What is the “Quality Assessment” (QA)?
In order to interpret the quality of the extractions, KOA has an automated
“quality assessment” (QA) grade, that uses the number of errors in
fitting the object profile and the number of pixels rejected during sky fitting.
The automated nature of this grading process is imperfect, so even the grade
may not be correct in the archive. Grading is done order-by-order, and the large
number of orders in the archive discourage manual grading of each order.
The automatic QA grade is either a “P” for “pass” or
“F” for “fail”. A “pass” means that reduction
artifacts, while they may be present, do not obscure the underlying astronomical
data. A “fail” means that no sign of the underlying data is visible
in the extraction; it is dominated by reduction artifacts.
Visual inspection of a random sample of HIRES orders, and comparison of the
visual grades with the automated grades, indicate that the automated grading
system does a good job on the “pass” grades; only 1.7% of the
visually graded passes were erroneously graded “fail”. Of the
visually graded 5s, 64.3% were erroneously graded “pass,”
indicating that the automated system does not provide a real good indication
of poor reduction. This emphasizes the need to inspect the browse products,
and perhaps the raw images themselves, to make a good determination of the
quality of the browse product in KOA.
The automated grades for each order are shown in a table on the
“Extracted Spectra” Web page.