The Nancy Grace Roman Space Telescope (RST), launched in August, is rapidly approaching its target, the L2 point on the path of Earth’s orbit around the Sun (the same location as the James Webb Space Telescope), and is expected to be inserted into orbit in early December.
As it makes its way, its instruments have been tested, and then brought online. Scientists and engineers have been carefully calibrating the secondary mirrors for the Wide Field Instrument (WFI), which are specially designed to be able to flex and be maneuvered by tiny actuators, such that they can be moved one-sixteenth the width of a human hair. The mirrors have been brought into nearly perfect alignment, allowing the WFI to produce an image with an optical error nearly 30% below the requirement—which will allow for exceptionally sharp cosmic images, reported ScienceDaily.
“‘All of Roman’s sweeping surveys will rely on the Wide Field Instrument,’ said Dave Hickey, a Wide Field Instrument systems engineer at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. ‘Many of the mission’s primary goals, like studying dark matter and dark energy, wouldn’t be possible without it, so it’s both exciting and a huge relief to see that it’s working well!’”
The team started by diving into the instrument’s 18 detectors—each about the size of a sticky note—along with the electronics that bring them to life. Then came the element wheel, a rotating carousel packed with filters and other optical components. By selecting which wavelengths reach the detectors, it can even split incoming light into its individual colors. It’s the kind of mechanism that makes you appreciate just how much precision goes into turning starlight into science.
Next, the team fired up the instrument’s internal calibration system. They switched on its tiny LEDs—adjustable light sources that can glow in different colors and brightness levels, based on commands from Earth. By watching how the detectors react to these precisely controlled flashes, scientists can spot any quirks or sensitivity differences and fine-tune the system. It’s like giving the instrument a set of known test signals, to be absolutely sure it’s seeing the universe accurately.
Engineers also tested the instrument’s alignment mechanism, and moved it from the deliberately unfocused position used during launch, to the position expected to provide the sharpest images. They finished by checking the thermal control system, which maintains the temperatures required for the instrument’s various components to function correctly.
The next milestone in the mission will be the insertion into the L2 orbit, where the telescope will undergo several additional weeks of calibration and commissioning. Far more details about the WFI—its parameters, wavelengths of observations, etc.—can be found on the NASA website.
