PTI raw data were processed into fringe amplitudes and other necessary information by a program called
The algorithms and applied calibrations are described in detail in
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
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
The Level 1 data are available
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.
Although PTI operates in several modes, only visibility amplitude (also
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:
As part of the Level 1 file set, we include information which
characterizes the data quality at different levels. For details, please
QA description page.
Return to PTI Support page
last updated April 5, 2013