James Webb Telescope

New Smarter Every Day with part two of his piece on the sun-shield. Some pretty cool info about how the layers are measured in 1g and the data used to predict their shape in microgravity. What strikes me is how even something as seemingly simple as the sun-shield is actually an incredibly complex feat of engineering. The way the shape of the gaps between the layers determine the efficiency of their ability to bounce the radiated energy between them and out the gaps away from the instrument is really cool.

 
Foster Zygote said:
New Smarter Every Day with part two of his piece on the sun-shield. Some pretty cool info about how the layers are measured in 1g and the data used to predict their shape in microgravity. What strikes me is how even something as seemingly simple as the sun-shield is actually an incredibly complex feat of engineering. The way the shape of the gaps between the layers determine the efficiency of their ability to bounce the radiated energy between them and out the gaps away from the instrument is really cool.
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And in no way did you intend that pun!
 
Puppycow said:
Maybe it's because the others are designed to be passively cooled while MIRI is designed to be actively cooled (thus passive cooling is less efficient for it due to having less radiator area or something like that)...
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Without knowing the construction it seems to make sense that since the MIRI needs to be well over 30 degrees colder than the passively cooled parts, it's probably insulated from them which would likely result in its own passive cooling being slower.
 
Step 5: Fine phasing has begun

Temperature updates

Red = Mar 16
Black = Feb 21
Green = Instrument target temperature reached

Frame and mirror
Primary Mirror -230° (44K) -228° (46K)
Instrument Radiator -234° (39K) -231° (42K)
Fine Steering Motor -238° (35K) -235° (39K)

Instruments
MIRI -176° (97K) -155° (118K)
NIRcam -232° (42K)-228° (46K)
NIRSpec -234° (39K)-227° (45K)
FGS/NIRISS -227° (46K)-221° (56K)

MIRI's temperature is still lagging behind, but is dropping faster than the others as they approach their target temperatures. It has dropped 21° in 24 days and has another 97° to go, so that looks like about 3-4 months to reach its target of 7K


ETA: The latest alignment evaluation image

https://www.space.com/james-webb-space-telescope-alignment-photo
 
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smartcooky said:
Step 5: Fine phasing has begun

Temperature updates

Red = Mar 16
Black = Feb 21
Green = Instrument target temperature reached

Frame and mirror
Primary Mirror -230° (44K) -228° (46K)
Instrument Radiator -234° (39K) -231° (42K)
Fine Steering Motor -238° (35K) -235° (39K)

Instruments
MIRI -176° (97K) -155° (118K)
NIRcam -232° (42K)-228° (46K)
NIRSpec -234° (39K)-227° (45K)
FGS/NIRISS -227° (46K)-221° (56K)

MIRI's temperature is still lagging behind, but is dropping faster than the others as they approach their target temperatures. It has dropped 21° in 24 days and has another 97° to go, so that looks like about 3-4 months to reach its target of 7K


ETA: The latest alignment evaluation image

https://www.space.com/james-webb-space-telescope-alignment-photo
Click to expand...

Another interesting image - Gaia observes Webb.

https://www.space.com/james-webb-space-telescope-gaia-photo
 
rjh01 said:

This is Dr. Becky in full emotional sexy flight.

The telescope mirrors are now aligned. Look at the image they have released! Wow!
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Staggeringly, that star is about 12th magnitude - 5 magnitudes (or 100x) dimmer that the dimmest star visible with the naked eye under perfect viewing conditions.

I just love her sheer joy and enthusiasm for science. The world needs more Dr Beckies!
 
smartcooky said:
MIRI's temperature is still lagging behind, but is dropping faster than the others as they approach their target temperatures. It has dropped 21° in 24 days and has another 97° to go, so that looks like about 3-4 months to reach its target of 7K
Click to expand...

I think it will reach 7K in about 3-4 weeks, rather than months. It just depends on when they turn on the cryocooler. Which should be right about now, if it hasn't already happened. We are now 82 days into the mission (since Christmas day).

See the article I linked in Post #637 again to refresh your memory, or maybe you didn't read what I quoted the first time.
 
smartcooky said:
Staggeringly, that star is about 12th magnitude - 5 magnitudes (or 100x) dimmer that the dimmest star visible with the naked eye under perfect viewing conditions.

I just love her sheer joy and enthusiasm for science. The world needs more Dr Beckies!
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I am surprised that it is not a point of light.
Are we going to be always treated to a hexagonal explosion?
Early days...
 
Samson said:
I am surprised that it is not a point of light.
Are we going to be always treated to a hexagonal explosion?
Early days...
Click to expand...

Almost any telescope shows artifacts when imaging something way over the sensitivity limit. Hubble shows 90 degree crosses due to the struts in the optical path for bright sources.

https://apod.nasa.gov/apod/ap160118.html

Point it at something a lot fainter and you won't notice.
 
Thank you both.
What a machine, and I really love that everyone is communal here.
 
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