lsst.pipe.tasks.computeExposureSummaryStats.ComputeExposureSummaryStatsTask Class Reference

Inheritance diagram for lsst.pipe.tasks.computeExposureSummaryStats.ComputeExposureSummaryStatsTask:

Public Member Functions
	__init__ (self, **kwargs)
	run (self, exposure, sources, background)
	update_psf_stats (self, summary, psf, bbox, sources=None, image_mask=None, image_ap_corr_map=None, sources_is_astropy=False)
	update_wcs_stats (self, summary, wcs, bbox, visitInfo)
	update_photo_calib_stats (self, summary, photo_calib)
	update_background_stats (self, summary, background)
	update_masked_image_stats (self, summary, masked_image)
	update_effective_time_stats (self, summary, exposure)
	update_magnitude_limit_stats (self, summary, exposure)

Static Public Attributes
	ConfigClass = ComputeExposureSummaryStatsConfig

Static Protected Attributes
str	_DefaultName = "computeExposureSummaryStats"

Detailed Description

Task to compute exposure summary statistics.

This task computes various quantities suitable for DPDD and other
downstream processing at the detector centers, including:
- expTime
- psfSigma
- psfArea
- psfIxx
- psfIyy
- psfIxy
- ra
- dec
- pixelScale (arcsec/pixel)
- zenithDistance
- zeroPoint
- skyBg
- skyNoise
- meanVar
- raCorners
- decCorners
- astromOffsetMean
- astromOffsetStd

These additional quantities are computed from the stars in the detector:
- psfStarDeltaE1Median
- psfStarDeltaE2Median
- psfStarDeltaE1Scatter
- psfStarDeltaE2Scatter
- psfStarDeltaSizeMedian
- psfStarDeltaSizeScatter
- psfStarScaledDeltaSizeScatter

These quantities are computed based on the PSF model and image mask
to assess the robustness of the PSF model across a given detector
(against, e.g., extrapolation instability):
- maxDistToNearestPsf
- psfTraceRadiusDelta
- psfApFluxDelta

This quantity is computed based on the aperture correction map, the
psfSigma, and the image mask to assess the robustness of the aperture
corrections across a given detector:
- psfApCorrSigmaScaledDelta

These quantities are computed based on the shape measurements of the
sources used in the PSF model to assess the image quality (i.e. as a
measure of the deviation from a circular shape):
- starEMedian
- starUnNormalizedEMedian

These quantities are computed to assess depth:
- effTime
- effTimePsfSigmaScale
- effTimeSkyBgScale
- effTimeZeroPointScale
- magLim

Definition at line 163 of file computeExposureSummaryStats.py.

Constructor & Destructor Documentation

__init__()

lsst.pipe.tasks.computeExposureSummaryStats.ComputeExposureSummaryStatsTask.__init__	(		self,
		**	kwargs )

Definition at line 224 of file computeExposureSummaryStats.py.

Member Function Documentation

run()

lsst.pipe.tasks.computeExposureSummaryStats.ComputeExposureSummaryStatsTask.run	(		self,
			exposure,
			sources,
			background )

Measure exposure statistics from the exposure, sources, and
background.

Parameters
----------
exposure : `lsst.afw.image.ExposureF`
sources : `lsst.afw.table.SourceCatalog`
background : `lsst.afw.math.BackgroundList`

Returns
-------
summary : `lsst.afw.image.ExposureSummary`

Definition at line 230 of file computeExposureSummaryStats.py.

update_background_stats()

lsst.pipe.tasks.computeExposureSummaryStats.ComputeExposureSummaryStatsTask.update_background_stats	(		self,
			summary,
			background )

Compute summary-statistic fields that depend only on the
background model.

Parameters
----------
summary : `lsst.afw.image.ExposureSummaryStats`
    Summary object to update in-place.
background : `lsst.afw.math.BackgroundList` or `None`
    Background model.  If `None`, all fields that depend on the
    background will be reset (generally to NaN).

Notes
-----
This does not include fields that depend on the background-subtracted
masked image; when the background changes, it should generally be
applied to the image and `update_masked_image_stats` should be called
as well.

Definition at line 531 of file computeExposureSummaryStats.py.

update_effective_time_stats()

lsst.pipe.tasks.computeExposureSummaryStats.ComputeExposureSummaryStatsTask.update_effective_time_stats	(		self,
			summary,
			exposure )

Compute effective exposure time statistics to estimate depth.

The effective exposure time is the equivalent shutter open
time that would be needed under nominal conditions to give the
same signal-to-noise for a point source as what is achieved by
the observation of interest. This metric combines measurements
of the point-spread function, the sky brightness, and the
transparency. It assumes that the observation is
sky-background dominated.

.. _teff_definitions:

The effective exposure time and its subcomponents are defined in [1]_.

References
----------

.. [1] Neilsen, E.H., Bernstein, G., Gruendl, R., and Kent, S. (2016).
       Limiting Magnitude, \tau, teff, and Image Quality in DES Year 1
       https://www.osti.gov/biblio/1250877/

Parameters
----------
summary : `lsst.afw.image.ExposureSummaryStats`
    Summary object to update in-place.
exposure : `lsst.afw.image.ExposureF`
    Exposure to grab band and exposure time metadata

Definition at line 589 of file computeExposureSummaryStats.py.

update_magnitude_limit_stats()

lsst.pipe.tasks.computeExposureSummaryStats.ComputeExposureSummaryStatsTask.update_magnitude_limit_stats	(		self,
			summary,
			exposure )

Compute a summary statistic for the point-source magnitude limit at
a given signal-to-noise ratio using exposure-level metadata.

The magnitude limit is calculated at a given SNR from the PSF,
sky, zeropoint, and readnoise in accordance with SMTN-002 [1]_,
LSE-40 [2]_, and DMTN-296 [3]_.

References
----------

.. [1] "Calculating LSST limiting magnitudes and SNR" (SMTN-002)
.. [2] "Photon Rates and SNR Calculations" (LSE-40)
.. [3] "Calculations of Image and Catalog Depth" (DMTN-296)


Parameters
----------
summary : `lsst.afw.image.ExposureSummaryStats`
    Summary object to update in-place.
exposure : `lsst.afw.image.ExposureF`
    Exposure to grab band and exposure time metadata

Definition at line 683 of file computeExposureSummaryStats.py.

update_masked_image_stats()

lsst.pipe.tasks.computeExposureSummaryStats.ComputeExposureSummaryStatsTask.update_masked_image_stats	(		self,
			summary,
			masked_image )

Compute summary-statistic fields that depend on the masked image
itself.

Parameters
----------
summary : `lsst.afw.image.ExposureSummaryStats`
    Summary object to update in-place.
masked_image : `lsst.afw.image.MaskedImage` or `None`
    Masked image.  If `None`, all fields that depend
    on the masked image will be reset (generally to NaN).

Definition at line 557 of file computeExposureSummaryStats.py.

update_photo_calib_stats()

lsst.pipe.tasks.computeExposureSummaryStats.ComputeExposureSummaryStatsTask.update_photo_calib_stats	(		self,
			summary,
			photo_calib )

Compute all summary-statistic fields that depend on the photometric
calibration model.

Parameters
----------
summary : `lsst.afw.image.ExposureSummaryStats`
    Summary object to update in-place.
photo_calib : `lsst.afw.image.PhotoCalib` or `None`
    Photometric calibration model.  If `None`, all fields that depend
    on the photometric calibration will be reset (generally to NaN).

Definition at line 514 of file computeExposureSummaryStats.py.

update_psf_stats()

lsst.pipe.tasks.computeExposureSummaryStats.ComputeExposureSummaryStatsTask.update_psf_stats	(		self,
			summary,
			psf,
			bbox,
			sources = None,
			image_mask = None,
			image_ap_corr_map = None,
			sources_is_astropy = False )

Compute all summary-statistic fields that depend on the PSF model.

Parameters
----------
summary : `lsst.afw.image.ExposureSummaryStats`
    Summary object to update in-place.
psf : `lsst.afw.detection.Psf` or `None`
    Point spread function model.  If `None`, all fields that depend on
    the PSF will be reset (generally to NaN).
bbox : `lsst.geom.Box2I`
    Bounding box of the image for which summary stats are being
    computed.
sources : `lsst.afw.table.SourceCatalog` or `astropy.table.Table`
    Catalog for quantities that are computed from source table columns.
    If `None`, these quantities will be reset (generally to NaN).
    The type of this table must correspond to the
    ``sources_is_astropy`` argument.
image_mask : `lsst.afw.image.Mask`, optional
    Mask image that may be used to compute distance-to-nearest-star
    metrics.
sources_is_astropy : `bool`, optional
    Whether ``sources`` is an `astropy.table.Table` instance instead
    of an `lsst.afw.table.Catalog` instance.  Default is `False` (the
    latter).

Definition at line 281 of file computeExposureSummaryStats.py.

update_wcs_stats()

lsst.pipe.tasks.computeExposureSummaryStats.ComputeExposureSummaryStatsTask.update_wcs_stats	(		self,
			summary,
			wcs,
			bbox,
			visitInfo )

Compute all summary-statistic fields that depend on the WCS model.

Parameters
----------
summary : `lsst.afw.image.ExposureSummaryStats`
    Summary object to update in-place.
wcs : `lsst.afw.geom.SkyWcs` or `None`
    Astrometric calibration model.  If `None`, all fields that depend
    on the WCS will be reset (generally to NaN).
bbox : `lsst.geom.Box2I`
    Bounding box of the image for which summary stats are being
    computed.
visitInfo : `lsst.afw.image.VisitInfo`
    Observation information used in together with ``wcs`` to compute
    the zenith distance.

Definition at line 452 of file computeExposureSummaryStats.py.

Member Data Documentation

_DefaultName

str lsst.pipe.tasks.computeExposureSummaryStats.ComputeExposureSummaryStatsTask._DefaultName = "computeExposureSummaryStats"

staticprotected

Definition at line 222 of file computeExposureSummaryStats.py.

ConfigClass

lsst.pipe.tasks.computeExposureSummaryStats.ComputeExposureSummaryStatsTask.ConfigClass = ComputeExposureSummaryStatsConfig

static

Definition at line 221 of file computeExposureSummaryStats.py.

---

The documentation for this class was generated from the following file:

• python/lsst/pipe/tasks/computeExposureSummaryStats.py