After more than ten years in operation, the European Space Agency's Gaia observatory is set to conclude its data collection mission this week. Astronomers are preparing to receive the final data burst from this groundbreaking mission.
Despite facing numerous challenges, including technical issues and damage from micrometeoroids and solar storms, Gaia has been recognized as one of the most successful space observatories in history. However, the spacecraft is now running low on nitrogen gas, essential for maintaining its position.
The data collection period for Gaia will officially end on January 15. Following the successful download of the final data and completion of a series of technical tests, expected by late March, ESA technicians will permanently shut down the spacecraft.
For Carme Jordi of the University of Barcelona, who has been involved in the project since the 1990s, witnessing the end of the mission is bittersweet. “Gaia is like our scientific child,” she remarked, reflecting on the decades of effort that led to its launch and operation.
The mission has produced a valuable legacy: a comprehensive catalog that, once completed, will include the positions, motions, brightness, colors, and distances of approximately 2 billion stars, measured with microsecond precision.
“Every day, Gaia generates over five peer-reviewed scientific publications,” stated Johannes Sahlmann, a project scientist at the European Space Astronomy Centre in Spain. “These results span nearly all areas of astrophysical research and often have transformative impacts.”
Last year, Gaia contributed to the discovery of the most massive stellar-origin black hole in the Milky Way. The data also revealed 9 million variable stars, 165,000 binary systems, 360,000 white dwarfs, at least 700 open clusters, and over 150,000 asteroids.
Before its retirement, Gaia will undergo several technical tests, including one crucial test related to the angle separating its twin telescopes as they scan the sky. This angle, approximately 106.5°, must be maintained to microsecond precision for accurate star positioning.
Initially, the angle varied significantly, prompting the team to use an internal laser system to correct the issue. Engineers will now utilize the remaining nitrogen fuel to reposition Gaia relative to the Sun, monitoring the telescope angle during this process.
These tests may disrupt scientific measurements requiring a fixed solar angle of 45°, with new measurements scheduled after January 15. “I don’t think the results will significantly impact the next two data releases, but they could be very important for future space astrometry missions,” Lindegren noted.
The variation in solar angle may also shed light on why Gaia appears three magnitudes fainter from Earth than predicted. ESA aims to resolve this unexpected dimming through larger telescopes.
As Gaia’s 11-meter sunshield adjusts the solar angle during testing, the spacecraft will shine at magnitude 14, visible through an 8-inch telescope. ESA invites amateur astronomers to submit magnitude and color measurements.
This engineering test is expected to enhance future space mission designs. ESA has proposed a successor to Gaia, named GaiaNIR, which will explore dust-obscured regions of the galaxy in near-infrared wavelengths and update Gaia’s astrometric framework, significantly improving the existing catalog.