Gaia status Anthony Brown Sterrewacht Leiden, Leiden University - - PowerPoint PPT Presentation

Gaia status

Anthony Brown

Sterrewacht Leiden, Leiden University brown@strw.leidenuniv.nl

Place - Date - 1/43

Gaia summary

• Gaia: science with 1 billion objects in

three dimensions

• ESA corner stone mission building
• n the Hipparcos heritage
• Astrometry, Photometry and

Spectroscopy

• Satellite and payload, by industry,

management and operations by ESA, and data processing by scientists (DPAC)

• Launch 19 December 2013 with

Soyuz from Kourou

• Commissioning formally completed

18 July 2014

• 5 years of operations at L2
• First intermediate data release

summer 2016, but Science Alerts start earlier

w w w . c

• s

m

• s

. e s a . i n t / g a i a

Place - Date - 2/43

Telescope and payload

Place - Date - 3/43

Telescope and payload

Place - Date - 4/43

Telescope and payload

Place - Date - 5/43

Focal plane

Astrometric Field CCDs Blue Photometer CCDs Sky Mapper CCDs 104.26cm 42.35cm Red Photometer CCDs Radial Velocity Spectrometer CCDs Image motion

Basic Angle Monitor Wave Front Sensor Basic Angle Monitor Wave Front Sensor

Figure courtesy Alex Short Total field:

• active area 0.75 deg2
• CCDs 106 = 14 + 62 + 14 + 12(+4)
• 4500 × 1966 pixels (TDI)
• pixel size = 10 × 30 µm2 = 59 × 177 mas2

Sky mappers

• detect all objects to G = 20
• rejection cosmic rays
• field-of-view discrimination

Astrometry

• total detection noise ∼ 6e−

Photometry

• prism spectra
• blue and red CCDs

Spectroscopy

• high-resolution spectra
• red CCDs

Place - Date - 6/43

Focal plane

Place - Date - 7/43

Science topics

Place - Date - 8/43

Commissioning

• Focal-plane switch-on on 3

January 2014

• L2-orbit-insertion burns on 7 +

14 January

• Ecliptic-pole scanning + 6-h spin

started on 8 January

• Commissioning concluded on

July 18 2014

Sky coverage Feb 7 to May 24 IDT team @ University of Barcelona

Detailed report: GAIA-CO-TN-LEI-AB-052

Place - Date - 10/43

Examples of Gaia imaging capabilities

NGC 2516 Gaia DSS

Place - Date - 11/43

Examples of Gaia imaging capabilities

M51

Place - Date - 12/43

Photometry

Diagrams courtesy C. Jordi and J.-M. Carrasco

Place - Date - 13/43

Photometry

Diagrams courtesy C. Jordi and J.-M. Carrasco

Place - Date - 14/43

Spectroscopy

Figure courtesy D. Katz,

• O. Marchal, C. Soubiran

Place - Date - 15/43

Spectroscopy

840 850 860 870 880 2000 4000 6000 8000 10000 Flux (photoelectron/sample)

Calibrated spectra on the 3 AL RVS CCD for a K-type star

internalApparentGrvs = 5.50 840 850 860 870 880 2000 4000 6000 8000 10000

Flux (Photoelectron/sample) 840 850 860 870 880 Wavelength (nm) 2000 4000 6000 8000 10000 Flux (Photoelectron/sample)

strip 1 strip 2 strip 3

RV(dir) = -68.89 +- 3.17 RV(fou) = -69.30 +- 1.87 RV(mdm) = -68.68 +- 0.07 Spectroscopic Radial Velocity = -68.89 +- 3.17 km/s

Early result from automated RVS processing

Credits: ESA/Gaia/DPAC/CNES/Yves Viala and Francoise Crifo

Place - Date - 16/43

Overall status after commissioning

• Good launcher and orbit insertion performance

◮ plenty of propellant left for future manoeuvres

• Service module commissioning went smoothly

◮ Chemical propulsion system for large manoeuvres ◮ Micro propulsion system to maintain Gaia’s spin rate and compensate solar radiation pressure torque ◮ Attitude and Orbit Control System works will within specs; thermal control fine ◮ Good link budget for phased array antenna → high data rates possible

