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  • richardmitnick 2:42 pm on January 14, 2015 Permalink | Reply
    Tags: , , ESA Gaia   

    From ESA: “A year on-station for Gaia” 

    ESASpaceForEuropeBanner
    European Space Agency

    ESA’s Gaia mission will produce an unprecedented 3D map of our Galaxy by mapping, with exquisite precision, the position and motion of a billion stars. The key to this is the billion-pixel camera at the heart of its dual telescope. This animation illustrates how the camera works.


    Watch, enjoy, learn.

    ESA Gaia satellite
    ESA/Gaia

    ESA Gaia Camera
    Gaia’ camera

    Today’s update provided by Gaia Spacecraft Operations Manager Dave Milligan at ESOC.

    Time flies when you’re mapping a billion stars!

    One year ago, Gaia performed its last major orbit insertion burn and was stable at ‘L2′ (see What’s an ell-two?).

    Gaia is an ambitious mission to chart a three-dimensional map of our Galaxy, the Milky Way, in the process revealing the composition, formation and evolution of the Galaxy. Credit: ESA–D. Ducros, 2013

    After a smooth, but operationally intense lift-off, LEOP (launch and early orbit phase) and transfer phase, in which Gaia travelled the 1.5 million km from Earth to the point at which the sky survey will be done, the work to start Gaia’s mapping task was only just beginning.

    14 January 2014, 15:55 UTC

    The five thrusters used to perform the orbit insertion are commanded to stop firing and there are smiles in the control room at ESOC as the telemetry on the screens confirm the last planned ‘critical operation’ is successfully completed.

    Thruster Firings

    Earlier, Gaia’s operators had to perform a number of critical operations in the initial post-launch period: the first autonomous flight activation; sun-shield deployment and three orbit manoeuvres – when the thrusters were heavily used – all between 2 and 27 days after launch.

    Had these gone wrong, the mission operations team would have been in a race against the clock to stop Gaia drifting off into interplanetary space.

    Today we are one year on from the last of these.

    The blue line in the Earth-centered plot below shows the correct trajectory (i.e. the nominal case when the manoeuvre worked) and the green shows what would have happened without this manoeuvre (drift around the Earth-Moon system followed by escape into interplanetary space).

    2
    Gaia L2 arrival – worst case scenario

    Now that this activity was over, the operations team could fully focus on the commissioning phase, testing and configuring the spacecraft and payload operations until system performance was ready to perform science.

    This was not time-critical, but was technically demanding, and this phase would eventually last six months.

    Gaia is a one-off, purpose-built spacecraft that is capable of mapping the positions of one billion stars to unprecedented precision (to the micro-arc-second level, comparable to the width of a smart phone on the Moon as viewed from Earth). This performance is far beyond anything previously achieved, and the Gaia spacecraft is a marvel of engineering in its own right.

    Spacecraft are complex

    Spacecraft such as Gaia are complex machines, which have layered operational modes.

    The spacecraft can be flown and operated, performing the more basic tasks, with a subset of service module units on and working. Just like the tip of a pyramid can only be placed on top after all other stones have been laid, all on-board prime units must be switched on and correctly configured for full performance. This, together with checking a number of redundant units and functions, is the task of teams on ground during the commissioning phase.

    The Gaia spacecraft has a relatively large fraction of ‘bespoke’ units i.e. custom designed, due largely to the incredible precision requirements. Not the least of these are the telescopes and camera.

    Gaia’s camera is the most impressive ever flown in space, containing 106 CCDs, which are around 90% light efficient (a CCD in a typical digital camera is around 20% efficient).

    These have to be linked to the on-board attitude control system to achieve the needed and incredible precision for mapping the stars.

    Gaia must rotate once every 6 hours to scan the heavens and this rate is so precisely controlled that the error is equivalent to one rotation every 410 years. There are (and can be) no moving parts on board, so the data is downlinked through a novel electromagnetically steerable antenna.

    Attitude control is provided by a micro propulsion system that has its first flight use with Gaia. This delivers micro-Newton levels of thrust primarily to oppose the quantum mechanical force exerted by sunlight falling onto the sunshield. An atomic clock is used for precise time-stamping, which in fact allows controllers to see the time dilation effects from Einstein’s Theory of General Relativity.

    Just after entry into the operational orbit, most of these hardware units were either off or had hardly been used at all.

    Solving problems with teamwork

    One year ago, the critical phases were over and the operations team began focusing on the complex task of bringing the spacecraft up to full performance.

    In terms of what was planned, this consisted of an iterative phase where teams on the ground send commands to move the mirrors and adjust the spacecraft spin rate and then industry (i.e. the spacecraft manufacturer) and the mission science teams analysed the results before the next tuning cycle. The other major element planned was the tuning of Gaia’s seven powerful video processing units, each connected to a row of the camera’s CCDs, responsible for identifying and characterizing the stars that will make up Gaia’s map.

