This page provides informations about the MIDI raw data and the status of the MIDI pipeline.

Data from MIDI are stored as FITS binary table files using generalized Optical/IR interferometry conventions. Find informations about this format here. More details can also be found in this document.

The reduction of MIDI data at Paranal and at QC Garching is done in an automatic manner. Only the raw data from a scientific object or an astronomical calibrator obtained with the instrument mode HIGH SENS are processed by the pipeline. All the supported P75 observations will be done using this instrument mode. Find general information about ESO reduction pipelines here.

All P75 data are taken in HIGH-SENS mode with the PRISM or the GRISM (more informations about this mode).

A set of raw data taken in HIGH-SENS mode includes :

• acquisition frames,
• fringe-search files (splitted in several raw files),
• fringe-track files (splitted in several raw files),
• photometry files
• one file (containing no data) marking the end of the template.

The following table shows some of the main keywords for the different raw files

The category of the file is set with the DPR CATG keyword in the primary header of the fringe-track FITS file.

Two different types of files carry a DPR CATG=CALIB :

• Technical and detector calibrations
• all the files associated to an astronomical calibrator.

All the files with a DPR CATG=CALIB are not proprietary and will be available from the science archive.

Only the files associated with a science target carry a DPR CATG=SCIENCE. This includes the target acquisition, the fringe search and the fringe track files.

The raw data taken with the VLTI are processed twice :

• at the VLTI complex on Paranal, using a fully automatic mode, and allowing the astronomer to have a quick look at the data and for on-site quality control,
• at the headquaters in Garching. This processing is done on full nights and is optimized for the data taken on astronomical calibrators. The quality of the results on the astronomical calibrators is assessed. The science data taken in service mode are then processed. Each product is named following some rules (product_codes.html for the calibration files and using the time stamp of the first raw file processed for the science product).

As of now (May 2005) the pipeline delivered Visibilities in dispersed mode (calibrated or not) in the HIGH_SENS - PRISM or GRISM mode.

The pipeline supported modes for P75 are the data taken with the template : MIDI_starintf_obs_fringe. These two templates concerned SCIENCE and CALIB objects taken in HIGH_SENS instrument mode using the PRISM or the GRISM. The following table shows the type of files and the pipeline recipes used to reduce them. More details on the pipeline recipes can be found here. More on the file associations can be found here.

The delivered products are in format of ASCII files in the logs directory of the Data Package (pipeline QC log and .paf files: duplication of the primary header of the product FITS), and FITS file. In both cases, the files contains informations about the instrument setup, the atmosphere at the time of the observation, various VLTI parameters, and the raw visibilities. In the case of a CALIB observation, parameters about the calibrator are added (estimated diameter, associated error, measured transfer function), while in the case of a SCIENCE observation, the product contains the calibrated visibility points, the value of the TF applied and informations about the CALIB observation used to calibrate the data (name of the CALIB product).