Fermi Gamma-ray Space Telescope

Summary of Fermi Data Policy

The following is the current (May 2006) data rights policy. While this webpage attempts to provide an accurate statement of the data policy, the definitive statement is provided by the Fermi Science Policy Document associated with the Project Data Management Plan (PDMP).

The data policies differ significantly between Phases 0 (the ~60 day mission checkout period after launch) and 1 (the first year), when the policy is relatively restrictive, and Phase 2 (the rest of the mission), when the policy is relatively open.

To Whom the Policies Apply

For the purposes of Fermi data there are four categories of scientists:

  1. The investigators associated with the instruments teams
  2. The four Interdisciplinary Scientists (IDSs) chosen to advise the mission and to carry out major data analysis projects in the first years of the mission
  3. Guest Investigators (GIs) whose proposals have been accepted
  4. All other scientists

Time Periods

The Fermi mission will have three phases after launch:

  1. Phase 0: the ~60 days after launch when the instruments are turned on and calibrated. During this phase the different operational modes will be tested, and bright sources will be observed.
  2. Phase 1: the first year of scientific operations. The instrument teams continue to calibrate their instruments while conducting a sky survey.
  3. Phase 2: the rest of the mission

During Phases 1 and 2, there will be yearly Guest Investigator (GI) cycles. Thus Cycle 1 will coincide with Phase 1, while subsequent cycles will occur during Phase 2.

Phases 0 and 1

During Phases 0 and 1, the instrument teams will use the Level 1 data to calibrate their instruments and refine the processing pipelines. Until one month after Phase 2 begins (i.e, until approximately 15 months after launch) photon lists from the LAT will be available only to investigators affiliated with the instrument teams and the IDSs. The LAT team will release certain data during Phases 0 and 1. In addition, the GIs selected during Cycle 1 may not alter the mission's observing plan.

During Phase 1, the IDSs will work with the instrument teams both in carrying out the scientific investigations the IDSs proposed and in understanding the data. During this first year the IDS investigations can use only data acquired by the planned operations of the Fermi Observatory, and cannot require pointed observations or special instrument operations; in this phase the IDSs will have access to the data through the instrument teams. In subsequent years, the IDSs may participate in the GI program to propose pointed observations.

Throughout the mission the instrument teams will notify the scientific community that a transient has occurred and release relevant data. The policy regarding transients is discussed separately.

In summary, during Phases 0 and 1 (the first ~14 months after launch), non-transient data are generally not available to the scientific community. These data will become public a month after Phase 2 begins. The scientific community unaffiliated with the Fermi mission may not affect the mission's observing plan.

Phase 2

During Phase 2, Fermi data will be available to the scientific community as soon as the required Level 1 processing preparing the data for scientific analysis has been performed and the resulting Level 1 data have been transmitted to the FSSC. This processing should be completed within a day after the Level 0 data arrives at the Level 1 pipeline at the IOCs, and the SSC will load the Level 1 data into the public databases within a day after it receives these data. Once the data are loaded into the FSSC databases, they will be publicly available to all scientists. The LAT will have a very large field-of-view (FOV), will generally scan the sky, and will slowly build up exposure on sources of interest. Restricting an entire observation that contains a source to one investigator would be inefficient, given the LAT's large FOV. The LAT's energy-dependent point spread function, which is broad at low energy, necessitates analyzing a ~10° region around a source of interest; restricting access to portions of the FOV would make it difficult for investigators to study nearby sources. Consequently, there is no proprietary period for data.

The FSSC will maintain an accurate, timely, and publicly-available list of accepted investigations.

In summary, during Phase 2, all data are publicly accessible.


The Fermi instrument teams have the duty to release data on transient gamma ray sources to the community. The Principal Investigators, in consultation with the User Community, Project Scientist and the SWG, shall release data of interest as soon as practical. The decisions on which data are to be released will be based on advice from scientists analyzing the data and an evaluation of the scientific interest that the data might generate. They will follow the general guidelines suggested below:

  1. Gamma-ray bursts: All data on gamma-ray bursts that trigger either the LAT or GBM will be released. The prompt data release will include direction, fluence estimate and other key information about the burst immediately on discovery. Individual GBM photon data and technical information for their analysis will be released by the GBM team as soon as practical. (This guideline also covers non-gamma ray burst triggers from the GBM, e.g., solar flares). The definition of "practical" will be refined based on data-processing limitations and feedback to the Fermi teams from observatory users such as Guest Investigators and members of multiwavelength collaborations monitoring Fermi sources. If one of the instruments does not trigger on a gamma-ray burst that is detected by the other instrument, information on any detected signal or upper limit will be released as soon as practical.
  2. Blazars and some other sources of high interest: 10-20 pre-selected sources will be monitored continuously and the fluxes and spectral characteristics will be posted on a publicly accessible web site. This list will be made available prior to launch, for comment by the user community. Another 10-20 scientifically interesting sources will be added to this list during the survey. The list will include known or newly discovered AGN selected to be of special interest by the TeV and other communities as well as galactic sources of special interest discovered during the survey.
  3. New transients: The community will be notified when a newly discovered source goes above an adjustable flux level of about (2-5)x10-6 photons (> 100 MeV) per cm2 s for the first time. (This corresponds to a peak counting rate of about 100 counts per hour in the LAT.) The flux level is to be adjusted to set the release rate to about 1-2 per week. A high flux derivative observed for a source having a minimum flux should also trigger a release when statistically significant; the derivative, flux and significance thresholds remain to be defined. The release rate for these sources should be included in the 1-2 per week overall release rate, and should be practical for the LISOC to implement.

The prompt data release for categories 2 and 3 will include information on source coordinates, flux and other key information such as critical timescales or spectral properties.

The IOCs are the implementing centers; the capability to do this will be validated following launch and will evolve as the ground processing and analysis procedures are tested and improved. Implementation must take account of the practicality of implementation and the guidelines are subject to revisions based on the actual experience in implementation.

The Project Scientist is responsible for implementation and review of this policy and will have the authority to modify the implementation procedures if required.

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