ESA Portal: Datos clave de la misión Gaia - Un proyecto para catalogar mil millones de estrellas -

 

Gaia mapping the stars of the Milky Way

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 HI-RES JPEG (Size: 693 kb)  HI-RES TIFF (Size: 668 kb) Credits: ESA/Medialab

La misión Gaia de la ESA censará mil millones de estrellas dentro de nuestra propia galaxia, determinando con precisión su magnitud, posición, distancia y desplazamiento. Para ello, observará cada uno de los astros más de 70 veces a lo largo de los cinco años que durará su misión.

Está previsto que esta misión descubra cientos de miles de nuevos objetos celestes, desde planetas extrasolares a estrellas ‘fallidas’, o enanas marrones. Dentro de nuestro propio Sistema Solar, Gaia catalogará cientos de miles de asteroides.

Entre las contribuciones que realizará a la astrofísica destacan la detección y caracterización de decenas de miles de sistemas planetarios extrasolares, y un completo estudio de una gran variedad de cuerpos celestes, tales como objetos menores en nuestro propio Sistema Solar, otras galaxias o más de medio millón de lejanos cuásares. Esta misión también pondrá a prueba la Teoría General de la Relatividad, enunciada por Albert Einstein.

Gaia payload module integration

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 Fully integrated Gaia payload module with nearly all of the multilayer insulation fabric installed. Nearest to the camera, the rear of one of the primary mirrors and one of the tertiary mirrors are visible. Beneath the tertiary (smaller) mirror, the Radial Velocity Spectrometer can be seen. To the right is the Focal Plane Assembly with its charge-coupled device sensors (blue). The focal plane array, with a total of almost a billion pixels, is the largest ever developed. The integration was carried out at Astrium, Toulouse. 

Credits: Astrium SAS

 Nombre
 El nombre de Gaia procede del acrónimo inglés de ‘Interferómetro Astrométrico Global para la Astrofísica’, que hacía referencia a las técnicas de interferometría óptica que se iban en un principio. Aunque se haya cambiado el método de observación, se decidió mantener el nombre de la misión. 

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 HI-RES JPG (Size: 312 kb)  HI-RES TIFF (Size: 8804 kb) Credits: ESA, image by C.Carreau 

 

Lanzamiento

 A finales de 2013, a bordo de un lanzador Soyuz-Fregat que despegará desde el complejo de Sinnamary en el Puerto Espacial Europeo, Guayana Francesa.

Estado actual
 En desarrollo, comenzando la fase de ensayos. El contratista principal es la compañía EADS Astrium SAS, con sede en Toulouse.

Lowering of Cryostat in Large Space Simulator

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 The Herschel cryostat is lowered into the Large Space Simulator, where it will undergo a three week test recreating scientific observing conditions. 

Credits: ESA

 Órbita

Gaia estudiará las estrellas de nuestra galaxia desde una órbita entorno al segundo punto de Lagrange, L2. Este punto, 1.5 millones de kilómetros más alejado del Sol que la Tierra, acompaña a nuestro planeta en su movimiento de traslación, de forma que el satélite, la Tierra y el Sol permanecerán siempre alineados. Este tipo de órbita permite garantizar que ninguno de estos cuerpos celestes se interpondrá con el campo de visión de Gaia.
 

Nota

Los instrumentos de Gaia son tan precisos que, si estuviese en la Tierra, sería capaz de medir el pulgar de una persona situada en la superficie de la Luna.

El transmisor de Gaia utilizará muy poca potencia, menos que una bombilla convencional de 100 W. A pesar de ello, será capaz de enviar datos a gran velocidad (cerca de 5 Mbit/s) a lo largo de los 1.5 millones de kilómetros que lo separarán de nuestro planeta. Para recibir su señal se utilizarán las estaciones de seguimiento más potentes de la ESA: las antenas de 35 metros de Cebreros, España, y Nueva Norcia, Australia.

Las cifras del censo celeste son impresionantes. De media, Gaia descubrirá cada día 10 estrellas rodeadas por su propio sistema planetario, 10 estrellas explotando en otras galaxias, 30 estrellas ‘fallidas’, o enanas marrones, y un gran número de cuásares alimentados por agujeros negros supermasivos.

Se estima que Gaia detectará unos 15.000 planetas fuera de nuestro Sistema Solar al analizar los minúsculos cambios en la posición de una estrella debidos a las perturbaciones gravitatorias de los planetas que la rodean.

Gaia también pondrá a prueba la Teoría General de la Relatividad de Albert Einstein, midiendo cómo afecta el campo gravitatorio del Sol a la luz de las estrellas con una precisión de dos partes por millón.

