GAIA A Stereoscopic Census of our Galaxy - ESA

GAIA A Stereoscopic Census of our Galaxy - ESA

Gaia A Stereoscopic Census of our Galaxy http://www.cosmos.esa.int/web/gaia December 2015 Gaia: Design Considerations Astrometry (G < 20 mag): completeness to 20 mag (on-board detection) 109 stars accuracy: 26 arcsec at G=15 mag (Hipparcos: 1 milliarcsec at 9 mag) scanning satellite, two viewing directions global accuracy, with optimal use of observing time principle: global astrometric reduction (as for Hipparcos) Photometry (G < 20 mag): astrophysical diagnostics (low-dispersion photometry) + chromaticity Teff ~ 100 K, log g, [Fe/H] to 0.2 dex, extinction (at G=15 mag) Radial velocity (GRVS < 16 mag): accuracy: 15 km s-1 at GRVS=16 mag application: third component of space motion, perspective acceleration dynamics, population studies, binaries spectra for GRVS < 12 mag: chemistry, rotation principle: slitless spectroscopy in Ca triplet (845-872 nm) at R = ~10,800 2

Gaia: Complete, Faint, Accurate Hipparcos Gaia Magnitude limit Completeness Bright limit 12 mag 7.3 9.0 mag 0 mag Number of objects 120,000 Effective distance limit 1 kpc 20 mag 20 mag 3 mag (assessment for brighter stars ongoing) 47 million to G = 15 mag 360 million to G = 18 mag 1192 million to G = 20 mag 50 kpc Quasars Galaxies Accuracy

1 (3C 273) None 1 milliarcsec Photometry Radial velocity Observing 2-colour (B and V) None Pre-selected 500,000 1,000,000 7 arcsec at G = 10 mag 26 arcsec at G = 15 mag 600 arcsec at G = 20 mag Low-res. spectra to G = 20 mag 15 km s-1 to GRVS = 16 mag Complete and unbiased 3 Stellar Astrophysics Comprehensive luminosity calibration, for example:

distances to 1% for ~10 million stars to 2.5 kpc distances to 10% for ~100 million stars to 25 kpc rare stellar types and rapid evolutionary phases in large numbers parallax calibration of all distance indicators e.g., Cepheids and RR Lyrae to LMC/SMC Physical properties, for example: clean HertzsprungRussell diagrams throughout the Galaxy Solar-neighbourhood mass and luminosity function e.g., white dwarfs (~400,000) and brown dwarfs (~500) initial mass and luminosity functions in star-forming regions luminosity function for pre-main-sequence stars detection and dating of all spectral types and Galactic populations detection and characterisation of variability for all spectral types 4 One Billion Stars in 3D will provide in our Galaxy

the distance and velocity distributions of all stellar populations the spatial and dynamic structure of the disk and halo its formation history a detailed mapping of the Galactic dark-matter distribution a rigorous framework for stellar-structure and evolution theories a large-scale survey of extra-solar planets (~7,000) a large-scale survey of Solar-system bodies (~250,000) and beyond definitive distance standards out to the LMC/SMC rapid reaction alerts for supernovae and burst sources (~6,000) quasar detection, redshifts, microlensing structure (~500,000) fundamental quantities to unprecedented accuracy: to 210-6 (210-5 present) 5 Exo-Planets: Expected Discoveries Astrometric survey: monitoring of ~150,000 FGK stars to ~200 pc detection limits: ~1MJ and P < 10 years complete census of all stellar types, P ~ 2-9 years masses, rather than lower limits (m sin i) multiple systems measurable, giving relative inclinations Results expected:

~2000 exo-planets (single systems) ~300 multi-planet systems displacement for 47 UMa = 360 asas orbits for ~1000 systems masses down to 10 MEarth to 10 pc 1.2 (") Photometric transits: ~5000 1/07/02 1 0.8 1/01/03 1/07/01 0.6 0.4 Plante : = 100 mas P = 18 mois 0.2 0 1/07/00 1/01/02 1/01/01

1/01/00 0 Figure courtesy 0.2 Franois 0.4 Mignard0.6 cos (") 0.8 6 1.0 Studies of the Solar System Asteroids etc.: deep and uniform (G=20 mag) detection of all moving objects ~250,000 objects observed, mainly main-belt asteroids orbits: 30 times better than present, even after 100 years spin-axis direction, rotation period, shape parameters for majority taxonomy/mineralogical composition versus heliocentric distance diameters for ~1000 to 20%, masses for ~150 to 10% Trojan companions of Mars, Earth, and Venus Kuiper-Belt objects: ~50 objects to G=20 mag (binarity, Plutinos) Centaurs: ~50 objects Near-Earth Objects: Amors, Apollos and Atens (4389, 5156, 811 known today) ~1600 Potentially Hazardous Asteroids (PHA) >1 km predicted (1435 currently known) detection limit: 260-590 m at 1 AU, depending on albedo

