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Gaia Phased Array Antenna delivered and integrated
Gaia will be about a million miles from earth, transmitting data at 8.7Mbps.
A mechanically pointed antenna would jitter the telescope,
so they will use a phase-array antenna.
"Gaia will create a three-dimensional map of the Milky Way, in the process revealing information about its composition, formation and evolution. The mission will perform positional measurements for about one billion stars in our Galaxy and Local Group with unprecedented precision, together with radial velocity measurements for the brightest 150 million objects. Gaia is scheduled to launch in 2013 for a nominal five-year mission, with a possible one-year extension." (wikipedia)
http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=50523
#04: Gaia Phased Array Antenna delivered and integrated
06 Jul 2012 10:38
The phased array antenna that Gaia will use to send its science data to Earth has been delivered and integrated onto the Service Module. The antenna provides the high gain and data rate needed to allow large volumes of data to be transmitted over the 1.5 million kilometres that will separate the spacecraft's operational orbit from Earth. The use of electronic beam steering allows the signal to be directed towards Earth as the spacecraft rotates; a conventional, mechanically pointed antenna would cause microvibrations, seriously impacting the performance of the telescope.
High data rate
The Gaia mission will perform astrometric measurements on over one billion objects in the Milky Way and its Local Group. To do this, the spacecraft will spend five years in a Lissajous orbit around the second Lagrange point of the Sun-Earth system (L2), which is located 1.5 million km from Earth in the anti-Sun direction.
Gaia will generate an enormous volume of data – about 200 TB (uncompressed) over its nominal five-year mission. Even with data compression, the restrictions imposed by the size of the on-board solid-state mass memory (constrained by cost, mass, power consumption and reliability considerations), the ~8 hour per day ground station downlink window and the desire not to discard data impose a requirement for an extremely high downlink rate of up to 8.7 Mbps, given the distance over which the data has to be communicated.
<snip>
Beam steering
Gaia will perform its measurements by simultaneously observing two target fields. The spacecraft will rotate around its longitudinal axis at a rate of 60 arcsec/s, equivalent to a spin period of six hours, to scan its fields of view across the sky. The downlink antenna is mounted on the Sun-pointing face of the Service Module, which is perpendicular to the rotation axis. The antenna beam must be steered, to keep it pointed at Earth both as the spacecraft rotates and as it moves through its orbit around L2.
<snip>
About Gaia
Gaia will create a three-dimensional map of the Milky Way, in the process revealing information about its composition, formation and evolution. The mission will perform positional measurements for about one billion stars in our Galaxy and Local Group with unprecedented precision, together with radial velocity measurements for the brightest 150 million objects. Gaia is scheduled to launch in 2013 for a nominal five-year mission, with a possible one-year extension.
<snip>
#04: Gaia Phased Array Antenna delivered and integrated
06 Jul 2012 10:38
The phased array antenna that Gaia will use to send its science data to Earth has been delivered and integrated onto the Service Module. The antenna provides the high gain and data rate needed to allow large volumes of data to be transmitted over the 1.5 million kilometres that will separate the spacecraft's operational orbit from Earth. The use of electronic beam steering allows the signal to be directed towards Earth as the spacecraft rotates; a conventional, mechanically pointed antenna would cause microvibrations, seriously impacting the performance of the telescope.
High data rate
The Gaia mission will perform astrometric measurements on over one billion objects in the Milky Way and its Local Group. To do this, the spacecraft will spend five years in a Lissajous orbit around the second Lagrange point of the Sun-Earth system (L2), which is located 1.5 million km from Earth in the anti-Sun direction.
Gaia will generate an enormous volume of data – about 200 TB (uncompressed) over its nominal five-year mission. Even with data compression, the restrictions imposed by the size of the on-board solid-state mass memory (constrained by cost, mass, power consumption and reliability considerations), the ~8 hour per day ground station downlink window and the desire not to discard data impose a requirement for an extremely high downlink rate of up to 8.7 Mbps, given the distance over which the data has to be communicated.
