Speaking of Hubble...

A few weeks ago I had the opportunity to talk about the Hubble and the Webb space telescopes to what is for me an unusual audience — elementary school kids in the grades K-5.

I took part in the science career fair at one of the Baltimore County elementary schools, and found it an interesting experience. The majority of the kids have heard about Hubble, even though some don’t have a clear idea of what it is. I started with Hubble and what it can do, then described  Webb and how it will improve over Hubble in the study of distant galaxies. I had a little model of Hubble and had built a paper model of Webb available on the Web. The paper model took me three days to build and left me with the feeling that the real observatory might be actually simpler. Still, it was a useful tool to show how different Hubble and Webb look.

The majority of the kids liked the Hubble pictures but were not so interested in learning how it works or how its successor will outperform it. But perhaps they will be the future taxpayers eager to look at Hubble and Webb pictures and willing to support them. One kid, the only one out of many, thanked me — and said he was not interested in getting a Hubble picture. I hope it’s because he already has plenty at home!

Finally, a significant minority wanted to listen to more details, and those occasions were the most gratifying for me. It was very satisfying to tell stories about Hubble and Webb and see these young  people’s eyes locked on you, eager to learn more. Perhaps these are the future researchers, scientists and engineers who will keep the country competitive and at the technological forefront in the next decades. One young girl fought back her shyness and told me in a soft voice that I had a very interesting job. I agreed and told her that some day she could have the same job. I really hope that she and many of her generation do.

Labeled diagram of the Webb Telescope's parts

Every major NASA project needs to undergo a number of reviews during its development. These reviews are occasions for everybody working on the project to get together and report on progress, designs, and plans in front of a group of independent engineers and specialists. The whole purpose is to verify that the development team has a credible design for the mission.

In April, the James Webb Space Telescope passed the most important of these reviews, the Critical Design Review. Several weeks ago I participated in the main rehearsal of the review — something that in our jargon is called the “dry run.” Anybody attending one would understand the “dry” part. The rehearsal is several days long and covers the whole project, including areas well outside one’s field of expertise. All this without many unexpected questions or the “suspense” of the real review!

But the dry-run is very important because this is the occasion when the various people working on the project can provide each other with feedback and make sure that there are no holes in the presentations.

The final review was held at the Northrop Grumman Redondo Beach facility in Los Angeles (CA) and every aspect of the program was presented, including the development of the individual observatory components the assembly of all components into the final observatory,  the testing of the observatory, and finally its launch, on-orbit testing and operations. Hundreds of pages of presentations were discussed over several days and  everybody attending this review was left with the clear feeling that the James Webb Space Telescope is a very complex satellite.

My expectation was that we would pass but I was curious about what areas the review team would consider the least mature and deserving of more attention. Fortunately,  the independent reviewers agreed that the development team has a sound plan forward. Though the shore is not yet in sight,  the ship is on the right course.

Engineers dressed from head to toe to avoid contaminating the Webb mirror pieces with unwanted particles are reflected in the mirror segments.

The James Webb Space Telescope, Hubble’s successor, is an infrared telescope. Warm materials glow in the infrared, and for this reason Webb optics have to be kept cold — all the way down to 40 Kelvin (or -233C or -388 F). Unfortunately, our technology doesn’t allow us to polish mirrors while working at 40K. Thus, the conundrum for Webb was that the mirrors had to be polished at ordinary temperatures but still had to be the right shape at 40K. When temperatures change so dramatically, mirrors warp and deform.

About 10 years ago, a study took place to select the best material for the Webb mirrors. Instead of glass, we decided to use a substance called Beryllium. We found that by using computer models, we could accurately predict the ways Beryllium would deform. The plan was to polish the 18 mirror segments that make up our primary mirror at a warm temperature, but give them exactly the wrong shape that would deform into the right shape once they were brought down to 40K.

It sounds like a bold plan and, while confident in our testing, we were all a bit concerned about whether this would work well and on the first try. One can always try again — but this entails extra cost and delays, so we were hoping to avoid it.

Finally, in January 2010, the first demonstration mirror segment for Webb went through the full polishing process and was frozen to 40K at the X-ray and Cryogenic Facility at the Marshal Space Flight Center in Huntsville, Ala. We measured the segment at the end, and found it had deformed to the right shape. This is a major success for the Webb project and lets us move on to developing the rest of the primary mirror segments.

Wide Field Camera 3's infrared view of the Hubble Ultra Deep Field

I am Massimo Stiavelli, an astrophysicist at the Space Telescope Science Institute (STScI). I am the STScI Project Scientist for Hubble’s successor, the James Webb Space Telescope. I came to the institute in 1995, and before working on Webb, I worked on all of Hubble’s cameras.

My main scientific interest is understanding the formation and evolution of galaxies and the processes occurring in the early universe. I led the team responsible for the Hubble Ultra Deep Field observations, the deepest view of the distant universe ever done in visible light. The telescope had to stare at the same spot for 27 days to make these observations, and I have continued to study this field, trying to understand as much as possible from this large investment of Hubble’s time.

Last summer, I was part of a team that used one of Hubble’s new cameras, Wide Field Camera 3, to look for infrared light in the Ultra Deep Field region. The ultraviolet light from galaxies in the early universe has been stretched by the expansion of space, transforming it into infrared light. Therefore, to see the early universe, we must look for infrared light.

The results were interesting not just because they involve the Ultra Deep Field — they also hint at what Webb’s sensitive infrared vision might detect once it is launched.

Early on, some were nervous that Webb had been optimized to study a population of objects we didn’t know for sure existed, even if they were predicted by models.

Now, thanks to Wide Field Camera 3, we can all breathe a sigh of relief. These galaxies are there and they are faint: the best possible outcome for Webb.

Wide Field Camera 3’s observations of the Ultra Deep Field beat even the most optimistic expectations. In particular, they revealed a population of galaxies existing in the first billion years of the universe. A preliminary analysis suggests that these objects are rare and dim, possibly indicating that we are beginning to see the era when galaxies first form.

This is very good news for the James Webb Space Telescope. With its large mirror  — about seven times the area of Hubble’s — and incredible infrared sensitivity, Webb will be able to study in greater detail this population of galaxies and measure their properties.