KI V2 data memos:
Level 1 file descriptions:
Incoherent V2 for the FATCAT white-light (WL) pixel. This is the basic V2 measurement, and this plot is useful for a quick assesment of the V2 data quality and to determine whether or not a given object is resolved, and by how much. Unresolved calibrators should have a V2 equal to the system visibility (V2 ~ 0.6 to 0.7) and resolved objects will have lower values of V2. An estimate of the calibrated V2 can be obtained by dividing the V2 measured on a target by the V2 measured on its calibrator(s) (if the calibrator(s) are resolved, then an additional correction will be necessary).
Same as (1) but based on an average of the V2 measured on the spectrometer pixels.
Same as (1) but using a coherent V2 estimator. See the Kvis manual for the algorithm defining the coherent estimator.
Same as (3) but based on an average of the spectrometer pixels.
Photon counts on the WL pixel. This plot is useful for assesing the overall flux throughput. For a given star and FATCAT frame rate, the flux trace should remain approximately constant. Large changes may indicate an alignment or weather (clouds) problem. The flux trace should scale appropriately (as long as FATCAT is below non-linear or saturation regime) with stellar magnitude (K-band or H-band, depending on which FATCAT filter is being used) and frame rate.
Same as (5) but for an average of the spectrometer pixels.
Angle tracker (KAT) flux (J-band), for the Keck-1 and Keck-2 beams.
Total optical delay introduced by the KI delay lines, and defined as (FDL - LDL), where FDL and LDL are the optical delays introduced by the long delay line and the fast delay line, respectively.
The rms of the points within the averaging time (typically 5 seconds) normalized by the photon count. The quantity is a measure of the amplitude stability of the fringe.
Ratio of Keck-2 beam to Keck-1 beam FATCAT Wideband fluxes.
The value of the correction factor that needs to be applied to the measured V2 to compensate for the loss of coherence due to flux mismatches between the Keck-1 and Keck-2 beams (for full details, see the memo on this topic in the links above).
Same as (10) but for an average of the spectrometer pixels.
Same as (11) but for an average of the spectrometer pixels.
The frame-to-frame RMS of fringe phase. This quantity will be high when the differential (between the Keck-1 and Keck-2 beams) optical path difference fluctuates significantly due to e.g. instrument vibrations and/or atmospheric piston. To the extent that it is dominated by atmospheric effects, it may used as a good indicator of seeing quality. A value of 0.8 radians or smaller is considered indicative of ``good'' conditions.
The number of times the fringe tracker looses/re-acquires lock during a block integration. If greater than 1, it indicates that fringe lock was lost frequently, and therefore the observing conditions may be marginal (e.g. low V2, low flux, bad seeing, bad AO or KAT locks).
The fractional time during the block (usually 5 seconds) in which the fringe tracker was locked. A minumum threshold of 0.5 for this value is used in the standard Kvis processing.
The visible flux counts (spectral sensitivity through I-band) on the AO wavefront sensors.
The readout rate of the AO wavefron sensors (Hz).
Observed object's elevation angle (degrees).
Observed object's azimuth angle (degrees).
Given the flux counts being detected by the fringe tracker (FATCAT), these are the counts that would be detected per msec from a star of 10th magnitude. This normalization is useful for comparing the instrument sensitivity across nights and runs. A unusually low value may indicate an alignment problem, or clouds. A typical value is 30 dn/msec/10thmag.
Same as above but for the angle tracker (KAT). A typical values is 150 dn/msec/10thmag.
Same as above but for the AO sensor. A typical values is 50 dn/msec/10thmag.