​​​​​​​ Frequently Asked Questions


Here you find answers to some of the most frequently asked questions about the Gaia mission, its science and its data. Additional FAQs are available on the ESA Gaia corporate website.

For registered users who have questions on their Cosmos account and password resets, please visit the Cosmos FAQ.

If you can not find what you are looking for, please contact the Gaia Helpdesk.






How shall I acknowledge Gaia? When do I acknowledge Gaia?

Where will I be able to find all scientific papers that use Gaia data?

When did Gaia's routine science operations phase start?

Which telescopes are being used to track Gaia from the ground?

What can amateur astronomers contribute to the mission?


What is Gaia's astrometric, photometric and spectroscopic performance?

How many objects in our solar system will Gaia detect?

What will be the most common type of star in the Gaia catalogue?

What is the Gaia scanning law and how does it work?

Is there an input catalogue for Gaia? If yes, how are transient objects like supernova discovered?

Is there any way to find out about transient objects immediately to do follow-up observations on-ground?

What does the first Gaia catalogue look like? What is the Robust Scatter Estimate (RSE)?

Where can I check how many times and when Gaia will observe my favourite object?

I'm not interested in stars, I'm interested in minor bodies in the Solar System. When will you start releasing information about them? Will you calculate orbital elements for them?

How can Gaia G, BP and/or RP values be transformed to V magnitudes?

I'm not interested in stars, I'm interested in galaxies. What can Gaia do for me?

What happens to newly detected solar system objects (Gaia asteroid observations)?

I can not find data for a bright star. Why is that?

The abstract of the Gaia DR1 release paper (Gaia Collaboration et al. 2016; http://adsabs.harvard.edu/abs/2016A%26A...595A...2G) states that "For the primary [TGAS] astrometric data set the typical uncertainty is about 0.3 mas for the ... parallaxes ... A systematic component of 0.3 mas should be added to the parallax uncertainties". This is confirmed at several places inside the paper. Is this really true? On the other hand, if a systematic error of 0.3 mas has been included already, how can many parallax standard errors in TGAS be close to 0.3 mas (or even be smaller)?

What is the meaning of ICRS, ICRF, J2000.0 epoch, and J2000.0 equinox?

Gaia Data

Where can I find information about upcoming data releases?

Where can I find all relevant information on a specific Gaia data release?

Is data access limited? How is it regulated?

What types of data are being downlinked?

Are the data from the Gaia-ESO survey already public? If yes, where can I access them?

How is the Gaia data transferred to Earth?


What is DPAC?

How does the on-board processing system work?

How do you mitigate the effects of radiation damage?

What are the different steps in the Gaia data processing?


What is the difference between Gaia's three different CCD variants?

Why does Gaia have two telescopes?

Why is there an angle of 106.5 degrees between the 2 telescopes?

The spinning axis of Gaia seems to be fixed at 45 degrees with respect to the Sun. Is there any special reason why this value was chosen?

What are the red and blue photometer used for?

How do you ensure the stability of the basic angle?

What kind of mode do the CCDs operate in?

When will Gaia stop observing? What happens with the satellite afterwards?

How does the Gaia scanning law work?

Gaia Archive

I have problems accessing the archive.

I exceeded my file quota.

What are the newest features of the Gaia Archive?

What are the celestial coordinates of my HEALPix identifier?

Why are there duplicate Hipparcos matches in table public.igsl_source_catalog_ids?

Where can I find the column descriptions and units of the data fields?

Why does my query time out after 90 minutes? Why is my query limited to 3 million rows?

I can not find a well known bright star in the Gaia Archive. Why?

Why do some sources have null 'parallax', 'pmra' and 'pmdec' values?

Why are some parallaxes less than zero?

How can I extract Gaia data for my list of targets with RA and DEC?

I have a problem uploading a list of targets in the simple form. Why?

The load_tables() method of astroquery.gaia.Gaia returns an SSL error. What is going wrong?

Is it possible to delete all the jobs in my jobs list at once?

Is there a different behaviour when using integer or float division in the query?

Where can I find information on the Gaia Mission and Gaia data releases?

My question is not in this list. Who can help me?

How can I download the entire Gaia Source catalogue?

How can I install the latest version of Astroquery.Gaia?

Why are the column names of my uploaded table formatted to lowercase?

Are there any duplicated sources in the Gaia catalogue?

Why are there cases with negative flux ratio F2/F1 in the binary_masses table?

Why are there no inclinations for astrometric or astrometric-spectroscopic orbits in the nss_two_body_orbit table?

Why do the Gaia measurements in the Archive include insignificant digits?

Why does my small (<150 MB) table not fit into my user space?