Time terminology

The data processing in Kvis involves the following basic time units:

Sample

This is the time over which one complete measurement of a fringe is made (a complete set of zabcd data, see Sec. 2.3, including multiple reads if applicable) and is the level at which fringe data is recorded in the archive. A typical value is 5 msec, corresponding to a fringe tracker rate of 200 Hz. Kvis obtains the fringe tracker rate from the data and this rate is reported on the SUM and SPEC output line (Table 5). This rate is automatically extracted from the data.

Frame

Configurable length of time over which samples are combined. Spectrometer phases are referenced to the average WB phase over this time. This time is set in ini.params and has a default value of 0.1 sec. The visibility (V²) is computed using incoherent and coherent estimates for each channel. This time scales affects the coherent V² and generally should not be longer than 0.1 sec for KI data.

Block

Configurable length of time over which frames are combined. These data are recorded in the SUM and SPEC Kvis output (Sec. 3.4) for the wide-band and spectrometer channels respectively (and in the .sum and .spec Level 1 files). The squared visibility (V²) is calculated coherently and incoherently for the WL channel, a weighted average of the spectrometer channels, and individually for each spectrometer channel. This time is set in ini.params and has a default value of 5 sec.

Integration

Complete observation of a source, including all the calibrations discussed below, which typically contains 125 seconds of fringe data.