In general, each scan is scored using a base quality number multiplied by two individual quality factors (score = base * photometric factor * sensitivity factor), as detailed below.
Scans with quality score > 3 are
loaded into the database.
- Base quality number (maximum of 10)
- For optimally dithered scans (after 970606n), base = 10
- For scans not optimally dithered (on or before 970606n), base = 5
-
Photometric quality factor (maximum of 1.0)
computed from mult1*mult2*mult3, where result is not to exceed mult4 - Downgraded if number of cal sets in block < 6 (old strategy) or 5 (new)
- Mult1 is computed from sqrt((number of cal sets)/6[or 5])
- Downgraded if dispersion in photometry for field stars> 0.04 mag
- Mult2 is computed from 2 - ((dispersion used)/0.04)
- Downgraded if dispersion in standard star photometry > 0.06 mag
- Mult3 is computed from 2 - ((dispersion used)/0.06)
- Downgraded if repeat differences in overlaps > 0.05 mag
- Mult4 = 1.0 if scatter in overlap differences is <0.050 mag
- Mult4 = 0.7 if scatter in overlap differences is 0.050-0.075 mag
- Mult4 = 0.4 if scatter in overlap differences is 0.075-0.100 mag
- Mult4 = 0.0 if scatter in overlap differences is >0.100 mag
- Sensitivity quality factor (maximum of 1.0)
- Downgraded if probability that sensitivity meets level-1 specs is <75%, as seen on qyymmddh.bg.see.ps plot
- For values falling above 75%, quality factor = 1.0
- For values falling between 50% and 75%, quality factor = 0.8
- For values falling between 25% and 50%, quality factor = 0.5
- For values falling between 0% and 25%, quality factor = 0.3
- For values falling below 0% line, quality factor = 0.1
Scans which would otherwise have higher scores are further demoted if any of the following problems are encountered:
QUALITY 0: Tiles for rescanning
- Photometric non-repeatability of sci scans:
- >0.10 mag uncertainty in overlaps for any pair of adjacent scans
- Photometric non-repeatability of cal scans:
- Dispersion in photometry of calibration field stars > 0.08 mag
- Large scatter in zero-point determination:
- Dispersion in photometric zero-point fit > 0.04 mag
- Uncertain photometric zero-point:
- Less than two valid calibration intervals
- RA slippage during scan:
- Double images produced (first seen on 970616n)
- Quadrant jumps in J array:
- Connector problems causing severe ADC offsets (first seen on 970714n; corrected on 970925n)
QUALITY 1: Not for database inclusion, but better than blank sky
- Severely degraded sensitivity:
- "Photometric" data with 0% chance of meeting level-1 sensitivity specs
- Severely elongated images:
- {band}rat2 > 1.17 or {band}rat2 < 0.77 for any band
QUALITY 2: Also not for database inclusion, but better than quality-1 data
- Galaxy extractions compromised:
- Untracked seeing