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ScienceWe fly ESA's Gaia mission to map 1 billion stars - Ask us anything!

Dec 6th 2016 by gaiaops • 27 Questions • 691 Points

Gaia’s primary objective is to survey one billion stars in our Galaxy and local galactic neighbourhood in order to build the most precise 3D map of the Milky Way and answer questions about its origin and evolution. Gaia is expected to find thousands of planets beyond our Solar System and map hundreds of thousands of asteroids and comets within it. The mission will also reveal tens of thousands of failed stars and supernovae, and will even test Einstein’s famous theory of General Relativity.

The Gaia flight control team work at ESA's ESOC mission control centre, in Darmstadt, Germany. This includes planning all flight activities, monitoring the health and status of the spacecraft, coordinating with the science operations centre at ESA's ESAC Establishment in Spain, scheduling ground station passes, downloading an immense amount of science data each day and generally making sure the satellite performs as expected.

The Gaia spacecraft is unique, with unprecedented dynamic and thermal performance. In ensuring the ambitious goals of this mission are met, the team have dealt with some interesting challenges.

We'll be live here starting at 16:00 CET - 10:00 EST - 15:00 GMT, for approximately 75 mins.

UPDATE 17:15 CET - Thank you for the excellent questions! We thoroughly enjoyed answering them and we'll take a look back here in the next day or so to see if we can respond to any others that come in. We'll log off now and get back to... Gaia! For more info and news, access http://www.esa.int/gaia

Providing replies for the Gaia AMA are:

At ESOC

  • David Milligan - Spacecraft Operations Manager (Flight control team leader) [DM]

Flight control team

  • Ed Serpell - Operations engineer (Payload) [ES]
  • Jonas Marie - Operations engineer (Attitude & orbit control system) [JM]
  • Ran Qedar - Operations engineer (Power & thermal) [RQ]
  • Peter Collins - Operations engineer (Data management system, Onboard software maintenance, Ground systems) [PC]
  • Jan Kolmas - Young Graduate Trainee (Star tracker) [JK]
  • Gary Whitehead – Operations engineer (Telemetry & telecommanding, Mission planning) [GW]

Flight dynamics

  • Ander Martinez De Albeniz (Flight dynamics) [AMA]

Moderator

  • Daniel Scuka, senior editor for spacecraft operations [DS]

at ESAC

  • Jose Hernandez - Science Operations Calibration Engineer [JH]

Proof links Rocket Science blog @esaoperations @esa

Q:

I imagine that working on a project this large involves a lot of boredom while you organize the data. What are the types of moments that cause the most excitement?

A:

Well, just like any job there are indeed days that are not as exciting as others! But in general I am extremely privileged to work at such a great place on such an interesting mission with a bunch of cool people. For me personally the moment of highest excitement was the launch day – in the first few moments after Gaia was separated from the rocket and we waited for the first signal from space, I could literally feel my heart pounding. The whole first year of operations was generally exciting, when we really got to “know” Gaia and how he/she/it (?!) behaves in her environment. Right now our task is about keeping Gaia operating as well as possible and making sure as much data as possible comes to ground to obtain as good a map as possible – and that in itself is an exciting, interesting and challenging thing to do every day! [PC]


Q:

Thanks for your reply! :-)

A:

You're welcome :-D [PC]


Q:

Can we expect to see an accurate 3D render of the Milky Way based on information collected by Gaia in a few years?

A:

[JH] Yes indeed we will and will also contain information about the motion of the stars so we can play it forward or backwards in time and see how they are moving. Gaia will reach up to the center of the milky way, further in regions outside the galactic plane which is more dusty.


Q:

This would be awesome in VR!

A:

The three ESA 35m deep-space stations are explained here: http://www.esa.int/estrack - look for Cebreros, Malargue and New Norcia [DS]


Q:

Thanks for the interesting insight!

A:

The critical launch and early orbit phases are always challenging as there is time pressure and you have to get it right. For this reason we have a great team and we rehearse, rehearse and rehearse again before launch. Once the final orbit was achieved the commissioning phase of 6 months was also pretty intense as all the subsystems of this unique machine were switched on and tested for the first time together in space. [DM]


Q:

Will Gaia be involved in the search for the Theorized Planet Nine?

Will the exoplanet search involve direct imaging, or will you be looking at star wobbles?

What sort of a network background do you need to work with satellite communications on this level?

A:

[JH] Regarding the Planet Nine I think it would be too dim for Gaia, I think its estimated magnitude would be 24-25 and Gaia "only" reaches up to magnitude 20-21, Gaia's contribution in the Solar System is more relevant in the field of the asteroids as Gaia sees them and sees them moving so it detects new ones and also send alerts for the known ones so that they can be followed up from ground in order to improve the knowledge of their orbit.


