Totally naive question here - can all this not be done automatically? It seems to me as if this is a largely manual process, and that's why it's going to take 3 months, no?
The processes are automatically executed, but are check-pointed rather than run end-to-end. This is to make sure partial failures can be detected.
Building the self-sensing and error-recovery logic to support a "level 5" automated unfolding is wasteful of taxpayer money when a few folks can just take a little longer to do it stepwise -- with much less development, hardware, and software cost overall.
Very true, especially if they tried to do all that the first time.
In a way, this stepwise deployment is a test run for a future version that can do it a little bit more automated.
In this case all but the fine-phasing and possibly FOV alignment are one-off operations during commissioning. The pre-launch simulations may not match the actual behaviour and results of the telescope so it makes sense to perform each step under engineer/scientist control and be able to spend time studying the data and possibly improving the process along the way and revisiting earlier steps and/or segments.
The Webb telescope is 10 light-seconds out, so manual adjustment will be really slow. NASA is being very cautious. It can't be serviced, and the US will probably never launch another one.
[1] https://www.osti.gov/biblio/6240189-alignment-calibration-ke...
Also note that JWST still hasn't cooled down to temp yet! Temps here: https://www.jwst.nasa.gov/content/webbLaunch/whereIsWebb.htm...
Mirror is supposed to be at ~50K, and it isn't there yet. (And the instruments are still at 100K+, a month after the sunshield deployed, and you sure aren't doing anything until the actual cameras are cold!) Every time you run an alignment motor you heat up a mirror segment a little bit, so you do want to run coarse alignment early, then gradually converge on fine alignment as the whole structure approaches design temp.
Remember, JWST is weird. Hubble was one big piece of (warm) glass. Multisegment telescopes down on Earth can be nailed to a hundred ton support structure, but JWST is comparatively big and floppy, since the frame had to be light enough to launch into space. (Every kilogram of mirror support structure is another kilogram of propellant lost, and once all the fuel is gone you don't have an observatory anymore...) Something like that is just going to inherently take a while to calibrate.
I'm not sure how much of that heat is coming through the sunshield and how much is heat from the equipment.
If the JWST were out by, say, Pluto, then you certainly could describe that vacuum as "cold" (inasmuch as a vacuum has a temperature), because you hardly get any sunlight. In fact, Pluto itself has a temperature around 40K.
Skimming this paper https://www.stsci.edu/files/live/sites/www/files/home/jwst/d... it looks like they expect 10.46mW optical module heat, and they've given themselves 36mW of headroom "for conductive and radiative loads." (Heat conducted from the structure, and radiant heat from the the comparatively warm primary mirror?)
Why 24 hours? The JWST is only 5 light-seconds away and has up to 28 Mbit/s downlink.
It's not because it's a manual process, it's because they opted for simplicity in the actuators department rather than having another coarse+fast mode in the physical mechanism, or redundant mechanisms.
But what I always think when a NASA control room erupts in joy after a landing, is that those people just learned they have a job for years.
I have to make an orderly retreat to my next cynical line: everyone in that room is aware that their reaction wis filmed and will be shown across the world.
Your team spent years researching something that had never been done before. Survived many rounds of "should we just cancel this project", continued to be funded after coming in no where near your proposed budget, delay after delay, to finally see the thing lift off. You wouldn't have the slightest bit of non-robotic emotion for yourself and fellow team members?
Hope I never have to work with someone as dull as that.
Cheers!
If you're a developer that has automated something that does something faster/cheaper/more accurately than a person and haven't had this thrown at you, then you're missing out! It's like a rite of passage.
No cynicism intended. Hence the ;-)