Basically, she offers a switch to 3-d. Gaia, with her twin telescopes and other sophisticated instruments will not only map the galaxy in 3-D and give the ESA’s flat map some pomp & circumstance, but also hopefully go a long way to revealing the history of our galaxy, Its origin, and evolution - galactic archeology of sorts.
Gaia’s predecessor, the Hipparcos satellite, was launched in 1989 and measured and mapped the position of about 100,000 stars. But alas, Gaia offers much as a superior machine, or as the ESA refers to her “ultimate discovery machine” due to her sophisticated instruments that will allow scientists to view wobbles in stars movement (an indicator of a nearby planet). Gaia will study the position, distance, movement, chemical composition, and brightness of what amounts to 1% of the Milky Way’s 100 billion stars. Expected is that she will locate possibly some new planets, definitely some previously un-noticed asteroids & comets, and hopefully can test a key part of Albert Einstein’s General Relativity Theory while she is at it. (General Relativity predicts dips and warps in space caused by the gravity of the planets.)
Science Operations will begin in about 4-5 months and extend 5 years. Scientists are already considering that if she’s still operational then, they will tack on another two years of service.
Gaia has three main instruments in her possession;
1) the astrometry instrument that can combine the measurements taken over five years of any star 5.7-20 magnitude and determine its parallax, distance, and motion and ultimately the velocity of the star as it moves across the sky.
2)A photometric instrument which allows for the acquisition of luminosity measurements of stars on the spectral band from 320-1000 mm, magnitude 5.7-20. Both the blue and the red photometers are capable of determining stellar properties such as temperature, mass, age, and composition. In addition, two low-resolution fused-silica prisms provide multi-color photometry.
And 3)Radial-Velocity Spectrometer which is used for the determination of the velocity of celestial objects. Measuring the Doppler shift of absorption lines in a high-resolution spectrum.
Moving parts are limited and the spacecraft’s subsystems are mounted on a rigid silicon-carbon frame preventing expansion or contraction due to heat or cold.
Gaia was launched via a Soyuz rocket from the Guiana Space Centre in French Guiana.