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Overview of HARPS-N Data Flow System and Processing Framework

The HARPS-N Data Flow System, presented by Christophe Lovis from Geneva Observatory, outlines the comprehensive workflow for managing astronomical observations on December 6-7, 2007, in Cambridge, MA. Key components include the real-time short-time scheduling of observations, systematic calibration procedures, data reduction methodologies, and archiving techniques. The presentation emphasizes the importance of precise coordination between the instrument, observer, and telescope for optimal data quality. Future enhancements to the Data Reduction Software (DRS) and archival processes are also discussed to adapt to evolving scientific demands.

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Overview of HARPS-N Data Flow System and Processing Framework

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  1. HARPS-N PDR, 6-7 December 2007, Cambridge MA HARPS Data Flow System Christophe Lovis Geneva Observatory

  2. Outline • Data flow overview • Short-time scheduler • Calibrations and observations • Data reduction software • Archiving • Data reprocessing and analysis • Some important points

  3. instrument machine observer machine telescope machine GUIDING reduction machine Data flow overview OS/ICS STS OB ,, … TCS RAW GUIDING IMAGES RAW Trigger + DRS REDUCED DAU RAW

  4. Set of parameters (coordinates, observing mode, etc.) Telescope parameters Raw frame with FITS header Interfaces Short-time scheduler TCS OS / ICS Trigger / DRS

  5. The RITZ control room

  6. The short-time scheduler (STS)

  7. The short-time scheduler (STS) • Real-time scheduling of observations • Possibility to prepare the night in advance • Easy-to-use cut-and-paste graphical interface • Input from catalogues: object name, coordinates, proper motion, approximate RV, spectral type, observing mode, desired SNR • Real-time computation of observing conditions (position on the sky, airmass, moon, …) • Exposure time computation using built-in ETC

  8. Calibrations and observations • « Standard calibration » sequence to be executed at the beginning of each night: • Bias measurement • Order localization • Flat-fielding • Wavelength calibration • Observations can be made in 3 different modes: • Object + simultaneous reference • Object + sky • Object only • -> Preparation of calibration and observation plan

  9. The online pipeline (trigger + DRS)

  10. The offline trigger + DRS

  11. Data reduction software • Major reduction steps for science raw frames: • Bias and dark subtraction • Order extraction with cosmic rejection • Flat-fielding • Wavelength calibration • Barycentric correction • Merging and rebinning of the orders • Cross-correlation with stellar template • Radial velocity and CCF bisector computation • Instrumental drift correction (if applicable) • Creation of reduced data products (FITS format)

  12. Data reduction software Calibration recipes: bias & dark, order definition, flat-fielding, wavelength calibration RAW CALIBRATION FRAME REDUCED CALIBRATION FRAMES Instrument + DRS configuration files Log files Calibration database RAW SCIENCE FRAME REDUCED SCIENCE FRAMES Science recipes: object+sim. reference, object+sky, object only

  13. Data reduction software • Still to be done: • Adapt DRS to HARPS-N (spectral format, keywords, etc.) • Adapt wavelength calibration to laser comb / Fabry-Perot • Correct background / straylight pollution • Optimize reduction of low-SNR data • Improve instrumental drift computation • Update barycentric correction process • Optimize cross-correlation process • Develop/extend stellar diagnostics (Ca II H&K index, bisectors, study of individual line shapes/shifts, …)

  14. Data archiving unit (DAU) transportable media • Raw frames • Reduced frames • Log files • Guiding images Data archive Cambridge / Geneva FTP ?

  15. DRS updates and data reprocessing/analysis • DRS continuously improved and updated • Coherence of the data is essential! • Periodic global reprocessing of the whole archive to always have the best-quality data • Extraction of the relevant information from all FITS headers and creation of a global database • Use of external tools to search for planetary signals (period search, orbit fitting, genetic algorithms, significance tests, etc.)

  16. Some important points • For the project: • Precisely define all interfaces (STS – ICS, FITS headers, etc.) and if possible keep close to HARPS-S choices • Use PM counting to determine the photocenter of the exposure • Need for perfect guiding and record integrated guiding image • While observing: • Always keep an eye on the guiding! • Carefully check ALL target-related parameters (coordinates, spectral type, …) in the input catalogues to avoid any spurious RV effects

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