KI V2 -- Description of Quality Assessment (QA) grade
Each sum line should have a single QA metric which can be
used for data evaluation and selection in the Level 2 calibration.
The current QA system calculates percentile scores for a list of data
attributes at the sum, integration and nightly levels (see
http://msc.caltech.edu/KISuppo../../../QAoverview.html). The grade
is designed to incorporate this information as well as other
factors to assign a value that less experienced interferometry
users can use in calibrating their data.
Similar to 2MASS, each grade will be a 3 digit field where the digits
run from 0 to 3 with the following meanings:
0 = good data with no known issues or problems
1 = fair data which may have minor issues but will still calibrate normally
2 = poor data (weather or instrument) that will need very careful calibration
3 = data severely comprised by weather or instrument problems, should only
be used with extreme caution
Each digit will represent a given time span:
1st: this record
2nd: this integration
3rd: this night
Thus the 2nd digit will be the same for all records in an integration
and the 3rd digit will be the same for all records in a night.
The grades will NOT be normalized. That is, there will be no effort
to make 1/4 of the grades be 0.
The grades digit assignment will have two phases. In the first
phase, a preliminary grade will be assigned at each level
based on the percentile scores from that level.
Preliminary grade assignment
In the preliminary grade assignment, each level attribute contributes
to the grade. This is derived simply from the percentile score with
the data in the top 25% getting a grade of 0, data in the middle 50%
getting a grade of 1 and data in the lowest 25% getting a grade of 2.
The flux attribute is not included in this calculation.
The preliminary grade at each level is the (rounded) average of
the attribute grades.
In the second phase, the preliminary grades are modified based on data
aspects not covered by the QA percentiles, or by absolute values
for some attributes which we know to be bad.
These modifications are given for each level
- Modifications based on cal flag value
cal flag grade
0 or 1 no change
2 thru 5 grade = 2 (unless was already a 3)
- Mofications based on ratio value
ratio correction < 1 grade = 3
ratio correction > 2 grade = 3
- Modifications based on numerically bad values
photon flux < 0 grade = 3
V2 < 0 grade = 3
V2 > 2 grade = 3
- The integration grade must be equal to or greater than the average
- If integration is a science target and no calibration data are
available within a specified interval, the grade is set as given below:
+/- 30 minutes grade = 2
+/- 1 hour grade = 3
- Modications based on ratio value
mean ratio correction < 1 grade = 3
mean ratio correction > 2 grade = 3
- Modifications based on numbers of records in this scan
(Note: the nominal number of records per scan is 25)
number of records = nr
nr >= 15 no change
7 >= nr > 15 grade = grade - 1
nr < 7 grade = grade - 2
- The night grade must be equal to or greater than the average
In exceptional circumstances, grades will be modified as needed by
the V2 contact scientist to reflect instrument problems. In general
this will apply to whole integrations and nights only.
Return to the KI Support page
Return to QA Overview
last updated Mar 30, 2005