    These tasks progressed well, but almost immediately after orbit insertion some problems became apparent.

    First noticed through an apparent dimming of the on-board laser used to track the angle between the telescope mirrors, and later confirmed by data from the stars themselves, ice was unexpectedly building up and had to be dealt with .

    Also apparent was more background light than expected .

    These issues, like many others, were dealt with and solved in a series of brainstorming review meetings between experts, some of which required in-orbit special operations to be developed and executed to provide the necessary data. For example, Gaia’s normally rock-stable sun-attitude was changed twice in special operations designed to characterise the stray-light problem.

    Examples elsewhere from the spacecraft commissioning period included a micro-propulsion thruster with unexpected performance levels and a back-up chemical thruster that had a failed valve (meaning it was permanently lost).

    Teamwork has been critical

    Again, teamwork in brainstorming review meetings was critical to solving these issues. The on-board software could be quickly reprogrammed to match the new performance of the micro-propulsion thruster and the on-board protection software was changed to make sure the system would never try to use the chemical thruster that had failed (for this was a thruster present in case the spacecraft was in trouble and needed to put itself into ‘Safe Mode’).
    An artist’s impression of a Type Ia supernova – the explosion of a white dwarf locked in a binary system with a companion star. Credit: ESA/ATG medialab/C. Carreau

    3
    An artist’s impression of a Type Ia supernova – the explosion of a white dwarf locked in a binary system with a companion star. Credit: ESA/ATG medialab/C. Carreau

    By the end of the commissioning phase, the teamwork between the ESA operations, project and science teams together with the industry experts at AirbusDS and the wider Gaia scientific community organised into the Data Processing and Analysis Consortium (DPAC) had delivered the spacecraft in excellent shape.

    The spacecraft was correctly configured and the software of the majority of on-board units had been changed based on the lessons learned to date. In getting to this stage, approximately 400 000 telecommands had been sent by ground teams.

    Shortly after the commissioning ended, a new Survival Mode was activated on board, using thrusters that are normally used only for orbit manoeuvres. This meant that single failure tolerance had been fully restored, even with a permanently lost thruster.

    The mapping begins

    By July 2014, Gaia was busy mapping parts of the sky that had been calibrated by ground telescopes, before its nominal scanning mode was entered in September.

    At this point Gaia was working so well that it was producing more data than originally foreseen, since it was able to see stars fainter than required. Towards the end of the year, operators had to come up with a method to partially automate ground operations allowing Gaia to take advantage of more ground station time and expand its mapping data set.

    It’s been a busy first year for Gaia, but at the one-year point there’s a good sense of achievement.

    The science data are now coming down in huge quantities (11 billion camera transits were recorded by the one-year launch anniversary), with anticipation slowly building for what Gaia may find in the coming years.

    But even before the first map release next year, Gaia is already making discoveries.

    Gaia discovers its first supernova

    12 September 2014

    For further information, please contact:

    Markus Bauer
    ESA Science and Robotic Exploration Communication Officer
    Tel: +31 71 565 6799
    Mob: +31 61 594 3 954
    Email: markus.bauer@esa.int

    Timo Prusti
    Gaia Project Scientist
    Email: timo.prusti@esa.int

    Simon Hodgkin
    Institute of Astronomy
    Cambridge, UK
    Tel: +44 1223 766657
    Email: sth@ast.cam.ac.uk

    Łukasz Wyrzykowski
    Warsaw University Astronomical Observatory
    Warsaw, Poland
    Tel: +48 608 648817
    Email: lw@astrouw.edu.pl

    Nadejda Blagorodnova
    Institute of Astronomy
    Cambridge, UK
    Tel: +44 1223 337548
    Email: nblago@ast.cam.ac.uk

    While scanning the sky to measure the positions and movements of stars in our Galaxy, Gaia has discovered its first stellar explosion in another galaxy far, far away.

    5
    Supernova Gaia14aaa and its host galaxy. Credit: M. Fraser/S. Hodgkin/L. Wyrzykowski/H. Campbell/N. Blagorodnova/Z. Kostrzewa-Rutkowska/Liverpool Telescope/SDSS

    This powerful event, now named Gaia14aaa, took place in a distant galaxy some 500 million light-years away, and was revealed via a sudden rise in the galaxy’s brightness between two Gaia observations separated by one month.

    Gaia, which began its scientific work on 25 July, repeatedly scans the entire sky, so that each of the roughly one billion stars in the final catalogue will be examined an average of 70 times over the next five years.

    “This kind of repeated survey comes in handy for studying the changeable nature of the sky,” comments Simon Hodgkin from the Institute of Astronomy in Cambridge, UK.

    Many astronomical sources are variable: some exhibit a regular pattern, with a periodically rising and declining brightness, while others may undergo sudden and dramatic changes.

    “As Gaia goes back to each patch of the sky over and over, we have a chance to spot thousands of ‘guest stars’ on the celestial tapestry,” notes Dr Hodgkin. “These transient sources can be signposts to some of the most powerful phenomena in the Universe, like this supernova.”

