GAIA Space Observatory Shutdown: End of ESA’s Landmark Mission

Europe’s space agency retires Gaia, the cartographer of the cosmos. Its data allowed scientists to recreate not just a 3D map of the galaxy, but also predict how it will change over time.

Launched on December 19, 2013, by the European Space Agency (ESA), Gaia (Global Astrometric Interferometer for Astrophysics) revolutionized our understanding of the Milky Way by creating a high-precision 3D map of over a billion celestial objects. This ambitious project targeted about 1% of the galaxy's stellar population, providing unprecedented details about their positions, distances, movements, brightness, temperature, and chemical composition.

Beyond stars, Gaia also observed exoplanets, asteroids, and comets, enriching planetary science. It played a crucial role in testing Einstein's theory of general relativity, measuring how massive celestial bodies bend light. By analyzing stellar movements, Gaia helped reconstruct the past and future trajectories of stars and unveiled new insights into the formation and evolution of the Milky Way.

Advanced Technology Behind Gaia

Gaia's success was driven by its cutting-edge instruments:

• Astrometric Instrument: The core system responsible for mapping stars by precisely measuring their positions, distances, and movements. It used a focal plane of 106 CCDs, capturing starlight and utilizing parallax measurements to determine distances.

• Photometric System: This instrument provided crucial data on temperature, luminosity, and chemical composition of stars by measuring light across different wavelengths (330 nm - 1050 nm).

• Radial Velocity Spectrometer: It tracked the movement of stars towards or away from the Sun by detecting Doppler shifts in starlight, which is essential for understanding stellar motions and gravitational influences.

Gaia was positioned at Lagrange Point 2 (L2), 1.5 million kilometers from Earth, an ideal spot where the gravitational forces of Earth and the Sun balanced, allowing minimal fuel consumption and a stable observational platform.

The five Lagrangian points for the Sun-Earth system. L1 and L2 are on the line joining the Sun to the Earth. (Image courtesy ISRO)

Decommissioning and Mission End

Originally planned as a five-year mission, Gaia far exceeded expectations, operating for over a decade before its decommissioning on March 27, 2025. The primary reason for its retirement was the depletion of fuel, along with gradual wear on critical components.

As part of the shutdown process, ESA implemented measures to overwrite onboard data and permanently disable the spacecraft to prevent accidental reactivation or interference with future missions. Gaia’s final trajectory was carefully planned to ensure it does not disrupt satellites around Earth-Sun Lagrange points.

Legacy and Ongoing Impact

Even though Gaia is no longer operational, the vast data archive it created remains a goldmine for astronomers. Its precise measurements continue to enhance our understanding of the Milky Way’s structure, evolution, and celestial dynamics. The information gathered will be crucial for years to come, helping scientists refine models of star formation, galactic movements, and cosmic interactions.

The European Space Agency officially GAIA Space Observatory Shutdown, but its contributions to astronomy will endure as one of the most significant milestones in mapping the universe.

Which ISRO satellite is positioned at L1?

• Aditya-L1 is India’s first solar observatory mission, launched by ISRO on September 2, 2023.

• It reached Lagrange Point 1 (L1) on January 6, 2024, after a four-month journey covering 1.5 million km from earth.

• The mission carries seven scientific instruments to study the Sun’s corona, solar flares, solar wind, and space weather impacts.

• Scientific Payloads (7 Instruments)

  • Visible Emission Line Coronagraph (VELC) – Studies the Sun’s corona.

  • Solar Ultraviolet Imaging Telescope (SUIT) – Observes the Sun’s photosphere and chromosphere.

  • Solar Low Energy X-ray Spectrometer (SoLEXS) – Measures soft X-ray emission.

  • Hard X-ray Spectrometer (HEL1OS) – Captures high-energy solar flares.

  • Aditya Solar wind Particle Experiment (ASPEX) – Studies the solar wind.

  • Plasma Analyser Package for Aditya (PAPA) – Measures solar particles.

  • Magnetometer – Observes interplanetary magnetic fields.

• Its VELC (Visible Emission Line Coronagraph) instrument provides real-time solar observations, helping predict coronal mass ejections (CMEs) that can affect Earth.

• Aditya-L1 operates in a halo orbit around L1, ensuring continuous, unobstructed solar observations without Earth’s atmospheric interference.

• Mission Duration: Expected 5 years

• The mission complements NASA’s Parker Solar Probe and ESA’s Solar Orbiter, contributing to global solar research.