Arthur T Knackerbracket has processed the following story:
The world is still reeling from the release of the James Webb Space Telescope's (JWST) first images. These provided a comprehensive overview of the kind of science operations that Webb will conduct over its 20-year mission. They included the most sensitive and detailed look at some iconic astronomical objects, spectra from an exoplanet atmosphere, and a deep field view of some of the most distant galaxies in the universe. Since their release, we've also been treated to glimpses of objects in the solar system captured by Webb's infrared instruments.
Meanwhile, the JWST collaboration released a full report titled titled "Characterization of JWST science performance from commissioning," in which they examined everything Webb has accomplished so far and what they anticipate throughout the mission. This paper recently appeared online and covers everything from the telescope's navigation and pointing to the performance of its many instruments. An interesting tidbit, which was not previously released, is how Webb suffered a series of micrometeoroid impacts, one of which caused "uncorrectable change" in one mirror segment.
[...] "During commissioning, wavefront sensing recorded six localized surface deformations on the primary mirror that are attributed to impact by micrometeoroids. These occurred at a rate (roughly one per month) consistent with pre-launch expectations. Each micrometeoroid caused degradation in the wavefront of the impacted mirror segment, as measured during regular wavefront sensing. Some of the resulting wavefront degradation is correctable through regular wavefront control; some of it comprises high spatial frequency terms that cannot be corrected."
[...] "The key outcome of six months of commissioning is this: JWST is fully capable of achieving the discoveries for which it was built. JWST was envisioned 'to enable fundamental breakthroughs in our understanding of the formation and evolution of galaxies, stars, and planetary systems'… we now know with certainty that it will. The telescope and instrument suite have demonstrated the sensitivity, stability, image quality, and spectral range that are necessary to transform our understanding of the cosmos through observations spanning from near-earth asteroids to the most distant galaxies."
Moreover, the Report's authors conclude that the JWST's performance has been better than expected, almost across the entire board. In terms of the optical alignment of its mirrors, the point spread function, the time-stability of its imaging, and the fine guidance system that points the observatory, Webb has exceeded expectations. They also indicate that the mirrors are cleaner, and the science instruments have generally provided higher total system throughput than pre-launch expectations. All of this adds up to some optimistic appraisals:
"Collectively, these factors translate into substantially better sensitivity for most instrument modes than was assumed in the exposure time calculator for Cycle 1 observation planning, in many cases by tens of percent. In most cases, JWST will go deeper faster than expected. In addition, JWST has enough propellant on board to last at least 20 years."
As noted in the full article, the performance degradation from the uncorrectable change is not significant.
The report: Characterization of JWST science performance from commissioning
(Score: 4, Insightful) by AnonTechie on Tuesday July 26 2022, @10:26AM (2 children)
With so much calamity and misery all around us, we eagerly wait for good news. It is indeed heartening to note that inspite of such micro-meteorite hits, the James Webb Space Telescope will continue to perform well and surpass expectations. We look forward to seeing many more detailed and clearer pics of the heavens around us. We hope James Webb Space Telescope has a long and productive life ahead !!
Albert Einstein - "Only two things are infinite, the universe and human stupidity, and I'm not sure about the former."
(Score: 2) by takyon on Tuesday July 26 2022, @10:44AM (1 child)
Because of unexpected performance during the launch, JWST could stick around for closer to 20 years than 5 years. That should raise the prospect of a servicing mission, although if it involves the replacement of mirrors in deep space, who knows.
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
(Score: 0) by Anonymous Coward on Tuesday July 26 2022, @11:41AM
I'd bet there's no easy way to remove any of those mirrors since it wasn't built for modularity. A refueling servicing mission would be interesting, but again, it would depend upon how accessible the fuel tanks are. I don't think they designed them with any thought for refueling back then. A manned mission to L2 would be interesting in itself: far enough away to be considered interplanetary practice, perhaps measure the radiation environment and effectiveness of shielding, etc., etc.
(Score: 2, Interesting) by shrewdsheep on Tuesday July 26 2022, @12:46PM (1 child)
They say it is roughly one impact per month one of which was already uncorrectable. I am wondering how fast this will degrade telescope performance. Is this the main bottleneck for its lifespan?
(Score: 1, Informative) by Anonymous Coward on Tuesday July 26 2022, @08:02PM
I haven't seen the anticipated particle density estimates, but I believe in the popular press article I read that what they've seen so far is on par with what they were expecting, though one of them was on the larger-than-expected side. The effect of the micrometeorides is to cause little pits in the mirror surface that can scatter light. The modeling and experiments they did a while ago showed that for the expected micrometeorid environment, after ten years the optical loss due to that would still be less than the light scatter it has now from particulate contamination that it launched with (how dirty the mirrors were at launch), which means that this isn't expected to be a significant performance factor over its lifetime.