Features
The Gaia payload consists of
- a 1.4 x 0.5 square metre primary mirror for each telescope
- A 1.0 x 0.5 m focal plane array on which light from both telescopes is projected. This in turn consists of 106 CCDs of 4500 x 1966 pixels.
Gaia contains 3 separate instruments:
- The astrometry instrument (ASTRO), which is dedicated to measuring the angular position of the stars of magnitude 5.7 to 20.
- The photometric instrument, which allows the acquisition of spectra of stars over the 320-1000 nm spectral band, over the same magnitude 5.7-20. Officially, the Blue and Red Photometers (BP/RP), used to determine stellar properties such as temperature, mass, age, elemental composition.
- The Radial-Velocity Spectrometer (RVS), used to determine the velocity of celestial objects along the line of sight by acquiring high-resolution spectra in the spectral band 847-874 nm (field lines of calcium ion) for objects up to magnitude 17. "radial velocities are measured with a precision between 1 km/sec (V=11.5) and 30 km/sec (V=17.5). The measurements of radial velocities are important to correct for perspective acceleration which is induced by the motion along the line of sight."
The telemetric link with the satellite is about 1 Mbit/s on average, while the total content of the focal plane represents several Gbit/s. Therefore only a few dozen pixels around each object can be downlinked. This means that detection and monitoring of objects on board is mandatory. Such processing is particularly complex when scanning dense stellar fields.
Read more about this topic: Gaia (spacecraft)
Famous quotes containing the word features:
“Each reader discovers for himself that, with respect to the simpler features of nature, succeeding poets have done little else than copy his similes.”
—Henry David Thoreau (1817–1862)
“All visible objects, man, are but as pasteboard masks. But in each event—in the living act, the undoubted deed—there, some unknown but still reasoning thing puts forth the mouldings of its features from behind the unreasoning mask. If man will strike, strike through the mask!”
—Herman Melville (1819–1891)
“These, then, will be some of the features of democracy ... it will be, in all likelihood, an agreeable, lawless, particolored commonwealth, dealing with all alike on a footing of equality, whether they be really equal or not.”
—Plato (c. 427–347 B.C.)