ParallaxCoverageMetric¶
- class rubin_sim.maf.metrics.ParallaxCoverageMetric(metric_name='ParallaxCoverageMetric', m5_col='fiveSigmaDepth', mjd_col='observationStartMJD', filter_col='filter', seeing_col='seeingFwhmGeom', rmag=20.0, sed_template='flat', atm_err=0.01, theta_range=0.0, snr_limit=5, **kwargs)¶
Bases:
BaseMetric
Check how well the parallax factor is distributed. Subtracts the weighted mean position of the parallax offsets, then computes the weighted mean radius of the points. If points are well distributed, the mean radius will be near 1. If phase coverage is bad, radius will be close to zero.
For points on the Ecliptic, uniform sampling should result in a metric value of ~0.5. At the poles, uniform sampling would result in a metric value of ~1. Conceptually, it is helpful to remember that the parallax motion of a star at the pole is a (nearly circular) ellipse while the motion of a star on the ecliptic is a straight line. Thus, any pair of observations separated by 6 months will give the full parallax range for a star on the pole but only observations on very specific dates will give the full range for a star on the ecliptic.
Optionally also demand that there are observations above the snr_limit kwarg spanning theta_range radians.
- Parameters:
- m5_col: str, optional
Column name for individual visit m5. Default fiveSigmaDepth.
- mjd_col: str, optional
Column name for exposure time dates. Default observationStartMJD.
- filter_col: str, optional
Column name for filter. Default filter.
- seeing_col: str, optional
Column name for seeing (assumed FWHM). Default seeingFwhmGeom.
- rmag: float, optional
Magnitude of fiducial star in r filter. Other filters are scaled using sedTemplate keyword. Default 20.0
- sedTemplate: str, optional
Template to use (can be ‘flat’ or ‘O’,’B’,’A’,’F’,’G’,’K’,’M’). Default ‘flat’.
- atm_err: float, optional
Centroiding error due to atmosphere in arcsec. Default 0.01 (arcseconds).
- theta_range: float, optional
Range of parallax offset angles to demand (in radians). Default=0 (means no range requirement).
- snr_limit: float, optional
Only include points above the snr_limit when computing theta_range. Default 5.
- Returns:
- metricValue: float
Returns a weighted mean of the length of the parallax factor vectors. Values near 1 imply that the points are well distributed. Values near 0 imply that the parallax phase coverage is bad. Near the ecliptic, uniform sampling results in metric values of about 0.5.
Notes
Uses the ParallaxFactor stacker to calculate ra_pi_amp and dec_pi_amp.
Methods Summary
run
(data_slice[, slice_point])Calculate metric values.
Methods Documentation
- run(data_slice, slice_point=None)¶
Calculate metric values.
- Parameters:
- data_slice
numpy.recarray
Values passed to metric by the slicer, which the metric will use to calculate metric values at each slice_point.
- slice_point
dict
or None Dictionary of slice_point metadata passed to each metric. E.g. the ra/dec of the healpix pixel or opsim fieldId.
- data_slice
- Returns: