James Webb Space Telescope – Hubble’s successor – passed final testing

The James Webb Space Telescope is the world’s most complex infrared telescope. In February 2021, It successfully passed its final functional performance tests, moving it closer to its launch in October.

The Webb telescope in a white room with various electrical components exposed while yellow machinery surrounds it.

During its final full systems test, technicians powered on all of the James Webb Space Telescope’s various electrical components installed on the observatory, and cycled through their planned operations to ensure each was functioning, and communicating with each other. Image via NASA/ Chris Gunn.

Significant progress was made in the development of NASA’s James Webb Space Telescope – also known as JWST or simply the Webb – last month, February 2021, marking the success of its final functional performance tests. The two testing milestones – the comprehensive systems test and the ground segment test – confirmed the observatory’s internal electronics are operating as intended. They also verified that it and its four science instruments can send and receive data, moving it closer to its planned launch in October.

The comprehensive systems test took place at Northrop Grumman in Redondo Beach, California, the industrial partner in the Webb project. Specifically, this test established a baseline of electrical functional performance for the entire observatory and all of the many components that work together in its composition. In other words, it’s the electrical version of the mechanical testing that successfully completed in October 2020. The ground segment test, however, was completed in collaboration with test engineers at the Space Telescope Science Institute in Baltimore, Maryland, the institute that will operate the telescope after launch. That test was designed to simulate the complete process from planning science observations to posting the scientific data to the community archive. Jennifer Love-Pruitt, the Webb’s electrical vehicle engineering lead, said in a NASA statement:

It’s been amazing to witness the level of expertise, commitment and collaboration across the team during this important milestone. It’s definitely a proud moment because we demonstrated Webb’s electrical readiness. The successful completion of this test also means we are ready to move forward toward launch and on-orbit operations.

NASA is targeting October 31, 2021, for the launch of the Webb telescope. The telescope will ride to orbit on an Ariane 5 rocket from the ELA-3 launch site at the European Spaceport located near Kourou, French Guiana. Once it lifts off, the massive observatory will make its way to Lagrange Point 2, a gravitationally stable point 930,000 miles (1.5 million km) from our planet. The Webb will then deploy its sunshield and begin studying the cosmos in infrared light using its dazzling mirror.

Diagram of Earth and moon, with Hubble and Webb's orbital distances shown.

The Webb will orbit the sun about a million miles (1.5 million km) away from the Earth, at what is called the 2nd Lagrange point or L2. Note that this graphic is not to scale. Image via NASA.

Development began in 1996 for a launch that was initially planned for 2007 and a $500 million budget. But the project has had considerable delays and cost overruns, and underwent a major redesign in 2005. Afterwards, the launch was planned for March 2020, but the ongoing coronavirus pandemic also caused major setbacks. Yet now, significant progress has been made, and existing program funding will have the Webb finished within its current $8.8 billion cost cap, NASA says. In December 2020, the sunshield of a fully assembled James Webb Space Telescope successfully completed its own final tests, including a complete unfolding, just as the telescope will need to do once in space.

Formerly known as the Next Generation Space Telescope, the Webb was renamed in September 2002 after James Webb, who was an esteemed former NASA administrator. The entire project is an international collaboration between NASA, the European Space Agency, and the Canadian Space Agency. NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the development effort, while Northrop Grumman serves as the project’s main industrial partner. As it did for the Hubble Space Telescope, the Space Telescope Science Institute will be operating the Webb telescope after launch.

One of the Webb’s most important and identifiable attributes is its golden 21-foot-wide (6.5-meter-wide) primary mirror. A reflecting telescope’s primary mirror determines how much light it can collect, and thus how deeply it can see into the universe. Webb’s mirror is nearly three times wider than Hubble’s primary mirror. It’s composed of 18 separate hexagonal-shaped segments made of ultra-lightweight beryllium, which will unfold after launch.

