Observation#

class gammapy.data.Observation(obs_id=None, obs_info=None, gti=None, aeff=None, edisp=None, psf=None, bkg=None, rad_max=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
rad_max: `~gammapy.irf.RadMax2D`: Only for point-like IRFs: RAD_MAX table (energy dependent RAD_MAX) For a fixed RAD_MAX, create a RadMax2D with a single bin.
gtiGTI: Table with GTI start and stop time
eventsEventList: Event list
obs_filterObservationFilter: Observation filter.

Attributes Summary

`aeff`	A lazy FITS data descriptor.
`available_hdus`	Which HDUs are available
`available_irfs`	Which IRFs are available
`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.
`obs_info`	Observation info dictionary.
`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_radec`	Pointing RA / DEC sky coordinates (`SkyCoord`).
`pointing_zen`	Pointing zenith angle sky (`Quantity`).
`psf`	A lazy FITS data descriptor.
`rad_max`
`target_radec`	Target RA / DEC sky coordinates (`SkyCoord`).
`tstart`	Observation start time (`Time`).
`tstop`	Observation stop time (`Time`).

Methods Summary

`check`([checks])	Run checks.
`copy`([in_memory])	Copy observation
`create`(pointing[, location, obs_id, ...])	Create an observation.
`peek`([figsize])	Quick-look plots in a few panels.
`read`(event_file[, irf_file])	Create an Observation from a Event List and an (optional) IRF file.
`select_time`(time_interval)	Select a time interval of the observation.
`write`(path[, overwrite, format, include_irfs])	Write this observation into `path` using the specified format

Attributes Documentation

aeff#

A lazy FITS data descriptor.

Parameters

cachebool: Whether to cache the data.

available_hdus#: Which HDUs are available

available_irfs#: Which IRFs are available

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.

obs_info#: Observation info dictionary.

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_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.

rad_max#

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

tstart#: Observation start time (Time).

tstop#: Observation stop time (Time).

Methods Documentation

check(checks='all')[source]#

Run checks.

This is a generator that yields a list of dicts.

copy(in_memory=False, **kwargs)[source]#

Copy observation

Overwriting arguments requires the ‘in_memory` argument to be true.

Parameters

in_memorybool: Copy observation in memory.
**kwargsdict: Keyword arguments passed to Observation

Returns

obsObservation: Copied observation

Examples

from gammapy.data import Observation

obs = Observation.read(
    "$GAMMAPY_DATA/hess-dl3-dr1/data/hess_dl3_dr1_obs_id_020136.fits.gz"
)

obs_copy = obs.copy(obs_id=1234)
print(obs_copy)

classmethod create(pointing, location=None, obs_id=0, livetime=None, tstart=None, tstop=None, irfs=None, deadtime_fraction=0.0, reference_time=<Time object: scale='utc' format='iso' value=2000-01-01 00:00:00.000>)[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
tstart: `~astropy.time.Time` or `~astropy.units.Quantity`: Start time of observation as Time or duration relative to reference_time
tstop: `astropy.time.Time` or `~astropy.units.Quantity`: Stop time of observation as Time or duration relative to reference_time
irfs: dict: IRFs used for simulating the observation: bkg, aeff, psf, edisp, rad_max
deadtime_fractionfloat, optional: Deadtime fraction, defaults to 0
reference_timeTime: the reference time to use in GTI definition

Returns

obsgammapy.data.MemoryObservation

peek(figsize=(15, 10))[source]#

Quick-look plots in a few panels.

Parameters

figsizetuple: Figure size

classmethod read(event_file, irf_file=None)[source]#

Create an Observation from a Event List and an (optional) IRF file.

Parameters

event_filestr, Path: path to the .fits file containing the event list and the GTI
irf_filestr, Path: (optional) path to the .fits file containing the IRF components, if not provided the IRF will be read from the event file

Returns

observationObservation: observation with the events and the irf read from the file

select_time(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

write(path, overwrite=False, format='gadf', include_irfs=True)[source]#

Write this observation into path using the specified format

Parameters

path: str or `~pathlib.Path`: Path for the output file
overwrite: bool: If true, existing files are overwritten.
format: str: Output format, currently only “gadf” is supported
include_irfs: bool: Whether to include irf components in the output file