ESA

 

 

Summary

The main goal of the Gaia mission is to make the largest, most precise three-dimensional map of our Galaxy by surveying an unprecedented one per cent of its population of 100 billion stars.
During the mapping, Gaia will detect and very accurately measure the motion of each star in its orbit around the centre of the Galaxy. Much of this motion was imparted upon each star during its birth and studying it allows astronomers to peer back in time, to when the Galaxy was first forming. By constructing a detailed map of the stars, Gaia will provide a crucial tool to study the formation of our Galaxy, the Milky Way.
While surveying the sky, Gaia is bound to make many other discoveries. During its anticipated lifetime of five years, Gaia will observe each of its one billion sources about 100 times, resulting in a record of the brightness and position of each source over time. Together with the unprecedented accuracy of the astrometric measurements, this will lead to the discovery of: planets around other stars, asteroids in our Solar System, icy bodies in the outer Solar System, brown dwarfs, and far-distant supernovae and quasars. The list of Gaia's potential discoveries makes the mission unique in scope and scientific return.
Huge databases of information will be compiled from the Gaia data, allowing astronomers to trawl the archives looking for similar celestial objects or events and other correlations that might just provide the clue necessary to solve their particular, seemingly intractable, scientific puzzle.

The Spacecraft

The Gaia spacecraft is comprised of a payload module, a mechanical service module and an electrical service module and has a launch mass of around 2 tonnes. The payload module is built around the hexagonal optical bench (~3m diameter) which provides the structural support for the single integrated instrument that comprises three functions: astrometry, photometry and spectrometry. It further contains all necessary electronics for managing the instrument operation and processing the raw data.
The mechanical service module comprises all mechanical, structural and thermal elements supporting the instrument and the spacecraft electronics. It also includes the micro-propulsion system, deployable sunshield, payload thermal tent, solar arrays and harness.
The electrical service module offers support functions to the Gaia payload and spacecraft for pointing, electrical power control and distribution, central data management and radio communications with the Earth.

The L2 Orbit

Gaia will be placed in an orbit around the Sun, at the second Lagrange point L2, which is named after its discoverer, Joseph Louis Lagrange (1736-1813). He was a French mathematician who discovered that there were five points of equilibrium in an orbital system containing two massive bodies, labelled L1 - L5. For the Sun-Earth system, the L2 point lies at a distance of 1.5 million kilometres from the Earth in the anti-Sun direction and co-rotates with the Earth in it's 1-year orbit around the Sun.
One of the principal advantages of an L2 orbit is that it offers uninterrupted observations, since the Earth, Moon and Sun all lay within the orbit of the L2 point. From L2 the entire celestial sphere can be observed during the course of one year. To ensure Gaia stays at L2, the spacecraft must perform small manoeuvres every month.
Gaia will not be the only ESA mission going to L2. Current plans call for the Herschel, Planck, JWST and Darwin spacecraft to be placed there, too.

The Hipparcos Mission

Gaia is not the first space mission to chart the heavens. In 1989, ESA launched Hipparcos. Sounding like the name of Hipparchus, the Greek astronomer, its different spelling reflects that the name was also an acronym for High Precision Parallax Collecting Satellite.
This entirely European mission was the first satellite to chart the positions of stars and produced a primary catalogue of about 118 000 stars, and a secondary catalogue, called Tycho, of over 2 million stars whose positions were determined to slightly less precision. The data is now widely used by the entire community of professional astronomers.
Among other results, Hipparcos' data contributed to the prediction of when comet Shoemaker-Levy 9 would collide with Jupiter. The data showed that many billions of years ago, the Galaxy swallowed a large group of stars. Hipparcos also helped astronomers to refine the age of the Universe.

The Challenge of Gaia

Gaia will significantly improve on Hipparcos for a number of different reasons. For example, the collecting area of the primary mirrors means that Gaia will collect more than 30 times the light of its predecessor, allowing for more sensitive and accurate measurements.
Gaia will be able to measure a star's position and motion 200 times more accurately than Hipparcos. Changes in a star's position and motion are registered as tiny angles. As a comparison, if Hipparcos could measure the angle that corresponds to the height of an astronaut standing on the Moon, Gaia will be able to measure his thumbnail!
Highly efficient cameras, CCDs, will be used to record the images, so wide-angle images of many celestial objects can be obtained at the same time. Devices known as photocathodes were used on Hipparcos, which meant that the satellite could only record information from a single celestial object at a time.
Astronomers will have the challenge of dealing with a flood of data when Gaia begins its work in 2013. Even after being compressed by software, the data produced by the five-year mission will fill over 30 000 CD ROMs. This data will be transmitted 'raw' and will need processing on Earth to turn it into a calibrated set of measurements that can be freely used by the astronomical community.
So, not only must ESA design and build the spacecraft itself, they must also develop new computer software that will ensure the data can be processed efficiently once it is back on Earth.
ESA

Guillermo Gonzalo Sánchez Achutegui

ayabaca@gmail.com

ayabaca@hotmail.com

ayabaca@yahoo.com
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