FAAM core instruments measuring true air temperature (in K) by using platinum resistance thermometers (currently, possibility of changing to thermistors in future) in de-iced and non-deiced housings.

The true air temperature is calculated based on the indicated temperature measured by two Rosemount type 102 probes (as well as the static and dynamic pressure RVSM measurements). Both sensors employ similar inlets to draw flow across a sensor (either a platinum PRT or glass bead thermistor) using inlets that have been designed to minimise water and particle ingress, as well as minimising interaction of the air with the inlet walls.

The deiced sensor contains a heater operated by the flight manager when icing is suspected (a correction is automatically applied to data during these periods).

The specific type of sensor used dictates the response time, for details see FAAM document FAAM013001A.

The data frequency is measured in 32 Hz. This frequency can be found in the full 32Hz core data file, or as 1 Hz in 1Hz data file. Parameters in the data files are: TAT_DI_R (True air temperature from the Rosemount deiced temperature sensor), TAT_ND_R (True air temperature from the Rosemount non-deiced temperature sensor).