The Webb’s biggest feature, however, is its tennis court-sized sunshield, designed to reduce the sun’s heat by more than a million times, to -364 degrees F (-220 degrees C). The purpose of the sunshield is to keep the mirror and instrumentation cold. If it were to be heated up by the sun, it would give off its own infrared radiation and drown out the faint infrared signals from the distant galaxies it’s meant to measure.

The Webb is equipped with four cameras and spectrometers with detectors able to record extremely faint signals. One of these, the Near InfraRed Spectrograph has programmable “microshutters” that let it observe up to 100 objects at the same time. The detectors of one of the other instruments require even colder temperatures to function than the sunshield can provide, so a cryocooler keeps it at around -447 Fahrenheit (7 kelvin or -266 degrees C).

Chart for comparison of sizes; human figure to the left, grey filled circle with white hole in center, larger structure made of 18 hexagons. in yellow/orange to the right.

Webb will have a 21-foot-diameter (6.5-meter-diameter) primary mirror. Hubble’s mirror is about 8 feet (2.4 meters) in diameter. Note the human figure for scale. Image via NASA.

The capabilites of the Webb extend beyond those of the Hubble Space Telescope and it is thus not a replacement but rather a successor (and the two telescopes will even collaborate side by side for a while, with a planned overlap). The Webb will observe further into the infrared regions of the electromagnetic spectrum and with greater sensitivity, allowing it to go even deeper than the Hubble, and to look further into the past and inside stellar dust clouds where stars and star systems form. Thaddeus Cesari, a communications specialist for the mission, wrote:

In addition to the groundbreaking science expected from it after launch, Webb has required an improvement in the testing infrastructure and processes involved in validating large complex spacecraft for a life in space … Lessons learned from previous space telescope development were invested into Webb, and future space telescopes will be built upon the same collective knowledge. Thousands of scientists, engineers, and technicians contributed to build, test, and integrate Webb. In total, 258 companies, agencies, and universities participated: 142 from the United States, 104 from 12 European nations, and 12 from Canada.

A 2-panel image with dense clouds in space on the left and the same clouds more tenuous with more stars on right.

How we see objects in space depends upon which wavelengths of the electromagnetic spectrum are being received by the telescope. Here’s a comparison of the Carina Nebula, a gas and dust cloud, viewed in visible light (left) and infrared (right), both images observed by the Hubble telescope. In the infrared image, we can see more stars that were hidden behind the dust in the optical light. Image via NASA/ ESA/ M. Livio & Hubble 20th Anniversary Team.

The Webb will be the largest, most powerful and most complex infrared telescope ever built. Thousands of astronomers worldwide will use it for a wide range of research projects, complementing and extending the discoveries of the magnificent Hubble Space Telescope, as well as the now-decommissioned Spitzer infrared space telescope. Once in space, above Earth’s obscuring atmosphere, the Webb will provide unobstructed views of the near and distant cosmos. Since light has a finite speed (186,000 miles per second, or 300,000 km per second), the new space telescope will also provide insights into our universe’s past: from the first light after the Big Bang, to the formation and evolution of galaxies, to our own and other planetary systems.

Thus, the Webb will be used for study of every phase in the history of our universe.

Diagram for size comparison of two satellite telescopes, larger Webb telescope with open gold reflector dish to the left and Hubble with tube to the right.

Artist’s concept of the overall size comparison of the Webb (left) and Hubble (right) telescopes. Image via GSFC/ NASA.

22 artists were selected nationwide to attend the James Webb Space Telescope Artist Event at NASA Goddard. They sat directly in front of the Webb telescope and were briefed on the mission by scientists, engineers and other project personnel while they worked; sketching, painting, writing, sewing, playing music. Visit this gallery to see their astonishing impressions of the Webb and its mission.

Bottom line: The James Webb Space Telescope is the world’s largest, most powerful, and most complex infrared telescope, built for astrophysical studies of the most distant universe. Two final testing milestones confirmed that the observatory’s electronics and science instruments are operating as intended, moving the telescope closer to being ready for launch in October.

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