MSC -- KI V^2 Data Products

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KI V² Data Products

Spectrometer (.spec) File

Spectrometer files are ASCII text files that contain the narrow-band L-1 V² data for KI. The following gives an example of a line from a KI summary file:

SPEC ../../../2001/05:46:51 5.780970 HDC202240         5.965783  40.000000  0.837  500  0 KI_K1K2      
4 2.400  175.8 0.645 0.482 1.200 2.300  195.8 0.569 0.420 1.200 2.200 189.1 0.507 0.369 1.200   
2.100 122.7 0.488 0.343 1.200

The line consists of a number of space-delimited fields. The meanings of these fields are summarized in the table below. Each line corresponds to a block average of data (typically 5 to 25 seconds of fringe data, not necessarily contiguous). All entries, including time and delay line position, are mean values for the block. A # as the leading character indicates a comment.

field#

content

comments

1
SPEC

File identifier. Each line starts with SPEC to support the grep extraction mechanism from the intermediate data file produced by the L1 reduction code (Kvis).

2
observation date

UTC date of the observation (../../../yyyy/hh:mm:ss)

3
observation time

Mean observation time (decimal UTC hours)

4
source designation

Source designation (ASCII string)

5
FDL optical path

Mean fast delay line optical path difference (m)

6
LDL optical path

Mean long delay line optical path difference (m)

7
phase jitter

RMS phase difference between consecutive fringe sample (radians)

8
frame rate

Fringe tracker rate (Hz)

9
cal flag

Internal calibration quality flag (*)

10
baseline

Baseline name

11
number of SPEC channels

Number of spectrometer channels

field#	content	comments
1	SPEC	File identifier. Each line starts with SPEC to support the grep extraction mechanism from the intermediate data file produced by the L1 reduction code (Kvis).
2	observation date	UTC date of the observation (../../../yyyy/hh:mm:ss)
3	observation time	Mean observation time (decimal UTC hours)
4	source designation	Source designation (ASCII string)
5	FDL optical path	Mean fast delay line optical path difference (m)
6	LDL optical path	Mean long delay line optical path difference (m)
7	phase jitter	RMS phase difference between consecutive fringe sample (radians)
8	frame rate	Fringe tracker rate (Hz)
9	cal flag	Internal calibration quality flag (*)
10	baseline	Baseline name
11	number of SPEC channels	Number of spectrometer channels

Then, for each pixel ("channel") i (1..n), the following fields are given:

field#

content

comments

12 + 5*(i - 1)

wavelength

Wavelength (microns)

13 + 5*(i - 1)

flux

Spectrometer channel flux. DN units (approximately 5 photons/DN)

14 + 5*(i-1)

Incoherent V²

Spectrometer channel incoherent visibility squared (dimensionless)

15 + 5*(i - 1)

Coherent V²

Spectrometer channel coherent visibility squared (dimensionless)

16 + 5*(i-1)

ratio correction

Spectrometer channel V² ratio correction (dimensionless)

field#	content	comments
12 + 5*(i - 1)	wavelength	Wavelength (microns)
13 + 5*(i - 1)	flux	Spectrometer channel flux. DN units (approximately 5 photons/DN)
14 + 5*(i-1)	Incoherent V²	Spectrometer channel incoherent visibility squared (dimensionless)
15 + 5*(i - 1)	Coherent V²	Spectrometer channel coherent visibility squared (dimensionless)
16 + 5*(i-1)	ratio correction	Spectrometer channel V² ratio correction (dimensionless)

(*) The calibration flag has the following possible values:

0: OK
1: time difference between fringe data and background > CalTime
2: time difference between foreground and ratio data > CalTime
3: both 1 and 2 true
4: no ratio data exists within CalTime
5: both 1 and 4 true

where CalTime = 10 minutes.