James Webb Telescope to face final test in space

The James Webb Telescope will see the birth of our origins as it tries to answer the questions about how our universe came to be. Before it peers at the edge of the universe, it will have to go through one final test after which the scientific operations will commence nearly 15,00,000 kilometers from Earth.

The world’s most powerful telescope recently completed the alignment process, stretching its mirrors into place and observing stars and galaxies to focus the lenses. While the mirrors cool down to their final operating temperatures, Nasa has said that the Webb team is preparing for the thermal stability test.

“During this final phase, the Webb team and instrument scientists will test all the fashion and operations for the four science instruments to measure their performance, calibration, and overall observatory operations,” Nasa said in an update.


The Webb team will conduct the thermal stability test on the telescope, during which scientists will measure the variations in heat by moving between the extremes of Webb’s field of view, from the hot to the cold attitude. Erin Smith, a scientist at the Webb deputy observatory project, said that as Webb points to different targets around the sky, the angle of the Sun on the sunshade changes, which changes the thermal profile of the observatory. These variations in temperature can induce small changes in the observatory.

The Webb team will conduct the thermal stability test on the telescope. (Photo: Nasa)

These changes in the sunlight can induce small changes in the observatory, and affect Webb’s optical quality, pointing, observed backgrounds, and other parameters.

The Webb team will point the telescope in the hot attitude at about zero degrees pitch, and keep it there for five days while it thermally stabilizes. The team will measure the stability, optical wavefront error, and any oscillations caused by the instrument electronics. Once this baseline has been established, the team will slew the observatory to the cold attitude, about +40 degrees pitch.

The telescope will spend more than a week in the cold attitude until the temperatures stabilize. Then Webb will slew back to the hot attitude. During this long test, the Observatory will not sit idle; some instrument commissioning activities are compatible with the hot and cold pointing.

Smith said that when assembled together, the data from the thermal stability tests will allow the observatory team to better understand how the observatory behaves thermally. Although the changes are expected to be very small, Webb is so sensitive that they could make a difference as we optimize the telescope’s performance.

Scientists are hopeful that once the test is completed the telescope will begin science operation by July this year.


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