Quality Control and
Data Processing

General information

PIPELINES AT ESO

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.

FUNCTIONALITIES

The main functionalities of the pipelines are:

• create master calibration data,
• reduce science frames,
• extract QC information from the data.

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

OPERATIONS

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 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.

GRAVITY part

The GRAVITY pipeline is publicly available here. Under this link you also find the pipeline Users Manual.

Raw Data

GRAVITY has three detectors: for the acquisition camera, for the science camera (SC), and for the fringe tracker camera (FT). File sizes depend on the used spectral resolution, the polarimetry mode, and on the number of the individual exposures (NDIT).

The SC detector has a windowed read-out so that only the actually used detector areas are stored depending on resolution and polarimetry mode (see table). From the FT detector, only few pixels at the fringe positions are saved in a binary table.

resolution	polarimetry	SC read-out window	SC read-out (until Dec. 2016)
low	split	50 x 606	50 x 241
low	combined	50 x 288	50 x 121
medium	split	360 x 606	360 x 337
medium	combined	360 x 288	360 x 169
high	split	2048 x 606	2048 x 606
high	combined	2048 x 606	2048 x 384

Extensions

Raw data come as FITS files with one primary header unit (HDU) and twelve extensions. 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. All data are stored in the extensions. The following table gives an overview of the content.

HDU	EXTNAME	data type	description
0	n/a	n/a	primary HDU, empty data part
1	ARRAY_DESCRIPTION	binary table	general description of telescopes, stations, and optical components of the inteferometer
2	ARRAY_GEOMETRY	binary table	description of actually used telescope array
3	OPTICAL_TRAIN	binary table	description of actually used optical components
4	IMAGING_DATA_ACQ	image	data cube with NDIT (typically NDIT=1) images from acquisition camera
5	IMAGING_DATA_SC	image	data cube with NDIT images from SC camera
6	IMAGING_DETECTOR_SC	binary table	fringe positions on SC detector
7	OPDC	binary table	OPD data
8	FDDL	binary table	delay line data
9	METROLOGY	binary table	metrology data
10	IMAGING_DATA_FT	binary table	binary table with pixel values from FT detector
11	IMAGING_DETECTOR_FT	binary table	fringe positions on FT detector
12	ACQ_ABS_REF_POSITION	binary table	reference position

Products

Pipeline products also have extensions which contain binary tables or pixel data. The actual format is highly individual to each pipeline recipe.