Fermi Gamma-ray Space Telescope

Observing Timeline

In this section you can determine where Fermi pointed in the past and is scheduled to point in the future. Also, you can learn the status of target-of-opportunity (TOO) observations that have been approved.

Timeline Utilities

The following are utilities that provide you with these capabilities:

  • Timeline posting - through this webpage you can determine Fermi's pointing history in the past, and find future observing plans. The most accurate observing information available is used.
  • TOO status - the status of accepted TOO requests is reported here. The utility presents all available information at the time of a query.
  • Time system conversions - different utilities and tools use different time systems (e.g., Mission Elapsed Time, calendar date, modified Julian date). Note that Fermi and Swift use the same 'Mission Elapsed Time' conventions. This is a HEASARC tool.
  • Coordinate conversions - this utility can convert between source names and coordinates for single sources and lists of sources. This is a HEASARC tool.

Overview of the Timeline Process

After guest investigator observing proposals for a given cycle are accepted, the FSSC will develop a long-term observing timeline. The long-term observing timeline schedules observations for specific times, but only the scheduling of observations for a given week should be regarded as relevant. The long-term observing timeline will implemented through a weekly observing timeline; all the observations scheduled for a given week in the long-term observing timeline will be rescheduled in creating the weekly observing timeline. The weekly observing timeline will go through a number of versions, starting with a preliminary draft about 3 weeks before the implementation, continuing with a final plan that is uploaded to the observatory, and ending with an as-flown version that includes the departures from the final plan resulting from unpredictable events such as TOO observations. These departures from the weekly observing timeline will necessitate the periodic revision of the long-term observing timeline. The latest version of the timelines will be posted.

The following table shows the different timelines and their reliability:

If an observation is on this timeline... Then...
Long-term observing timeline Only the week of the observation is relevant, and may be revised.
Preliminary weekly observing timeline The observation will most likely occur when scheduled, but could be rescheduled.
Final weekly observing timeline The observation will occur when scheduled, unless disrupted by a TOO or an autonomous repoint.
As-flown timeline Observation occurred at the reported time

The FSSC compares the timeline as actually implemented with the planned timeline and updates the observing timeline with the results.

Fermi will be operated primarily in survey mode. Guest investigators may ask for pointed observations, but because such observations disrupt the uniformity of the sky coverage, at most 20% of the observing time will be in this mode.