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A Mirror Milestone, part 3

I was lucky enough to get to witness the next mirror milestone for the James Webb Space Telescope. (Here are parts two and one.)

I got word that our second shipment of mirrors were arriving at Goddard, which would consist of our flight secondary mirror and our 3rd flight primary mirror segment. The secondary mirror is a small round mirror (though it’s nearly the size of the Spitzer Space Telescope’s primary mirror) that will go out at the end of a boom opposite the primary mirror. Its job is to reflect the light from the primary mirror into the guts of the telescope where the instruments are. JWST has 18 hexagonal mirror segments that will together act as one mirror. Though I’d seen our flight spare segment on display, I hadn’t yet seen flight mirrors in person.

I missed seeing them unloaded from the truck, but I was able to see them sitting in front of the big blue door to the cleanroom. Here techs cleaned off the protective canisters, prepping them to go in the cleanroom.

Mirror ArrivalsCredit: Maggie Masetti


Mirror ArrivalsCredit: Maggie Masetti

I watched while Liz Bonnin, a presenter with BBC Stargazing, interviewed Dr. John Mather near the mirror segments:


Mirror ArrivalsCredit: Maggie Masetti

When it’s time to wheel the segments in, which happened the next morning, the big door opens and the cans are wheeled in and handed off to techs in the cleanroom wearing bunny suits. Know how they can open the cleanroom door without contaminating the cleanroom? It’s because the cleanroom has a slightly higher air pressure than outside it. When the door is opened, air goes out, not in!

I’d been told they were likely to be opening the cans around 9am that morning, which just happened to be election day. I tried to go vote in the morning, but the lines were too long and I didn’t want to miss this event, so I planned to go back later in the day and instead rushed to work.

I was in time to watch from the cleanroom observation window as they connected the big crane to the top of the can holding the secondary mirror. Slowly the mirror was revealed:

Mirror Arrivals
Credit: Maggie Masetti

Next the techs carefully inspected the mirror to make sure it was undamaged by transport:

Mirror ArrivalsCredit: Maggie Masetti

After inspection, the cover was put back on and the can hoisted up to the balcony to be stored.

Mirror ArrivalsCredit: Maggie Masetti

At this point, it looked like they were going to be taking a break, so I took the chance to run home to go vote. I wasn’t allowed to have my cell phone out on line for voting, and when I got out, I had a text saying they were going to open the other can in just a few minutes! It was lunchtime by this point and I was hungry, but I didn’t want to miss seeing the primary mirror segment. I remembered our live webcam (http://jwst.nasa.gov/webcam.html) and checked that on my phone to see if if the crane was hooked up to the can lid yet. It wasn’t. Since I was closest to home, I made a quick stop, shoveled in some leftovers, reassured myself again with a peek at the webcam, and then it was back to work.

I made it to the cleanroom observation area just in time to see the lid lifted up to reveal the beautiful, golden mirror segment inside.


Mirror ArrivalsCredit: Maggie Masetti

Mirror ArrivalsCredit: Maggie Masetti

Next it too was inspected. I liked seeing the reflections of the techs in the mirror.


Mirror ArrivalsCredit: Maggie Masetti


Mirror ArrivalsCredit: Maggie Masetti

Finally it too was covered up:


Mirror ArrivalsCredit: Maggie Masetti

And like the secondary mirror, it too was hoisted up to the balcony:


Mirror ArrivalsCredit: Maggie Masetti

We were asked on Twitter whether touching the mirror would be enough to remove the gold coating from it. The answer is that touch is not enough to debond the gold and there is actually a protective overcoating on it. Of course, we would never want to touch the mirrors because besides leaving fingerprints, we would scratch and otherwise contaminate them!

I had been (as you might be able to tell) posting pics to Instagram – and my favorite comment came from our friend Erik Trinidad, with whom we shot a special NASA Fancy Fast Food video.

Mirror Arrivals

(If you haven’t seen it yet, you can watch it here and then you’ll get the joke!)

Lastly, I’ll leave you with these two beautiful photos our photographer Chris Gunn took from inside the cleanroom.


Webb Telescope's Secondary Mirror Looks Like a Giant SunCredit: NASA/Chris Gunn


A Clear Reflection on the Webb Telescope's Secondary MirrorCredit: NASA/Chris Gunn

We’ll have more professional photos coming out of the primary mirror segment – watch for the latest on JWST’s Flickr: http://www.flickr.com/photos/nasawebbtelescope/. I’ll try to post some here as well!

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