Keeping An Eye On Gaia

by Jason Major on February 18, 2014

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ESA's Gaia spacecraft as seen by the VLT (Credit: ESO)

ESA’s Gaia spacecraft as seen by the VST (Credit: ESO)

Gaia, ESA’s long-anticipated mission to map the stars of our galaxy (as well as do a slew of other cool science things) is now tucked comfortably in its position in orbit around Earth-Moon L2, a gravitationally stable spot in space 1.5 million km (932,000 miles) away.

Once its mission begins in earnest, Gaia will watch about a billion stars an average of 70 times each over a five-year span… that’s 40 million observations every day. It will measure the position and key physical properties of each star, including its brightness, temperature and chemical composition, and help astronomers create the most detailed 3D map of the Milky Way ever.

But before Gaia can do this, its own position must be precisely determined. And so several of the world’s most high-powered telescopes are trained on Gaia, keeping track daily of exactly where it is up to an accuracy of 150 meters… which, with the ten-meter-wide spacecraft one and a half million kilometers away, isn’t too shabby.

Called GBOT, for Ground Based Orbit Tracking, the campaign to monitor Gaia’s position was first set up in 2008 — long before the mission launched. This allowed participating observatories to practice targeting on other existing spacecraft, like NASA’s WMAP and ESA’s Planck space telescopes.

The image above shows an image of Gaia (circled) as seen by the European Southern Observatory’s Very Large Telescope Survey Telescope (VST) atop Cerro Paranal in Chile, one of the supporting observatories in the GBOT campaign. The images were taken with the 2.6-meter Survey Telescope’s 268-megapixel OmegaCAM on Jan. 23, 6.5 minutes apart. With just the reflected sunlight off its circular sunshield, the distant spacecraft is about a million times fainter than what your eyes could see unaided.

Gaia mapping the stars of the Milky Way. (ESA/ATG medialab; background: ESO/S. Brunier)

Gaia mapping the stars of the Milky Way. (ESA/ATG medialab; background: ESO/S. Brunier)

It’s also one the closest objects ever imaged by the VST.

Currently Gaia is still undergoing calibration for its survey mission. Some problems have been encountered with stray sunlight reaching its detectors, and this may be due to the angle of the sunshield being a few degrees too high relative to the Sun. It could take a few weeks to implement an orientation correction; read more on the Gaia blog here.

Read more: Ghostly Cat’s Eye Nebula Shines In Space Telescope Calibration Image

Of the billion stars Gaia will observe, 99% have never had their distances accurately measured. Gaia will also observe 500,000 distant quasars, search for brown dwarfs and exoplanets, and will conduct experiments testing Einstein’s General Theory of Relativity. Find out more facts about the mission here.

Gaia launched on December 19, 2013, aboard a Soyuz VS06 from ESA’s spaceport in Kourou, French Guiana. Watch the launch here.

Source: ESA

About 

A graphic designer in Rhode Island, Jason writes about space exploration on his blog Lights In The Dark, Discovery News, and, of course, here on Universe Today. Ad astra!

Cyrus February 18, 2014 at 10:44 PM

Good article,

Love this mission, have always wondered why “scientists” couldn’t just supply us with a detailed map of the Milky Way Galaxy, either the scientists, or Google. Anyway, get that Galaxy mapped!

Jason Major February 18, 2014 at 10:59 PM

It’s still a work in progress! We’re getting there… one star at a time.

deswelch February 19, 2014 at 3:48 PM

Great article, Jason. One minor quibble–Gaia is at Sun-Earth L2, not Earth-Moon.

Aqua4U February 19, 2014 at 7:16 PM

Exciting times! A MAJOR contribution to astronomy is in progress…. Hopefully the early bugs get worked out. ‘Teething pains’ are to be expected considering the complexity of this spacecraft?

Peter D February 20, 2014 at 1:53 AM

deswelch, your criticism is incorrect.
Lagrangian point 2 (& 1 etc.) is a product of Earth-Moon (& Sun) gravity not just Earth-Sun gravity.

Tihomir February 24, 2014 at 1:11 AM

PeterD, for each two body system there are 5 Lagrange points. The Earth-Moon-System (EM) has its own, and the Earth-Sun (ES) its other 5 own Lagrange-Points. The Moon is approx 400 000 km from the Earth and the EM L2 is approx 60 000 km from the Moon (and thus less than 0.5 Million km from the Earth). The ES L2 is the one Gaia orbits and is more than 3 times as far away (1.5 million km, and not even in the same direction as the EM L2).

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