomes more active).

 

[gentlegreen]

I suppose a thermo-nuclear generator would have been too heavy ?

 

[Crispy]

I suppose a thermo-nuclear generator would have been too heavy ?

Europe doesn't build RTGs, for political reasons
Besides, Plutonium 238 is a very rare commodity these days.

EDIT: But yes, it would have been too heavy

 

[2hats]

I suppose a thermo-nuclear generator would have been too heavy ?

We covered that earlier. Too heavy for various reasons. A political hot potato too. Which means ESA has never developed the tech for it so it was out of the question anyway. So the lander was designed with sufficient power from the primary battery to complete the primary scientific mission. The rechargeable secondary battery is there for the extended mission (bonus game).

 

[2hats]

Plutonium 238 is a very rare commodity these days.

However, there are something like 100 tonnes of PuO2 at Sellafield/NNL which has potential for production of Am241 based batteries. Not as handy as Pu238 - Am241 delivers ~100 W/kg with high gamma, Pu238 ~500 W/kg with low gamma. But with electronics becoming more power efficient the idea could have legs (eg Curiosity has an RTG with about 5kg Pu238, but with various advances this would be met with maybe a 15-20 kg Am241 RTG). ESA commissioned a study into the possibility of going down this route a few years ago and apparently has just set up a small scale pilot project with NNL.

PS NNL has an incentive to get rid of the Am241 from the Pu stockpile before it makes further processing far harder (once the proportion of Am241 gets too high - takes a few years - the gamma makes it a lot harder, more expensive to handle).

 

[weltweit]

Comet landing: Organic molecules detected by Philae
http://www.bbc.co.uk/news/science-environment-30097648

The Philae lander has detected organic molecules on the surface of its comet, scientists have confirmed.
Carbon-containing "organics" are the basis of life on Earth and may give clues to chemical ingredients delivered to our planet early in its history.

The compounds were picked up by a German-built instrument designed to "sniff" the comet's thin atmosphere.
Other analyses suggest the comet's surface is largely water-ice covered with a thin dust layer.

 

[Piers Gibbon]

this is exciting news

 

[Crispy]

We knew this already tbf. Organic molecules have been deteced via spectroscopy of comets' comas

 

[ferrelhadley]

Organic just means lots of carbon and bastard hard to remember names. Although everyone always remembers benzine because of the dream snake.

That said the "it began out there" mob will be going daft.

 

[2hats]

Organic molecules have been observed in the interstellar medium for over 70 years.

 

[Fingers]

I am very much looking forward to he day that 2hats lands a Routemaster bus crammed full of rave sound systems on Neptune. I think he may well have the knowledge

 

[Fingers]

On a serious note, what percentage of the critical science was done on it's first battery charge before it had a kip? And how much science will not be able to be completed? I assume the proper sexy stuff was done first.

Edit: another question. It is widely accepted that Philae will become inoperable after the Perihelion due to over heating of the components (what temperature?) but what will happen to Rosetta?

Stay orbiting the comet due to human intervention/let to drift in space/die off due to same reasons as Philae?

 

[2hats]

The estimate was something like 80% of the planned science programme was completed.

Barring component failure, Rosetta will probably remain functional until it runs out of fuel for manoeuvres, at which point it would continue to be loosely gravitationally bound to the comet, eventually being perturbed into heliocentric orbit. Though there has been some discussion of using the final fuel to set the orbiter down on the surface of the nucleus where it would remain until the surface is disrupted at some future perihelion pass.

 

[Fingers]

The estimate was something like 80% of the planned science programme was completed.

Barring component failure, Rosetta will probably remain functional until it runs out of fuel for manoeuvres, at which point it would continue to be loosely gravitationally bound to the comet, eventually being perturbed into heliocentric orbit. Though there has been some discussion of using the final fuel to set the orbiter down on the surface of the nucleus where it would remain until the surface is disrupted at some future perihelion pass.

80%? Impressive!

Is there any scientific benefit on setting Rosseta down? Is she equipped with surface based science equipment or would it just be a tribute to her?

 

[Crispy]

80%? Impressive!

Is there any scientific benefit on setting Rosseta down? Is she equipped with surface based science equipment or would it just be a tribute to her?

If Rosetta "lands" then it should be able to stay there and travel with the comet for another full orbit round the sun (6.45 years), rather than drift away. They'll be able to study it throughout its life cycle. If they're clever, they can land it on one lobe of the comet, with the instruments pointing a the other lobe. That's a long time to extend a mission though.

 

[2hats]

That's a long time to extend a mission though.

If it lasts that long the limiting factor will be funding. (Though setting it down on the surface would create subsequent power and communications issues.)

 

[2hats]

In a happy twist it looks like some cometary material managed to 'contaminate' the alpha particle x-ray spectrometer (APXS) on which the shutter failed to open. Much more analysis is required to determine what the data is telling the investigators.

In other news data from the MUPUS package has led to a:

preliminary assessment that the upper layers of the comet’s surface consist of dust of 10–20 cm thickness, overlaying mechanically strong ice or ice and dust mixtures.

At greater depths, the ice likely becomes more porous, as the overall low density of the nucleus – determined by instruments on the Rosetta orbiter – suggests.

More here.

That would certainly help explain the bounce and the difficulty for the landing feet ice screws to gain any purchase on the surface. The (inoperative) thruster almost certainly would have been needed to achieve a successful landing as was intended.

 

[Crispy]

What I take from that is that the whole thing is a loose jumble of lumps of ice, the surface of which has been knocked about, chipped off and pulverised, sublimed and re-condensed as it goes round the sun, forming a more solid "crust". Dust comes from impacts and just general solar system detritus.

 

[Lord Camomile]

Yeah, that's... that's what I thought too.

 

[2hats]

What I take from that is that the whole thing is a loose jumble of lumps of ice, the surface of which has been knocked about, chipped off and pulverised, sublimed and re-condensed as it goes round the sun, forming a more solid "crust". Dust comes from impacts and just general solar system detritus.

Yeah, it's probably like a minstrel that you have accidentally dropped under the sofa

If one considers how pulverised the surface of our moon is by micrometeorite bombardment, imagine that for this comet (which can be travelling up to ~30% faster about the Sun).

 

[Limejuice]

That would certainly help explain the bounce and the difficulty for the landing feet ice screws to gain any purchase on the surface. The (inoperative) thruster almost certainly would have been needed to achieve a successful landing as was intended.

It seems to me they planned pretty well for unknown / uncertain conditions (but one or two components let them down).

But we learn.

So I think we should have another go.

 

[Limejuice]

Yeah, that's... that's what I thought too.

Me too.

 

[Lord Camomile]

Yeah, I think we're all the same page here.

 

[Lord Camomile]

I think we should have another go.

Quick trip to the moon first?

We plan to send an unmanned robotic landing module to the South Pole of the Moon – an area unexplored by previous missions.

We’re going to use pioneering technology to drill down to a depth of at least 20m – 10 times deeper than has ever been drilled before – and potentially as deep as 100m. By doing this, we will access lunar rock dating back up to 4.5 billion years to discover the geological composition of the Moon, the ancient relationship it shares with our planet and the effects of asteroid bombardment. Ultimately, the project will improve scientific understanding of the early solar system, the formation of our planet and the Moon, and the conditions that initiated life on Earth.

 

[Limejuice]

Quick trip to the moon first?

Excellent.

I'll make a packed lunch and bring some pop.

When do we go?