    Dr Hodgkin is part of Gaia’s Science Alert Team, which includes astronomers from the Universities of Cambridge, UK, and Warsaw, Poland, who are combing through the scans in search of unexpected changes.

    6
    Discovery of supernova Gaia14aaa.
    Credit: ESA/Gaia/DPAC/Z. Kostrzewa-Rutkowska (Warsaw University Astronomical Observatory) & G. Rixon (Institute of Astronomy, Cambridge)

    It did not take long until they found the first ‘anomaly’ in the form of a sudden spike in the light coming from a distant galaxy, detected on 30 August. The same galaxy appeared much dimmer when Gaia first looked at it just a month before.

    “We immediately thought it might be a supernova, but needed more clues to back up our claim,” explains Łukasz Wyrzykowski from the Warsaw University Astronomical Observatory, Poland.

    Other powerful cosmic events may resemble a supernova in a distant galaxy, such as outbursts caused by the mass-devouring supermassive black hole at the galaxy centre.

    However, in Gaia14aaa, the position of the bright spot of light was slightly offset from the galaxy’s core, suggesting that it was unlikely to be related to a central black hole.

    So, the astronomers looked for more information in the light of this new source. Besides recording the position and brightness of stars and galaxies, Gaia also splits their light to create a spectrum. In fact, Gaia uses two prisms spanning red and blue wavelength regions to produce a low-resolution spectrum that allows astronomers to seek signatures of the various chemical elements present in the source of that light.

    7
    Gaia spectrum of supernova Gaia14aaa. Credit: ESA/Gaia/DPAC/N. Blagorodnova, M. Fraser, H. Campbell, A. Hall (Institute of Astronomy, Cambridge)

    “In the spectrum of this source, we could already see the presence of iron and other elements that are known to be found in supernovas,” says Nadejda Blagorodnova, a PhD student at the Institute of Astronomy in Cambridge.

    In addition, the blue part of the spectrum appears significantly brighter than the red part, as expected in a supernova. And not just any supernova: the astronomers already suspected it might be a ‘Type Ia’ supernova – the explosion of a white dwarf locked in a binary system with a companion star.

    While other types of supernovas are the explosive demises of massive stars, several times more massive than the Sun, Type Ia supernovas are the end product of their less massive counterparts.

    Low-mass stars, with masses similar to the Sun’s, end their lives gently, puffing up their outer layers and leaving behind a compact white dwarf. Their high density means that white dwarfs can exert an intense gravitational pull on a nearby companion star, accreting mass from it until the white dwarf reaches a critical mass that then sparks a violent explosion.

    To confirm the nature of this supernova, the astronomers complemented the Gaia data with more observations from the ground, using the Isaac Newton Telescope (INT) and the robotic Liverpool Telescope on La Palma, in the Canary Islands, Spain.

    A high-resolution spectrum, obtained on 3 September with the INT, confirmed not only that the explosion corresponds to a Type Ia supernova, but also provided an estimate of its distance. This proved that the supernova happened in the galaxy where it was observed.

    “This is the first supernova in what we expect to be a long series of discoveries with Gaia,” says Timo Prusti, ESA’s Gaia Project Scientist.

    Supernovas are rare events: only a couple of these explosions happen every century in a typical galaxy. But they are not so rare over the whole sky, if we take into account the hundreds of billions of galaxies that populate the Universe.

    Astronomers in the Science Alert Team are currently getting acquainted with the data, testing and optimising their detection software. In a few months, they expect Gaia to discover about three new supernovas every day.

    In addition to supernovas, Gaia will discover thousands of transient sources of other kinds – stellar explosions on smaller scale than supernovas, flares from young stars coming to life, outbursts caused by black holes that disrupt and devour a nearby star, and possibly some entirely new phenomena never seen before.

    “The sky is ablaze with peculiar sources of light, and we are looking forward to probing plenty of those with Gaia in the coming years,” concludes Dr Prusti.
    Background Information

    Gaia is an ESA mission to survey one billion stars in our Galaxy and local galactic neighbourhood in order to build the most precise 3D map of the Milky Way and answer questions about its origin and evolution. Gaia’s scientific operations begun on 25 July 2014 with the special scanning through a narrow region in the sky, while the normal scanning procedure was switched on a month later, on 25 August.

    The mission’s primary scientific product will be a catalogue with the position, motion, brightness and colour of the surveyed stars. An intermediate version of the catalogue will be released in 2016. In the meantime, Gaia’s observing strategy, with repeated scans of the entire sky, will allow the discovery and measurement of transient events across the sky.

    This first such discovery is the Type Ia supernova described in this article, named Gaia14aaa. The name follows the convention used for naming transient astronomical sources, which acknowledges the name of the survey followed by the year of discovery and by a combination of letters to indicate the order of discovery. The supernova’s host galaxy, SDSS J132102.26+453223.8, is about 500 million light-years away.

