As Gaia Maps Our Galaxy, This Telescope Keeps an Eye on the Spacecraft

Europe's star-mapping spacecraft,  Gaia, streaks across the Milky Way in a new image captured by a ground telescope. The image will help refine scientists' knowledge of Gaia's orbit.

The observations by the VLT Survey Telescope (VST) in Chile are supposed to help Gaia managers better track the spacecraft's orbit and thus improve the accuracy of the star map Gaia generates, according to a statement from the European Southern Observatory (ESO), which oversees VST. During this observing process, VST tracks Gaia's position every second night to help the spacecraft in its own mission of recording the positions and velocities of stars. Several other ground telescopes also keep a watchful eye on Gaia.

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The VLT Survey Telescope in Chile caught this composite view of the Gaia space telescope streaking across the sky. The telescope's crossing appears as a faint series of dots in the lower half of the frame. (Image credit: ESO)

Finding the spacecraft in the sky is no small challenge; ESO officials said that Gaia is very dim compared to nearby stars. "The spacecraft is what we call a 'moving target,' as it is moving quickly relative to background stars — tracking Gaia is quite the challenge," Monika Petr-Gotzens, who has coordinated the execution of ESO's observations of Gaia since 2013, said in the statement.

However, this unique collaboration allows for precise science. A part of Gaia's second release of data late last year, which mapped 1.7 billion stars, allowed researchers to identify the spacecraft's position in space to an incredible precision of up to 20 milliarcseconds, a tiny fraction of a degree of arc. Scientists accomplished this through ground observations and by identifying the stars in Gaia's field of view.

New information about Gaia's orbital track will be fed into future observations of the spacecraft, and scientists plan to apply it to the observations Gaia already performed, ESO officials added. Both procedures will help to better refine our understanding of Gaia's orbit in space over time.

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Elizabeth Howell
Staff Writer, Spaceflight

Elizabeth Howell (she/her), Ph.D., is a staff writer in the spaceflight channel since 2022 covering diversity, education and gaming as well. She was contributing writer for for 10 years before joining full-time. Elizabeth's reporting includes multiple exclusives with the White House and Office of the Vice-President of the United States, an exclusive conversation with aspiring space tourist (and NSYNC bassist) Lance Bass, speaking several times with the International Space Station, witnessing five human spaceflight launches on two continents, flying parabolic, working inside a spacesuit, and participating in a simulated Mars mission. Her latest book, "Why Am I Taller?", is co-written with astronaut Dave Williams. Elizabeth holds a Ph.D. and M.Sc. in Space Studies from the University of North Dakota, a Bachelor of Journalism from Canada's Carleton University and a Bachelor of History from Canada's Athabasca University. Elizabeth is also a post-secondary instructor in communications and science at several institutions since 2015; her experience includes developing and teaching an astronomy course at Canada's Algonquin College (with Indigenous content as well) to more than 1,000 students since 2020. Elizabeth first got interested in space after watching the movie Apollo 13 in 1996, and still wants to be an astronaut someday. Mastodon: