AFxMeasurement¶

class lsst.validate.drp.calcsrd.AFxMeasurement(x, matchedDataset, amx, bandpass, specName, verbose=False, job=None, linkedBlobs=None, metricYamlDoc=None, metricYamlPath=None)[source]¶

Bases: lsst.validate.drp.base.MeasurementBase

Measurement of AFx (x=1,2,3): The maximum fraction of astrometric distances which deviate by more than ADx milliarcsec (see AMx) (%).

Parameters:

x : int

Variant of AMx metric (x=1, 2, 3), which in turn sets the radius of the annulus for selecting pairs of stars.

matchedDataset : lsst.validate.drp.matchreduce.MatchedMultiVisitDataset

amx : lsst.validate.drp.calcsrd.AMxMeasurement

And AMx measurement, providing the median astrometric scatter in the annulus.

bandpass : str

Bandpass (filter name) used in this measurement (e.g., ‘r’).

specName : str

Name of a specification level to measure against (e.g., design, minimum, stretch).

verbose : bool, optional

Output additional information on the analysis steps.

job : lsst.validate.drp.base.Job, optional

If provided, the measurement will register itself with the Job object.

linkedBlobs : dict, optional

A dict of additional blobs (subclasses of BlobBase) that can provide additional context to the measurement, though aren’t direct dependencies of the computation (e.g., `matchedDataset).

Raises:

ValueError

If x isn’t in [1, 2, 3].

Notes

This table below is provided validate_drp‘s metrics.yaml.

LPM-17 dated 2011-07-06

Specification:: The rms of the astrometric distance distribution for stellar pairs with separation of D arcmin (repeatability) will not exceed AMx milliarcsec (median distribution for a large number of sources). No more than AFx % of the sample will deviate by more than ADx milliarcsec from the median. AMx, AFx, and ADx are specified for D=5, 20 and 200 arcmin for x= 1, 2, and 3, in the same order (Table 18).

The three selected characteristic distances reflect the size of an individual sensor, a raft, and the camera. The required median astrometric precision is driven by the desire to achieve a proper motion accuracy of 0.2 mas/yr and parallax accuracy of 1.0 mas over the course of the survey. These two requirements correspond to relative astrometric precision for a single image of 10 mas (per coordinate).

Astrometric Repeatability	Specification
Metric	Design	Minimum	Stretch
AM1 (milliarcsec)	10	20	5
AF1 (%)	10	20	5
AD1 (milliarcsec)	20	40	10
AM2 (milliarcsec)	10	20	5
AF2 (%)	10	20	5
AD2 (milliarcsec)	20	40	10
AM3 (milliarcsec)	15	30	10
AF3 (%)	10	20	5
AD3 (milliarcsec)	30	50	20

Table 18: The specifications for astrometric precision. The three blocks of values correspond to D=5, 20 and 200 arcmin, and to astrometric measurements performed in the r and i bands.

Attributes Summary

`label`
`metric`
`units`
`value`

Attributes Documentation

label = 'AFx'¶

metric = None¶

units = ''¶

value = None¶