<snip>
Beam steering
Gaia will perform its measurements by simultaneously observing two target fields. The spacecraft will rotate around its longitudinal axis at a rate of 60 arcsec/s, equivalent to a spin period of six hours, to scan its fields of view across the sky. The downlink antenna is mounted on the Sun-pointing face of the Service Module, which is perpendicular to the rotation axis. The antenna beam must be steered, to keep it pointed at Earth both as the spacecraft rotates and as it moves through its orbit around L2.
<snip>
About Gaia
Gaia will create a three-dimensional map of the Milky Way, in the process revealing information about its composition, formation and evolution. The mission will perform positional measurements for about one billion stars in our Galaxy and Local Group with unprecedented precision, together with radial velocity measurements for the brightest 150 million objects. Gaia is scheduled to launch in 2013 for a nominal five-year mission, with a possible one-year extension.
<snip>
http://en.wikipedia.org/wiki/Gaia_mission
Gaia (originally an acronym for Global Astrometric Interferometer for Astrophysics) is a European Space Agency (ESA) space mission in astrometry to be launched in August 2013. Successor to the Hipparcos mission, it is part of ESA's Horizon 2000 Plus long-term scientific program. The mission aims to compile a catalogue of approximately 1 billion stars, or roughly 1% of stars in the Milky Way[2][3]. It will monitor each of its target stars about 70 times to a magnitude 20 over a period of 5 years. Its objectives comprise:
Gaia will create an extremely precise three-dimensional map of stars throughout our Milky Way galaxy and beyond, and map their motions which encode the origin and subsequent evolution of the Milky Way. The spectrophotometric measurements will provide the detailed physical properties of each star observed, characterising their luminosity, effective temperature, gravity and elemental composition. This massive stellar census will provide the basic observational data to tackle a wide range of important problems related to the origin, structure, and evolutionary history of our Galaxy. Large numbers of quasars, galaxies, extrasolar planets and Solar System bodies will be measured at the same time.
Arianespace expects to launch Gaia for ESA in August 2013,[6] using a Soyuz rocket from its Guiana Space Centre (GSC) in French Guiana.[7] It will be operated in a Lissajous orbit around the Sun–Earth L2 Lagrangian point.
<snip>
Gaia (originally an acronym for Global Astrometric Interferometer for Astrophysics) is a European Space Agency (ESA) space mission in astrometry to be launched in August 2013. Successor to the Hipparcos mission, it is part of ESA's Horizon 2000 Plus long-term scientific program. The mission aims to compile a catalogue of approximately 1 billion stars, or roughly 1% of stars in the Milky Way[2][3]. It will monitor each of its target stars about 70 times to a magnitude 20 over a period of 5 years. Its objectives comprise:
- determining the positions, distances, and annual proper motions of 1 billion stars with an accuracy of about 20 µas (microarcsecond) at 15 mag, and 200 µas at 20 mag
- radial velocity measurements with expected detection of tens of thousands of extra-solar planetary systems[4]
- capacity to discover Apohele asteroids with orbits that lie between Earth and the Sun, a region that is difficult for Earth-based telescopes to monitor since this region is only in the sky during or near the daytime.[5]
- detection of up to 500 000 distant quasars
- more accurate tests of Albert Einstein’s general relativity theory
Gaia will create an extremely precise three-dimensional map of stars throughout our Milky Way galaxy and beyond, and map their motions which encode the origin and subsequent evolution of the Milky Way. The spectrophotometric measurements will provide the detailed physical properties of each star observed, characterising their luminosity, effective temperature, gravity and elemental composition. This massive stellar census will provide the basic observational data to tackle a wide range of important problems related to the origin, structure, and evolutionary history of our Galaxy. Large numbers of quasars, galaxies, extrasolar planets and Solar System bodies will be measured at the same time.
Arianespace expects to launch Gaia for ESA in August 2013,[6] using a Soyuz rocket from its Guiana Space Centre (GSC) in French Guiana.[7] It will be operated in a Lissajous orbit around the Sun–Earth L2 Lagrangian point.
<snip>
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