PTI Data Overview and Access

Data Flow

  • PTI raw data were processed into fringe amplitudes and other necessary information by a program called vis. The algorithms and applied calibrations are described in detail in this paper This processing was done automatically at the end of each observing night.
  • The output of this reduction is called Level 1 data, i.e. fringe data that have been corrected for detector biases and averaged, but not yet corrected for the system visibility.
  • The Level 1 data are contained in a group of files, described in detail in the links below. The primary data files are called .sum and .spec files and contain the wideband (or white light) and narrow band data respectively. The prefix for Level 1 files is the UT observation date in the form yyyyddd.
  • The sum and spec files also contain all other information (delay line positions, time, etc.) needed to calibrate the data for the system visibility (by the programs wbCalib and nbCalib as described below).
  • Other Level 1 files contain other instrument information such as the baseline (.baseline).
  • Once the PTI user has obtained his/her Level 1 data for science targets and corresponding calibrators, the programs wbCalib and nbCalib take these files as input in order to produce fully calibrated data (Level 2 files). At this time, PTI users must calibrate their own data, a task that is greatly simplified if making use of our calibration packages, which may be obtained from our software download page. A guide to calibrating PTI data using these programs is available here.

Data access

The Level 1 data are available online and can be downloaded for a single observation day, an entire year, or all the PTI data. The proprietary period for all data has ended.

Interferometer modes

Although PTI operates in several modes, only visibility amplitude (also called V 2 or NIRV2) data are publicly available.

Formats for L1 and L2 files

The PTI Level 1 and Level 2 data are available in both FITS and ASCII formats. The following links detail the file format in each case:

Quality Assessment

As part of the Level 1 file set, we include information which characterizes the data quality at different levels. For details, please consult the QA description page.

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last updated April 5, 2013