NASA plans to resume preflight tests on the James Webb Space Telescope soon, after the spacecraft had a small hiccup during a test at the end of last year. The telescope had an “unexpected response” to a vibrational test in December, prompting NASA to put testing of the spacecraft on hold until the agency figured out what happened. Now, NASA says it is close to zeroing in on the source of the problem, and tests should pick back up again later this month.

NASA says it is close to zeroing in on the source of the problem

The James Webb Space Telescope — or JWST — has been in development for the past two decades, and when complete, it will be the most powerful space telescope ever built. In November, NASA announced the completion of the James Webb’s optics — the giant mirror and instruments the spacecraft will use to peer deeper into the Universe than scientists ever have before. But before JWST can start spying on distant galaxies and stars, its hardware still needs to undergo rigorous testing over the course of the next few years to determine if the vehicle is ready for its trip into space.

That includes acoustic and vibrational tests, aimed at simulating the conditions the telescope will experience when it’s launched on an Ariane 5 rocket in less than two years. But on December 3rd, accelerometers attached to JWST picked up an abnormal response during a vibration test, prompting a nearly immediate shutdown of the procedure. Since then, NASA engineers have been trying to decipher why JWST didn’t perform as expected. The agency has done three successful low-level vibration tests since the incident, and the JWST team plans to have a full analysis of what happened ready in time for testing to start again in January.

"This is why we test -- to know how things really are, as opposed to how we think they are," Paul Geithner, deputy project manager for JWST at NASA, said in a statement. Meanwhile, the telescope looks like it’s in good condition, and ultrasonic exams show that its structure is holding up just fine.

Once acoustic and vibration testing is complete, the telescope won’t be done with its exams. JWST will then head to Houston where it will undergo cryogenic testing. The telescope is designed to operate 1 million miles out from Earth, at a frosty -370 degrees Fahrenheit (-225 degrees Celsius), so NASA needs to make sure the spacecraft is hardy enough for such frigid temperatures. After that, JWST will head to California, where it will meet up with its sunshield — thin layers of a material called Kapton that will guard the telescope from the Sun’s heat. Following a few more tests, the entire spacecraft will head to French Guiana for its scheduled launch in 2018.