NASA has said the launch of its James Webb Space Telescope (JWST), the agency’s most ambitious space mission till date, has been pushed to May 2020 at the earliest, according to a statement released on March 27. This delay, caused by rising costs and technical failures, could lead to the telescope overshooting the budget cap set by the US Congress at $8.8 billion (inclusive of operational charges once the telescope is in space).
Before this, a delay announced in September 2017 had pushed the telescope’s launch date from October 2018 to spring 2019.
The JWST, colloquially called the Hubble space telescope’s ‘successor’, is designed to study the universe in the infrared part of the em spectrum. Among other goals, it will seek to capture ‘first light’, the light from the universe’s first stars..
For this, the telescope needs a primary mirror larger than the one on the Hubble. The primary mirror ‘collects’ radiation from space and focuses it into instruments for study; so the larger the mirror, the more data the telescope can analyse. The Hubble, launched in 1990, was revolutionary for its time with a 2.4-m-wide mirror. India’s AstroSat has a 30-cm wide mirror. The JWST, however, boasts of a 6.5-m-wide mirror. And unlike its predecessors, the mirror isn’t a single piece but is an array of 18 hexagonal lightweight gold-coated beryllium panels.
Another difference between the two space telescopes is that while the Hubble was in low orbit around Earth, a feature that allowed NASA to ‘service’ it, the JWST will be placed at a point in space about 1.5 million km from Earth, past the orbit of the Moon, called Lagrange point 2. As a result, the agency won’t be able to service the satellite should anything go wrong after launch.
The JWST ensemble also features a large shield that will block the Sun and ensure the star’s light doesn’t overwhelm the telescope’s instruments, as well as keep the assembly cool (the JWST’s instrument’s ideal operating temperature is equal to the average temperature on the surface of Pluto: -223 ºC). It is made of an ultrathin film made of a material called Kapton and about as big as the surface area of an Olympic-size swimming pool.
All together, the telescope will be launched by an Ariane 5 rocket.
Problems galore for JWST
NASA admitted on March 27 that integration and testing were taking longer than planned, but that they intended to successfully kickoff the mission. The final stages of assembly, integration and testing are underway at Northrop Grumman, NASA’s prime collaborator for JWST, at Redondo beach, California. The agency build and assembled the primary mirror and scientific payload and delivered them to Northrop in February.
One of the major issues facing the JWST’s construction has been the Kapton films. Engineers discovered multiple tears reflecting poor workmanship. A part of the shield snagged during a test, which resulted in seven tears, including two 10-cm-long ones, that forced the team to alter the way it would be packed inside the rocket.
Other more avoidable issues that the team faced included damage caused to the propulsion system due to an incorrect solvent being used, which took three months to fix; application of a higher-than-necessary voltage, damaging the transducers; and improper cleaning of valves in the thrusters, leading to leaks that took nearly a year to repair.
To make up for these delays, Northrop started working round the clock – but that wasn’t enough because it couldn’t work on different telescope components simultaneously. The additional labour brought expenditure on the telescope dangerously close to the cap of $8.8 billion.
However, the team is determined to make it all work, probably because the JWST has become too big to fail. “Webb is the highest priority project for the agency’s science mission directorate,” according to Robert Lightfoot, the acting NASA administrator. “The issues brought to light with the spacecraft element are prompting us to take the necessary steps to refocus our efforts on the completion of this ambitious and complex observatory.”
Implications for science
A decadal survey conducted in 2000 had hailed JWST as NASA’s important upcoming space mission (these surveys, according to Marcia Rieke, an astronomer at the University of Arizona, are “a measure of what’s actually achievable”). However, the delays have raised questions about whether the 2020 decadal survey should be postponed. Thomas Zurbuchen, NASA’s associate administrator for science, had asked, “Should that be done when we have real data from Webb in our hands, or before?”
Postponing the decadal survey for astronomy could also affect surveys in other fields, like the planetary sciences. So NASA currently has two options: ignore the telescope and conduct the survey or wait until the telescope is functional. Either way, the path forward seems unclear.
Some researchers also believe the scientific community has put in a lot of effort and money into the JWST, so much so that there is no other option for the mission but to be successful.
Others disagree. David Spergel, an astrophysicist at Princeton University, told Scientific American, “We are all disappointed; so many of us are eagerly awaiting Webb’s science. However, it is better to have a modest delay and a modest overrun (as a fraction of Webb’s cost) and have a successful mission.”
Even others have speculated that JWST’s issues could discourage future investments in big telescopes and turn the tide in favour of smaller telescopes with lower risks. However, in the short-term, even this switch is unlikely.
On a similar note, NASA scientists had planned to increase funding for the Wide-Field Infrared Survey Telescope (WFIRST) once the JWST’s demands died down. The WFIRST is expected to be able to answer questions in infrared astrophysicists and conduct studies related to dark energy and exoplanets. However, with JWST set to remain on the horizon until 2020 at least, the WFIRST mission have to part with some of its funds allocation.
This isn’t WFIRST’s first major roadblock. Earlier, President Donald Trump had proposed to cancel the project. But following protests from the scientific community, Congress restored it together with a $150 million allocation.
However, thanks to JWST’s delay and the Congressional expenditure cap, WFIRST may be delayed further. This is troubling because the WFIRST had originally been conceived to work together with the JWST to unravel the universe’s oldest mysteries.