The Rosetta probe has woken up ...

[grmcdorman]

Just fantastic!

This is working out to be a banner year for solar-system science: Rosetta/Philae, Dawn, New Horizons.

 

[Pianoro]

On the other hand, with Churyumov-Gerasimenko now being fairly close to the sun and still no message from the lander, chances for re-establishing contact don't look the greatest at the moment.

Awesome, only two days to prove my pessimistic assessment wrong. I should make those more often.

This whole mission is just a fantastic achievement all around!

 

[Denver]

Fantastic!

More info: http://www.bbc.co.uk/news/science-environment-33126885

This!

And this!

For the first time, we will have a hitchhiker riding on a comet and describing what happens to a comet as it heats up on its journey through space

And this!

One ambition not fulfilled before the robot went to sleep was to try to drill into the comet, to examine its chemical make-up. One attempt was made last year, and it failed. A second attempt will now become a priority.

And other this's to come!

 

[GlennB]

While Philae work better as it warms up? Experience with my car battery suggests "yes" but I know little of the technicalities in this case

 

[tusenfem]

While Philae work better as it warms up? Experience with my car battery suggests "yes" but I know little of the technicalities in this case

a higher temperature will be better for the batteries, but the the instruments and computers were developed to work in cold temperatures. when rosetta approaches perihelion the instruments and computer will die a heat death.

 

[slyjoe]

a higher temperature will be better for the batteries, but the the instruments and computers were developed to work in cold temperatures. when rosetta approaches perihelion the instruments and computer will die a heat death.

Are you sure about that? It's currently 205 million km from the sun. It's closest approach is about 186 million km in August. Current temperature is estimated at -35C. I question the "heat death" - not sure what the highest temperatures will be.

 

[tusenfem]

Are you sure about that? It's currently 205 million km from the sun. It's closest approach is about 186 million km in August. Current temperature is estimated at -35C. I question the "heat death" - not sure what the highest temperatures will be.

I would need to check what the maximum temperature is that the instruments can take, or ask my colleague when I am at work again. Although the location at which Philea is standing now improves the conditions because ot the lot of shade.

 

[slyjoe]

I would guess 50C, maybe 85. What I don't know is what the expected temperature will be on the comet.

 

[jonesdave116]

Somebody asked elsewhere about the current temp on 67P. I nicked the below formula from Tom Bridgman's blog: http://dealingwithcreationisminastronomy.blogspot.co.uk/2014/11/electric-comets-ii-of-water-ice.html, so if it's wrong, blame him!

Temp Sun (K) * sqrt (radius Sun (AU)/distance (AU))
Albedo ignored in this equation.

The comet was 218m km from the Sun on 11 June. That is ~1.45 AU.
Radius of the Sun = 0.00468 AU, and the temperature is 5780 K.
So, that gives ~328 K, or 55 C.

Of course, the temp that Philae will measure will be dependent on the height above the ground that the "thermometer" is. Temp will drop off very quickly with height on an essentially airless body, and I'm not sure what sort of reflectivity Philae has either.

So what I'm basically saying is, "I haven't got a clue", and it's probably time for a couple of pints before bedtime.

 

[CapelDodger]

While Philae is getting all the coverage, and it is indeed an engagingly plucky little crash-test dummy, you have to hand it to the engineers who built it. Outstanding work to which I am about to drink a toast.

 

[a_unique_person]

This!

And this!


And this!


And other this's to come!

Being able to drill into the Comet would depend on which way it landed.

 

[Rincewind]

While Philae is getting all the coverage, and it is indeed an engagingly plucky little crash-test dummy, you have to hand it to the engineers who built it. Outstanding work to which I am about to drink a toast.

I agree 100%!

And thanks to the Clangers for looking after it...

 

[Craig B]

I agree 100%!

And thanks to the Clangers for looking after it...

Will the Soup Dragon's soup warm up at perihelion?

 

[Rincewind]

Will the Soup Dragon's soup warm up at perihelion?

Well, obviously!

What d'you think is fuelling the probe?

 

[lpetrich]

The comet was 218m km from the Sun on 11 June. That is ~1.45 AU.
Radius of the Sun = 0.00468 AU, and the temperature is 5780 K.
So, that gives ~328 K, or 55 C.

Doing this calculation a bit more precisely, I used:
Solar constant^WP: 1361 W/m^2
Stefan–Boltzmann constant^WP: 5.670373*10^(-8) W/m^2/K^4
Astronomical unit^WP: 149597870700 m

For a surface at 1 AU whose normal direction points at the Sun, and whose absorption and emission albedos are the same, I find a temperature of 394 K or 121 C.

