ESA’s Gaia Observatory has photographed the James Webb Telescopein the orbit they share around Lagrange point 2, 1.5 million kilometers from Earth in the opposite direction to the Sun.
On February 18, 2022, the two spacecraft were 1 million kilometers apart, with a view of Gaia edge-on to Webb’s huge sunshield. Very little reflected sunlight reached Gaia’s path and thus Webb appears as a tiny, faint speck of light in Gaia’s two telescopes without any visible detail, the ESA reports.
A few weeks before Webb’s arrival at L2, Gaia experts Uli Bastian of the University of Heidelberg, Germany, and Francois Mignard of the Nice Observatory, France, noticed that during Gaia’s continuous scan of the entire sky , its new neighbor on L2 should occasionally cross Gaia’s fields of viewlaunched into space in 2014.
Gaia is not designed to take actual photos of celestial objects. Instead, it collects very precise measurements of their positions, movements, distances, and colors. However, a part of the instruments on board take a kind of images of the sky. It is Gaia’s ‘seeker telescope’, also called a sky mapper.
Every six hours, the sky mapper of Gaia scans a narrow 360-degree strip around the entire celestial sphere. Successive strips are slightly tilted toward each other, so that every few months the entire sky is covered, touching everything there that is bright enough to be seen by Gaia. In a matter of seconds, these slices are automatically examined for star images, whose positions are then used to predict when and where those stars might be recorded by Gaia’s main science instruments. They are then routinely removed.
But the computer can be manually requested to exceptionally keep a part of the image data. The sky mapper was originally planned for technical service purposes, but during the mission it also found some scientific uses. Why not use it for a snapshot of Webb?
After Webb reached its destination at L2, Gaia scientists calculated when the first opportunity for Gaia to detect Webb would arise, which turned out to be February 18, 2022.
Gaia now has a companion spacecraft at L2, and together they will discover our home galaxy and the Universe beyond. (I)
Source: Eluniverso
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