    Converting the telemetry received from Gaia into scientific data products is the responsibility of the Gaia Data Processing and Analysis Consortium (DPAC). Within the Photometric Processing coordination unit of DPAC, the Science Alert Team is responsible for identifying transient sources.

    During the first few months of Gaia’s scientific operations, astronomers in the Science Alert Team will be compiling a preliminary catalogue of transients on a daily basis, depending on the data availability.

    Follow-up observations from the ground to assess the nature of these sources will be carried out by the collaborating partners from Europe and elsewhere. Schools and amateur astronomers will also be involved in following up these targets.

    Scientists from the Gaia mission and other astronomers studying transient events are gathered this week at the 5th Gaia Science Alerts Workshop, hosted at Warsaw University, Poland from 9 to 12 September 2014.

    See the full article here.

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    The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

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  • richardmitnick 2:59 pm on November 7, 2014 Permalink | Reply
    Tags: , , , , ESA Gaia,   

    From SPACE.com: “European Spacecraft Could Find 70,000 New Alien Worlds” 

    space-dot-com logo

    SPACE.com

    November 06, 2014
    Mike Wall

    A European spacecraft that launched late last year could eventually discover 70,000 exoplanets, helping researchers better understand the number and characteristics of alien worlds throughout the galaxy, a new study reports.

    The European Space Agency’s star-monitoring Gaia mission, which launched in December 2013, should find about 21,000 alien planets over the course of its five-year mission and perhaps 70,000 distant worlds if it keeps operating for 10 years, the study found.

    ESA Gaia satellite
    ESA/Gaia

    “It’s not just about the numbers. Each of these planets will be conveying some very specific details, and many will be highly interesting in their own way,” lead author Michael Perryman of Princeton University said in a statement. “If you look at the planets that have been discovered until now, they occupy very specific regions of discovery space. Gaia will not only discover a whole list of planets, but in an area that has not been thoroughly explored so far.”

    The first alien world around a sunlike star was spotted in 1995. Since then, astronomers have found nearly 2,000 exoplanets, with more than half of the discoveries made by NASA’s Kepler space telescope.

    NASA Kepler Telescope
    NASA/Kepler

    But there are many more out there, waiting to be discovered. Astronomers think that, on average, every star in the Milky Way hosts at least one planet, meaning the galaxy probably teems with more than 100 billion alien worlds.

    The $1 billion Gaia mission operates from a gravitationally stable spot 930,000 miles (1.5 million kilometers) from Earth called the Earth-Sun Lagrange Point 2. The spacecraft’s main goal is to catalog and closely monitor 1 billion Milky Way stars, helping researchers create a detailed 3D map that should shed light on the galaxy’s structure and evolution.

    But Gaia’s precise tracking work should also reveal the presence of many alien planets by noting how their gravity tugs the stars slightly this way and that, researchers say.

    Perryman and his colleagues wanted to get a better idea of just how many alien worlds Gaia could be expected to find. They arrived at their estimates after integrating a number of sources of information, including a comprehensive model of Milky Way star and planet positions, the latest exoplanet-distribution data (much of it from Kepler) and details of Gaia’s measurement capabilities, researchers said.

    “Our assessment will help prepare exoplanet researchers for what to expect from Gaia,” Perryman said. “We’re going to be adding potentially 20,000 new planets in a completely new area of discovery space. It’s anyone’s guess how the field will develop as a result.”

    The new study has been accepted for publication in The Astrophysical Journal and is available now on the preprint site arXiv.

    See the full article, with further material, here.
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  • richardmitnick 9:03 am on September 12, 2014 Permalink | Reply
    Tags: , , , , ESA Gaia   

    From ESA: “Gaia Discovers its First Supernova” 

    ESASpaceForEuropeBanner
    European Space Agency

    12 September 2014

    Markus Bauer 



    ESA Science and Robotic Exploration Communication Officer




    Tel: +31 71 565 6799





    Mob: +31 61 594 3 954





    Email: markus.bauer@esa.int




    Timo Prusti



    Gaia Project Scientist


    Email: timo.prusti@esa.int

    Simon Hodgkin
    Institute of Astronomy
    Cambridge, UK
    Tel: +44 1223 766657
    Email: sth@ast.cam.ac.uk

    Lukasz Wyrzykowski
    Warsaw University Astronomical Observatory
    Warsaw, Poland
    Tel: +48 608 648817
    Email: lw@astrouw.edu.pl

    Nadejda Blagorodnova
    Institute of Astronomy
    Cambridge, UK
    Tel: +44 1223 337548
    Email: nblago@ast.cam.ac.uk

    While scanning the sky to measure the positions and movements of stars in our Galaxy, Gaia has discovered its first stellar explosion [supernova] in another galaxy far, far away.