• Rubidium atomic clock working to required accuracy at this stage

◮ Validation of high accuracy time correlation pending

• Payload module

◮ 106 CCDs and 106 back-end electronics units all working fine ◮ 7 on board computers managing the CCDs and electronics ◮ Payload and data handling unit for storing and down-linking data ◮ Telescopes aligned and focused; good image quality over full FPA

• Gaia → ESOC → DPAC/SOC → AirbusDS chain working smoothly

◮ Excellent flight control team at ESOC ◮ DPAC operations teams calm and competent ◮ About 40 DPAC Payload Experts analyzed the data; supported commissioning ◮ Many S/W patches and fixes but all in controlled manner

Place - Date - 17/43

Optical tracking of Gaia

Gaia seen by ESO-VST: image courtesy ESO

Place - Date - 18/43

Optical tracking of Gaia

Background

• Orbit should be known to 150 m in position (solar system object parallaxes)

and 2.5 mm/s in each velocity axis (aberration correction bright stars)

◮ 1 mm/sec upper limit on systematic error!

• 20 mas accurate position of Gaia on the sky needed, every day

◮ Can only be achieved after first AGIS solution

Status

• Gaia fainter than hoped for at r ∼ 20.5
• GBOT team worked hard to revise observing and data processing strategies

◮ VST@ESO can deliver the required astrometric precision most of the time and is now the backbone of GBOT ◮ Observing/processing strategy being adapted at Liverpool Telescope, which should deliver the required astrometric precision ◮ Test observations underway with Las Cumbres 2m telescopes

• ESOC can complement with VLBI-type observations (few mas accuracy)
• GBOT issue is under control

Place - Date - 19/43

Micro and Chemical Propulsion System anomalies

• Malfunctioning mass-flow sensor in one of the thrusters (#3A) of the micro

propulsion system

◮ Erroneous feedback from this thruster to the Attitude and Orbit Control System, leading to increased gas consumption, and possibly degraded attitude control

• MPS anomaly root cause still under investigation
• AOCS now working on B-branch

◮ AOCS works very well ◮ Slight cold gas over-consumption due to thruster bias drifts ◮ Bias being monitored and calibrated ◮ Studies ongoing to optimize MPS usage

• Chemical thruster #3B is electrically dead
• Using the redundant unit now

◮ lost redundancy for this CPS thruster ◮ New CPS mode implemented which makes Gaia robust against thruster 3A failure

Place - Date - 20/43

Stray light

• Strong stray light levels all
• ver focal plane
• In the peaks orders of

magnitude above requirements

• Sun light diffracted and/or

scattered at sun-shield edges

◮ Varies over 6 hour spin period

• Light from night sky sources

along unforeseen paths

◮ Varies according to sky scanned

SAA= 45◦ SAA= 0◦ Figures by M. Davidson Sun dominates Night sky dominates time → Flux [e−/pix/s]

Place - Date - 21/43

Throughput loss

• 0.1

0.0 0.1 0.2 0.3 Response loss [mag] 260 380 500 620 740 860 980 1100 1220 1340 1460 OBMT [rev] FoV 1 FoV 2 SP6 SP1 Figure by C. Fabricius

Decon 1 (FOV2) Decon 2 Decon 3 Decon 4

Monitoring of response by comparison to Tycho-2 photometry

Place - Date - 22/43

Throughput loss

Figure by FL Scientist team

Place - Date - 23/43

Throughput loss

• 0.1
• 0.08
• 0.06
• 0.04
• 0.02

0.0 0.02 1320 1340 1360 1380 1400 1420 1440 1460

FFF,Fovf∆Grevτ

OBMT [rev] AF FoV1 BP FoV1 RP FoV1 AF FoV2 BP FoV2 RP FoV2

Figure by FL Scientist team

• Throughput loss in AF, BP, and RP (FLS report 2014-10-28)
• Future decontamination campaigns unavoidable

