Two halves of James Webb Space Telescope come together for testing in California

Curt Godwin

After years of development, and having undertaken rounds of discrete testing, the two major components of NASA‘s James Webb Space Telescope (JWST) have arrived in California for fully-integrated testing. The flagship mission is referred to as the scientific successor to the stalwart Hubble Space Telescope (HST) and is set to launch on an Arianespace Ariane 5 rocket in the Spring of 2019 from Kourou, French Guiana.

Not always a smooth path

Though both of the telescope’s major components, the observatory’s optical telescope and integrated science instrument module (OTIS), and the main spacecraft bus – have been tested individually, they have yet to be tested as a combined unit.

The optical assembly was recently subjected to conditions similar to those it would encounter on orbit. This was done to help validate the alignment of the mirror cells. That test of the telescope, which was held at NASA’s Johnson Space Flight Center had to not only contend with an extreme environment inside the test chamber, but also had to survive a meteorological “curve ball” thrown by Mother Nature.

Hurricane Harvey made landfall on the Texas Coast at Category 4 strength,, but quickly weakened to a tropical storm. Unfortunately, the weather system remained relatively stationary and drenched the area in more than 50 inches (127 centimeters) of rain. Many of the personnel involved in testing Webb remained at Johnson throughout the storm to ensure the telescope’s testing was not interrupted and the optics could be validated.

Ensuring the mirrors were properly aligned prior to launch is critical to the mission’s success. With its location at a gravitationally stable orbit nearly 1 million miles (1.5 million kilometers) from Earth, mounting any sort of repair mission as has been done to correct the flawed primary mirror on the Hubble Space Telescope would not be practical (several servicing missions were also sent to Hubble by NASA’s now-retired fleet of shuttle orbiters).

Unlike Hubble, however, Webb has the ability to reshape each of its 18 mirror elements once in space. Each mirror is outfitted with small motors – also known as actuators – that are capable of adjusting each segment in very small amounts.

“They can move in steps that are a fraction of a wavelength of light, or about 1/10,000th the diameter of a human hair,” stated Lee Feinberg, optical telescope element manager for the Webb telescope at Goddard, in a release issued by the agency.

Special hardware to move a special telescope

Transporting a multi-billion dollar instrument like Webb across the country requires more than standard packing crates and a few rolls of bubble wrap. To transport the large telescope, NASA makes use of the specially-designed Space Telescope Transporter for Air Road and Sea (STTARS) shipping container.

The 165,000-pound (74,843-kilogram) container was custom-built by Nelson Manufacturing, and proved to be almost as much of a challenge to move as the telescope itself.

“The major challenge in this transport is the size,” stated Adam Carpenter, one of the mechanical integration engineers on the STTARS team, in a release issued by NASA. “The container weighs 165,000 pounds. There is a tremendous amount of planning going through this move.”

Though STTARS weighs nearly 75 metric tons, the container can actually be maneuvered in tight spaces by “floating” it on a series of air pads, much like one would see with a puck on an air hockey table.

Once clear of the constrained spaces, a series of hydraulic wheels are attached to the container and it is connected to a semi truck to be towed to a specially-modified C-5C Galaxy cargo jet for shipping anywhere in the world.

Some assembly required

Before the observatory can be completely tested, though, it has to be assembled. This critical step in the telescope’s preparation for launch will take place at Northrop Grumman Aerospace Systems in California.

“It’s exciting to have both halves of the Webb observatory – OTIS and the integrated spacecraft element – here at our campus,” noted Scott Willoughby, vice president and program manager for Webb at Northrop Grumman, in a release issued by NASA.

After assembly is completed, the fully integrated observatory is scheduled to be subjected to further tests to ensure the spacecraft is ready for launch. Years in the making, this occasion marks one of the final acts before the spacecraft’s launch, which is currently slated to take place in 2019.

“This is a major milestone,” stated Eric Smith, director of the James Webb Space Telescope Program at NASA, in a release issued by the agency. “The Webb observatory, which is the work of thousands of scientists and engineers across the globe, will be carefully tested to ensure it is ready to launch and enable scientists to seek the first luminous objects in the universe and search for signs of habitable planets.”

Video courtesy of NASA