Data organisation

Layout

The content of the 1dc folder should be as follows:

caldb/
caldb/data
caldb/data/cta
caldb/data/cta/1dc
caldb/data/cta/1dc/caldb.indx
caldb/data/cta/1dc/bcf
...
data/baseline/agn
data/baseline/agn/agn_baseline_510000.fits
data/baseline/agn/agn_baseline_510001.fits
...
data/
data/baseline/
data/baseline/egal
data/baseline/egal/egal_baseline_210000.fits
data/baseline/egal/egal_baseline_210001.fits
...
data/baseline/gc
data/baseline/gc/gc_baseline_310000.fits
data/baseline/gc/gc_baseline_310001.fits
...
data/baseline/gps
data/baseline/gps/gps_baseline_110000.fits
data/baseline/gps/gps_baseline_110001.fits
...
models/
models/models_agn.xml
models/models_egal.xml
models/models_gc.xml
models/models_gps.xml
...
obs/
obs/obs_agn_baseline.xml
obs/obs_egal_baseline.xml
obs/obs_gc_baseline.xml
obs/obs_gps_baseline.xml

Instrument Response Functions

The caldb folder contains the instrument response functions that are necessary for the analysis of the simulated CTA data. The folder contains the 1dc response that should be used for the first CTA Data Challenge. Specifically, the following response functions are available:

Response name	Site	Configuration	Zenith	Duration
South_z20_50h	South	Baseline	20 deg	50 hours
South_z40_50h	South	Baseline	40 deg	50 hours
North_z20_50h	North	Baseline	20 deg	50 hours
North_z40_50h	North	Baseline	40 deg	50 hours

Event data

The data folder contains the calibrated, reconstructed and background reduced event data that were procuded for the first CTA Data Challenge and that were stored into FITS files. Event data are split into observations with a fixed pointing direction (observations are also known as runs). The duration of an observation is 25 minutes for the Extragalactic Survey, 30 minutes for the Galactic Plane and Centre surveys, and 15 min for the AGN monitoring program. The properties of the event data for all simulations are summarised in the table below:

Parameter	GPS	GC	EGAL	AGN
Number of observations	3270	1671	1271	3840
Duration of each observation	1800 s	1800 s	1500 s	900 s
Deadtime fraction	2%	2%	2%	2%
Total exposure time of simulation	1635 h	835.5 h	529.58 h	960.00 h
Simulated event energies	30 GeV - 160 TeV	30 GeV - 160 TeV	30 GeV - 160 TeV	30 GeV - 50 TeV
Maximum off-axis angle	5 deg	5 deg	5 deg	5 deg
Start date of observations	2021-01-01	2021-01-01	2021-01-01	2021-01-01
End date of observations	2021-04-18	2021-03-29	2021-02-25	2022-07-09

Each event file contains the events for an observation and comprises an event list and a good time intervals binary table extension (see figure below).

Structure of an event file

The header of the EVENTS table contains information about the observation such as the start and stop date and time, the duration and livetime of the observation, and the pointing direction in Right Ascension and Declination. In addition, the header contains the names and identifiers of the sources that have been simulated (see figure below).

Header of an event list

Warning

Only the following header keywords in the EVENTS table have meaningful values:

• DSTYPx - Data sub-space type

• DSUNIx - Data sub-space unit

• DSVALx - Data sub-space value

• DSREFx - Data sub-space reference

• NDSKEYS - Number of data sub-space keys

• NMCIDS - Number of Monte Carlo identifiers

• MIDxxxxx - Monte Carlo identifier

• MMNxxxxx - Model name for Monte Carlo identifier

• OBS_ID - Observation identifier

• DATE_OBS - start date of observation (UTC)

• TIME_OBS - start time of observation (UTC)

• DATE_END - end date of observation (UTC)

• TIME_END - end time of observation (UTC)

• TSTART - start time of observation, counted from time reference (s)

• TSTOP - stop time of observation, counted from time reference (s)

• MJDREFI - integer part of time reference MJD (days)

• MJDREFF - fractional part of time reference MJD (days)

• TIMEUNIT - time unit

• TIMESYS - time system

• TIMEREF - time reference

• TELAPSE - elapsed time (s)

• ONTIME - exposure time (s)

• LIVETIME - livetime (s)

• DEADC - deadtime correction factor, livetime / exposure time

• TIMEDEL - time resolution

• RA_PNT - Right Ascension of pointing direction (deg)

• DEC_PNT - Declination of pointing direction (deg)

• RADECSYS - Coordinate system

• EQUINOX - Coordinate epoch

All remaining header keywords have arbitrary values and should not be used for the analysis.

Each row of the EVENTS table corresponds to a single event. Each event is characterised by

Column	Meaning	Unit
EVENT_ID	Event number in file	unitless
TIME	Time stamp, countered from time reference	s
RA	Reconstructed Right Ascension	deg
DEC	Reconstructed Declination	deg
ENERGY	Reconstructed energy	TeV
DETX	Reconstructed camera X coordinate	deg
DETY	Reconstructed camera Y coordinate	deg
MC_ID	Monte Carlo identifier	unitless

An example of an EVENTS table is shown below.

Content of an event list

Warning

The time stamps in the TIME column are not necessarily in ascending order.

Observation Definition Files

The files obs_agn_baseline.xml, obs_egal_baseline.xml, obs_gc_baseline.xml, and obs_gps_baseline.xml are so called observation definition files containing the information (or metadata) of a list of observations. The file is a plain ASCII files in XML format that can be inspected and manipulated by any text editor.

Models

The models folder contains the definitions of all source and background models that were used for simulating the data. The files models_agn.xml, models_egal.xml, models_gc.xml and models_gps.xml are so called model definition files collecting the definition of all model components used for the three surveys. Since the same sky model was used for all surveys the four files are identical. The other files in the folder are ASCII and FITS files containing spectral, temporal and spatial information that was used in the simulations.

Warning

The ASCII and FITS files should always reside in the same folder as the model definition XML files since the latter reference the former.