FACT Open Data

Crab Nebula Observations

In November 2017 the FACT Collaboration decided to make a first step into the direction of Open Data and release a sample of 17.7 hours of Crab Nebula observations measured in November 2013 available to the general public, along with simulations needed to perform analysis of this data sample.

We encourage to use this data for training, education and outreach for FACT and gamma-ray astronomy in general.

Please cite [1] and [2] if you use the data provided here.


Important metadata for the data runs is available in csv format here

CORSIKA simulation metadata on every simulated gamma shower is available in hdf5 format here.

Raw Data

The raw data as saved on disk by the Telescope is provided in zfits[3] format. The data is available here.

Both FACT Data Analysis chains start from this data format.

To analyse the data, telescope metadata is needed. This data is provided as one standard fits file per service for each night here. Especially important for the analysis are the YYYYMMDD_DRIVE_CONTROL_TRACKING_POSITION.fits files, containing the pointing direction of the telescope measured every two seconds and the YYYYMMDD_DRIVE_CONTROL_SOURCE_POSITION.fits containing information about the currently observed source. These two files are needed for the FACT-Tools standard analysis.

PhotonStream Data

The data sample in the PhotonStream format, arrival times of each individual photon that FACT measured for the events. A more in-depth description and the data is available here. This data might be the most approachable for newcomers to gamma-ray astronomy.

Data Level 1

Number of photons and mean arrival time per pixel are available in FITS format here.

Data Level 2

Reconstructed and parameterized events using FACT-Tools up to 1.1.2 are available as hdf5 file here. These files can easily be read into pandas dataframes using pyfact's fact.io.read_data.

Data Level 3

Reconstructed gamma-ray events using FACT-Tools for raw data calibration, signal extraction, cleaning and image parameterisation and the classifier-tools to estimate the origin, energy and gammaness of the events. The data as single hdf5 file is available here.


  1. Anderhub et al., Design and operation of FACT – the first G-APD Cherenkov telescope, 2013.
  2. Biland et al., Calibration and performance of the photon sensor response of FACT — the first G-APD Cherenkov telescope
  3. Ahnen et al., Data compression for the First G-APD Cherenkov Telescope, 2015.