Although the MODIS/VIIRS layer is considered to be a near real-time picture by NASA (three to five hours from satellite passing), please keep in mind that it takes time to download data, run the algorithm, georeference data, and then share the information to Intterra.

How often?  There are two MODIS and one VIIRS satellites that make two passes each 24-hour period - one during the day and one at night.  Due to overlap at mid-latitudes, this means seven to eight passes per day. 

When?  This depends on your location, and there is some variation by day.  If you are in an area with overlap (the VIIRS satellite travels across the U.S. about every two hours, so you may get some detections from two adjacent passes), you can expect data from:
  • Daytime: Noon - 1400 Local
  • Nighttime: 2200 - 0300 Local
For additional details, check the NASA FIRMS FAQ site to see their VIIRS and MODIS FAQs.  From this link, you will also be able to find additional links to view the actual orbit paths and times for all three satellites.