JWST Grand opening

SteveB

Well-known member
Hi all.
The present day goal is July 12, 2022 for the James Webb Space Telescope to start showing imagery.


So, for those who have been waiting with baited breath.....

3 weeks and a day....
 

4tune8chance

Active member
Bit of bad news, one of the primary mirror segments was struck by a micrometeorite, not sure if functionality will be affected.
 

SteveB

Well-known member

inertia

Super Member
Bit of bad news, one of the primary mirror segments was struck by a micrometeorite, not sure if functionality will be affected.

The good news is that optical engineers anticipated micrometeor strikes and added margin into the design in order to maintain enough performance for scientific missions.

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inertia

Super Member
Hi all.
The present day goal is July 12, 2022 for the James Webb Space Telescope to start showing imagery.


So, for those who have been waiting with baited breath.....

3 weeks and a day....

Anticipation: It's making me wait.

Metrics: specifications include diffraction from the primary mirror aperture and secondary mirror strut obscurations

Resolution: 0.1 arcsec
Waveband: 0.6 - 28.5 microns
Strehl Ratio > 0.8 (at 2 microns) Note: diffraction limited performance occurs at 0.8

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Reference: Ball Aerospace optical performance characteristics
 

inertia

Super Member
Lets hope so. I wonder how they compensate for damage, some sort of software solution where it subtracts that part of the mirror?

James Webb engineers employed adaptive optics to actively control and compensate for optical aberrations. For earth-locked telescopes adaptive optics are incorporated to remove aberrations caused by atmospheric turbulence and aberrations caused by internally generated issues such as misalignment, pits in optics and diffraction from struts for example.


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4tune8chance

Active member
You sound like you think the damage is a lot.

Just how much do you think it is?
I was listening to the podcast 'Astronomy Cast' episode 646, where they stated (from memory) the impact was a little bit bigger than current measures could compensate, but still waiting on clarification.
 

4tune8chance

Active member
James Webb engineers employed adaptive optics to actively control and compensate for optical aberrations. For earth-locked telescopes adaptive optics are incorporated to remove aberrations caused by atmospheric turbulence and aberrations caused by internally generated issues such as misalignment, pits in optics and diffraction from struts for example.


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I really hope it can compensate. In a standard mirror you just paint over a chip and wait until the next mirror overhaul. Adaptive optics is really a big solution for fine tuning the entire surface, but it's entirely feasible I would think, that you could permanently lower one controller below the chipped area such that it would take it out of the observing surface. Although if the chip is an awkward shape reflections in multiple directions might be problematic.
 

inertia

Super Member
I really hope it can compensate. In a standard mirror you just paint over a chip and wait until the next mirror overhaul. Adaptive optics is really a big solution for fine tuning the entire surface, but it's entirely feasible I would think, that you could permanently lower one controller below the chipped area such that it would take it out of the observing surface. Although if the chip is an awkward shape reflections in multiple directions might be problematic.

I stand corrected. As it turns out the telescope only employs active optics instead of adaptive optics to help correct optical aberrations that engineers expect to encounter over time. Adaptive optics in a space environment is overkill because wavefront aberrations in space occur at a rate orders-of-magnitude slower than aberrations caused from atmospheric turbulence.

For those that are inclined to watch, here is a presentation from a long ago friend of mine: FSM = fine steering mirror


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