Webb telescope to spend summer chilling in Houston
While Houston, Texas, may be sweltering in 95-degree Fahrenheit (35 °C) heat this week, NASA’s James Webb Space Telescope (JWST) will soon be chilling in a vibration-insolation “hammock”, hanging from the ceiling of Chamber A – an enormous thermal vacuum testing facility at NASA’s Johnson Space Center. The “Hammock” – six support rods attached to the platform on which the JWST is sitting – will isolate the telescope from vibrations that Chamber A could produce once testing begins, as well as isolate it from any disturbances that might occur outside of the chamber.
“Remember that the system is designed to work in space, where the disturbances are highly controlled and only come from the spacecraft,” said Gary Matthews, an integration and testing engineer at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who is testing the Webb telescope while it is at Johnson. “On Earth, we have to deal with all the ground-based disturbances, such as the pumps and motors, and even traffic driving by.”
The JWST was suspended in the chamber just a few inches above the rails on the chamber floor that were used to roll it into place. Once the telescope was suspended, engineers gave it a “push test”, where they nudged it enough just to move it a few millimeters to make sure the suspension system was working properly.
Chamber A is famous for its role in testing Apollo Moon mission hardware and has been designated as a National Historic Landmark. The chamber had to undergo major upgrades in the last several years in order to test the JWST.
The vault-like 40-foot (about 12-meter) diameter, 40-ton door of Chamber A was sealed shut on July 10, 2017, beginning about 100 days of cryogenic testing for the telescope. It will take about 10 days to remove the air inside the chamber, and about one month to lower the temperature of the JWST and its science instruments to the levels required for testing.
“There are many thermal sensors that monitor temperatures of the telescope and the support equipment,” said Gary Matthews, an integration and testing engineer at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who is testing the Webb telescope while it is at Johnson. “Specialized camera systems track the physical position of the hardware inside the chamber, monitoring how Webb moves as it gets colder.”
In space, the telescope must be kept extremely cold in order to detect infrared light from very faint, distant objects. To protect the telescope from external sources of heat and light, such as the Sun, Earth, and Moon, as well as heat generated by JWST’s science instruments, a five-layer sunshield the size of a tennis court acts like a parasol that provides shade. The sunshield separates the observatory into a warm, sun-facing side (reaching temperatures close to 185 °F / 85 °C) and a cold side (400 °F / 204.4 °C below zero). The sunshield also prevents sunlight from interfering with the telescope’s sensitive instruments.
The JWST is the scientific successor to NASA’s Hubble Space Telescope. It will be the most powerful space telescope ever built. The telescope is scheduled to be launched on an Ariane 5 rocket from French Guiana in October 2018.
Jim Sharkey is a lab assistant, writer and general science enthusiast who grew up in Enid, Oklahoma, the hometown of Skylab and Shuttle astronaut Owen K. Garriott. As a young Star Trek fan he participated in the letter-writing campaign which resulted in the space shuttle prototype being named Enterprise. While his academic studies have ranged from psychology and archaeology to biology, he has never lost his passion for space exploration. Jim began blogging about science, science fiction and futurism in 2004. Jim resides in the San Francisco Bay area and has attended NASA Socials for the Mars Science Laboratory Curiosity rover landing and the NASA LADEE lunar orbiter launch.