MakeRawVisitInfo¶

class lsst.obs.base.MakeRawVisitInfo(log=None)[source]¶

Bases: object

Base class functor to make a VisitInfo from the FITS header of a raw image.

A subclass will be wanted for each camera. Subclasses should override:

setArgDict, The override can call the base implementation,

which simply sets exposure time and date of observation
getDateAvg

The design philosophy is to make a best effort and log warnings of problems, rather than raising exceptions, in order to extract as much VisitInfo information as possible from a messy FITS header without the user needing to add a lot of error handling.

However, the methods that transform units are less forgiving; they assume the user provides proper data types, since type errors in arguments to those are almost certainly due to coding mistakes.

Parameters:

log : lsst.log.Log or None

Logger to use for messages. (None to use Log.getLogger("MakeRawVisitInfo")).

Methods Summary

`__call__`(md, exposureId)	Construct a VisitInfo and strip associated data from the metadata.
`altitudeFromZenithDistance`(zd)	Convert zenith distance to altitude (lsst.afw.geom.Angle)
`centigradeFromKelvin`(tempK)	Convert temperature from Kelvin to Centigrade
`defaultMetadata`(value, defaultValue[, ...])	Return the value if it is not NaN and within min/max, otherwise return defaultValue.
`eraFromLstAndLongitude`(lst, longitude)	Return an approximate Earth Rotation Angle (afw:Angle) computed from local sidereal time and longitude (both as afw:Angle; Longitude shares the afw:Observatory covention: positive values are E of Greenwich).
`getDarkTime`(argDict)	Get the darkTime from the DARKTIME keyword, else expTime, else NaN,
`getDateAvg`(md, exposureTime)	Return date at the middle of the exposure.
`offsetDate`(date, offsetSec)	Return a date offset by a specified number of seconds.
`pascalFromMBar`(mbar)	Convert pressure from millibars to Pascals
`pascalFromMmHg`(mmHg)	Convert pressure from mm Hg to Pascals
`pascalFromTorr`(torr)	Convert pressure from torr to Pascals
`popAngle`(md, key[, units])	Pop an lsst.afw.geom.Angle, whose metadata is in the specified units, with a default of Nan
`popFloat`(md, key)	Pop a float with a default of NaN.
`popIsoDate`(md, key[, timesys])	Pop a FITS ISO date as an lsst.daf.base.DateTime
`popItem`(md, key[, default])	Remove an item of metadata and return the value.
`popMjdDate`(md, key[, timesys])	Get a FITS MJD date as an `lsst.daf.base.DateTime`.
`setArgDict`(md, argDict)	Fill an argument dict with arguments for VisitInfo and pop associated metadata

Methods Documentation

__call__(md, exposureId)[source]¶

Construct a VisitInfo and strip associated data from the metadata.

Parameters:

md : lsst.daf.base.PropertyList or lsst.daf.base.PropertySet

Metadata to pull from. Items that are used are stripped from the metadata (except TIMESYS, because it may apply to other keywords).

exposureId : int

exposure ID

Notes

The basic implementation sets date and exposureTime using typical values found in FITS files and logs a warning if neither can be set.

static altitudeFromZenithDistance(zd)[source]¶: Convert zenith distance to altitude (lsst.afw.geom.Angle)

static centigradeFromKelvin(tempK)[source]¶: Convert temperature from Kelvin to Centigrade

static defaultMetadata(value, defaultValue, minimum=None, maximum=None)[source]¶

Return the value if it is not NaN and within min/max, otherwise return defaultValue.

Parameters:

value : float

metadata value returned by popItem, popFloat, or popAngle

defaultValue : float`

default value to use if the metadata value is invalid

minimum : float

Minimum possible valid value, optional

maximum : float

Maximum possible valid value, optional

Returns:

float

The “validated” value.

static eraFromLstAndLongitude(lst, longitude)[source]¶

Return an approximate Earth Rotation Angle (afw:Angle) computed from local sidereal time and longitude (both as afw:Angle; Longitude shares the afw:Observatory covention: positive values are E of Greenwich).

NOTE: if we properly compute ERA via UT1 a la DM-8053, we should remove this method.

getDarkTime(argDict)[source]¶

Get the darkTime from the DARKTIME keyword, else expTime, else NaN,

If dark time is available then subclasses should call this method by putting the following in their __init__ method:

argDict['darkTime'] = self.getDarkTime(argDict)

Parameters:

argdict : dict

Dict of arguments.

