Last Wednesday the Guiana Space Centre saw the launch of an Ariane 5 space vehicle carrying a space telescope whose upcoming installation marks the climax of an international effort spanning nearly 30 years. Named after a former NASA administrator, the James Webb Space Telescope – or JWST, as the device is commonly called – is expected to transmit its first images of the early universe some six months from now.
The product of a joint effort by the European Space Agency, the Canadian Space Agency, and the National Aeronautics and Space Administration, The telescope’s primary purpose is to capture the universe in its earliest states, some 13.5 billion years in the past, so as to enable scientist to better understand reionization – the process that marked the transition from the dark ages, the time before stars and galaxies, to the time dominated by matter, about halfway through which our own Milky Way galaxy came into being. The telescope is also expected to aid in the study of the atmospheres of potentially habitable exoplanets previously surveyed by other telescopes.
|Rough chronology of the universe. The James Webb telescope’s primary purpose is to capture structures formed during the reionization era. Image courtesy of the European Southern Observatory, https://www.eso.org/public/australia/images/eso1620a/?lang|
The task of surveying these distant structures is rendered all the more challenging by the fact that the sparse light they emit is at risk of being lost amid the light of the sun, meaning that the telescope needs to be as shielded from the sun’s light as possible. In order to ensure as much, the JWST is currently traveling toward Lagrange Point 2 – a particular set of spatial coordinates about 1.5 million kilometers from Earth, at which the gravitational mechanics of the sun and the earth reconcile with the centripetal force required for satellites to travel alongside them, allowing smaller structure such as the JWST to remain in a stable position relative to these two celestial bodies. The particular point chosen for this mission, L2, lies on the side of the earth opposite the sun, and would thus allow the telescope to avoid much of the interference the star would otherwise introduce.
|The five Lagrange points between the Earth and the Sun. Small structures at each of these points will travel alongside the sun and the earth with relative stability and without having to burn much fuel. Image courtesy of NASA, https://solarsystem.nasa.gov/resources/754/what-is-a-lagrange-point/.|
The telescope itself is composed of a reflective, layered sun shield that will protect the device from the heat it would otherwise receive from the sun’s radiation, gold-plated beryllium mirrors that serve to redirect the extremely sparse light JWST’s target structures are emitting towards a smaller, secondary mirror that plays a key role in the telescope’s calibration, and a spacecraft bus that features thrusters and control machinery that allow the craft to maneuver space as needed. Smaller – though no less crucial – components, such as a cryocooler, antennae, and solar arrays, are also included.
|The James Webb Space Telescope and its major components. The structure as a whole is approximately the size of a tennis court. Image courtesy of NASA, https://www.nasa.gov/mission_pages/webb/observatory/index.html.|
The successful construction and launch of the James Webb Space Telescope has served as a testament to the state of science and engineering even amid the many challenges that delayed the project’s original 2007 launch date. An end is finally in sight as the telescope is expected to become operational some time in the summer of 2022. Before that can happen, the craft will first need to complete its journey, successfully unfold its sun shield, align and calibrate its mirrors and imaging technologies, and eventually cool down to operational temperatures – all challenges in their own right, but ones whose every step and potential failure points have been charted and considered.
Kevin W. Rusch
Kevin W. Rusch is a scientist specializing in computational cognitive neuroscience at the UC Davis Moxon Neurorobotics Laboratory. Following thesis work at the University of Cambridge's Consciousness and Cognition Laboratory and aided by an interdisciplinary background ranging from biochemistry to data science, he is primarily interested in data-driven investigations into complex issues.