[X] My Assistant

[Prakshepak]

It appears that ISRO did not anticipate the quantum of heat from Lunar surface, so the spacecraft has cabin temp of 50 deg - 10 deg higher than expected.

Really speaking if that is the cabin temp then it should not be a problem for space qualified components but one possibility is that there may be certain Hot Spots of which ISRO may be weary.

Open it in Internet Explorer. Firefox will not work

[Guest_Zvezdichko_*]

Thank you, it works with IE.

[Bhas_From_India]

Good News...
Chandrayaan working normally: ISRO
Link: http://www.thehindubusinessline.com/busine...us/14261420.htm

[jamescanvin]

That makes no sense.

"working normally" but also "not work on all the payloads at a given time"

"summer on the moon"

"temperature in the moon's atmosphere"

Never has such a short article confused me so much!

[Stu]

Never has such a short article confused me so much!

Yes, hard to believe isn't it, when phone conversations with Call Centres are always so easy to follow...

[Hungry4info]

I'm not sure I buy into the idea that the lunar atmosphere is causing Chandrayaan-1's problems. The moon has a very low axial tilt, "summer" on the moon is probably quite similar to "winter". Doesn't Chandrayaan-1 orbit well above the lunar atmosphere anyway? And given how tenuous the atmosphere is, could it even really affect Chandrayaan-1's temperature if it were orbiting within it (assuming it didn't hit a mountain or something)?

[Phil Stooke]

It's nothing to do with the atmosphere, or summer, or anything else that's been said like that. I don't know whether we are getting really bad journalism, or if ISRO is straining to explain things to an audience it thinks knows nothing about the subject, and straying into very weak explanations. Poor choice of analogy, or things like that.

Phil

[mcaplinger]

They're picking up 1200W/m^2 from the Moon, and 1300 from the Sun??? That doesn't sound right... Or, are we talking about waste heat from surface re-radiation as a contributing factor?

It's counterintutive, but yes, the Moon radiates in the IR on the day side a lot. And the huge surface temperature excursions make simple dayside heat rejection hard to do without cooling off too much on the nightside. This was a big challenge for us on LROC as well.

[mcaplinger]

It's nothing to do with the atmosphere, or summer, or anything else that's been said like that.

Bad translations at a minimum. The main variable for thermal design is "beta angle", the angle between the sun and the orbit plane. For most systems, beta=0 is the worst/hottest case, so they may be in that geometry now.

[jekbradbury]

Here's an anaglyph made from the first bit of the new movie:

[Vultur]

I really have no idea what that's trying to say - does the moon even have summer?

[Doc]

I dont think this about lunar summer (whatever that is). This may simply be, as Phil Stooke put it, a problem with their position in relation to the sun and the radiating lunar surface, or their heat management system has a design flaw.

[Doc]

Check out the post on the 'heat issue' at New scientist. Its just as we thought. Isro referred to the current situation as a 'local' summer, not a 'lunar' summer.

[Phil Stooke]

Back to the summer issue. I think that what is intended is this: the spacecraft's orbit plane right now is roughly aligned with the sun - i.e. the sun is now in or close to the orbit plane, so the spacecraft fies over the sub-solar longitude on every orbit. Three months from now the orbit will be over the terminators, which will give a lot less heating from the ground. Six months from now, it will be passing over the sub-solar longitude again. Put another way, the orbit plane is fixed in space. It's not like Mars Odyssey etc., crossing the equator at a fixed time of day on every orbit, which requires the orbit plane to rotate during a Mars year.

But summer this is not!

Phil

[mcaplinger]

...the sun is now in or close to the orbit plane...

Isn't that what I said in post #279?

At any rate, does anyone know what the current orbital geometry really is? For some situations beta=90 (constantly over the terminator) could be the worst case, since it will always get solar input on the same side. beta=0 is stressing for lunar IR.