Fermi Gamma-ray Space Telescope

Fermi Timeline Posting Glossary

Table Columns

Obs ID -- Identification number for an observation. This number consists of the proposal ID, the source number (proposals may request observations of more than one source), the source number for this proposal ID (proposals may have many sources), and the observation number of this source (proposals may request that the source be observed more than once). Note that a given source may be observed a number of times for different proposals.

Mission Week -- The Fermi planning week number. The week begins Thursdays at 00:00:00 UTC. To convert this, please see HEASARC's xTime (Date/Time Conversion) Utility.

Start Time -- The beginning of the snapshot (UTC), or group of snapshots, given as yyyy:ddd:hh:mm:ss and yyyy-MM-dd hh:mm:ss.

Stop Time -- The end of the snapshot (UTC), or group of snapshots, using the same convention as the start time.

Duration -- The difference between the start time and stop time for the snapshot, or group of snapshots, given in seconds.

RA -- The right ascension of the target, in decimal degrees (J2000).

Dec -- The declination of the target, in decimal degrees (J2000).

Mode -- Observing mode: either Pointed, Profiled, or Sunpoint.

Type -- Observation type:

  • Pointed - Pointed observation
  • Survey - Sky Survey
  • Downtime - LAT Downtime
  • Non-science - LAT calibration or other non-science time
  • ToO - Target of Opportunity
  • ARR - Autonomous Repoint
  • Freeze - Brief pointed observation needed when a new profile is loaded

Target -- Name of observed source as provided by the ToO request or guest investigator proposal that resulted in the observation.

PI -- The principal investigator for the ToO request or guest investigator proposal that resulted in the observation.

Notes -- Additional information or comments about the observation.

Other Terms

Snapshot -- A single uninterrupted pointed observation or period in survey mode. Snapshots begin and end with events such as transitions between pointed and survey mode or pointing changes. An SAA passage in the middle of an observation is not considered to interrupt the observation (i.e., does not start or stop the snapshot).

Proposal ID -- Identification number for the guest investigator proposal that resulted in the observation.