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James Webb Telescope

Interesting that they have temperature data in both F and C, but not Kelvin, which would be the most useful.

Currently -153 C on the cold side, which is 120 K, if my math is correct. Seems that the heat shield is already working, even though it isn't even deployed yet.
 
After a successful launch of NASA’s James Webb Space Telescope Dec. 25, and completion of two mid-course correction maneuvers, the Webb team has analyzed its initial trajectory and determined the observatory should have enough propellant to allow support of science operations in orbit for significantly more than a 10-year science lifetime. (The minimum baseline for the mission is five years.)
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Something told me they were lowballing it. This is great news though. But still a lot of things left to do before we pop the champange.
 
Puppycow said:
Currently -153 C on the cold side, which is 120 K, if my math is correct. Seems that the heat shield is already working, even though it isn't even deployed yet.
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-153 C isn't particularly cold for the dark side of an object in this region of space. Night time temperatures on the Moon can get colder than that.
 
RecoveringYuppy said:
-153 C isn't particularly cold for the dark side of an object in this region of space. Night time temperatures on the Moon can get colder than that.
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yes, but on a stellar body, heat can be transferred through other means than just radiation - James Webb can only cool itself via radiation.
 
The Great Zaganza said:
yes, but on a stellar body, heat can be transferred through other means than just radiation - James Webb can only cool itself via radiation.
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Huh? How many stars do you think there are near Earth? I only know of the one. And how do stars cool themselves besides radiation? I wouldn't think the solar wind is doing much of the cooling of the Sun.
 
RecoveringYuppy said:
Huh? How many stars do you think there are near Earth? I only know of the one. And how do stars cool themselves besides radiation? I wouldn't think the solar wind is doing much of the cooling of the Sun.
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any mass in space can transmit heat via thermal conduction, thermal convection and thermal radiation. Colder patches on the Moon (or relatively colder patches on the Sun) can act as heat sinks.
the Heat shield of James Webb, on the other hand, can only remove the heat of photon absorption via radiation. it does that by cleverly letting the infrared radiation reflect until it is bounced out at the side.
people say that space is cold, but it would be more accurate to say that it has no temperature.
 
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Still confused by what you are saying. I was talking about the night side of the Moon. There would be no convection there and conduction would be from other parts of the Moon which would make it a warming mechanism, not a cooling mechanism.

And what stellar object were you referring to?
 
RecoveringYuppy said:
Still confused by what you are saying. I was talking about the night side of the Moon. There would be no convection there and conduction would be from other parts of the Moon which would make it a warming mechanism, not a cooling mechanism.

And what stellar object were you referring to?
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only the top layer of the Moon gets exposed to photons (even the dark side is catching some) that heat is conducted deeper into the ground, which acts as a heat sink.
Webb can't do that.
therefore, your comparison of Moon and Webb was not appropriate.
 
The Great Zaganza said:
only the top layer of the Moon gets exposed to photons (even the dark side is catching some) that heat is conducted deeper into the ground, which acts as a heat sink.
Webb can't do that.
therefore, your comparison of Moon and Webb was not appropriate.
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Uh, no. The Moon's surface would be a heat source on the night side. And besides, my statement is true for astronauts floating in space and for the ISS. The cold side temperature of Webb right now is not unusual. It's not unusually cold for an object that isn't explicitly trying to be cold.
 
Puppycow said:
Interesting that they have temperature data in both F and C, but not Kelvin, which would be the most useful.

Currently -153 C on the cold side, whicJWSTh is 120 K, if my math is correct. Seems that the heat shield is already working, even though it isn't even deployed yet.
Click to expand...

RecoveringYuppy said:
-153 C isn't particularly cold for the dark side of an object in this region of space. Night time temperatures on the Moon can get colder than that.
Click to expand...

The Great Zaganza said:
yes, but on a stellar body, heat can be transferred through other means than just radiation - James Webb can only cool itself via radiation.
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It is expected that JWST will take many weeks too cool down to its operational temperature of 40°K. The instruments must be cooled slowly to avoid outgassing, so they have begun cooling and will continue to do so throughout the telescope commissioning.

MIRI (Mid-Infrared Instrument) is the most sensitive to temperature of all the instruments on board, and it will take at least three months to reach its final operating temperature.
 
The Deployable Tower Assembly (the structure that holds the mirrors and the instrument housing) has now been deployed. It has been extended "up" about two metres to give clearance for the sun shield to deploy.
 
The Aft Momentum Flap has been deployed (this used to minimize the effect of solar pressure that would otherwise push the telescope out of its orbit)

The sun shield covers have been opened, so they are getting ready to extend, first the port then the starboard sun shield - nervous times!
 
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