HARPS Data Flow System

Christophe LovisGeneva Observatory

HARPS-N PDR, 6-7 December 2007, Cambridge MA

Data flow overview

Short-time scheduler

Calibrations and observations

Data reduction software

Archiving

Data reprocessing and analysis

Some important points

Outline

STS OS/ICS

TCS

Trigger + DRS

instrument machineobserver machine

telescope machine

reduction machine

OB

,, …

RAW

GU

IDIN

G I

MA

GE

SDAU

RAW

REDUCED

Data flow overview

RA

W

GUIDING

Interfaces

Short-time scheduler

OS / ICS

Trigger / DRS

TCS

Set of parameters (coordinates, observing

mode, etc.)

Raw frame with FITS header

Telescope parameters

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

Calibration recipes:

bias & dark, order definition, flat-fielding, wavelength calibration

Science recipes:

object+sim. reference, object+sky, object only

Calibration databaseInstrument + DRS configuration files

Log files

RAW CALIBRATION

FRAME

RAW SCIENCE FRAME

REDUCED CALIBRATION

FRAMES

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

- Reduced frames

- Log files

- Guiding images

transportable media

FTP ?

Data archive Cambridge /

Geneva

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