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Ripley

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I've just noticed that NASA's "eyes on the solar sytem" website still shows a closed/undeployed WEBB...
 

Thunder Chicken

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Need to coarse tune all 18 mirror. This will start any moment and continue next 2 weeks.
Then L2 insert burn.
Than 3 month fine mirror alignment and instrument calibration.
Why do the optics tuning and alignments take so long? I understand that the telescope has to chill and reach thermal equilibrium to avoid thermal distortion, but my back of the envelope heat transfer calculations suggest that should take days to a few weeks, not months. Maybe they are looking for "more 9s" closer to equilibrium before doing the fine alignments and taking first data? Shedding the last few degrees will be a slow process.
 

JDat

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Why do the optics tuning and alignments take so long? I understand that the telescope has to chill and reach thermal equilibrium to avoid thermal distortion, but my back of the envelope heat transfer calculations suggest that should take days to a few weeks, not months. Maybe they are looking for "more 9s" closer to equilibrium before doing the fine alignments and taking first data? Shedding the last few degrees will be a slow process.

From my knowledge how it works:
18 mirror segments on main mirror and 1 segment(?) on secondary mirror
Each segment on main mirror have 6 servos on corners + 1 servo to change shape/bending for segment.
Secondary mirror have 6 servos/

Calibration process ( program in GWBASIC ):
10) Coll down sensors
20) Point JWST to "calibration star".
30) Take photo.
40) Download image.
50) Analyse.
60) Send tuning commands to servo.
70) Repeat (goto 20) until all segments aligned.
80) L2 insert burn
90) More sensor chilling
100) Imaging (detector) Sensor test and calibration
110) More mirror aligment.

Couterquestion: why origami deployment took 2 weeks? You can activate all deployment mechanisms and do it in 16 hours...

;)
 

GLS

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Couterquestion: why origami deployment took 2 weeks? You can activate all deployment mechanisms and do it in 16 hours...
My guesses are: (1) DSN time, (2) available power several motors at once, and probably the big one is (3) making sure the previous step was well performed and things are ok before continuing.
Anyway, there's no rush as it will take a long time for the telescope to cool to it's operating temperature.
 
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