Returns:

float

Dark time, as inferred from the metadata.

getDateAvg(md, exposureTime)[source]¶

Return date at the middle of the exposure.

Parameters:

md : lsst.daf.base.PropertyList or PropertySet

Metadata to pull from. Items that are used are stripped from the metadata (except TIMESYS, because it may apply to other keywords).

exposureTime : float

Exposure time (sec)

Notes

Subclasses must override. Here is a typical implementation:

dateObs = self.popIsoDate(md, "DATE-OBS")
return self.offsetDate(dateObs, 0.5*exposureTime)

offsetDate(date, offsetSec)[source]¶

Return a date offset by a specified number of seconds.

date : lsst.daf.base.DateTime: Date baseline to offset from.
offsetSec : float: Offset, in seconds.

Returns:

lsst.daf.base.DateTime

The offset date.

static pascalFromMBar(mbar)[source]¶: Convert pressure from millibars to Pascals

static pascalFromMmHg(mmHg)[source]¶

Convert pressure from mm Hg to Pascals

Notes

Could use the following, but astropy.units.cds is not fully compatible with Python 2 as of astropy 1.2.1 (see https://github.com/astropy/astropy/issues/5350#issuecomment-248612824): astropy.units.cds.mmHg.to(astropy.units.pascal, mmHg)

static pascalFromTorr(torr)[source]¶: Convert pressure from torr to Pascals

popAngle(md, key, units=Unit("deg"))[source]¶

Pop an lsst.afw.geom.Angle, whose metadata is in the specified units, with a default of Nan

The angle may be specified as a float or sexagesimal string with 1-3 fields.

Parameters:

md : lsst.daf.base.PropertyList or PropertySet

Metadata to pull key from and remove.

key : str

Key to read and remove from md.

Returns:

lsst.afw.geom.Angle

Value of the requested key as an angle; Angle(NaN) if the key is not found.

popFloat(md, key)[source]¶

Pop a float with a default of NaN.

Parameters:

md : lsst.daf.base.PropertyList or PropertySet

Metadata to pull key from and remove.

key : str

Key to read and remove from md.

Returns:

float

Value of the requested key as a float; float(“nan”) if the key is not found.

popIsoDate(md, key, timesys=None)[source]¶

Pop a FITS ISO date as an lsst.daf.base.DateTime

Parameters:

md : lsst.daf.base.PropertyList or PropertySet

Metadata to pull key from and remove.

key : str

Date key to read and remove from md.

timesys : str

Time system as a string (not case sensitive), e.g. “UTC” or None; if None then look for TIMESYS (but do NOT pop it, since it may be used for more than one date) and if not found, use UTC.

Returns:

lsst.daf.base.DateTime

Value of the requested date; DateTime() if the key is not found.

popItem(md, key, default=None)[source]¶

Remove an item of metadata and return the value.

Log a warning if the key is not found.

Parameters:

md : lsst.daf.base.PropertyList or PropertySet

Metadata to pull key from and remove.

key : str

Metadata key to extract.

default : object

Value to return if key not found.

Returns:

object

The value of the specified key, using whatever type md.getScalar(key) returns.

popMjdDate(md, key, timesys=None)[source]¶

Get a FITS MJD date as an lsst.daf.base.DateTime.

Parameters:

md : lsst.daf.base.PropertyList or PropertySet

Metadata to pull key from and remove.

key : str

Date key to read and remove from md.

timesys : str

Time system as a string (not case sensitive), e.g. “UTC” or None; if None then look for TIMESYS (but do NOT pop it, since it may be used for more than one date) and if not found, use UTC.

Returns:

lsst.daf.base.DateTime

Value of the requested date; DateTime() if the key is not found.

setArgDict(md, argDict)[source]¶

Fill an argument dict with arguments for VisitInfo and pop associated metadata

Subclasses are expected to override this method, though the override may wish to call this default implementation, which:

sets exposureTime from “EXPTIME”
sets date by calling getDateAvg

Parameters:

md : lsst.daf.base.PropertyList or PropertySet

Metadata to pull from. Items that are used are stripped from the metadata (except TIMESYS, because it may apply to other keywords).

argdict : dict

dict of arguments

Notes

Subclasses should expand this or replace it.

Navigation

MakeRawVisitInfo¶