    ESA Gaia satellite
    ESA/Gaia

    This powerful event, now named Gaia14aaa, took place in a distant galaxy some 500 million light-years away, and was revealed via a sudden rise in the galaxy’s brightness between two Gaia observations separated by one month.

    ia
    Type Ia supernova

    Gaia, which began its scientific work on 25 July, repeatedly scans the entire sky, so that each of the roughly one billion stars in the final catalogue will be examined an average of 70 times over the next five years.

    “This kind of repeated survey comes in handy for studying the changeable nature of the sky,” comments Simon Hodgkin from the Institute of Astronomy in Cambridge, UK.

    Many astronomical sources are variable: some exhibit a regular pattern, with a periodically rising and declining brightness, while others may undergo sudden and dramatic changes.
    Light curve

    “As Gaia goes back to each patch of the sky over and over, we have a chance to spot thousands of ‘guest stars’ on the celestial tapestry,” notes Dr Hodgkin. “These transient sources can be signposts to some of the most powerful phenomena in the Universe, like this supernova.”

    Dr Hodgkin is part of Gaia’s Science Alert Team, which includes astronomers from the Universities of Cambridge, UK, and Warsaw, Poland, who are combing through the scans in search of unexpected changes.

    It did not take long until they found the first ‘anomaly’ in the form of a sudden spike in the light coming from a distant galaxy, detected on 30 August. The same galaxy appeared much dimmer when Gaia first looked at it just a month before.

    light
    Light curve

    “We immediately thought it might be a supernova, but needed more clues to back up our claim,” explains Łukasz Wyrzykowski from the Warsaw University Astronomical Observatory, Poland.

    Other powerful cosmic events may resemble a supernova in a distant galaxy, such as outbursts caused by the mass-devouring supermassive black hole at the galaxy centre.

    sn
    Supernova Gaia14aaa and its host galaxy

    However, in Gaia14aaa, the position of the bright spot of light was slightly offset from the galaxy’s core, suggesting that it was unlikely to be related to a central black hole.

    So, the astronomers looked for more information in the light of this new source. Besides recording the position and brightness of stars and galaxies, Gaia also splits their light to create a spectrum. In fact, Gaia uses two prisms spanning red and blue wavelength regions to produce a low-resolution spectrum that allows astronomers to seek signatures of the various chemical elements present in the source of that light.

    spec
    Gaia spectrum of supernova

    “In the spectrum of this source, we could already see the presence of iron and other elements that are known to be found in supernovas,” says Nadejda Blagorodnova, a PhD student at the Institute of Astronomy in Cambridge.

    In addition, the blue part of the spectrum appears significantly brighter than the red part, as expected in a supernova. And not just any supernova: the astronomers already suspected it might be a ‘Type Ia’ supernova – the explosion of a white dwarf locked in a binary system with a companion star.

    While other types of supernovas are the explosive demises of massive stars, several times more massive than the Sun, Type Ia supernovas are the end product of their less massive counterparts.

    Low-mass stars, with masses similar to the Sun’s, end their lives gently, puffing up their outer layers and leaving behind a compact white dwarf. Their high density means that white dwarfs can exert an intense gravitational pull on a nearby companion star, accreting mass from it until the white dwarf reaches a critical mass that then sparks a violent explosion.

    To confirm the nature of this supernova, the astronomers complemented the Gaia data with more observations from the ground, using the Isaac Newton Telescope (INT) and the robotic Liverpool Telescope on La Palma, in the Canary Islands, Spain.

    Isaac Newton 2.5m telescope
    Isaac Newton 2.5m telescope interior
    Isaac Newton Telescope

    lt
    Liverpool Telescope

    A high-resolution spectrum, obtained on 3 September with the INT, confirmed not only that the explosion corresponds to a Type Ia supernova, but also provided an estimate of its distance. This proved that the supernova happened in the galaxy where it was observed.

    “This is the first supernova in what we expect to be a long series of discoveries with Gaia,” says Timo Prusti, ESA’s Gaia Project Scientist.

    Supernovas are rare events: only a couple of these explosions happen every century in a typical galaxy. But they are not so rare over the whole sky, if we take into account the hundreds of billions of galaxies that populate the Universe.

    Astronomers in the Science Alert Team are currently getting acquainted with the data, testing and optimising their detection software. In a few months, they expect Gaia to discover about three new supernovas every day.

    In addition to supernovas, Gaia will discover thousands of transient sources of other kinds – stellar explosions on smaller scale than supernovas, flares from young stars coming to life, outbursts caused by black holes that disrupt and devour a nearby star, and possibly some entirely new phenomena never seen before.

    “The sky is ablaze with peculiar sources of light, and we are looking forward to probing plenty of those with Gaia in the coming years,” concludes Dr Prusti.

    See the full article here.

