The Gaia Data - project.lsst.org · Building the Gaia Data System DPAC CU9: Gaia Data Access 12 Sept 2013 Nic Walton - Gaia Data @ LSST, Cambridge 18 Services WP910 Coordination Management

Nicholas Walton (IoA, University of Cambridge)

Anthony Brown

(Leiden Observatory) Xavier Luri

(University of Barcelona) William O’Mullane

(ESAC, ESA)

The Gaia Data: Science Driven Data Access

12 Sept 2013 Nic Walton - Gaia Data @ LSST, Cambridge 1


Gaia: Launch 20 Nov 2013 Post launch performance

meets specifications

Jos De Bruijne (2012 see arXiv1201.3238D)

http://www.rssd.esa.int/index.php?project=GAIA&page=Science_Perfor

mance

Gaia Prepares Arrival in Kourou


Photo credits: ESA/ C

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riancespace


Detailed chemical composition and vsini Radial velocity &

chemical composition

Simulations - Robin et al: arXiv:1202.0132

The Gaia Sky simultaneous astrometric, photometric and spectroscopic

observations – typically 70 observations over 5 years

•  109 stars to G = 20 •  106-107 galaxies •  500,000 quasars •  3x105 solar system obj •  Many 104 exoplanets

Gaia End-of-Mission Parallax Errors


Figure from http://w

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1.  bright-star regime (calibration errors, CCD saturation) 2.  photon-noise regime, with sky-background noise and electronic noise

setting in around G ~ 20 mag (equivalent to V = 20 to 22)

1 2

Non-uniformity over the sky: 70% – 116%

Apply factors of ~ 0.7 and ~ 0.5 for positions and proper motions

Gaia Science Spans Astrophysics

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•  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 (~20,000) –  quasar detection, redshifts, microlensing structure (~500,000) –  fundamental quantities to unprecedented accuracy: e.g. relativistic

light bending due to gravity: PPN σγ ~10-6 (~2×10-5 present)

Gaia: transformational science astrometry + spectrophotometry + spectroscopy

The Gaia Sky

12 Sept 2013 Nic Walton - Gaia Data @ LSST, Cambridge 8 Simulated view of R136 (Jos de Bruijne and Guido de Marchi

Gaia Data: Large, Rich and Complex

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Single field-of-view-transit photometric standard errors

Credit: Jos De Bruijne - ESA

Survey capabilities

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More info at www.rssd.esa.int/gaia (‘Science Performance’ button) and in arXiv:1201.3238

6 8 10 12 14 16 18 20 22V [mag]

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Figure by Jos de Bruijne

Gaia Archive and data access Early data releases Extra Schloss Ringberg 13.04.2012 - p.4/37

Data products include the full prism spectra as well as integrated fluxes.

Tangential Velocity Precision


Fig: Fancois Mignard – G

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Astrophysical Parametrisation

●  The BP and RP spectro-photometric enable a range of stellar parameters to be determined

Credit: Coryn Bailer-Jones See Liu et al 2012

Five-year scanning survey mission: sky-coverage non-uniformity §  Average ~70 observations over 5 years (~20% dead time) §  Varies over the sky between ~50 and ~130 (~20% dead time)

Crowding: incompleteness at high densities and faint magnitudes §  Astrometric limit is ~1,000,000 stars deg-2 (without bright stars) §  Up to ~3,000,000 stars deg-2 can be handled

Spatial resolution: unresolved close binaries §  Detection depends on separation and magnitude difference

On-board processing: not optimised for extended objects §  The paper limit is detection up to 200 mas §  In reality, extended objects up to 700 mas are detected

Dynamic range: existence of a bright limit §  The paper limit is G = 5.7 mag (V = 6 mag is normally quoted) §  The real limit is a bit better (and varies from CCD row to row)

Gaia’s “limitations”



Data Release Timeline Constraints

●  Launch: current schedule 20th Nov 2013 ●  L+6m: voyage to L2/ commissioning/ initialisation ●  L+12m: first full sky coverage (6m of nominal scans) ●  L+24m: fully non-degenerate solutions for parallaxes

and proper motions (18m of data required) ●  Processing, calibration, validation (3-6m) ●  Preparation of a data release (3-6m) ●  L+6m initialisation phase contains 2m ecliptic pole

scanning (~500 repeat scans over 2x3sq deg) and 6m nominal scans → early flux alerts


Baseline Gaia Data Release Schedule Each release updates and expands the previous

●  L+22m: positions, G-magnitudes (all sky, single stars) proper motions for Hipparcos stars (~50 µarcsec/yr) – the

Hundred Thousand Proper Motions (HTPM) catalogue ●  L+28m: + radial velocities for bright stars, two band photometry

and full astrometry (α, δ, ϖ, µα, µδ ) where available for intermediate brightness stars

●  L+40m: + first all sky 5 parameter astrometric results (α, δ, ϖ, µα, µδ ) BP/RP data, RVS radial velocities and spectra, astrophysical parameters, orbital solutions short period binaries

●  L+65m: + variability, solar system objects, updates on previous releases, source classifications, astrophysical parameters, variable star solutions, epoch photometry

●  End+3yr: final data release (thus in 2022/23)

~ 9/15

~ 3/16

~ 3/17

~ 5/19

Gaia Data Access: Guiding Principles

•  Effective and efficient access to the Billion source catalogue and related data

•  No boundaries – seamless interfaces to related missions and survey data

•  Science enabling and visualisation applications •  Long term access – data preservation and data re-use •  Gaia data access relevant to all users from research

scientists to the wider public


Building the archive and access system is now underway with requirements from the

community driving its shape and scope

Gaia is a Complex Mission Industry and Science combining to deliver the final data


DPAC: Data Processing & Analysis Consortium

Building the Gaia Data System DPAC CU9: Gaia Data Access


Catalogue and Web Portal Services

WP910 CoordinationManagement

Architecture andTechnical Dev.