◮ Not clear at the moment how many more

PE analyses ◆ Modelling effects of ice

• n mirrors

◮ XP spectral signatures ◮ image quality

◆ Optimization of the decontamination procedure

◮ heating all mirrors seems necessary

Place - Date - 24/43

Basic angle variations

• 110
• 105
• 100
• 95
• 90
• 85
• 80
• 75
• 70
• 65
• 60
• 55

∆(δγ) [mas]

• 110
• 105
• 100
• 95
• 90
• 85
• 80
• 75
• 70
• 65
• 60
• 55

500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 6000 6500 7000

no of 5-minute-interval

791.007 799.007 807.007 815.007 823.007 831.007 839.007 847.007 855.007 863.007 871.007 879.007 887.007

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 white-light fringe experiment slew to NSL

→ Time [spin period] → BA variation [mas] Figure by First Look team BA variation according to BAM BA variation according to ODAS

• Trends and jumps with 6 hour period variation superposed

◮ 6 hour variations can cause systematic errors in astrometry ◮ Basic Angle Monitor (BAM) in place to measure the variations so they can be accounted for in processing

• Astrometric solutions indicate that BAM measures real variations
• Analysis shows BAM measurements precise to ∼ 10 µas level or better

Place - Date - 25/43

Including: BR CA DZ ESA IL US DPAC participating countries October 2013 450 members DPCI DPCG DPCC DPCB DPCT DPCE

• Gaia data processing is a

Pan-European cooperation

◮ Academic institutions and national space agencies ◮ Supported through national funding ◮ Processing power spread

• ver 6 centres

◮ SOC/DPCE integral part

• f DPAC

DPAC overview

CU3 Initial Data Treatment First Look ESAC CU3 Astrometric core processing ESAC/Torino CU5 Photometric processing Cambridge CU6 Spectroscopic processing CNES MDB ESAC CU3 Intermediate Data Update Barcelona CU7 Variability analysis Geneva/ISDC CU4 Complex object processing CNES CU8 Astrophysical characterization CNES Telemetry ESOC CU1 System/IT architecture CU2 Simulations Barcelona/CNES CU9 Archive and Catalogue access ESAC Alerts Transients, new SSOs, . . . Cambridge/CNES

Upstream Downstream

Place - Date - 27/43

Data collection stats

Example TM time line with Galactic plane crossings (OBMT rev 516–517, courtesy J. Hern´ andez)

Place - Date - 28/43

Data collection stats

Statistics up to October 10 Data collected or processed Type of Data Amount Science telemetry 7.6 TB Astrometry transits 9.0 × 109 90 × 109 images Photometry transits 8.8 × 109 17.6 × 109 images Spectroscopy transits 1 × 109 3 × 109 spectra

Place - Date - 29/43

Early astrometric performance assessment

20000 40000 60000 80000 100000 120000 50000 100000 150000 200000 250000 300000 350000

• 4
• 3
• 2
• 1

1 2 3 4

• 4
• 3
• 2
• 1

1 2 3 4

frequency primary sources, FoV1, WC1 frequency ǫη [mas] secondary sources, FoV1, WC1 primary sources, FoV2, WC1 ǫη [mas] secondary sources, FoV2, WC1

• Residuals from one-day astrometric

solution at G = 15 already better than 1 mas

• Caveats at this stage

◮ unstable instrument ◮ poor PSF calibrations ◮ imperfect stray light corrections ◮ throughput loss

• For clean telescopes throughput is as

expected

• Read noise within requirements
• Corrections for bias non-uniformity

under control

• High accuracy timing works

nominally (detailed verification pending)

Figure courtesy First Look team

Place - Date - 30/43

Early photometric performance assessment

• Spectra appear as expected:

classification and parametrization possible

• For clean telescopes throughput

is as expected

• Read noise within requirements
• Corrections for bias

non-uniformity under control

Figure courtesy C. Jordi & J.-M. Carrasco

Place - Date - 31/43

Early spectroscopic performance assessment

• Resolving power nominal
• Read noise within requirements
• Corrections for bias non-uniformity under control
• Wavelength zero point stability pending

Figure courtesy D. Katz &

• O. Marchal

Place - Date - 32/43

Preliminary RVS performance at bright end

Figure by CU6 Payload Experts

• Differences between measured and expected vrad for bright (GRVS < 7)

ground based radial velocity standards

• 68% of measurements are within 1.1 km s−1 from the median!