    The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

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  • richardmitnick 12:26 pm on July 29, 2014 Permalink | Reply
    Tags: , , , , ESA Gaia   

    From ESA: “GAIA: ‘Go’ For Science” 

    ESASpaceForEuropeBanner
    European Space Agency

    29 July 2014
    Markus Bauer


    ESA Science and Robotic Exploration Communication Officer


    Tel: +31 71 565 6799


    Mob: +31 61 594 3 954



    Giuseppe Sarri


    Gaia Project Manager


    Email: giuseppe.sarri@esa.int

    Timo Prusti 


    Gaia Project Scientist


    Email: timo.prusti@esa.int

    Following extensive in-orbit commissioning and several unexpected challenges, ESA’s billion-star surveyor, Gaia, is now ready to begin its science mission.

    ESA Gaia satellite
    ESA/GAIA

    The satellite was launched on 19 December 2013, and is orbiting a virtual location in space 1.5 million kilometres from Earth.

    Gaia’s goal is to create the most accurate map yet of the Milky Way. It will make extremely accurate measurements of the positions and motions of about 1% of the total population of roughly 100 billion stars in our home Galaxy to help answer questions about its origin and evolution.

    Repeatedly scanning the sky, Gaia will observe each of its billion stars an average of 70 times each over five years. Small apparent motions in the positions of the stars will allow astronomers to determine their distances and movements through the Milky Way.

    In addition, Gaia will also measure key physical properties of each star, including its brightness, temperature and chemical composition.

    Gaia spins slowly once every six hours, sweeping its two telescopes across the sky and focusing the light from their separate fields simultaneously onto a single focal plane – the largest digital camera ever flown in space, with nearly a billion pixels.

    ESA Gaia Camera
    ESA/Gaia’s camera

    As the stars drift across the camera, the relative positions of all detected stars are measured and downlinked to Earth. Over time, a complete network of positions of stars covering the whole sky is built up, before being analysed to yield a highly accurate 3D map.

    The accuracy required is astonishing: Gaia must be able to measure positions to a level equivalent to the width of a human hair seen at 2000 km. In turn, these measurements demand a very rigorous calibration of the satellite and its instruments, a painstaking procedure that has taken the first part of the year to complete.

    Gaia is now ready to begin its five-year science phase, but the commissioning also uncovered some unexpected anomalies.

    One problem detected early in the commissioning was associated with water freezing on some parts of the optics, causing a temporary reduction in transmission of the telescopes.

    This water was likely trapped in the spacecraft before launch and emerged once it was in a vacuum. Heating the affected optics to remove the ice has now largely solved this problem, but it is likely that one or two more ‘decontamination’ cycles will be required during the mission to keep it in check.

    Another problem is associated with ‘stray light’ reaching Gaia’s focal plane at a level higher than predicted before launch. This appears to be a mixture of light from the Sun finding its way past Gaia’s 10 m-diameter sunshield and light from other astronomical objects, both making their way to the focal plane as a diffuse background.

    The effect on Gaia’s performance is negligible for brighter objects at magnitude 15 and above, and a slight degradation in the positional accuracy is seen for fainter stars, reaching 50% for stars at Gaia’s nominal faint limit of magnitude 20.

    There is also some effect on the accuracy to which stellar brightnesses will be measured.

    The impact of the stray light should, in principle, be more significant for faint stars seen by Gaia’s Radial Velocity Spectrometer (RVS).

    “However, we are optimising the onboard software to mitigate as much as possible the impact caused by these higher background levels of light, and we are confident that we will not be far off our initial and somewhat conservative estimate of studying 150 million stars with RVS, as planned,” says Giuseppe Sarri, ESA’s Gaia Project Manager.

    “We will still be able to analyse one billion – if not more – stars with the astrometry and photometry instruments, measuring each star’s position and motion up to 100 times more accurately than Gaia’s predecessor Hipparcos and for a far larger number of stars.”

    Further tests made during commissioning have shown that it may be possible to extend Gaia’s reach to stars even fainter than magnitude 20, while at the other end, software changes enable Gaia to measure almost all of the brightest stars in the sky, previously ruled out as being too bright for such a sensitive system. Both of these extensions will need further analysis before being implemented.

    Finally, Gaia also contains a laser device called the ‘basic angle monitor’, designed to measure the angle of separation between Gaia’s two telescopes to an extremely high level of accuracy. This is necessary in order to correct for expected periodic variations in the separation angle caused by thermal changes in the payload as Gaia spins.

    Although this system is working, the detected variations in the basic angle are larger than expected. Further efforts are being made to measure and accurately calibrate the variations, with the aim of largely eliminating them during the overall data analysis.

    The commissioning has not only focused on the spacecraft performance, but also on the flow of data on the ground, testing procedures that will be used to process and analyse the vast amount of data that will be transmitted to Earth on a daily basis for the next five years.

    Thus, after extensive testing and analysis of systems both in space and on the ground, Gaia is now in a position to begin routine operations.

    “The commissioning phase has been challenging, and although some activities are ongoing, all in all Gaia is in good shape to fulfil its promise – all of the core scientific goals are still achievable, as hoped,” says Timo Prusti, ESA’s Project Scientist for Gaia.

