James Webb Space Telescope

[Dr Sardonicus]

Originally Posted by firejuggler

xkcd

2564

In space, no one can hear you say, "SMILE!"

[chalsall]

Originally Posted by Dr Sardonicus

In space, no one can hear you say, "SMILE!"

That is why sign language is so important. All scuba divers (et al) are trained in this.

There are some who cannot hear, and they rely solely on the visual. Reading lips, etc. I am one of those.

The last episode of last year's The Expanse had an excellent example of just how much can be communicated in a narrow bandwidth channel using only photons.

[firejuggler]

Webb is fully deployed!

https://twitter.com/NASAWebb/status/1479880178021060609

[Uncwilly]

The actuators still need to align the mirror segments.

[firejuggler]

another piece of news :
https://twitter.com/SpaceflightNow/status/1479900879218221060

Originally Posted by Twitter

Mike Menzel, JWST’s mission systems engineer at NASA, says 49 of the mission’s original list of 344 single-point failures remain open, and won’t be retired for the rest of the mission. "These 49 are typical of all missions, things like propulsion tanks."

[a1call]

Is winner of the list includes design flaws:

https://www.nasa.gov/content/hubbles-mirror-flaw

I don’t have a lot of confidence in the Wikipedia-Generation designers.

[LaurV]

Originally Posted by firejuggler

xkcd

2564

that's a bitter joke, think about what a formidable weapon that mirror is, if retina gets the control of the gyroscopes...

[Dr Sardonicus]

Originally Posted by a1call

Is winner of the list includes design flaws:

https://www.nasa.gov/content/hubbles-mirror-flaw

I don’t have a lot of confidence in the Wikipedia-Generation designers.

With the Hubble mirror, the problem was with the test equipment that was supposed to insure that the mirror was correctly ground.

Identifying and precisely quantifying the error was vital for enabling the creation of corrective optics. Luckily, the test equipment hadn't been moved or disassembled since it was used.

The Optical Systems Failure Report described the error:

In the "reflective null corrector" (RNC), the "field lens" was too far from the "lower mirror" by about 1.3 mm.

The report also identified how the error occurred.

With the Webb telescope, the equipment used to test the optics is called ASPA (AOS Source Plate Assembly, AOS = Aft Optics Subsystem). If there turns out to have been a problem with this test equipment, I suppose a failure analysis would be an academic exercise, since there's no way to fix the optics if they're messed up. So I suppose the question of whether the ASPA has been carefully preserved to enable a possible failure analysis is also academic...

[kriesel]

Originally Posted by Dr Sardonicus

With the Webb telescope, the equipment used to test the optics is called ASPA (AOS Source Plate Assembly, AOS = Aft Optics Subsystem). If there turns out to have been a problem with this test equipment, I suppose a failure analysis would be an academic exercise, since there's no way to fix the optics if they're messed up. So I suppose the question of whether the ASPA has been carefully preserved to enable a possible failure analysis is also academic...

Academic only if NASA neither attempts a robotic repair nor producing another instrument to replace or supersede JWST. It's so much more interesting to learn from past mistakes, by puzzling out the old ones, so one can make new ones, rather than to repeat the old ones.

Originally Posted by a1call

winner of the list includes design flaws:
https://www.nasa.gov/content/hubbles-mirror-flaw
I don’t have a lot of confidence in the Wikipedia-Generation designers.

Sad part of that story includes that there were warnings that were ignored. Its reflectivity was measured as anomalously good. Its corrective optics was both an engineering feat and a political one. The space allocated to COSTAR required eviction of one of the original onboard instruments. Sacrificed was the HSP (high speed photometer), which was a mechanically simple less costly yet innovative instrument with less political support from the scientific community.

[retina]

Originally Posted by Dr Sardonicus

With the Hubble mirror, the problem was with the test equipment that was supposed to insure that the mirror was correctly ground.

Yes, but it is more than that. Test equipment doesn't align or calibrate itself.

The root problem was with procedures that were not followed to ensure such a basic error never occurred. The procedures had all the potential to catch the error, but some humans assumed too much and never bothered to verify. Perhaps a bit of arrogance was in the mix also with someone saying "I know what I am doing, I'm the expert, just trust me, it'll be fine."

Blaming inanimate objects? Isn't that like the bad workers blaming their tools?

[retina]

Originally Posted by LaurV

... think about what a formidable weapon that mirror is, if retina gets the control of the gyroscopes...

Pointing the mirror directly to the Sun would make for a nice temporary light show. A $10B firework. Thanks for the idea.