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CU9 Releases


http://great.ast.cam.ac.uk/Greatwiki/GaiaDataAccess

Defining the Requirements via Community Input


GUMS: Gaia Universe Model model data in preparation for Gaia

The real sky http://www.cfa.harvard.edu/~rkirshner/MilkyWay.jpg

The simulated sky – G < 20 GUMS-10

Robin et al (2012) arXiv 1202.0132v2

See http://gaia.am.ub.es/GUMS-10/


GUMS data available now via Strasbourg CDS: VI/137

Realistic Simulated Gaia Data GOG: Gaia Object Generator

•  GOG simulations (combined data) to be made available via CU9 and CDS early 2014 •  Provide community with access to a realistic

representation of Gaia data


GOG billion star simulations: left – parallax; right photometry (credit: CU2/Luri)


Timeline for the data flow: can be quick Alerts data is released in near real-time

16h 8h visibility

backlog real time acquisition Gaia

transmission MOC

transmission SOC

0 24 one operational day

d-1 d d+1 48

Initial Data Treatment

First Look

Science Alerts (Cambridge)

Figure courtesy Francois Mignard, updated by LW+STH- NAW

Madrid, Spain

Astrometry (50 mas) (100 µas) Astrometry

SSA ASA PSA ASA? SSA?

Figure courtesy Francois Mignard, updated by LW+STH Figure courtesy Francois Mignard, updated by

LW+STH

The Gaia-LSST Data Driven Connection

Seamless interoperability of data products


6.12 A Comparison of Gaia and LSST Surveys

Table 6.6: Adopted Gaia and LSST Performance

Quantity Gaia LSST

Sky Coverage whole sky half sky

Mean number of epochs 70 over 5 yrs 1000 over 10 yrs

Mean number of observations 320a over 5 yrs 1000b over 10 yrs

Wavelength Coverage 320–1050 nm ugrizy

Depth per visit (5�, r band) 20 24.5; 27.5c

Bright limit (r band) 6 16-17

Point Spread Function (arcsec) 0.14⇥0.4 0.70 FWHM

Pixel count (Gigapix) 1.0 3.2

Syst. Photometric Err. (mag) 0.001, 0.0005d 0.005, 0.003e

Syst. Parallax Err. (mas) 0.007f 0.40f

Syst. Prop. Mot. Err. (mas/yr) 0.004 0.14a One transit includes the G-band photometry (data collected over 9 CCDs), BP and RP spec-trophotometry, and measurements by the SkyMapper and RVS instruments.b Summed over all six bands (taken at di↵erent times).c For co-added data, assuming 230 visits.d Single transit and the end-of-mission values for the G band (from SkyMapper; integrated BPand RP photometry will be more than about 3 times less precise).e For single visit and co-added observations, respectively.f Astrometric errors depend on source color. The listed values correspond to a G2V star.

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Chapter 6: Stellar Populations

Figure 6.26: A comparison of photometric, proper motion and parallax errors for SDSS, Gaia and LSST, as a functionof apparent magnitude r, for a G2V star (we assumed r = G, where G is the Gaia’s broad-band magnitude). Inthe top panel, the curve marked “SDSS” corresponds to a single SDSS observation. The red curves correspond toGaia; the long-dashed curve shows a single transit accuracy, and the dot-dashed curve the end of mission accuracy(assuming 70 transits). The blue curves correspond to LSST; the solid curve shows a single visit accuracy, andthe short-dashed curve shows accuracy for co-added data (assuming 230 visits in the r band). The curve marked“SDSS-POSS” in the middle panel shows accuracy delivered by the proper motion catalog of Munn et al. (2004).In the middle and bottom panels, the long-dashed curves correspond to Gaia, and the solid curves to LSST. Notethat LSST will smoothly extend Gaia’s error vs. magnitude curves four magnitudes fainter. The assumptions usedin these computations are described in the text.

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See discussion session

Inputting to the Requirements Process •  You can add your requirements through the GREAT

wiki pages at http://www.great.ast.cam.ac.uk/Greatwiki/GaiaDataAccess

•  The first collection of requirements have set a baseline for the data access system development •  See the process and resulting rankings in Brown et al 2012:

http://www.rssd.esa.int/SA/GAIA/docs/library/AB-026.htm


Additional requirements are welcome – ideas generated at this meeting for instance – please add to wiki above

Find Out More http://gaia.esa.int


ESA/CNES/ARIANESPACE - S. Corvaja, 2011

Documents

The Gaia Data - project.lsst.org · Building the Gaia Data System DPAC CU9: Gaia Data Access 12 Sept 2013 Nic Walton - Gaia Data @ LSST, Cambridge 18 Services WP910 Coordination Management