Q:

Will Gaia be involved in the search for the Theorized Planet Nine?

Will the exoplanet search involve direct imaging, or will you be looking at star wobbles?

What sort of a network background do you need to work with satellite communications on this level?

A:

[JH] Gaia will detect exoplanets and binary systems in different ways, one of them will indeed be by measuring the star wobbling which will give a lot of information about the orbit and mass of the exoplanet, this will work for jupiter like planets. Other methods like the variation seen in the star luminosity when the planet transits the star or the changes in the spectra of the star will also be exploited by Gaia.


Q:

How does the change in the spectra of the star method work? I'm assuming you're referring to something different than Doppler shifts in the spectrum (since I understand that's what the wobble method is)

A:

[JH] Gaia also has an spectrometer on board and will use the doppler effect as you said so it will detect spectroscopic binaries, the wobbling I was referring to is not based on the spectroscopy, basically Gaia will measure the change in the position of the star around the center of gravity of the Star-Planet system, a large planet causes the star to move around the center of gravity of the Star-Planet system and Gaia is so precise that can measure that change in the position of the star relative to the center of gravity of the system.


Q:

Will Gaia be able to collect information about exoplanet atmospheres and thereby detect signs of possible life (high oxygen concentrations, for example)?

A:

Gaia collects data on any point sources passing across the field of view. If planet nine is bright enough Gaia will see it (it would have to be brighter than around 20.5 mag though and it is theorised to be less than this I understand). For exoplanets there is the astrometric 'wobble' technique and also transits may work. [DM].


Q:

What turned out to be the problem that caused the AMA to be delayed a few days?

A:

From time to time glitches can occur onboard the spacecraft. Just before our last scheduled AMA Gaia’s Phased Array Antenna (used to downlink high rate data) was switched off by the main computer, which believed it may have a problem. We were able to recover it within the same day and it's working fine. These types of things can happen from time to time. There was no permanent problem. Sometimes units can suddenly switch off due to a radiation hit in a particular component (known as a ‘ Single Event Upset’) but work perfectly fine after being re-activated. [DM]


Q:

I imagine GAIA has some pretty cool radiation hardening going on for its software - can you describe some of the techniques used for this? Also, how often do these glitches tend to happen?

A:

Indeed the onboard computer has several of protection for its software against radiation, some are physical such as isolation and electronic design and some in the software level are in the form of Error Detection And Correction (EDAC) techniques which checks for bit changes constantly and corrects them if possible. This happens once-twice a day but most glitches are automatically correctly. [RQ]


Q:

Coordinates!? a) What sort of coordinate system do you use for mapping the positions of the objects? --b) Where is the origin of your coord system - Earth? Sun? --c) Given that everything is moving relative to everything else, aren’t the coordinates of everything out of date the minute you record them in your database? --d) Do you compile multiple observations and can you get direction & velocity vectors for everything you locate and record? --e) Do you assume a uniform uncertainty value for each object?

A:

The Gaia archive uses the International Celestial Reference System (ICRS) which has the sun at the origin. It is correct that everything is moving, so it is important to provide a reference time for the data. Each source is observed on average 70 times, so velocity measurements are also made. [ES]


Q:

What are the challenges you have to face everyday, what can go wrong in this type of missions?

A:

Gaia is a unique, complex spacecraft with incredible performance. There are 42,000 telemetry parameters to monitor. Many things could go wrong but Gaia is well designed and robust. It has redundancy onboard (there tends to be two of most units - in case one fails or is temporarily out of action we can use the redundant unit). There is software onboard that can be changed to adapt to new situations if needed. [DM]


Q:

Oh wow, that must be awesome. As a future aerospace systems engineer student, I would love to work in a project as complex as Gaia some day. Thanks for your answer!

A:

Well I look forward to meeting you one day in ESOC! Good luck in your studies :-) [PC]


Q:

Will the public eventually be able to access the found data? Flying through a realistic simulation of the Milky Way would be awesome.

A:

[JH] Yes the data will be publicly available, the first release was done already and is available to everybody, in the first release there were already positions, distances and proper motions for ~ 2 million stars and indeed there are movies and VRs being made for the general public and there will be many more to come when we release the positions distances and motions for a billion stars.


Q:

Thanks! Add-on question: are there any plans for the capability to make 3-D star maps/visualizations (not sky visualizations, but 3-D star maps centered around coordinates other than Earth) using Gaia data? That's one thing I haven't been able to find anywhere.

A:

Yes, you can already access the first data release : https://gea.esac.esa.int/archive/. But you will have to make your own simulation. However, if you go to the web page of our colleagues in Heidelberg you can also get a 3D simulation :https://zah.uni-heidelberg.de/gaia/outreach/gaiasky/. [ES]


Q:

Interesting. I'll definitely try it out.

