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

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
Data flow overview
OS/ICS
STS
OB
RAW
GUIDING IMAGES
instrument machine
observer machine
TCS
telescope machine
Trigger + DRS
REDUCED
RAW
reduction machine
,, …
DAU
Interfaces
Short-time scheduler
Set of parameters (coordinates,
observing mode, etc.)
OS / ICS
Raw frame with FITS header
Trigger / DRS
Telescope
parameters
TCS
The RITZ control room
The short-time scheduler (STS)
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
The online pipeline (trigger + DRS)
The offline trigger + DRS
Data reduction software
Major reduction steps for science raw frames:
1. Bias and dark subtraction
2. Order extraction with cosmic rejection
3. Flat-fielding
4. Wavelength calibration
5. Barycentric correction
6. Merging and rebinning of the orders
7. Cross-correlation with stellar template
8. Radial velocity and CCF bisector computation
9. Instrumental drift correction (if applicable)
10. Creation of reduced data products (FITS format)
Data reduction software
RAW
CALIBRATION
FRAME
Instrument + DRS
configuration files
RAW
SCIENCE
FRAME
Calibration recipes:
bias & dark, order definition,
flat-fielding, wavelength
calibration
Calibration database
Science recipes:
object+sim. reference,
object+sky, object only
REDUCED
CALIBRATION
FRAMES
Log files
REDUCED
SCIENCE
FRAMES
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)
- Raw frames
transportable
media
- Reduced frames
Data archive
Cambridge / Geneva
- Log files
- Guiding images
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