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Gaia Commissioning update and flux calibration

Gaia Commissioning update and flux calibration. by Elena Pancino. Gaia timeline. Launch 19 Dec 2013 L2 orbit insertion 1-15 Jan 2014 Commissioning until 18 Jul 2014 EPSL will last 28 days NSL from then on (5 years).

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Gaia Commissioning update and flux calibration

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  1. GaiaCommissioning updateand flux calibration by Elena Pancino

  2. Gaia timeline • Launch 19 Dec 2013 • L2 orbit insertion 1-15 Jan 2014 • Commissioning until 18 Jul 2014 • EPSL will last 28 days • NSL from then on (5 years) Gaia at HST Calibration Workshop Elena Pancino Baltimore August 2014 INAF- Bologna Observatory

  3. The Gaia mission • All Sky – 109 point-like sources – few μasastrometry • 6Dphase space sampling – SEDs – Astrophysical parameters • Focused on Galactic Science – but huge discovery space Two telescopes inside Encased view Gaia at HST Calibration Workshop Elena Pancino Baltimore August 2014 INAF- Bologna Observatory

  4. All-sky scanning • Each object observed 10-250 times (average ≈70-80) • Maximum number of passages around ±45° from EP Sky Coverage Map Nominal Scanning Law Gaia at HST Calibration Workshop Elena Pancino Baltimore August 2014 INAF- Bologna Observatory

  5. Scan width: 0.7° Astrometry principle Sky scans (highest accuracy along scan) 1. Object matching in successive scans 2. Attitude and calibrations are updated 3. Objects positions etc. are solved 4. Higher terms are solved 5. More scans are added 6. System is iterated (Global Iterative Solution - GIS) Gaia at HST Calibration Workshop Elena Pancino Baltimore August 2014 INAF- Bologna Observatory

  6. To give you the feeling… Distance to the Pleiades attainable by Gaia: tiny errorbars and a large sample of stars Each plotted star will also have a radial velocity, magnitude, color, and astrophysical parameters by means of high-resolution spectroscopy in the CaT region Gaia at HST Calibration Workshop Elena Pancino Baltimore August 2014 INAF- Bologna Observatory

  7. Science possibilities • Focus on the Milky Way • Solar system objects • Distant galaxies and QSO • Fundamental physics • Transients & variables • Distance scale Gaia at HST Calibration Workshop Elena Pancino Baltimore August 2014 INAF- Bologna Observatory

  8. Focal plane & instruments • Sky mappers (SM) • Astrometric field (AF) • Spectro-photometers (BP & RP) • Radial velocity spectrometer (RVS) Gaia at HST Calibration Workshop Elena Pancino Baltimore August 2014 INAF- Bologna Observatory

  9. Sky Mappers & object detection Bright stars (V<13 mag) Intermediate stars (13 <V<16 mag) squares for Gaia spin rate measurements Faint stars (16<V<20 mag) 1D profile only Each detected object is assigned a 2D window Gaia at HST Calibration Workshop Elena Pancino Baltimore August 2014 INAF- Bologna Observatory

  10. Astrometric field • White light (G-band ≈ V band) • Photometry and astrometry • Astrometric performance (G2V) • 3<V<12 mag: 5-14 μas • V=15 mag: 24 μas • V=20 mag: 540 μas • NGC 2516, commissioning image • Later 1 star = 1 little window First images: Sadalmelik (α Aqr) Telescope not aligned nor focused then Gaia at HST Calibration Workshop Elena Pancino Baltimore August 2014 INAF- Bologna Observatory

  11. Tuning Gaia Spin rate adjustment (Telescope focus & alignment) Courtesy of SOC calibration team First images: Cat’s eye nebula before and after spin rate adjustment This might be one of the last images – Gaia is not an imaging mission! Gaia at HST Calibration Workshop Elena Pancino Baltimore August 2014 INAF- Bologna Observatory

  12. BP/RP dispersed images • Blue and red channels • R≈100 dispersed images • Color-correction for AF • SEDs for: • Classification • Parametrization Courtesy of Jordi & Carrasco First images: NGC 1818 in the LMC 2.85 sec integration, 212 x 212 arcsec2 Gaia at HST Calibration Workshop Elena Pancino Baltimore August 2014 INAF- Bologna Observatory

  13. Gaia integrated magnitudes • Four bands (G, BP, RP, RVS) • Four integrated magnitudes • One important colour (GBP-GRP) • G band performance (G2V) • V=15 mag, 1 mmag • V=18 mag, 2 mmag • V=20 mag, 6 mmag • BP performance (G2V) • V=15 mag, 4 mmag • V=18 mag, 13 mmag • V=20 mag, 80 mmag • RP performance (G2V) • V=15 mag, 4 mmag • V=18 mag, 11 mmag • V=20 mag, 59 mmag Gaia at HST Calibration Workshop Elena Pancino Baltimore August 2014 INAF- Bologna Observatory

