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 on 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 w w w . c ● 5 years of operations at L2 o s m o s . e s a . i ● First intermediate data release n t / g a i a summer 2016, but Science Alerts start earlier 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 Figure courtesy Alex Short 104.26cm Blue Photometer CCDs Red Photometer CCDs 42.35cm Image motion Wave Front Sensor Wave Front Radial Velocity Sensor Spectrometer CCDs Basic Angle Monitor Basic Angle Monitor Sky Mapper Astrometric Field CCDs CCDs Total field: Sky mappers Photometry - active area 0 . 75 deg 2 - detect all objects to G = 20 - prism spectra - CCDs 106 = 14 + 62 + 14 + 12 (+ 4 ) - rejection cosmic rays - blue and red CCDs - 4500 × 1966 pixels (TDI) - field-of-view discrimination Spectroscopy - pixel size = 10 × 30 µ m 2 = 59 × 177 mas 2 Astrometry - high-resolution spectra - total detection noise ∼ 6e − - 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 Detailed report: GAIA-CO-TN-LEI-AB-052 Sky coverage Feb 7 to May 24 IDT team @ University of Barcelona 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 Calibrated spectra on the 3 AL RVS CCD for a K-type star internalApparentGrvs = 5.50 10000 Flux (photoelectron/sample) strip 1 8000 Early result from automated RVS 6000 processing RV(dir) = -68.89 +- 3.17 RV(fou) = -69.30 +- 1.87 RV(mdm) = -68.68 +- 0.07 4000 2000 Spectroscopic Radial Velocity = -68.89 +- 3.17 km/s 0 840 850 860 870 880 10000 Flux (Photoelectron/sample) strip 2 8000 6000 4000 2000 0 840 850 860 870 880 10000 Flux (Photoelectron/sample) strip 3 8000 6000 4000 Credits: ESA/Gaia/DPAC/CNES/Yves Viala 2000 and Francoise Crifo 0 840 850 860 870 880 Wavelength (nm) 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 time → ● Strong stray light levels all Flux [e − /pix/s] over focal plane ● In the peaks orders of magnitude above SAA = 45 ◦ requirements ● Sun light diffracted and/or scattered at sun-shield edges Varies over 6 hour spin ◮ Night sky dominates period ● Light from night sky sources along unforeseen paths Varies according to sky ◮ scanned Sun dominates SAA = 0 ◦ Figures by M. Davidson Place - Date - 21/43
Throughput loss SP6 SP1 FoV 1 0.3 FoV 2 Figure by C. Fabricius Decon 1 (FOV2) 0.2 Response loss [mag] 0.1 Decon 2 Decon 4 0.0 Decon 3 -0.1 260 380 500 620 740 860 980 1100 1220 1340 1460 OBMT [rev] 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 AF FoV1 AF FoV2 Figure by FL Scientist team BP FoV1 BP FoV2 PE analyses 0.02 RP FoV1 RP FoV2 ◆ Modelling effects of ice on mirrors 0.0 XP spectral signatures ◮ image quality ◮ FFF , Fov f ∆ G rev τ -0.02 ◆ Optimization of the decontamination -0.04 procedure -0.06 heating all mirrors ◮ seems necessary -0.08 -0.1 1320 1340 1360 1380 1400 1420 1440 1460 OBMT [rev] ● Throughput loss in AF, BP, and RP (FLS report 2014-10-28) ● Future decontamination campaigns unavoidable Not clear at the moment how many more ◮ Place - Date - 24/43
Basic angle variations → Time [spin period] 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 -55 -55 -60 -60 -65 -65 white-light fringe -70 experiment -70 BA variation according to ODAS → BA variation [mas] -75 -75 ∆( δγ ) [mas] -80 -80 slew to NSL -85 -85 -90 -90 -95 -95 Figure by First Look team -100 -100 BA variation according to BAM -105 -105 -110 -110 18 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 19 20 21 22 0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 6000 6500 7000 no of 5-minute-interval ● 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 µ as level or better Place - Date - 25/43
● Gaia data processing is a Pan-European cooperation Academic institutions and ◮ national space agencies Supported through ◮ national funding Processing power spread ◮ DPAC over 6 centres participating countries October 2013 SOC/DPCE integral part ◮ 450 members of DPAC Including: BR DPCI CA DZ ESA IL DPCG US DPCC DPCT DPCB DPCE
DPAC overview Upstream Downstream CU5 CU4 Photometric Telemetry Complex object ESOC processing processing Cambridge CNES CU3 CU3 CU7 Initial Data Treatment Astrometric core MDB Variability analysis First Look processing ESAC Geneva/ISDC ESAC ESAC/Torino CU1 CU3 System/IT Intermediate Data Update CU6 CU8 architecture Barcelona Spectroscopic Astrophysical processing characterization CNES CNES CU2 Simulations Barcelona/CNES CU9 Alerts Archive and Transients, new SSOs, . . . Catalogue access Cambridge/CNES ESAC Place - Date - 27/43
Recommend
More recommend