Place - Date - 33/43

Detection efficiencies

• Faint end efficiencies

measured against dedicated Ecliptic Pole survey

• Bright end extended to

G < 6 through detection algorithm improvements and employment of special

• bserving mode

Figures courtesy U. Bastian and SOC Calibration Team

Place - Date - 34/43

First supernova discovery

Credits: M. Fraser/ S. Hodgkin/ Ł. Wyrzykowski/

• H. Campbell/ N. Blagorodnova/
• Z. Kostrzewa-Rutkowska/ Liverpool Telescope/

SDSS Place - Date - 35/43

Gaia performance predictions at IOCR (July 2014)

Performance predictions for G2V star V magnitude Astrometry Photometry Spectroscopy (parallax) (BP/RP integrated) (radial velocity) 3 to 12 5–14 µas 4 mmag 3 to 12.3 1 km s−1 15 24 µas 4 mmag 15.2 15 km s−1 20 540 µas 60 (RP) – 80 (BP) mmag Up-to-date information always at: http://www.cosmos.esa.int/web/gaia/science-performance

Place - Date - 36/43

Gaia performance predictions at IOCR (July 2014)

• Stray light impact assessed with respect to extra noise

◮ Systematics not accounted for

• On the assumption that BA variations and micro-meteoroid hits can be

accounted for perfectly, the current numbers provide an optimistic performance estimate

• Too early to provide quantitative estimates of the effects of:

◮ Basic Angle variations ◮ Throughput loss (with corresponding optical quality degradation) ◮ Micro-meteoroid hits ◮ Radiation damage

Place - Date - 37/43

Gaia performance predictions at IOCR (July 2014)

Gaia will still deliver a fantastic survey

• f our Galaxy and the Solar system

Place - Date - 38/43

Impact on data release scenario

Impacts on data processing

• 3 months longer commissioning period

◮ Later start of nominal operations and processing

• Extra development and processing effort needed to deal with:

◮ Effect of future decontamination campaigns ◮ Stray light effects ◮ Change in RVS observing strategy ◮ Account for basic angle variations through BAM measurements ◮ Deal with high rate of micro-meteoroid hits ◮ More complex data validation

First data release expected by mid-2016

Place - Date - 39/43

Operations since IOCR

• Start of nominal operations on July 25
• 28 days of undisturbed EPSL data collection July 25 – August 21
• Orbit maintenance manoeuvres 25/7, 21/8, 9/9, 9/10
• Transition to NSL on August 22
• PDHU configured to deal with G=21 survey
• Latest decontamination on September 23
• Switch to GAREQ optimized NSL on September 25
• One occurrence of 10 minutes data loss due to rain at Cebreros

◮

• nly data loss so far

◆ Gaia now routinely observes all sources 3 ≤ G ≤ 21

◮

• bjects at G < 3 via special mode (SIF)

◆ Data collected: 150 GB HKTM, > 6.5 TB science data

◮ Operational data base 62 TB

Place - Date - 40/43

Post commissioning actions

Basic angle related Working group will look into root cause of BA variations (Airbus DS, ESA, DPAC). Research and development on calibrating the BA variations using a combination of AGIS adaptations and BAM measurements − → will take time! Contamination Optimize strategy to deal with future decontamination campaigns (with Airbus DS support): procedure when to do decontamination, thermal conditions, recovery time Stray light related Support from Airbus DS to develop and implement an

• ptimized observing strategy for RVS and AF (i.e. VPU S/W

changes to be managed by Airbus).

Place - Date - 41/43

Credits

DPAC Payload Experts at institutes throughout Europe Initial Data Treatment, First Look, and AVU/BAM+AIM teams Operations teams at ESAC, Torino, CNES-Toulouse, Cambridge, Barcelona, Geneva ESA Gaia-SOC calibration team DPAC Project Office ESA Gaia Project Scientist team ESOC flight control team ESA Gaia project team Airbus Defence & Space Arianespace, Soyuz, CNES-Kourou launch teams

Place - Date - 42/43