A:

(Posted by Nathanial Bradford via ESA's Rocket Science blog): Is it possible to see/image Gaia from the earth's surface? What optical setup would be required to do this? Thank you :)) [DS]


Q:

I'm really interested in the Gaia mission as a whole. But, since I live in Spain, I must say I'm curious about what has been the role of the ESAC, could you explain it a little bit? Cheers to everyone involved in the project! :D

A:

ESAC takes care of the science operations, we get the science data daily from the Gaia flight control team and process it as it arrives to verify that the quality of the data is good for science. ESAC is also part of the consortium in charge of doing the data processing (the DPAC) acting as the HUB with 5 other processing centres. Some of the scientific processing like the Astrometric Core Solution are executed at ESAC, we are also involved in aspects related to the calibration of the Gaia instruments. [JH]


Q:

What sort of processing is required for quality verification?

A:

(This question posted via twitter) Nicola Willetts @PinkLady2202020 -->@esaoperations @ESAGaia @reddit_AMA will we be able to see any photos taken by Gaia mission craft? Saw Gaia people at science festival in uk?


Q:

What sort of processing is required for quality verification?

A:

On the processing side (there are 6 data processing centres in Europe) and 400 people from research institutions and universities, there are the typical challenges from a large scientific project, communication, funding, working practices but overall things are on good shape and usually the motivation to get the best results possible overcomes the difficulties.[JH]


Q:

Hey guys, thanks for doing this AMA. I've been following your project for some time now. It's really ambitious but I'm certain that you can do it.

What is the designation for the stars in the Gaia catalogue? For example, stars in the Hipparcos catalogue has HIP (number).

A:

[JH] We use a long 64-bit number where we encode some information which is useful in the data processing, things like the Data Processing centre that created the source and the healpix (a sort of sky index related to the position of the star) and then a counter within each healpix. With so many sources (>1000,000,000) compared to HIP making sure the stars don't get the same identifier and that the history of their creation and deletion is kept is quite a challenge.


Q:

Hello, are there plans for a Gaia successor ? Is it pertinent to envisage a kind of copy of it, with some "simple" improvements (based on the experience accumulated) in order to get an extended period of measure ? Or a completly new and improved satellite, to make even better ?

A:

[GW] There are no plans at the moment. It should be noted that the Gaia implementation is pretty much itself at the limit of present technological capabilities and is a major leap forward. Gaia will keep astronomers busy for decades, however as technological capabilities increase in the future it may be worth doing (also other wavelengths e.g. infra red would allow us to see through the dust clouds).


Q:

Gaia tracks stars, is there any hope that a future machine could be able to do the same but with planets instead of stars?

A:

Well actually Gaia basically detects anything that passes across its field of view that is bright enough to be observed (around 20.5 mag is the limit), so in principle it can detect planets that way. Also the technique of measuring the star “wobble” is being exploited by Gaia to observe exoplanets (see the answer from [JH] to the question from stille). This is one example of a “bonus” data set that can be obtained from the Gaia data – by the time the mission is over it is hoped that very many more exoplanets will have been discovered by Gaia than we know about today! [PC]


Q:

Just want to say thank you guys for such an amazing mission. The information that comes back from this venture will have benefits that greatly accelerate science. My question is " What has been the most fascinating discovery for the team up to this point?"

A:

In terms of operating the Gaia mission, it is so precise we information in the engineering data that other missions would never see. For example, Gaia is so thermally stable that a small temperature change of the sun shield was exactly correlated with a sunspot group transit across the sun (i.e. Gaia never looks at the sun but thermistors on the Gaia spacecraft can ‘notice’ there has been a sunspot since the overall power output of the sun changed – affecting Gaia’s temperature). [DM]


Q:

Just want to say thank you guys for such an amazing mission. The information that comes back from this venture will have benefits that greatly accelerate science. My question is " What has been the most fascinating discovery for the team up to this point?"

A:

I think it is still too early to say, the first release was only a small teaser and gave positions and distances for stars which had been quite well known up to now, still there are already tens of papers based on this data, if I had to pick one thing may be the unexpected usage of the first release data in the determination of the Hubble constant related to the age of our universe, still a lot more will come in the next years. [JH]


A:

We're still trying to sort out which of the 'aliens-on-67P' reports are credible... Now we have to worry about zombies, too? :-) [DS]


Q:

how does a band with such mediocre songs such as yourself make such good music videos?

A:

Hmmmm... a somewhat off-topic question, so it's hard to know how to answer. If you're referring to music videos, though, we certainly like this one! [DS] http://www.esa.int/spaceinvideos/Videos/2015/09/Ground_station_chillax