If you want to understand the importance of NASA’s James Webb Space Telescope – one of whose primary science instruments recently arrived at the Goddard Space Flight Center in Greenbelt, Maryland, for integration – you must leap forward in time and venture almost a million miles beyond Earth, to a peculiar spot in space, known as the L2 Lagrange Point. Here, the gravitational influences of our planet and the Sun are finely balanced, enabling a semi-stable location at which a number of international space telescopes presently reside. From 2018, L2 will also be home to the tennis-court-sized successor to the Hubble Space Telescope: a giant observatory, nicknamed ‘The Webb’, whose tortured childhood, complex development and planned five years of operation will cost upwards of $8 billion…but whose pledge of scientific discovery should whet the appetites and pique the curiosity of even the most hardened anti-space sceptics.
Named in honour of former NASA Administrator James Webb, under whose leadership America strove for the Moon in the 1960s, the observatory promises to open our eyes and our minds as never before to the deepest enigmas of the cosmos. Its Mid Infrared Instrument (MIRI) is one of four detectors that will deliver this astrophysical bonanza and arrived in Maryland on 29 May for final testing before integration into Webb’s Integrated Science Instrument Module (ISIM). Built at the Rutherford-Appleton Laboratory in Chilton, Oxfordshire, MIRI is the product of ten European science institutions and NASA’s Jet Propulsion Laboratory. Together with three other instruments, it will peer back in time to just a few hundred thousand years after the Big Bang, shedding new light on the earliest known stars, the first galaxies, the formation and evolution of planetary systems and, perhaps, even offering insights into the origins of life itself.
“MIRI will enable Webb to distinguish the oldest galaxies from more evolved objects that have undergone several cycles of star birth and death,” said Matt Greenhouse, the ISIM project scientist at Goddard. “MIRI will also provide a unique window into the birthplaces of stars which are typically enshrouded by dust that shorter-wavelength light cannot penetrate.” Amongst its targets are cool stars in far-off galaxies, evolving stars in the Milky Way, infrared ‘signatures’ of forming exoplanets and closer-to-home objects in our own Solar System, including comets and the Kuiper Belt. Alongside MIRI will be the University of Arizona’s Near Infrared Camera, the European Space Agency’s Near Infrared Spectrograph and Canada’s Fine Guidance Sensor and Tunable Filter Imager.
Unlike Hubble, the work of Webb will occur entirely in the infrared, since this is a difficult region to examine from Earth and many of its scientific targets emit strongly in this portion of the electromagnetic spectrum. Under Webb’s gaze, areas of star birth and planet formation will be observed with crystalline clarity and the cores of active galaxies – normally cloaked in gas and dust – will blaze brightly.
Planning for the mission officially began in 1996, under the original designation of ‘Next Generation Space Telescope’. It was renamed for James Webb in 2002. From the start, advocates called for a distant orbit to offer unprecedented resolution and sensitivity and, indeed, Webb will operate from a location 930,000 miles beyond Earth, occupying a large, half-million-mile-radius ‘halo orbit’ around L2. At this point, the gravitational influences of Earth and the Sun are balanced, enabling Webb to keep up with the home planet in its orbit and allowing it to benefit from a single radiation shield. As well as protecting the observatory from radiation interference from the Sun, Earth and Moon, the shield will cool Webb’s scientific payload to an operating temperature of -230 degrees Celsius and thus ensure that emissions from its own instruments do not disrupt its observations.
In fact, it is this fan-fold shield, measuring more than 65 feet across when fully unfolded, which is one of Webb’s most visible elements. The other is its impressive primary mirror, almost 20 feet in diameter, which is composed of 18 hexagonal segments and has a collecting area of 270 square feet – about five times larger than that of Hubble. After launch, these segments will be unfurled and positioned using very precise micro-motors.
It is the process of getting Webb into space, however, which has caused major headaches. Original plans called for a launch in 2014, but an independent review, two years ago, determined that even with much-needed additional funding a delay was inevitable. Technically, the project itself has long been in an excellent position, but Webb fell foul to management difficulties and the effects of an unrealistic initial budget. Nonetheless, it sailed through its Preliminary Design Review in 2008, its ISIM and Optical Telescope Element reviews in 2009 and its Sunshield and Mission Critical Design reviews in 2010. Yet even in the wake of these triumphs, Webb came within a whisker of having the carpet snatched from beneath its feet and an ignominious cancellation.
Last July, the House of Representatives Appropriations Committee on Commerce, Justice and Science harshly attacked the project, criticising it for being billions of dollars over-budget and plagued by issues of poor management. Original plans for a $1.6 billion mission had now morphed into a dollar-guzzling monster whose costs threatened to peak at more than $8 billion and its original launch date, scheduled for early in the decade, was slipping inexorably to the right. Even some astronomers berated Webb and in October 2010 the journal Nature labelled it “the telescope that ate astronomy”. Others were more supportive, including Barbara Mikulski, senior senator for Maryland, the home of the Goddard Space Flight Center and Baltimore’s Space Telescope Science Institute, which will operate Webb. By this stage, three quarters of the observatory’s hardware was built or undergoing testing and the prospect of cancellation was a difficult pill to swallow.
Thankfully, Congress reversed the proposal to cancel the mission in November 2011. Launch itself is still several years into the future, but perhaps the delivery of MIRI can be taken as an indicator that Webb’s prospects are brightening once more. When the observatory finally flies, atop a European Ariane 5 booster from Kourou, French Guiana, we can only hope that Webb will prove its scientific worth. Moreover, just like Hubble, perhaps a difficult and troubled childhood will give way to one of the grandest missions of discovery ever undertaken in human history. In a sense, the delivery of Webb’s first major science instrument shows that, only months after the spectre of cancellation withdrew, MIRIcles can really happen.