longer transmission period of one second, with 250 transmitted bits, 202 of those being message bits. Additionally, the information sent in the message bits from one transmission to the next can be changed on a rotating transmission schedule ("rotating message fields") to allow significantly more information to be communicated over the course of a series of transmission bursts. In response to recent commercial aviation disasters and subsequent ICAO requirements for autonomous tracking of aircraft in distress, Cospas-Sarsat has finalized specifications for ELTs for distress tracking (ELT(DT)s) to meet the ICAO requirements (amended Annex 6, Part I of the Convention on International Civil Aviation). Whereas present ELTs are designed to activate on impact or by manual activation by the flight crew, ELT(DT)s will activate autonomously when an aircraft enters threatening flight configurations that have been predetermined by expert agencies. In this way, ELT(DT)s will allow a plane in distress to be tracked in-flight, prior to any crash, without human intervention aboard the aircraft. ELT(DT)s have been specified using both the existing beacon transmission method (narrowband BPSK) and the second-generation (spread-spectrum QPSK) modulation schemes. Cospas-Sarsat capability for receiving and processing distress messages from ELT(DT)s using the narrowband BPSK transmission method has been declared operational effective 1 January 2023. Declaration for ELT(DT)s using the spread-spectrum QPSK modulation method is expected early in 2023. History First Legal framework On 23 November 1979, a "memorandum of understanding concerning cooperation in a joint experimental satellite-aided search and rescue project" was signed in Leningrad, USSR, among the U.S. National Aeronautics and Space Administration, the USSR Ministry of Merchant Marine, the Centre National d'Etudes Spatiales of France, and the Department of Communications of Canada. Under Article 3 of the memorandum, it was stated that: "Cooperation will be achieved through effecting interoperability between the SARSAT project and the COSPAS project at 121.5MHz, 243MHz and in the 406.0 – 406.1 MHz band and conducting of tests, mutual exchange of test results and preparation of a joint report. The objective of this cooperation is to demonstrate that equipment carried on low-altitude, near polar-orbiting satellites can facilitate the detection and location of distress signals by relaying information from aircraft and ships in distress to ground stations, where the information processing is completed and passed to rescue services." "This joint Project will permit the Parties to make recommendations on follow-on global applications." Development The first system satellite, "COSPAS-1" (Kosmos 1383), was launched from