Gaia aus der Sicht eines [-1.5ex]'First Look Scientists'€¦ · Michael Biermann Gaia aus FLS...

Gaiaaus der Sicht eines

”First Look Scientists”

Michael Biermann (ZAH–ARI)

MPIA AstroTechTalk, 16. September 2016

MPIA AstroTechTalk,16.09.16

Michael Biermann Gaia aus FLS Sicht MPIA AstroTechTalk,16.09.16 1 / 40

Gaia is an ESA Astrometry Space mission

December 2013 Gaia launchJuly 2014 Start of nominal operationsJune 2019 End of nominal operationsmid 2022 final catalogue


What Gaia is about

• Positions, parallaxes, proper motions, magnitudes, colours, ...for > 1 billion stars (20–25 µas at G = 15, 300 µas at G = 20)

• Spectroscopy for 10% of these stars


DPAC teamwork to deliver the promise of Gaia:DPAC = Data Processing and Analysis Consortium

10+ years of effort

450 scientists/engineers

160 institutes

24 countries and ESA

6 data processing centres


Why having First Look Scientists?

Astrometric space missions like Gaia have to simultaneouslydetermine a tremendous number of (source, attitude, calibration,global) parameters.

To reach the targeted level of precision, many months ofobservational data have to be incorporated in a global, coherent andinterleaved data reduction.

By no means neither the instrument nor the data health can beguaranteed by standard procedures.

Since it is undesirable not to know the measurement precision andinstrument stability until more than half a year of the mission haselapsed, one needs a Detailed First Look.


First Look

is the in-depth assessment of scientific data health and quality within1 day after reception of data,

uses science data and satellite housekeeping data,

assists Science Operations Center in solving any occurring problem.

Since Week 2, 2014:

131 FLS & PE Weekly Reports


The sad fate of the First-Look Scientist(s):

If you are constantly watching outfor rain and hail,

you risk to miss all the sunny days.


The many problems and oddities around Gaia

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Example I: Detection efficiency (ω Cen)


Example II: Image centroid distributions

2D Gaia image (star brighter than G = 13)

1D Gaia image (star fainter than G = 13)



What we expect:

frequency

window pixel coordinate

1 pixel

windowcenter

⊗frequency


=

frequency


And what we get ...



0

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36 38 40 42 44 46 36 38 40 42 44 46

frequency


FoV1, G ≥ 16, SM1 1

frequency

window pixel coordinate window pixel coordinate

FoV2, G ≥ 16, SM2 1



Example II: Add-on – Spurious detections


Example III: Astrometric along-scan scatter

Measure for the astrometric accuracy= astrometric along-scan scatter= width σ of a Gaussian fit

to the astrometric residuals

frequency

εη [mas]

2σ

↪→ target at G = 15.8 mag:330 µas for a single CCD transit.



0

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20000

-5 -4 -3 -2 -1 0 1 2 3 4 5-5 -4 -3 -2 -1 0 1 2 3 4 5

frequency

εη [mas]

FoV1, AF, WC0 ←| |→ 0.0%

frequency

εη [mas] εη [mas]

FoV2, AF, WC0 ←| |→ 0.0%

εη [mas]

bright stars, G < 13



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frequency

εη [mas]

FoV1, AF, WC1 ←| |→ 0.0%

frequency


FoV2, AF, WC1 ←| |→ 0.0%

εη [mas]

medium-bright stars, 13 < G < 16



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frequency

εη [mas]

FoV1, AF, WC2 ←| |→ 1.6%

frequency


FoV2, AF, WC2 ←| |→ 2.0%

εη [mas]

faint stars, G > 16g



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astrom

etricALscatter

[mas]

OBMT [rev]

FoV1FoV2

target

jump in the astrometric scatter

refocussing



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astrom

etricALscatter

[mas]

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FoV1FoV2

target

new FL software release



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astrom

etricALscatter

[mas]

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FoV1FoV2

new FL software

?

target




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astrom

etricALscatter

[mas]

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target

jumps in the astrometric scatter



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etricALscatter

[mas]

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target




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astrom

etricALscatter

[mas]

OBMT [rev]

FoV1FoV2

target




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astrom

etricALscatter

[mas]

OBMT [rev]

FoV1FoV2

target




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astrom

etricALscatter

[mas]

OBMT [rev]

FoV1FoV2

target

Station Keeping Maneuvers



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astrom

etricALscatter[m

as]

OBMT [rev]

FoV1FoV2

target

propellant movement

Jumps in astrometric scatter are caused by sudden changes in Gaia’s massmoment of inertia due to propellant movements.


Example III: Add-on: micro-clanksWhy hasn’t ODAS reached yet the target precision?

Thermal disturbances↪→ mirror movementof ' 20 Si atoms


Example IV: Response lossFrom the very beginning, Gaia suffered from ice contamination.

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pons

e lo

ss [m

ag]

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FoV 1FoV 2

SP6 SP1


Example IV: Response loss

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respon

seloss

[mag

]

OBMT [rev]

AF FoV1BP FoV1RP FoV1

AF FoV2BP FoV2RP FoV2


Summary

By and large, Gaia is working well and producing tremendousquantities of unprecedented data.

On Sep 14, we (DPAC) have released the first Gaia Data Release.I 2D positions, 2D proper motions and parallaxes of 2 million sources

down to G ' 12 with accuracies of about 0.3 mas and 1 mas/yr.I 2D positions of 1.1 billion sources down to G = 20.7 with a positional

accuracy of about 10 mas or better.I Mean G -band magnitudes for all sources.I Light curves of 3 194 variables (Cepheids, RR Lyrae) around the south

ecliptic pole over 28 days with around 200 epochs.I Special A&A issue. 19 papers.

There are already science papers out based on Gaia DR1.

Gaia DR1 is just an appetiser!20 times more (and three times more accurate) than Hipparcos, butonly 0.2% of Gaia DR2 (Q4 2017).


Last but not least:

During this presentation Gaia has

observed 0.7 million stars,

collected 7 million astrometric measurements, and

collected 275.000 spectra of 80.000 stars.

Thanks for your attention!


Gaia aus der Sicht eines [-1.5ex]'First Look Scientists'€¦ · Michael Biermann Gaia aus FLS...

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