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)

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.
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')

Run checks.

This is a generator that yields a list of dicts.

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>)

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

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))

Quick-look plots in a few panels.

Parameters

figsizetuple

Figure size

classmethod read(event_file, irf_file=None)

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)

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)

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