  14. RVS spectra • R≈10000 CaT spectra • Down to V ≈ 16.5 mag • Full objectparametrization • Chemical abundances • RVS performances (GV2) • V=12 mag, 1 km/s • V=15 mag, 15 km/s Pre-launch simulations First spectra: the bright star HIP 86564 Courtesy of Katz, Marchal, & Soubiran Gaia at HST Calibration Workshop Elena Pancino Baltimore August 2014 INAF- Bologna Observatory

  15. Second part:Commissioning update

  16. (1) Gaia brightness • Optical tracking necessary for attaining max performance • Gaia is 3 mags fainter than expected (V≈20.5 mag) • The GBOT group negotiated time at 2-4m telescopes Gaia seen by ESO-VST, image courtesy ESO Gaia at HST Calibration Workshop Elena Pancino Baltimore August 2014 INAF- Bologna Observatory

  17. (2) L2 environment • Large hits ok, small hits orders of mag more frequent than expected • Attitude control system copes very well with this dusty environment • Attitude modeling more complex – some noise at bright end Micro-meteoroid hit, courtesy van Leeuwen Gaia at HST Calibration Workshop Elena Pancino Baltimore August 2014 INAF- Bologna Observatory

  18. (3) Stray light • Higher than expected backround levels, varying with time • Caused by scattered sunlight, affecting mostly faint sources • The solution is a redesign of the background treatment software Sun light dominates SAA = 0° (commissioning maneuver) night sky dominates SAA = 45° (nominal operation angle) Figures by Davidson Gaia at HST Calibration Workshop Elena Pancino Baltimore August 2014 INAF- Bologna Observatory

  19. (4) Contamination 1st decontamination • Response loss (water ice) – heating to decontaminate • Unintended outgassing path from service to payload module 2nd decontamination Figure by Fabricius Gaia at HST Calibration Workshop Elena Pancino Baltimore August 2014 INAF- Bologna Observatory

  20. (5) BAM variations • The BAM measures 6h variations - some are confirmed – open issue 1 day astro solution BAM measurements Figure by First Look Team Gaia at HST Calibration Workshop Elena Pancino Baltimore August 2014 INAF- Bologna Observatory

  21. Gaia status summary • Five unexpected issues emerged after commissioning • Two are minor (GBOT and L2 dust) • Three have an impact on Gaia performances • Stray light, contamination, BAM variations • Excellent maneuvers from launch to L2 orbit insertion • We have a good propellant reservoir for the future • Some minor micro-thruster problems • Service module commissioning ok • The downlink allows for highdata rate • The rubidium clock and GB phased array antennaes are ok • Payload module works well (Electronics, CCDs, optics) • Gaia -> ESOC -> DPAC chain working excellently so far Gaia at HST Calibration Workshop Elena Pancino Baltimore August 2014 INAF- Bologna Observatory

  22. Third part:Flux calibration

  23. Gaia flux calibration Ground processing On-board pre-processing Internal Calibration (internal standards) External Calibration (external standards) Gaia at HST Calibration Workshop Elena Pancino Baltimore August 2014 INAF- Bologna Observatory

  24. External calibration model Gaia obs SED Instrument LSF • In matricial form: • Sobs =D x Strue • Strue = D-1x Sobs • Two problems: • Matrix is rectangular • Stars ≠ orthogonal set • You need many (200) stars of different spectral types • with <1% calibration wrt Vega Sample Wavelength Gaia at HST Calibration Workshop Elena Pancino Baltimore August 2014 INAF- Bologna Observatory

  25. SPSS observing campaign • 450 nights at 6 telescopes, • started in 2006 (end 2015) • Four campaigns • Spectroscopy (R≈2000) • Absolute photometry • Constancy monitoring (>10 mmag) • Short term (2 h) • Long term (3 yrs) • 215 remaining candidates • From CALSPEC & literature • One CALSPEC variable found • Preliminary results published • (Pancino et al., 2012) BFOSC@Cassini, Loiano EFOSC2@NTT, La Silla ROSS@REM, La Silla Dolores@TNG, La Palma CAFOS@2.2m, Calar Alto LaRuca@1.5m, San Pedro Martir Gaia at HST Calibration Workshop Elena Pancino Baltimore August 2014 INAF- Bologna Observatory

  26. Data analysis Gaia at HST Calibration Workshop Elena Pancino Baltimore August 2014 INAF- Bologna Observatory

  27. The pre-launch (internal) release • October 2013 • 94 SPSS • Photometric sky • Pipeline testing • Quality • <1% central • Red: fringing (10%) • Blue: noisy (3-5%) • To do for borders • 330-1050 nm • More S/N • Models extension Gaia at HST Calibration Workshop Elena Pancino Baltimore August 2014 INAF- Bologna Observatory

  28. Next steps • First Gaia release expected 2017 – SPSS release in 2016 • Will build on the best 94 SPSS increasing their quality • Later releases will expand on the number of SPSS as well • Data will be available @ ASDC archive (under works) • 100000 raw frames + 3000 calibration masterframes Gaia at HST Calibration Workshop Elena Pancino Baltimore August 2014 INAF- Bologna Observatory

  29. That’s all,Thank you!

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