The Gaia spacecraft was launched in 2013 by the European Space Agency. According to NASA, “Its goal is to create the largest, most precise three-dimensional map of the Milky Way by surveying about 1% of the galaxy's 100 billion stars.” Photometry and spectroscopy are also possible for many of the observed objects. The observation mode is based on continuous scanning by two telescopes simultaneously with a 64-day precession movement around the Sun. This scanning mode allows Gaia to map the entire sky in several months and also makes it impossible to follow-up a specific target when necessary.
During the sky scan, Gaia provides many alerts for transient phenomena, in particular for Solar system objects (SSO) that are not included in its existing reference catalog. The group in charge of Solar system objects for the Gaia mission has set up a special task force to provide public alerts to ground-based observers, who belong to the Gaia-FUN SSO network. Chilean astronomers with access to LCO are members. Observations on alert require a fast reaction on the order of a few hours to be successful, since the predicted search areas can expand in a few days, and it also requires a large geographical coverage. This is why the LCO 1m telescope network has proven to be extremely well adapted and effective for follow-up observations.
By confirming Gaia's detection of potentially new objects in the Solar system, astronomers have significantly improved the database of known objects. Ground-based measurements combined with the short arc observed by Gaia are sufficient to determine very precise orbital parameters of these Solar system objects. Asteroids that could be lost are immediately recovered and have the possibility of being found again in the future.
The use of the LCO 1-meter telescope network since 2019 has allowed astronomers to detect and measure nearly 300 potentially new Solar system objects. One new object is the recently discovered Near-Earth Asteroid 2021 PO41. Gaia data show how the ongoing surveys are less sensitive to certain populations, such as those of asteroids having orbits strongly inclined on the ecliptic. These results are illustrated in the figure below, where biases in semi-major axis, eccentricities, and inclinations, with respect to the population observed by Gaia and LCO, are clearly present in the current census of known objects. The uncatalogued objects detected by Gaia and validated by our LCO ground-based observations are objects with highly inclined orbits and generally large eccentricities. These results have been detailed in a recent article published by Carry et al. in Astronomy & Astrophysics.
This observing program continues. Further observations are expected in order to better physically characterize these objects and to understand their nature in connection with the asteroid population in the Solar System. The LCO global network has proven to be a superb partner in this research, since it offers ease of scheduling on a robotic system, quick response times, wide geographic coverage, calibrated data products, and excellent support from the staff. Astronomers around the world plan to continue using it for the lifetime of the Gaia satellite.
