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A Major Step for the James Webb Space Telescope

The James Webb Space Telescope has been assembled for the first time, meaning its two halves — the spacecraft and the telescope — have been connected, following up earlier testing in which the two parts were temporarily connected by ground wiring. The latter took place almost a year ago, in September of 2018, allowing spacecraft and telescope test teams to begin working together as the process pointed to the physical connection that has now been achieved.

The connection was completed at Northrop Grumman’s facilities in Redondo Beach, California, with the telescope, its mirrors and science instruments, lifted by crane above the sunshield and spacecraft, which had already been combined. With the mechanical connection complete, the next step will be the electrical connection of the two halves and subsequent testng.

Image: The fully assembled James Webb Space Telescope with its sunshield and unitized pallet structures (UPSs) that fold up around the telescope for launch, are seen partially deployed to an open configuration to enable telescope installation. Credits: NASA/Chris Gunn.

“This is an exciting time to now see all Webb’s parts finally joined together into a single observatory for the very first time,” says Gregory Robinson, the Webb program director at NASA Headquarters in Washington, D.C. “The engineering team has accomplished a huge step forward and soon we will be able to see incredible new views of our amazing universe.”

The next round of testing includes full deployment of the JWST sunshield. Its critical role: To keep the observatory’s mirrors and scientific instruments cold to allow its infrared observations to achieve maximum resolution. The sunshield, layered in five sections, will have one side, facing the Sun, that can reach 383 Kelvin (110 degrees Celsius), while the other side has a modeled minimum temperature of 36 Kelvin, or -237 degrees Celsius. And it’s big, measuring 21.197 m x 14.162 m (this makes it about the size of a tennis court, a fact I throw in for those Centauri Dreams readers who enjoy sports comparisons in relation to space topics).

Image: Integration teams carefully guide Webb’s suspended telescope section into place above its Spacecraft Element just prior to integration. Credit: NASA/Chris Gunn.

The sunshield should allow the telescope, once at the L2 Lagrangian point, to cool down below 50 Kelvin (-223 degrees Celsius) by simply radiating its heat into space. This will allow successful functioning of the near-infrared instruments, which include the Near Infrared Camera (NIRCam), the Near InfraRed Spectrograph (NIRSpec) and the Fine Guidance Sensor / Near Infrared Imager and Slitless Spectrograph (FGS/NIRISS) — all of these work at 39 K (-234°C). The Mid-Infrared Instrument (MIRI) will operate at 7 K (-266 degrees Celsius) using a cryocooler system. Thermal stability will allow proper alignment of the primary mirror segments.

Image: NASA’s James Webb Space Telescope, post-integration, inside Northrop Grumman’s cleanroom facilities in Redondo Beach, California. Credit: NASA/Chris Gunn.

With launch scheduled for 2021, extensive environmental and deployment testing will now be undertaken for the fully assembled observatory. All of the telescope’s major components have gone through rounds of environmental tests including launch stress and vibration, but we now have to put the integrated assembly through its paces. As if launch wasn’t stressful enough, we’ll have to sweat out deployment of the sunshield and the 6.5-meter primary mirror, all destined for Earth-Sun L2, which is far beyond the orbit of the Moon. Plenty of suspense ahead as we tune-up for 2021. Getting this expensive bird in place is going to be a nail-biter.

{ 10 comments… add one }
  • jonW August 29, 2019, 22:21

    Probably many people here knew this already, but I was curious about what the first observing missions will be after JWST is operational (i.e. 1 month travel time after launch and 6 months calibration etc.). So I looked into it and the first 5 months of pre-approved missions are listed here: http://www.stsci.edu/jwst/observing-programs/approved-ers-programs

    Two exoplanet missions are announced there and it would be great if Paul were able to dig up and share any more information about what we might dare hope for from these missions: “The Transiting Exoplanet Community Early Release Science Program” and “High Contrast Imaging of Exoplanets and Exoplanetary Systems with JWST”

    • Paul Gilster August 30, 2019, 6:35

      Will see what I can find out, jonW. Interesting question!

  • ljk August 30, 2019, 13:00

    Two animations on the launch and deployment of JWST in space. The second video is briefer and labels the process:



    • Bruce D. Mayfield September 4, 2019, 9:54

      Thank you for posting those links ljk. Seeing all the moving parts that MUST work perfectly together helps with understanding the delays.

  • Paul Wilson August 30, 2019, 14:21

    I was so excited when Hubble first launched! I remember somehow finding live radio coverage on my car radio. I actually pulled over to the side of the road and took deep breaths! Imagine the chagrin some days later when it was found that the mirror had not been properly ground, and it’s vision was blurred! The agony!!! But, it was fixable! That was the beauty of it. And it has since lived up to my fantasies.
    No such fall back position this time around. At the L2 point, “no one can hear you scream” (well they may hear you, but they ain’t ridin’ to the rescue). I’m just as excited, and just as nervous, as I was about Hubble.

    • ljk August 30, 2019, 15:00

      And NASA learned the hard way never to name any spacecraft or satellite with a word that rhymes with Trouble. :^)

  • ljk September 4, 2019, 13:14

    Will the Webb telescope be able to detect life signs at nearby exoplanets?

    Posted by Paul Scott Anderson in Space | September 2, 2019

    The Webb Telescope is Hubble’s successor, due to launch in 2021. A new study says it’ll be powerful enough to search for life signatures in the atmospheres of the 7 Earth-sized planets in the TRAPPIST-1 system, just 39 light-years away.


  • Harry R Ray September 11, 2019, 10:06

    It now appears that HST has BEATEN JWST to one of the holy grails of exoplanet characterization: The detection of water vaper in the clouds of a HABITABLE ZONE exoplanet! K2- 18b is a Kepler 22b clone(it would be a TWIN except for the fact that it orbits an M dwarf star instead of a K dwarf star, so it is probably tidally locked whereas Kepler 22b probably isn’t). The BIG DIFFERENCE is that we know the MASS of K2-18b and determine that it is neither a true super-earth nor a true sub-neptune, but something in-between. My take: K2-18b DEFINITELY has a CLEARLY DEFINED BOUNDARY between its atmosphere and a global ocean, but the atmospheric pressure at its surface is ALMOST CERTAINLY many hundreds(and perhaps THOUSANDS)that of the atmospheric pressure at the surface of Venus. This means that is HIGHLY UNLIKELY that K2-18 is visable at the surface. Perameters for K2-18b are as follows: Mass – 8.92 Earth mass, Radius – 2.37 Earth radii, Orbital period – 32.9 days, Teff(at the cloud tops)~260K, Distance – 124 light years, Density – ~3.3grams/cm3. I am sure that Andrew Le Page will have a lot to say about this VERY SOON!

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