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HARPS-N PDR, 6-7 December 2007, Cambridge MA HARPS Data Flow System Christophe Lovis Geneva Observatory
Outline • Data flow overview • Short-time scheduler • Calibrations and observations • Data reduction software • Archiving • Data reprocessing and analysis • Some important points
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
Set of parameters (coordinates, observing mode, etc.) Telescope parameters Raw frame with FITS header Interfaces Short-time scheduler TCS OS / ICS Trigger / DRS
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
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
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)
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
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, …)
Data archiving unit (DAU) transportable media • Raw frames • Reduced frames • Log files • Guiding images Data archive Cambridge / Geneva FTP ?
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.)
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