BACK TO THE FUTURE

BACK TO THE FUTURE

NASA looking for the emergence of the universe

BY SABINE FUSS

(Published in The Produktkulturmagazin issue 2 2018)

In a galaxy of a billion stars, unknown luminaries and unchartered spheres, humans only seem to be a tiny, barely recognisable spark within the infinity of the universe. The question of how the universe came about has been asked since the year dot. We know of the Big Bang theory, but what really lies behind it all? NASA is discussing this question in cooperation with the European and Canadian space agency. The James Webb Space telescope, a giant golden mirror, is now taking a big step in the endeavour to explore the universe. Not only is the infrared telescope supposed to investigate the beginning of our universe and the genesis of our planetary system, but it will also be deployed in the search for exoplanets and the feasibility of life on them. Lee Feinberg, Optical Telescope Element Manager at NASA, talks to us about the work behind the cosmic project.

Mr Feinberg, you have been working for NASA for many years now. What is the concrete nature of your work? What does a typical day at work look like for you?

For the last 16 years, every day has been different as we have gone from the Webb telescope technology development to the design to the fabrication to the testing of the telescope. My day could mean sitting in a review meeting for hours making sure every detail of a design or test is right. Or it could mean acting as a test director or even going into the cleanroom to help troubleshoot a problem. 

The Hubble Space Telescope was successfully launched into space in 1990. How does the work on its successor, the James Webb Space Telescope, differ from that on the Hubble Telescope?

I actually started my career at NASA working on the repair mission for Hubble which was primarily about building next generation instruments that would contain small corrective optics that fixed Hubble. Hubble itself is somewhat simple: it runs at room temperature, has a large solid outer barrel and has a single heavy primary mirror. Webb is actually much more challenging in a lot of ways. Despite being larger, it is significantly lighter than Hubble, runs incredibly cold, has 18 individual mirror segments, unfolds in space, and uses a large sunshield.   

Webb stands out above all as a result of its extraordinary appearance. What lies behind this?

Webb was ultimately designed to see the formation of the early universe, which meant it had to be a huge infrared telescope. This meant it was so big that it couldn’t fit in a rocket without unfolding. Being infrared means you have to cool it, or the thermal radiation will swamp what you are trying to see. And the best mirror material for these cold temperatures is beryllium, which could be optimally packaged in 18 segments with two wings that unfold.  So, it started with a science objective but really evolved based on engineering constraints.

What were the specific characteristics and challenges of building the best ever telescope to date?

The amount of mass and volume available in the rocket coupled with the required size and extremely cold temperature altogether presented a challenge, as did the making of those 18 mirror segments and the huge sunshield.  And of course, as soon as you have built it, you have to test it. But first you have to figure out how to test it and then you actually have to do it. We’ve had to test during blizzards and were even testing the telescope in a huge vacuum chamber at cryogenic temperatures when Hurricane Harvey came along and hung right above us for about a week.

Why do the telescope’s instruments have to be protected against the sun?

For a lot of reasons really. First, they are really cold and the sun would heat them up.  Also, the sun could focus light on areas that could damage coatings and detectors.

What additional requirements have to be mastered for deployment in space?

One big requirement is that you have to design and test for the gravity field of the earth but deploy and operate in zero gravity. We had to compensate for the effects of gravity in the mirrors and the structures, which meant a lot of modelling and testing.

In contrast to the Hubble Telescope, it will not be possible to make subsequent adjustments to the Webb Telescope. How will you ensure that the telescope is able to cope with all manner of unforeseen events prior to its launch in 2020?

Well, we can adjust mirror positions in space, but we can’t actually fix things that stop working. So we do what planetary missions do and we use a lot of redundancy and also test everything and then crosscheck it. 

Webb will be sent approximately 1.5 million kilometres into space. What requires special attention during the telescope’s transport into and positioning in space?

On the way there we deploy the telescope and the sunshield, and that is really the most complicated thing we do. Then we spend several months aligning the mirrors - which will have cooled to about 50 degrees above absolute zero - so that the ensemble of 18 mirrors is aligned to about 1/20,000th the diameter of a human hair.

The transmitted data will be evaluated once the telescope has completely unfurled and positioned itself. What kind of information is this, to be precise?

Some of the most important data will come from the instruments and will be images of stars,  similar to a mobile phone picture. The images will start out as 18 separate unfocused images as each individual segment will act like its own out of focus telescope. Over a few months we will align the mirrors until we have a sharp image of a star. After that, we will do some instrument calibration and then we are ready for some science. 

What knowledge does NASA hope to acquire through the new findings?

Webb is so incredibly powerful that we can expect major findings in nearly every branch of astronomy, from how the universe formed to how planets formed, to which molecules are in the atmospheres of Exoplanets that orbit other stars, to giving new perspectives of the planets in our own solar system. This is kind of like climbing Everest. It’s a challenging endeavour, but once you get to the top it’s going to be an absolutely amazing view.

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nasa.com

LEE FEINBERG

In 1987 Lee Feinberg passed his Bachelor of Science in optics, in 1998 he was awarded a Masters in Applied Physics. Since 2001 he has been the Optical Telescope Element Manager and technical leader for the James Webb Space telescope in the Goddard Space Flight Centre in Greenbelt, USA. Before he had worked for ten years on the Hubble Space Telescope and was part of the team which developed its optical correction and upgrade instruments.

Picture credit © NASA/MSFC/David Higginbotham


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