Gazing deep into the universe
The launch of an Ariane rocket from the Guiana Space Centre in the next few days will mark the fulfilment of a long-held dream for Adrian Glauser. On board will be the James Webb Space Telescope (JWST), which is bound on a mission scheduled to last up to ten years. Glauser, a physicist at ETH Zurich, has spent the past 18 years working on this challenging project, which is the follow-up to the Hubble Space Telescope. Time and time again, it has been postponed. “Over the years, I’ve learnt to stay calm whenever there’s a setback,” he says. “But now that the launch really seems to be going ahead, I’m pretty excited!”
Well protected against the sun
With a budget of around 10 billion dollars, the JWST has cost more than any other scientific project in the field of unmanned spaceflight. It is also one of the most complex space missions ever. Unlike its predecessor, the new telescope will not enter orbit around Earth. Instead, it will be stationed at the outer Lagrange point, L2, some 1.5 million kilometres out into space. This is one of the five points at which an artificial object will orbit the sun at the same speed as the Earth without changing its position relative to Earth.
As a location for a space telescope, it is ideal because at this distance it’s much easier to shield it against the sun’s radiation than if it were in orbit around the Earth. In the case of the JWST, this is vital since its four infrared instruments function properly only when solar radiation and temperature fluctuations are reduced to a minimum. Alongside two infrared spectrographs, the JWST is also equipped with a near-infrared camera, which is passively cooled to 50 kelvins, and an observation instrument for the mid-infrared range called MIRI, which is actively cooled right down to 7 kelvins.
It was as a doctoral student, in the former astronomy group at the Paul Scherrer Institute (PSI) in Villigen, that Glauser took part in the development of MIRI. Now he is project manager for the Swiss contribution to the mission. “We worked closely with two industrial partners, Ruag Aerospace and Syderal, to develop a special cover made of aluminium and electrical connector cables for this specific instrument,” Glauser says. It might not sound particularly spectacular, but these components have to perform reliably over a number of years at extremely low temperatures in space. That explains why a lot of work has gone into their development.
The electrical connector cables are made of stainless steel and are much thinner than a human hair. This ensures they transmit as little heat as possible to the instrument. In addition, they are insulated with a special plastic that won’t become brittle at such low temperatures. “All the parts are designed not to give off any atoms or molecules while in space,” Glauser adds. “These would otherwise condense onto the MIRI mirror, which acts as a cold trap because of the extremely low temperature. And that, in turn, would compromise the observations.” For this reason, the plastic used to sheath the connecting cables has been pretreated before assembly so as to prevent any outgassing when in space.
Repair is not an option
MIRI’s other Swiss-made part – its contamination control cover – must meet the same standard. This cover is designed to protect MIRI during the cool-down phase, before regular operation commences. It will also be used for later calibration of the instrument. “The contamination control cover mechanism has to function reliably, else the entire instrument will be rendered inoperable,” Glauser says. “Repairs are out of the question, as it’s far too far away from Earth.”
The development of the two components threw up a number of surprises. During inspection and approval of the contamination control cover, for example, it was discovered that 13 of the screws were coated with a material containing the heavy metal cadmium. In the eyes of the European Space Agency (ESA), this is a problematic material since it can become unstable in chemical compounds under a vacuum. “I then had to develop a special measurement procedure to show that the screws haven’t released any cadmium so far,” Glauser says.
Messages from the early universe
The new telescope, in the conception of which Simon Lilly, Professor of Experimental Astrophysics at ETH Zurich, was significantly involved, has been designed with four mission objectives in mind, which require extremely sensitive instrumentation. Among other things, the astrophysicists intend to use the JWST to gaze back to the origins of the universe with a view to discovering how the earliest stars and other structures were formed after the Big Bang. Furthermore, scientists want to investigate planets that might support life. “We won’t be using the JWST to look for new planets,” Glauser says, “but instead to take a closer look at ones we’ve already identified. To do this, we will directly measure the light of the planets spectrally.”
In his capacity as a research physicist, Glauser will now benefit from the favourable access to observation time granted to the MIRI consortium. “That’s the big advantage of being involved in the development of instruments like these. It will mean we can make a start on our projects ahead of other research groups.”
Thinking about the next mission
Glauser regrets the demise of the astronomy group at PSI. “It’s true, we have a lot of know-how here at ETH. But if you want to participate in instrument development, you need structures that are firmly bedded in for the long haul. And that’s not easy to achieve at a university.” A long time horizon is essential for projects like these. Indeed, Glauser is already involved in preparations for a mission, which will investigate exoplanets in a few decades that have a temperate climate and may have liquid water in their atmosphere or on their surface.
“I won’t get to witness the launch of that mission in my working life,” Glauser says, “but it’s fascinating to be thinking now about how a future telescope will have to be built in order to answer questions like these.” With this kind of project, he explains, there’s no simple division between scientists, who just use the instruments, and engineers, who merely build them: “You need people like me – instrument developers – who can define, based on a scientific perspective, what the instruments are supposed to measure.” At the same time, there’s a further advantage in being involved as a research institution: “You also have a say in what kind of research questions get spotlighted in the future.”
In anticipation of the first images
For now, however, Glauser is focusing on the short term. Soon after the launch of the Ariane rocket, the critical phase of the JWST mission will begin. In the course of a one-month journey to its destination, the telescope will progressively unfold in a complex manoeuvre until it has reached its full size. There will then follow a period of several months during which the instruments cool down to the requisite temperature and are calibrated. If all the various components function as planned, the first scientific observations can start next summer. Glauser, for one, is already looking forward to studying the images that the new telescope will deliver to Earth.