Several SIGINT tasks are performed at Leitrim. "The Communications Research projects never cease at Leitrim. The operations area is manned on a continuous basis so the bulk of the station's personnel are shift keepers. The primary function of the station during most of its existence almost certainly has been the interception of diplomatic radio traffic between Ottawa and foreign capitals.
Leitrim contains a wide variety of antennae, including a Pusher HF-DF circularly-disposed antenna array (CDAA), three other large circular arrays, four satellite dishes, and a number of other, small antennae
Maintenance of the High Arctic Data Communications System (HADCS), the link between Ottawa and Alert, is conducted out of Leitrim. It is possible that the station also does some processing of intercepts received from Alert through the HADCS. The station also performs signal development (SIG DEV) work and "provides engineering, technical, and special logistics support to the other stations of the [Supplementary Radio] system."
Leitrim's most recent and most important mission, however, is the interception of satellite communications, begun with the installation of a small satellite dish, probably in 1985. By November 1986 at the latest, a medium-sized satellite dish (ca. 10 metres) had been added, and by the end of 1987 two medium-sized dishes were in service. By July 1990, another small dish had been added to the station's inventory, for a total of two medium-sized and two small dishes now in service.
The targets of Leitrim's dishes are probably Mexican and/or Brazilian communications satellites. Both countries' satellite constellations were established in 1985, at about the same time as Leitrim's new dishes started to be installed. A focus on these satellites would also explain CSE's rumoured increase in Spanish language activities.