7 Light Bending in Solar System Light bending in microarcsec, after subtraction of the much larger effect by the Sun Movie courtesy Jos de Bruijne 8 Satellite and System ESA-only mission Launch: 19 December 2013 Launcher: SoyuzFregat from French Guiana Orbit: L2 Lissajous orbit Ground stations: Cebreros, New Norcia + Malarge Lifetime: 5 years (1 year potential extension) Downlink rate: 4 - 8 Mbps 9 Figure Soyuz: Arianespace; figure Gaia: ESA - C. Carreau Payload and Telescope Two Sic primary mirrors 1.45 0.50 m2 at 106.5

Rotation axis (6h) Basic-Angle-Monitoring (BAM) system SiC torus (optical bench) Combined Focal-Plane Assembly (FPA) with 106 CCD detectors Superposition of two Fields of View (FoV) Figure courtesy EADS-Astrium Radial-Velocity Spectrometer (RVS) 10 Figure courtesy Alex Short Focal Plane 104.26cm 42.35cm Basic Angle Monitor

Basic Angle Monitor Red Photometer CCDs Wave Front Sensor Blue Photometer CCDs Wave Front Sensor Radial-Velocity Spectrometer CCDs Star motion in 10 s Sky Mapper CCDs Astrometric Field CCDs Total field: - active area: 0.75 deg2 - CCDs: 14 + 62 + 14 + 12 (+ 4) - 4500 x 1966 pixels (TDI) - pixel size = 10 m x 30 m = 59 mas x 177 mas

Sky mapper: - detects all objects to G=20 mag - rejects cosmic-ray events - field-of-view discrimination Astrometry: - total detection noise ~ 4 e- Photometry: - spectro-photometer - blue and red CCDs Spectroscopy: - high-resolution spectra 11 - red CCDs On-Board Object Detection Requirements: unbiased sky sampling (magnitude, colour, resolution) all-sky catalogue at Gaia resolution (0.1 arcsec) to G~20 mag does not exist Solution is on-board detection: no input catalogue or observing programme good detection efficiency to G~21 mag Gaia will therefore detect:

variable stars (eclipsing binaries, Cepheids, etc.) supernovae: ~6,000 gravitational-lensing events: ~1000 photometric and ~100 astrometric Solar-system objects, including near-Earth asteroids and Kuiper-Belt objects 12 Sky-Scanning Principle Spin axis Scan rate: Spin period: 45o to Sun 60 arcsec s-1 6 hours 13 Figure ESA Photometry Measurement Concept (1/2) Blue photometer: 330 - 680 nm Red photometer: 640 - 1050 nm 14 Figure courtesy EADS-Astrium Photometry Measurement Concept (2/2) 700

40 1050 18 650 35 1000 16 25 500 20 450 15 400 10 350 5 300

0 0 5 10 15 20 AL pixels 25 30 35 14 Red photometer 900 12 850 10

800 8 750 6 700 4 650 2 600 spectral dispersion per pixel (nm) . 550 950 wavelength (nm) wavelength (nm) 30 spectral dispersion per pixel (nm) . Blue photometer

600 0 0 5 10 15 20 25 30 35 AL pixels RP spectrum of M dwarf (V = 17.3 mag) Red box: data sent to ground White contour: sky-background level Colour coding: signal intensity 15 Figures courtesy Anthony Brown Radial-Velocity Measurement Concept (1/2)

Spectroscopy: 845 - 872 nm (resolution ~10,800) 16 Figure courtesy EADS-Astrium Radial-Velocity Measurement Concept (2/2) Field of view RVS spectrograph CCD detectors RVS spectra of F3 giant (V = 16 mag) S/N = 7 (single measurement) S/N = 130 (summed over mission) 17 Figures courtesy David Katz Data-Reduction Principles Scan width = 0.7 Sky scans (highest accuracy along scan) Figure courtesy Michael Perryman 1. Object matching in successive scans 2. Attitude and calibrations are updated

3. Objects positions etc. are solved 4. Higher-order terms are solved 5. More scans are added 18 6. System is iterated Scientific Organisation Gaia Science Team (GST): 7 members + ESA Project Scientist + DPAC Executive Chair Scientific community: organised in Data Processing and Analysis Consortium (DPAC) 450+ scientists in 20+ countries active at some level GREAT network for post-mission science exploitation Community is active and productive: regular Science Team / DPAC meetings growing archive of scientific and processing-software reports advance of algorithms, calibration models, accuracy models, etc. Data-distribution policy: final catalogue ~2022 intermediate catalogues defined intermediate releases starting 2016 with positions; parallaxes and proper motions will be added in 2017

science-alerts data released immediately no proprietary data rights 19 Data Processing Concept 20 19 93 19 94 19 95 19 96 19 97 19 98 19 99 20 00 20 01 20 02 20 03 20 04 20

05 20 06 20 07 20 08 20 09 20 10 20 11 20 12 20 13 20 14 20 15 20 16 20 17 20 18 20 19 20 20 20 21

20 22 Schedule Proposal Concept & Technology Study Mission Selection Definition Re-Assessment Study Phase B1 Selection of Prime Contractor (EADS Astrium SAS) Phase B2 Phase C/D Implementation Launch December 2013 Scientific operation Operation Studies Data Processing Software Development (DPAC) Data Processing Mission Products Figure courtesy Michael Perryman and Franois Mignard Intermediate

Today Final 21 Gaia Unraveling the chemical and dynamical history of our Galaxy 22

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