James Webb topic #2 Space, the final frontier

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Mid Course Correction Burn 1b

Nominal Event Time: Launch + 2 days

This burn fine-tunes Webb's trajectory after launch. The duration of the burn will depend on Ariane 5 launcher performance.

There are three mid-course correction (MCC) maneuvers: MCC-1a, MCC-1b, and MCC-2. This is the second. The first burn, MCC-1a, is the most important and the only other time-critical operation aside from solar array deployment during Webb’s commissioning period.

The second, MCC-1b, is a shorter burn performed before the sunshield deployment is scheduled to start. The final maneuver, MCC-2, performed 29 days after launch, is designed to insert Webb into the optimum orbit around L2.

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Op dinsdag 28 december 2021 09:52 schreef StateOfMind het volgende:
Vandaag lanceert, als het goed is, de opvolger van de Hubble; de James Webb telescoop. Deze telescoop zal hopelijk het licht kunnen zien van het moment dat de eerste sterrenstelsels gevormd werden, meer dan 13 miljard jaar geleden.

- Ontwikkeling is begonnen in 1996, dus de planning en bouw heeft bijna 26 jaar geduurd

- De telescoop zal gepositioneerd worden in een baan om het zogenaamde L2 punt 1,5 miljoen kilometer van de aarde.

[ afbeelding ]

Livestream:

James Webb Space Telescope Launch — Official NASA Broadcast

Animatie:

James Webb Space Telescope Deployment Sequence (Nominal)

Waar is Webb:

https://jwst.nasa.gov/content/webbLaunch/whereIsWebb.html

Als alles goed gaat kunnen we over een aantal maanden weer prachtige plaatjes gaan krijgen zoals de Hubble dat voor ons gedaan heeft (en nog doet)

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Op dinsdag 28 december 2021 10:48 schreef Frutsel het volgende:

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Hadden ze in het begin met de Hubble geen problemen? Dat er ergens een haartje of beschadiging zat op een spiegel ofzo waardoor alles wazig binnen kwam?

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Analysis of the flawed images revealed that the primary mirror had been polished to the wrong shape. Although it was believed to be one of the most precisely figured optical mirrors ever made, smooth to about 10 nanometers,[32] the outer perimeter was too flat by about 2200 nanometers (about 1/450 mm or 1/11000 inch).[71] This difference was catastrophic, introducing severe spherical aberration, a flaw in which light reflecting off the edge of a mirror focuses on a different point from the light reflecting off its center.[72]

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Origin of the problem
A commission headed by Lew Allen, director of the Jet Propulsion Laboratory, was established to determine how the error could have arisen. The Allen Commission found that a reflective null corrector, a testing device used to achieve a properly shaped non-spherical mirror, had been incorrectly assembled—one lens was out of position by 1.3 mm (0.051 in).[77] During the initial grinding and polishing of the mirror, Perkin-Elmer analyzed its surface with two conventional refractive null correctors. However, for the final manufacturing step (figuring), they switched to the custom-built reflective null corrector, designed explicitly to meet very strict tolerances. The incorrect assembly of this device resulted in the mirror being ground very precisely but to the wrong shape. A few final tests, using the conventional null correctors, correctly reported spherical aberration. But these results were dismissed, thus missing the opportunity to catch the error, because the reflective null corrector was considered more accurate.[78]

The commission blamed the failings primarily on Perkin-Elmer. Relations between NASA and the optics company had been severely strained during the telescope construction, due to frequent schedule slippage and cost overruns. NASA found that Perkin-Elmer did not review or supervise the mirror construction adequately, did not assign its best optical scientists to the project (as it had for the prototype), and in particular did not involve the optical designers in the construction and verification of the mirror. While the commission heavily criticized Perkin-Elmer for these managerial failings, NASA was also criticized for not picking up on the quality control shortcomings, such as relying totally on test results from a single instrument.[79]
https://en.wikipedia.org/wiki/Hubble_Space_Telescope

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Op dinsdag 28 december 2021 13:01 schreef Zwoerd het volgende:
Het worden weer een paar spannende dagen met het uitvouwen van het hitteschild

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Op dinsdag 28 december 2021 18:47 schreef Asschen_sukar het volgende:
[ twitter ]

[ twitter ]

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If something goes wrong, NASA can’t send out a rescue squad for orbitside assistance. Instead, engineers tried to make the system reliable by using highly durable parts and including backup systems. Not every element of the design could be duplicated, though. They have two different electrical ways to control the pins, for example, but they don’t have two sets of pins.

So engineers built in extra deployment features in case the sunshield gets stuck: push-and-pull, shimmy, twirl, and fire-and-ice. Those are nicknames for the “tools” in the spacecraft’s toolbox.

Like working on a jammed desk drawer, the ground crew could push or pull harder on devices to try to unstick them. Or imagine gently shaking that drawer to loosen the clutter lodged in it. The crew could also initiate a low-level vibration — a “shimmy” — by firing its rockets in different sequences.

The “twirl” could come into play if they want some parts to fly outward. The team has a way to spin the entire observatory like a carousel. They could also heat and cool it to loosen things up, like running hot water over a stubborn jar lid.

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Op dinsdag 28 december 2021 20:42 schreef Eyjafjallajoekull het volgende:

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Hoe de fuck is daar door iemand een foto van gemaakt Sterk staaltje werk.

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Op dinsdag 28 december 2021 21:21 schreef vaarsuvius het volgende:
Hij gaat nu met een mooie 1km per seconde. In 10 seconden naar mijn werk, dat zou wat zijn....

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Op dinsdag 28 december 2021 21:21 schreef vaarsuvius het volgende:
Hij gaat nu met een mooie 1km per seconde. In 10 seconden naar mijn werk, dat zou wat zijn....

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Op dinsdag 28 december 2021 21:35 schreef StateOfMind het volgende:
Bijna 500.000 km ver weg nu.

Waarom is de snelheid eigenlijk verlaagd?

Eerste dag ging ie geruime tijd met ruim 4000 km/u, nu net iets meer dan 1000.

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Getting Webb to its orbit around L2 is like reaching the top of a hill by pedaling a bicycle vigorously only at the very beginning of the climb, generating enough energy and speed to spend most of the way coasting up the hill so as to slow to a stop and barely arrive at the top.

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Op dinsdag 28 december 2021 22:02 schreef Gremen het volgende:
Uiteraard moet ie steeds langzamer gaan, anders vlieg je er voorbij