Fermi Timeline Posting Glossary

Below are descriptons of the columns in the Fermi posted timeline.

Note: As used in the table, a snapshot is 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).

Parameter	Description
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 types include: Type Description 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.