    “Given the somewhat longer-than-expected commissioning and taking into account the time needed to develop some new software, we anticipate that the first intermediate catalogue of science data will be released to scientists and the public in summer 2016.

    “However, if rapidly-changing objects such as supernovas are detected, open alerts will be made as soon as possible – a service we hope to have up and running before the end of this year.”

    See the full article here.

    The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

    ESA50 Logo large


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  • richardmitnick 9:15 am on February 7, 2014 Permalink | Reply
    Tags: , , , , ESA Gaia   

    From ESA: “Gaia comes into focus” 

    ESASpaceForEuropeBanner
    European Space Agency

    ESA Gaia
    GAIA

    6 February 2014
    Markus Bauer
    ESA Science and Robotic Exploration Communication Officer
    Tel: +31 71 565 6799
    Mob: +31 61 594 3 954

    Giuseppe Sarri
    Gaia Project Manager
    Email: giuseppe.sarri@esa.int

    Timo Prusti
    Gaia Project Scientist
    Email: timo.prusti@esa.int

    ESA’s billion-star surveyor Gaia is slowly being brought into focus. This test image shows a dense cluster of stars in the Large Magellanic Cloud, a satellite galaxy of our Milky Way.

    Once Gaia starts making routine measurements, it will generate truly enormous amounts of data. To maximise the key science of the mission, only small ‘cut-outs’ centred on each of the stars it detects will be sent back to Earth for analysis.

    This test picture, taken as part of commissioning the mission to ‘fine tune’ the behaviour of the instruments, is one of the first proper ‘images’ to be seen from Gaia, but ironically, it will also be one of the last, as Gaia’s main scientific operational mode does not involve sending full images back to Earth.

    Gaia was launched on 19 December 2013, and is orbiting around a virtual point in space called L2, 1.5 million kilometres from Earth.

    Gaia’s goal is to create the most accurate map yet of the Milky Way. It will make precise measurements of the positions and motions of about 1% of the total population of roughly 100 billion stars in our home Galaxy to help answer questions about its origin and evolution.

    Repeatedly scanning the sky, Gaia will observe each of its billion stars an average of 70 times each over five years. In addition to positions and motions, Gaia will also measure key physical properties of each star, including its brightness, temperature and chemical composition.

    ESA Gaia Camera
    Inside Gaia’s billion-pixel camera

    To achieve its goal, Gaia will spin slowly, sweeping its two telescopes across the entire sky and focusing the light from their separate fields simultaneously onto a single digital camera – the largest ever flown in space, with nearly a billion pixels.

    But first, the telescopes must be aligned and focused, along with precise calibration of the instruments, a painstaking procedure that will take several months before Gaia is ready to enter its five-year operational phase.

    As part of that process, the Gaia team have been using a test mode to download sections of data from the camera, including this image of NGC1818, a young star cluster in the Large Magellanic Cloud. The image covers an area less than 1% of the full Gaia field of view.

    cal
    Calibration image

    The team is making good progress, but there is still work to be done to understand the full behaviour and performance of the instruments.

    While all one billion of Gaia’s target stars will have been observed during the first six months of operations, repeated observations over five years will be needed to measure their tiny movements to allow astronomers to determine their distances and motions through space.

    As a result, Gaia’s final catalogue will not be released until three years after the end of the nominal five-year mission. Intermediate data releases will be made, however, and if rapidly changing objects such as supernovae are detected, alerts will be released within hours of data processing.

    Eventually, the Gaia data archive will exceed a million Gigabytes, equivalent to about 200 000 DVDs of data. The task of producing this colossal treasure trove of data for the scientific community lies with the Gaia Data Processing and Analysis Consortium, comprising more than 400 individuals at institutes across Europe.

    See the full article here.

    The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.


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  • richardmitnick 4:43 pm on December 19, 2013 Permalink | Reply
    Tags: , , , , ESA Gaia   

    From ESA: “Liftoff for ESA’s billion-star surveyor” 

    ESASpaceForEuropeBanner
    European Space Agency

    19 December 2013
    No Writer Credit

    ESA’s Gaia mission blasted off this morning on a Soyuz rocket from Europe’s Spaceport in Kourou, French Guiana, on its exciting mission to study a billion suns.

    Gaia is destined to create the most accurate map yet of the Milky Way. By making accurate measurements of the positions and motions of 1% of the total population of roughly 100 billion stars, it will answer questions about the origin and evolution of our home Galaxy.

    The Soyuz launcher, operated by Arianespace, lifted off at 09:12 GMT (10:12 CET). About ten minutes later, after separation of the first three stages, the Fregat upper stage ignited, delivering Gaia into a temporary parking orbit at an altitude of 175 km.

    A second firing of the Fregat 11 minutes later took Gaia into its transfer orbit, followed by separation from the upper stage 42 minutes after liftoff. Ground telemetry and attitude control were established by controllers at ESA’s operations centre in Darmstadt, Germany, and the spacecraft began activating its systems.

