A mobile communications terminal (T) for a cellular communications network comprises an assisted satellite positioning device (D) connected to a satellite positioning installation connected to an assistance data server, a USSD management module (MGT) for setting up USSD transport channels, and a processor (MT) for coupling the management module (MGT) to the device (D) on request in order for a USSD transport channel to be set up between the device (D) and a location management equipment of the cellular network connected to the assistance data server. The USSD channel is then used to send the device (D) assistance data representative of identifiers of at least three satellites visible in the cell in which the terminal (T) is situated so that it can lock onto said satellites to estimate at least the distances between the satellites and its terminal (T).