Observation¶

class gammapy.data.Observation(obs_id=None, obs_info=None, gti=None, aeff=None, edisp=None, psf=None, bkg=None, events=None, obs_filter=None)[source]¶

Bases: object

In-memory observation.

Parameters

obs_idint: Observation id
obs_infodict: Observation info dict
aeffEffectiveAreaTable2D: Effective area
edispEnergyDispersion2D: Energy dispersion
psfPSF3D: Point spread function
bkgBackground3D: Background rate model
gtiGTI: Table with GTI start and stop time
eventsEventList: Event list
obs_filterObservationFilter: Observation filter.

Attributes Summary

`aeff`	A lazy FITS data descriptor.
`bkg`	A lazy FITS data descriptor.
`edisp`	A lazy FITS data descriptor.
`events`
`fixed_pointing_info`	Fixed pointing info for this observation (`FixedPointingInfo`).
`gti`
`muoneff`	Observation muon efficiency.
`observation_dead_time_fraction`	Dead-time fraction (float).
`observation_live_time_duration`	Live-time duration in seconds (`Quantity`).
`observation_time_duration`	Observation time duration in seconds (`Quantity`).
`observatory_earth_location`	Observatory location (`EarthLocation`).
`pointing_altaz`	Pointing ALT / AZ sky coordinates (`SkyCoord`).
`pointing_radec`	Pointing RA / DEC sky coordinates (`SkyCoord`).
`pointing_zen`	Pointing zenith angle sky (`Quantity`).
`psf`	A lazy FITS data descriptor.
`target_radec`	Target RA / DEC sky coordinates (`SkyCoord`).
`tstart`	Observation start time (`Time`).
`tstop`	Observation stop time (`Time`).

Methods Summary

`check`(self[, checks])	Run checks.
`create`(pointing[, obs_id, livetime, tstart, …])	Create an observation.
`from_caldb`(pointing[, obs_id, livetime, …])	Create an observation using IRFs from a given CTA CALDB.
`peek`(self[, figsize])	Quick-look plots in a few panels.
`select_time`(self, time_interval)	Select a time interval of the observation.

Attributes Documentation

aeff¶

A lazy FITS data descriptor.

Parameters

cachebool: Whether to cache the data.

bkg¶

A lazy FITS data descriptor.

Parameters

cachebool: Whether to cache the data.

edisp¶

A lazy FITS data descriptor.

Parameters

cachebool: Whether to cache the data.

events¶

fixed_pointing_info¶: Fixed pointing info for this observation (FixedPointingInfo).

gti¶

muoneff¶: Observation muon efficiency.

observation_dead_time_fraction¶

Dead-time fraction (float).

Defined as dead-time over observation time.

Dead-time is defined as the time during the observation where the detector didn’t record events: https://en.wikipedia.org/wiki/Dead_time https://ui.adsabs.harvard.edu/abs/2004APh….22..285F

The dead-time fraction is used in the live-time computation, which in turn is used in the exposure and flux computation.

observation_live_time_duration¶

Live-time duration in seconds (Quantity).

The dead-time-corrected observation time.

Computed as t_live = t_observation * (1 - f_dead) where f_dead is the dead-time fraction.

observation_time_duration¶

Observation time duration in seconds (Quantity).

The wall time, including dead-time.

observatory_earth_location¶: Observatory location (EarthLocation).

pointing_altaz¶: Pointing ALT / AZ sky coordinates (SkyCoord).

pointing_radec¶: Pointing RA / DEC sky coordinates (SkyCoord).

pointing_zen¶: Pointing zenith angle sky (Quantity).

psf¶

A lazy FITS data descriptor.

Parameters

cachebool: Whether to cache the data.

target_radec¶: Target RA / DEC sky coordinates (SkyCoord).

tstart¶: Observation start time (Time).

tstop¶: Observation stop time (Time).

Methods Documentation

check(self, checks='all')[source]¶

Run checks.

This is a generator that yields a list of dicts.

classmethod create(pointing, obs_id=0, livetime=None, tstart=None, tstop=None, irfs=None, deadtime_fraction=0.0, reference_time='2000-01-01')[source]¶

Create an observation.

User must either provide the livetime, or the start and stop times.

Parameters

pointingSkyCoord: Pointing position
obs_idint: Observation ID as identifier
livetime~astropy.units.Quantity`: Livetime exposure of the simulated observation
tstartQuantity: Start time of observation w.r.t reference_time
tstopQuantity w.r.t reference_time: Stop time of observation
irfsdict: IRFs used for simulating the observation: bkg, aeff, psf, edisp
deadtime_fractionfloat, optional: Deadtime fraction, defaults to 0
reference_timeTime: the reference time to use in GTI definition

Returns

obsgammapy.data.MemoryObservation

classmethod from_caldb(pointing, obs_id=None, livetime=None, tstart=None, tstop=None, caldb='prod2', irf='South0.5hr', deadtime_fraction=0.0)[source]¶

Create an observation using IRFs from a given CTA CALDB.

Parameters

pointingSkyCoord: Pointing position
obs_idint: Observation ID as identifier
livetime~astropy.units.Quantity`: Livetime exposure of the simulated observation
tstartQuantity: Start time of observation
tstopQuantity: Stop time of observation
caldbstr: Calibration database
irfstr: Type of Instrumental response function.
deadtime_fractionfloat, optional: Deadtime fraction, defaults to 0

Returns

obsgammapy.data.Observation

peek(self, figsize=(12, 10))[source]¶

Quick-look plots in a few panels.

Parameters

figszietuple: Figure size

select_time(self, time_interval)[source]¶

Select a time interval of the observation.

Parameters

time_intervalastropy.time.Time: Start and stop time of the selected time interval. For now we only support a single time interval.

Returns

new_obsObservation: A new observation instance of the specified time interval