The Terrain Integrated Rough Earth Model (TIREM) capability adds fidelity to RF calculations so that you can apply irregular terrain, seawater, and non-line-of-sight effects to link performance analysis in STK.
The TIREM model only applies when both the transmitter and the receiver are below 30,000 meters. This restriction comes from TIREM capability.
STK will split the link at the 30,000-meter boundary when computing links that have objects above this altitude. STK uses the TIREM method for atmospheric absorption loss and free space loss up to 30km and the default models for free space loss for the rest of the link.
There are no TIREM-related computations above 30km altitude, and there is no significant atmospheric loss above 30km altitude.
You can learn more about the TIREM capability at: STK Help > Add-on Modules > Communications & Radar > RF Environment > Environment Properties > Atmospheric Absorption > TIREM 5.50
You can learn how to use the TIREM capability at: STK Help > Training > Level 3- Focused > Feature Specific > TIREM Tutorial
