A method for determining EIRP of user terminals in a satellite communications system comprises measuring a return uplink thermal noise at one or more frequencies, obtaining a target return uplink signal density relative to thermal noise density, and determining a target signal power at a gateway in the satellite communications system for one or more frequency channels. The target signal power may be based at least in part on the return uplink thermal noise and the target return uplink signal density relative to the thermal noise density. The method also comprises obtaining a message signal power at the gateway of one or more messages from a user terminal, and determining the EIRP of the user terminal based at least in part on a difference between the target signal power and the message signal power.