Extreme precision in the first tests of the future Roman telescope

April 17 () –

The first tests with the ten mirrors of the future Nancy Grace Roman space telescope show that it will direct light towards the observatory's scientific instruments with “extreme precision.”

This will produce sharp images of space once the observatory launches, NASA predicts. “This is the first light before launch, the first time we see through the entire telescope,” he said. it's a statement Joshua Abel, principal systems engineer for the Roman Space Optical Telescope at NASA's Goddard Space Flight Center. “We are excited to enter the next phase of the project!”

Each of Roman's mirrors had passed individual tests, but this was the first time they had been evaluated together. Engineers had to ensure that light moved through the entire optics in a strictly controlled manner, or else the telescope images would appear blurry.

“The telescope's optics are crucial to all future Roman observations,” said Bente Eegholm, Roman's optical engineer at Goddard. “In addition to the large primary mirror and secondary mirror, eight relay mirrors serve Roman's two scientific instruments. The telescope's 10 mirrors must be aligned within the width of a human hair to optimize the telescope's image quality. so that Roman can fully achieve his scientific goals.”

The meticulous, month-long alignment process involved a series of iterations to bring the test images into sharper and sharper focus. Once all the mirrors were in place correctly, technicians permanently fixed them in place. Three of the mirrors will remain mobile in space thanks to actuators (mechanisms that control the mirrors' positions) that will allow astronomers to further fine-tune the alignment once Roman begins his observations.

The IOA (Imaging Optics Assembly) vision test, establishes a basis for upcoming acoustic and vibration tests. Engineers will compare measurements before and after those tests to make sure the optics will withstand the strong shaking and intense sound waves during launch.

After that, the IOA will undergo a final “ophthalmological” examination, this time under vacuum conditions at its cold operating temperature. Materials expand and contract with changes in temperature, and Roman's optics will go from room temperature conditions on Earth at a frigid -13 degrees Celsius in space.

“Our prediction of the small change we expect to see when going from ambient temperatures to these colder temperatures is very important,” Abel said. The test will also measure the IOA's performance at extremely low pressures to evaluate how it will perform in the vacuum of space.

The entire optical telescope assembly, of which the IOA is a central component, is expected to be complete and delivered to Goddard this fall. Its launch into space is scheduled for 2027.