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The Gaia spacecraft relies on a cold gas propellant to keep it spinning and scanning the sky at it’s orbit around L2. The amount of remaining cold gas decreases by about a dozen grams per day and is reaching its end in early 2025. The Gaia science observations will therefore end on 15 January 2025, meaning that after more than 11 years of astrometric observations no more nominal science data will be acquired by Gaia after that date. This is, however, far from being the end of this transformative mission!
The Gaia scientific and engineering teams will continue to work full steam on the preparations for Gaia Data Release 4, which is not “more of the same” but will make new groundbreaking science possible by including a much larger data volume, many more data products, and data of overall better quality compared to Gaia Data Release 3. In the course of 2025, once all of Gaia’s nominal science data have been downlinked to Earth, the processing for the final Gaia Data Release 5 will ramp up to full speed and run in parallel to the processing of Gaia Data Release 4. Gaia Data Release 4, covering 5.5 years of mission data, is expected in 2026 and Gaia Data Release 5, covering the full 10.5 years of mission data, around the end of the decade (!).
After Gaia’s science observations end on 15 January 2025, a period of technology tests will commence. These technology tests will allow us to study in more detail the behaviour of some spacecraft and instrument components, with the potential of further improving the Gaia calibrations and aiding the design of future space missions. After these tests, which will last several weeks, the Gaia spacecraft will leave its orbit around the Lagrange point L2 to be put into its final heliocentric orbit, away from Earth’s sphere of influence. Eventually, the Gaia spacecraft will be passivated in March 2025 and reach its well-deserved retirement.
More details about the disposal can be found on the ESA webpage (-this is also where I shamelessly copied most of the text above): https://www.cosmos.esa.int/web/gaia/end-of-observations
In case you haven’t heard of Gaia,I can highly recommend Fraser Cain’s videos about the telescope: https://youtu.be/RyEVmDH5Cdk?si=OxrJFrbNIlc_rEx7
I actually created this post because I wanted to point out the following two things:
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Gaia has always been very faint and difficult to follow-up for amateur astronomers (at a magnitude of about 21). During the technology tests, Gaia’s solar aspect angle will change and its brightness will change accordingly (to a magnitude of about 15). This will give the unique opportunity to view Gaia with also smaller telescopes from ground. So if you want to take the challenge to take a picture of Gaia, you can find it’s location here: https://www.cosmos.esa.int/web/gaia/observe-gaia
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The final passivation of Gaia is scheduled for the end of March. I actually work at the ESA Control Center as part of the Gaia flight control team. While my role in the disposal process isn’t a major one, I will be reconfiguring parts of the Mission Control System used to command the disposal (as shown in the picture). This responsibility allows me to modify the command descriptions or the mnemonics for the reports received from the spacecraft. The final passivation sequence will conclude with two final reports being sent from Gaia before it falls silent forever. Any recommendations what the two final messages from Gaia shall be? (Character limit per message is 64 characters)