The Earth does not get nearly that hot, so one has to do the calculation more carefully. Doing the calculation for a sphere, assuming a constant temperature over it, one gets 1/sqrt(2) * the previous number. For the Earth, that is 279 K or 6 C. The Earth's actual average temperature is around 15 C.

For 1.45 AU, the two numbers are 54 C and -42 C. The latter number is about right for Philae's current temperature.

 

[davefoc]

Doing this calculation a bit more precisely, I used:
Solar constant^WP: 1361 W/m^2
Stefan–Boltzmann constant^WP: 5.670373*10^(-8) W/m^2/K^4
Astronomical unit^WP: 149597870700 m

For a surface at 1 AU whose normal direction points at the Sun, and whose absorption and emission albedos are the same, I find a temperature of 394 K or 121 C.

The Earth does not get nearly that hot, so one has to do the calculation more carefully. Doing the calculation for a sphere, assuming a constant temperature over it, one gets 1/sqrt(2) * the previous number. For the Earth, that is 279 K or 6 C. The Earth's actual average temperature is around 15 C.

For 1.45 AU, the two numbers are 54 C and -42 C. The latter number is about right for Philae's current temperature.

I am confused as to what is being calculated here. The temperature of the comet's atmosphere would be irrelevant to the temperature the probe would be at.

The temperature of the probe would be determined by the direct heat gain from solar radiation, the radiation from the surface of the comet, the heat gained from the waste heat of probe devices and the heat lost to radiation from the probe. I don't think it would matter much how far above the surface the probe happened to be unless it was close enough that substantial conductive heat transfer was possible.

Is the above calculation being used to estimate the temperature of the surface of the comet? If so, isn't it necessary to take the other heat sources and sinks of the probe to come up with an estimate for the temperature of the probe?

 

[Belz...]

Brilliant!

Cool ! I need to go get my sexy gun girls shirt.

 

[Corsair 115]

Cool ! I need to go get my sexy gun girls shirt.

Are you trying to trigger all those poor, sensitive souls on Twitter and Tumblr?!?

 

[lpetrich]

I am confused as to what is being calculated here. The temperature of the comet's atmosphere would be irrelevant to the temperature the probe would be at.

This is a radiation-balance calculation that's independent of the comet's atmosphere.

The temperature of the probe would be determined by the direct heat gain from solar radiation, the radiation from the surface of the comet, the heat gained from the waste heat of probe devices and the heat lost to radiation from the probe. I don't think it would matter much how far above the surface the probe happened to be unless it was close enough that substantial conductive heat transfer was possible.

Then why not try to calculate it? See if you can find some appropriate numbers. Be sure to source every number that you have found and give your calculation methods, as I have done.

What I'm doing is a very rough estimate, a guide as to what numbers that one can expect. I concede that I'm taking several shortcuts in it.

Is the above calculation being used to estimate the temperature of the surface of the comet? If so, isn't it necessary to take the other heat sources and sinks of the probe to come up with an estimate for the temperature of the probe?

The interior of the comet likely has essentially zero internal heating. But evaporation of comet material will likely cool the surroundings.

 

[davefoc]

This is a radiation-balance calculation that's independent of the comet's atmosphere.

Then why not try to calculate it? See if you can find some appropriate numbers. Be sure to source every number that you have found and give your calculation methods, as I have done.

What I'm doing is a very rough estimate, a guide as to what numbers that one can expect. I concede that I'm taking several shortcuts in it.

The interior of the comet likely has essentially zero internal heating. But evaporation of comet material will likely cool the surroundings.

Thank you for the response and my apologies, but I want to make sure I understood your response. Is the formula you used a formula for calculating the surface temperature of a body floating in space without an atmosphere that the "absorption and emission albedos are the same"?

I wasn't sure what "absorption and emission albedos are the same" meant but I took it to mean that half the incoming solar radiation was reflected and the other half was absorbed into the surface.

OK, that seems like a useful thing to know if one were trying to calculate the temperature of the probe since it might be a major contributor to the heat gain of the probe. But the heat gain from the sun might be a big factor as well I would think and possibly heat produced within the probe might be an issue as well. I'm leaving to try to do work that might result in me achieving an economic gain but if I understand what you've said and somebody hasn't provided more information I'll take a shot at trying to figure out what besides the temperature of the comet is significant with regard to the temperature of the probe this evening.