Webb Telescope Sunshield Passes Launch Depressurization Tests to Verify Flight Design

NASA's James Webb Space Telescope continues to make significant progress, successfully completing a series of sunshield vent tests that validate the telescope's sunshield design.

"While adequate venting is a design consideration for all spaceflight hardware, this was a particularly unique challenge for the sunshield given the large volume of trapped air in the membrane system at launch," said Keith Parrish, Webb telescope sunshield manager at NASA's Goddard Space Flight Center in Greenbelt, Md. "From the beginning of its development venting features have been a critical part of the overall sunshield design. Since we cannot vent test the actual flight article these test have shown the design works and the sunshield will vent safely on its way to orbit."

The sunshield on the Webb telescope will block the heat of the Sun and Earth from reaching the cold section of the Observatory. That's a critical function because the telescope and instruments must be cooled below 50 Kelvin (~-369.7 Fahrenheit) to allow them to see faint infrared emissions from astronomical objects. The sunshield consists of five layers of Kapton ®E with aluminum and doped-silicon coatings to reflect the sun's heat back into space.

Using flight-like sunshield membranes, the tests are designed to mimic the rapid change in air pressure the folded sunshield will experience the first minutes of launch. Several different folding configurations each underwent a series of 90-second depressurization tests and proved that the stowed sunshield will retain its shape during launch and allow trapped air to escape safely, both critical to sunshield deployment and performance.

Goddard Team attains the 'Unobtainium' for NASA's Next Space Observatory

Imagine building a car chassis without a blueprint or even a list of recommended construction materials.

In a sense, that's precisely what a team of engineers at the NASA Goddard Space Flight Center in Greenbelt, Md., did when they designed a one-of-a-kind structure that is one of 9 key new technology systems of the Integrated Science Instrument Module (ISIM). Just as a chassis supports the engine and other components in a car, the ISIM will hold four highly sensitive instruments, electronics, and other shared instrument systems flying on the James Webb Space Telescope, NASA's next flagship observatory.

From scratch — without past experience to help guide them — the engineers designed the ISIM made of a never-before-manufactured composite material and proved through testing that it could withstand the super-cold temperatures it would encounter when the observatory reached its orbit 1.5-million kilometers (930,000 miles) from Earth. In fact, the ISIM structure survived temperatures that plunged as low as 27 Kelvin (-411 degrees Fahrenheit), colder than the surface of Pluto.

"It is the first large, bonded composite spacecraft structure to be exposed to such a severe environment," said Jim Pontius, ISIM lead mechanical engineer.

The 26-day test was specifically carried out to test whether the car-sized structure contracted and distorted as predicted when it cooled from room temperature to the frigid — very important since the science instruments must maintain a specific location on the structure to receive light gathered by the telescope's 6.5-meter (21.3-feet) primary mirror. If the structure shrunk or distorted in an unpredictable way due to the cold, the instruments no longer would be in position to gather data about everything from the first luminous glows following the big bang to the formation of star systems capable of supporting life.

"The tolerances are much looser on the Hubble Space Telescope," said Ray Ohl, a Goddard optical engineer who leads ISIM's optical integration and test. "The optical requirements for Webb are even more difficult to meet than those on Hubble."

NASA's Webb Telescope MIRI device Takes One Step quicker To Space

A major instrument due to fly aboard NASA's James Webb Space Telescope is getting its first taste of space in the test facilities at the Rutherford Appleton Laboratory (RAL) in the United Kingdom. The Mid-InfraRed Instrument (MIRI) has been designed to contribute to areas of investigation as diverse as the first light in the early Universe and the formation of planets around other stars.

"The start of space simulation testing of the MIRI is the last major engineering activity needed to enable its delivery to NASA. It represents the culmination of 8 years of work by the MIRI consortium, and is a major progress milestone for the Webb telescope project," said Matt Greenhouse, NASA Project Scientist for the Webb telescope Integrated Science Instrument Module, at NASA's Goddard Space Flight Center, Greenbelt, Md.

The James Webb Space Telescope represents the next generation of space telescope and, unlike its predecessor Hubble, it will have to journey far from home. Its ultimate destination is L2, a gravitational pivot point located 1.5 million kilometers (930,000 miles) away, on the opposite side of the Earth from the Sun. Here it is cool enough for the MIRI to obtain exquisite measurements that astronomers will use to help decipher the Universe. "At L2 we are at an environmentally stable point where we can be permanently shaded from light from the Sun and Earth. That allows us to reach the very low temperatures - as low as 7K (- 447.1 Fahrenheit) in the case of MIRI – that are necessary to measure in the mid-infrared," says Jose Lorenzo Alvarez, MIRI Instrument Manager for European Space Agency (ESA).

The MIRI provides imaging, coronagraphy and integral field spectroscopy over the 5-28 micron wavelength range. It is being developed as a partnership between Europe and the U.S. The MIRI is one of four instruments flying aboard the Webb telescope. The other instruments include: NIRSpec (a near-infrared spectrograph), NIRCam (a near-infrared camera), and TFI (a tunable filter imager).

One of the jewels in the MIRI's crown is the potential to observe star formation that has been triggered by an interaction between galaxies. This phenomena has been difficult to study with Hubble or ground-based telescopes since the optical and near-infrared light from these newly formed stars is hidden from view by clouds of dust that typically surround newly formed stars This will not be a problem for MIRI, as it is sensitive to longer wavelengths of light in the range 5 to 28 microns, which can penetrate the dust.

However, keeping the MIRI at a colder temperature than on Pluto, for a sustained period of time, was one of the biggest engineering challenges facing those charged with constructing the instrument. "A critical aspect, to achieving the right sensitivity, is to ensure stable operation at 7 Kelvin (- 447.1 Fahrenheit) that will last for the five years of the mission," explains Alvarez.