    The sunshield, which keeps Gaia at its working temperature and carries solar cells to power the satellite, was deployed in a 10-minute automatic sequence, completed around 88 minutes after launch.

    Gaia is now en route towards an orbit around a gravitationally-stable virtual point in space called L2, some 1.5 million kilometres beyond Earth as seen from the Sun.

    Tomorrow, engineers will command Gaia to perform the first of two critical thruster firings to ensure it is on the right trajectory towards its L2 home orbit. About 20 days after launch, the second critical burn will take place, inserting it into its operational orbit around L2.

    A four-month commissioning phase will start on the way to L2, during which all of the systems and instruments will be turned on, checked and calibrated. Then Gaia will be ready to begin its five-year science mission.

    Gaia’s sunshield will block heat and light from the Sun and Earth, providing the stable environment needed by its sophisticated instruments to make an extraordinarily sensitive and precise census of the Milky Way’s stars.

    gaia
    Gaia mapping the stars of the Milky Way

    “Gaia promises to build on the legacy of ESA’s first star-mapping mission, Hipparcos, launched in 1989, to reveal the history of the galaxy in which we live,” says Jean-Jacques Dordain, ESA’s Director General.

    “It is down to the expertise of Europe’s space industry and scientific community that this next-generation mission is now well and truly on its way to making ground-breaking discoveries about our Milky Way.”

    Repeatedly scanning the sky, Gaia will observe each of the billion stars an average of 70 times each over the five years. It will measure the position and key physical properties of each star, including its brightness, temperature and chemical composition.

    By taking advantage of the slight change in perspective that occurs as Gaia orbits the Sun during a year, it will measure the stars’ distances and, by watching them patiently over the whole mission, their motions across the sky.

    The position, motion and properties of each star provide clues about its history, and Gaia’s huge census will allow scientists to piece together a ‘family tree’ for our home Galaxy.

    The motions of the stars can be put into ‘rewind’ to learn more about where they came from and how the Milky Way was assembled over billions of years from the merging of smaller galaxies, and into ‘fast forward’ to learn more about its ultimate fate.

    deployment
    Deployment of Gaia’s DSA

    “Gaia represents a dream of astronomers throughout history, right back to the pioneering observations of the ancient Greek astronomer Hipparchus, who catalogued the relative positions of around a thousand stars with only naked-eye observations and simple geometry,” says Alvaro Giménez, ESA’s Director of Science and Robotic Exploration.

    See the full article here.

    The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.


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  • richardmitnick 6:12 am on September 6, 2013 Permalink | Reply
    Tags: , , , , ESA Gaia   

    From ESA: “ESA’s billion-star surveyor passes crucial live test” 

    ESASpaceForEuropeBanner
    European Space Agency

    6 September 2013

    An engineering copy of ESA’s Gaia satellite in Toulouse was linked to the mission control system at ESOC in Germany this week, enabling flight controllers to send commands and receive data just as they will once the actual satellite is in orbit.

    ESA Gaia satellite
    GAIA

    The System Validation Test (SVT) on 5–6 September was the final in a series of nine live linkups over the past four years as Gaia has moved through various stages of construction and integration.

    Some were performed using the actual flight model, while some – like this week – involved engineering models of the satellite’s subsystems and flight hardware. Until now, all have been conducted between ESOC, the European Space Operations Centre, and the Gaia manufacturing facilities at Astrium Toulouse in France and Stevenage in the UK.

    The first SVT addressed basic telecommanding procedures, such as switching satellite units on and off. Over time, the tests increased in complexity and duration, as assembly of the spacecraft in Toulouse progressed.

    “The testing is exhaustive, starting with basic system testing, progressing all the way up to the most complex flight modes and switching on of the full payload,” says Gaia Spacecraft Operations Manager David Milligan.

    “In addition to ensuring that the ground and onboard software interact well, it is important to test the procedures we must execute in case something goes wrong. Gaia is protected against failure by autonomous software, but engineers on the ground must intervene in some situations. Our contingency recovery procedures were fully validated through the SVT campaign.”

    This week’s final two-day test focused on telescope and payload commissioning procedures.

    In total, the nine SVTs ran for close to 500 hours over 39 days, and more than 1000 procedure executions were logged, with close to 500 000 telecommands sent.

    See the full article here.

    The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

    ESA Space Engineering Banner


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  • richardmitnick 7:49 am on December 8, 2011 Permalink | Reply
    Tags: , , , , ESA Gaia   

    From ESA Space Science: “Gaia spreads its wings” 

    7 December 2011
    No Writer Credit

    ESA’s Gaia star-mapper has passed a critical test ahead of its launch in 2013: the spacecraft’s sunshield has been deployed for the first time.
    Gaia’s sunshield is an essential component of the mission. It keeps Gaia in shadow, maintaining the scientific instruments at a constant temperature of around –110°C.”

    i1
    GAIA when she flies

    See the full article here.

     
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