. 24/7 Space News .
STELLAR CHEMISTRY
Preparing JWST for launch
by Staff Writers
Paris (ESA) Dec 23, 2016


JWST centre of curvature test. Image courtesy NASA-C. Gunn. For a larger version of this image please go here.

In the second half of 2016, the James Webb Space Telescope (JWST) was readied for an intensive series of environmental tests, an essential step in ensuring that it will survive the stresses of launch and complete its groundbreaking survey of the infrared sky. After integration of the combined Optical Telescope element / Integrated Science instrument module (OTIS) was completed in the summer of 2016, it was subjected to an extensive "pre-environmental", warm functional test campaign.

These tests were called the WIF (Warm ISIM Functional) and WOF (Warm Optical telescope Functional). Both tests took place at "normal" temperature and checked all the electrical connections, settings and functionalities of the various subsystems that are on OTIS. The same test campaign will be repeated after OTIS undergoes launch environment tests.

Accurate measurements of the main structural elements of OTIS were made during the autumn, in preparation for a series of launch environment tests that were to begin later in the year.

Once these vibration and acoustics tests are completed, the measurements will be repeated to verify the integrity of the structure. Making the same optical measurements before and after the simulated launch environment testing and comparing the results is fundamental to JWST's development, assuring that it will work in space.

This "optical metrology" involved the use of laser and radar tracking equipment to make extremely accurate measurements of the main structural elements on OTIS.

Typically accurate to within 35-40 microns (about the width of a human hair), the measurements established the positions of a large number of critical reference points on the OTIS and confirmed whether anything had moved as a result of the extreme environmental conditions. The test data confirmed that the OTIS was ready for integration on the back of the telescope.

Particularly challenging in this respect were the "centre of curvature" measurements conducted at NASA's Goddard Space Flight Center (GSFC) in Greenbelt, Maryland. To perform these tests optical engineers set up a specially designed interferometer, an instrument capable of measuring the shape of JWST's primary mirror with incredible accuracy.

Since waves of visible light are less than a thousandth of a millimetre long, the telescope's optics need to be shaped and aligned even more accurately than this to work correctly. Using beams of laser light to make measurements of the mirror shape and position prevents physical contact and damage (scratches to the mirror). By using an interferometer to measure light reflected off the optics, scientists can measure extremely small changes in shape or position.

During the test, temperature and humidity conditions in the cleanroom were kept as stable as possible to minimise drift in the sensitive optical measurements over time. To avoid tiny vibrations in the cleanroom that could cause jitter during measurements, the 'high-speed' interferometer was designed to take 5000 'frames' every second - faster than the background vibrations themselves. This allowed engineers to subtract out jitter and obtain good, clean results.

OTIS is the largest space flight payload tested at GSFC to date, so a new shaker system had to be specially built. This shaker system is needed to conduct the vibration tests, part of the launch environment campaign. During these tests, the vibrations that the payload will experience during a launch aboard the Ariane 5 rocket are simulated.

In November, in preparation for the environmental campaign, a special "tent" was built and placed around the payload to ensure that OTIS would not be contaminated by dust or dirt during the vibration and acoustics tests.

Meanwhile, the JWST Pathfinder structure was placed in the giant cryovacuum chamber at Johnson Space Center, prior to commencement of a series of temperature and vacuum tests similar to those that the actual JWST telescope will have to pass in spring 2017. The Pathfinder is a test version of the structure that supports the real JWST telescope.

The giant test chamber, which was built during the Apollo Moon programme, has been refurbished specifically to test JWST. These tests are intended to spot any potential problem with the test equipment and procedure, thereby minimising the chances of delays with the actual space observatory.

Excellent progress is also being made with development of the huge sunshield that will protect JWST from background heat from the Sun that would interfere with the telescope's infrared sensors. The fifth and final sunshield layer was completed in September. The size of a tennis court, the sunshield, along with the rest of the spacecraft, will fold origami-style into the fairing on top of the Ariane 5 rocket that will blast JWST into space.


Comment on this article using your Disqus, Facebook, Google or Twitter login.


Thanks for being here;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.
SpaceDaily Contributor
$5 Billed Once


credit card or paypal
SpaceDaily Monthly Supporter
$5 Billed Monthly


paypal only


.


Related Links
James Webb Space Telescope at ESA
Stellar Chemistry, The Universe And All Within It






Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle

Previous Report
STELLAR CHEMISTRY
'Thank the aliens': Thousands displaced for China's huge telescope
Pingtang, China (AFP) Nov 30, 2016
Humanity's best bet at detecting aliens is a giant silver Chinese dish the size of 30 football fields - one that simultaneously showcases Beijing's abilities to deploy cutting-edge technologies and ignore objectors' rights as it seeks global prominence. The Five-hundred-metre Aperture Spherical Telescope (FAST) in the country's southwest, which began operations in September and cost 1.2 bil ... read more


STELLAR CHEMISTRY
Spacewalk for Thomas Pesquet at ISS

NASA's Exo-Brake 'Parachute' to Enable Safe Return for Small Spacecraft

Trump sits down with tech execs, including critics

Trump sits down with tech execs, including critics

STELLAR CHEMISTRY
United Launch Alliance launches EchoStar XIX satellite

NASA Engineers Test Combustion Chamber to Advance 3-D Printed Rocket Engine Design

Ultra-Cold Storage - Liquid Hydrogen may be Fuel of the Future

Technical glitch postpones NASA satellite launch

STELLAR CHEMISTRY
All eyes on Trump over Mars

Opportunity performs several drives to ancient gully

Full go-ahead for building ExoMars 2020

Skimming an alien atmosphere

STELLAR CHEMISTRY
Chinese missile giant seeks 20% of a satellite market

China-made satellites in high demand

Space exploration plans unveiled

China launches 4th data relay satellite

STELLAR CHEMISTRY
OneWeb announces key funding form SoftBank Group and other investors

Space as a Driver for Socio-Economic Sustainable Development

SoftBank delivers first $1 bn of Trump pledge, to space firm

Telecom satellite system to encircle globe

STELLAR CHEMISTRY
Uncovering the secrets of water and ice as materials

The hidden side of sulfur

Chemical trickery corrals 'hyperactive' metal-oxide cluster

High Resolution Imaging of Hypervelocity Impacts

STELLAR CHEMISTRY
Astronomers discover dark past of planet-eating 'Death Star'

Microlensing Study Suggests Most Common Outer Planets Likely Neptune-mass

Are planets like those in 'Star Wars

Exciting new creatures discovered on ocean floor

STELLAR CHEMISTRY
Juno Captures Jupiter 'Pearl'

Juno Mission Prepares for December 11 Jupiter Flyby

Research Offers Clues About the Timing of Jupiter's Formation

New Perspective on How Pluto's "Icy Heart" Came to Be









The content herein, unless otherwise known to be public domain, are Copyright 1995-2024 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. All articles labeled "by Staff Writers" include reports supplied to Space Media Network by industry news wires, PR agencies, corporate press officers and the like. Such articles are individually curated and edited by Space Media Network staff on the basis of the report's information value to our industry and professional readership. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. General Data Protection Regulation (GDPR) Statement Our advertisers use various cookies and the like to deliver the best ad banner available at one time. All network advertising suppliers have GDPR policies (Legitimate Interest) that conform with EU regulations for data collection. By using our websites you consent to cookie based advertising. If you do not agree with this then you must stop using the websites from May 25, 2018. Privacy Statement. Additional information can be found here at About Us.