whether this satisfies safety requirements depends on local regulations. A Cospas-Sarsat beacon does not transmit until it is activated in an emergency (or when certain testing features are activated by the user). Some beacons are designed to be manually activated by a person pressing a button, and some others are designed for automatic activation in certain circumstances (e.g., ELTs may be automatically activated by a physical shock, such as in a crash, and EPIRBs may be automatically activated by contact with water). There are no subscription or other costs imposed by Cospas-Sarsat for beacon ownership or use. (Some countries may impose licensing and/or registration charges for beacon ownership, and some jurisdictions may assess costs for rescue operations.) See below for recent beacon innovations. Space segment The Cospas-Sarsat system operational space segment consists of SARR and/or SARP instruments aboard: Five satellites in polar low-altitude Earth orbit with LEOSAR (low-altitude Earth orbit search-and-rescue) payloads Eleven satellites in geostationary Earth orbit with GEOSAR (geostationary Earth orbit search-and-rescue) payloads More than 50 satellites in medium-altitude Earth orbit with MEOSAR (medium-altitude Earth orbit search-and-rescue) payloads A SARR or SARP instrument is a secondary payload and associated antennas attached to those satellites as an adjunct to the primary satellite mission. A SARR instrument retransmits a beacon distress signal to a satellite ground station in real time. A SARP instrument records the data from the distress signal so that the information can later be gathered by a ground station when the satellite passes overhead. Ground segment The satellites are monitored by receiving ground stations (LUTs) equipped to track (point at and follow) the satellites using satellite dishes or phased antenna arrays. LUTs are installed by individual national administrations or agencies. The distress messages received by a LUT are transferred to an associated mission control centre which uses a detailed set of computer algorithms to route the messages to rescue coordination centres worldwide. System architecture When a distress beacon is activated, the Cospas-Sarsat system: decodes the binary coded message of the beacon, which contains information such as the identity of the vessel/aircraft and, for beacons equipped with the feature, the location of the beacon derived from a local navigation source (such as a GPS receiver incorporated into the beacon's design). performs a mathematical analysis of the signal to calculate the location of the beacon, even if the beacon's location is not reported in the distress message. The Cospas-Sarsat