An array of high tech instruments are being put through their paces ahead of becoming part of the James Webb Space Telescope (JWST). The successor to the Hubble Space Telescope – JWST engineers are currently testing hardware to ensure it will be able to function properly 1.5 million miles from Earth. The spacecraft is preparing for a launch late in 2018.
The JWST is one of NASA’s flagship programs and will be tasked with investigating the birth and evolution of galaxies, and the formation of stars and planets.
The hugely expensive project came close to cancellation in 2011, after the program suffered with schedule slips and budget overruns. With $3 billion already spent on the JWST program, along with 75 percent of its hardware already in production, the telescope was given a stay of execution, albeit with costs capped at $8 billion.
It was originally forecast to cost just $1.6 billion.
The project has NASA, ESA and the CSA as the lead partners, but includes a collaboration of about 17 countries in total.
To be located 1.5 million kilometers from Earth at the Earth-Sun Lagrangian point L2, JWST’s 6.5-meter diameter primary mirror – a gold coated beryllium reflector – and four specialized instruments ensure the spacecraft will provide unprecedented resolution and sensitivity from long-wavelength visible to the mid-infrared.
Unlike Hubble’s single monolithic primary mirror, JWST’s primary mirror is made up of 18 individual, adjustable segments that will be aligned in space.
The spacecraft’s array of instrumentation is currently being tested to ensure it can survive the extremes of space, with the most recent test involving the Near Infrared Camera (NIRCam) instrument, which is the primary imager covering the infrared wavelength range 0.6 to 5 microns.
NIRCam will detect light from the earliest stars and galaxies in the process of formation, the population of stars in nearby galaxies, as well as young stars in the Milky Way and Kuiper Belt objects.
NIRCam is equipped with coronagraphs, instruments that allow astronomers to take pictures of very faint objects around a central bright object, like stellar systems. Its coronagraphs work by blocking a brighter object’s light, making it possible to view the dimmer object nearby.
With the coronagraphs, astronomers hope to determine the characteristics of planets orbiting nearby stars, which is of great interest over recent years, thanks to the discoveries made by NASA’s Kepler spacecraft.
However, all of this will be for nothing if the instrument doesn’t work once in space. As such, engineers are – as would be expected – fully testing the hardware to mitigate against the potential for failures.
NIRCam was produced under contract with the University of Arizona and Lockheed Martin, with the latter noting this week that the instrument is surpassing expectations during testing – per the results of the first integrated, cryogenic testing program at Goddard Space Flight Center, Maryland.
The test follows on from the installation of the instrument alongside others in the Integrated Science Instrument Module (ISIM), which finished cryogenic and vacuum testing late last year.
“We designed NIRCam to stringent optical and environmental requirements so it can deliver images from the early origins of the universe,” noted Alison Nordt, NIRCam program manager at Lockheed Martin.
“JWST is an infrared observatory, requiring all of the optical components to operate at a cryogenic temperature under 40 Kelvin, which is six times colder than your average freezer. That’s a significant challenge when you’re building low-distortion optical mounts, aligning optics at room temperature and designing mechanisms to move precisely.”
NIRCam – as part of the ISIM – is now preparing for vibration testing, scheduled to occur in early 2015.
A JWST structural model will also be tested in NASA’s giant thermal vacuum chamber, called Chamber A, at Johnson Space Center (JSC) this spring.
The model of the telescope – called “Pathfinder” – will begin cryogenic optical testing inside the famous chamber.
“Maintaining the schedule with a very large number of optical and ground support equipment integration efforts, while securing the telescope to a suspension system inside the chamber and conducting a cryo-strength test is an incredible integration and test challenge,” noted Mark Voyton, manager for the Optical Telescope Element and Integrated Science Instrument Module (OTIS).
These key milestones follow on from the successful unfurling of the secondary mirror support structure inside the giant cleanroom at NASA’s Goddard Space Flight Center late last year.
(Images via NASA).