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Quality Control and
Data Processing

CAL | HC | refs | QC
Trending & QC1
general info
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General information | Data format

General information


Pipelines are used at ESO to process both calibration data and science data and to retrieve quality information. There is a dedicated pipeline for each VLT and VLTI instrument. Find general information about ESO reduction pipelines here.


The main functionalities of the pipelines are:

  • create master calibration data,
  • reduce science frames,
  • extract QC information from the data.
QC Garching creates master calibration data from all raw calibration data. The raw data are stored in the ESO Archive and are public. They are quality-checked and used for data reduction and for trending.

For selected instrument modes, we offer science-grade data products processed with the pipelines.


There are two instances of the data reduction pipelines:

  • at the instrument workstation on Paranal, running in automatic mode,
  • at HQ Garching, run by the Quality Control Group in the optimized mode.
The automatic mode is used for quick look and for on-site quality control. It processes all raw data sequentially, as they arrive from the instrument. If calibration products ("master calibrations") are required for processing science data, these are taken from a database with standard, pre-manufactured calibration products. The automatic mode is not tuned to obtain the best possible results.

The optimized mode is the mode, which uses all data of a night, including the daytime calibrations. The calibration data are sorted and grouped according to their dependencies. Master calibration data are created. Their quality is checked.

Data format
General information | Data format

Raw Data

The ESPRESSO detector consists of two e2v CCDs, each with 9216x9232 optically active pixels.

file type binning size of raw file
calibration or science frame 1x1 352 MB
calibration or science frame 2x1 176 MB
calibration or science frame 4x2 44 MB
calibration or science frame 8x4 11 MB


Raw calibration and science data come as FITS files with one primary header unit (HDU) and at least two extensions, one for each chip. The primary HDU has all keywords necessary to identify the observation and the state of the telescope and the instrument; the data part is empty. Pixel data are stored in the extensions.

Observations of standard stars and of science targets have additional extensions which contain data from the exposure meter (as binary table) and integrated images of the fibre heads. The size of these extensions is negligible compared to the first two extensions.

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