As a result of this visit, the developers came to the conclusion that each Buk transporter erector launcher (TEL) should have its own fire control radar, rather than being reliant on one central radar for the whole system as in Kub. The result of this move from TEL to transporter erector launcher and radar (TELAR) was development of a system able to shoot at multiple targets in multiple directions at the same time. In 1974 the developers determined that although the Buk missile system is the successor to the Kub missile system, both systems could share some interoperability. The result of this decision was the 9K37-1 Buk-1 system. Interoperability between Buk TELAR and Kub TEL meant an increase in the number of fire control channels and available missiles for each system, as well as faster entry of Buk system components into service. The Buk-1 was adopted into service in 1978 following completion of state trials, while the complete Buk missile system was accepted into service in 1980 after state trials took place between 1977 and 1979. The naval variant of the 9K37 "Buk", the 3S90 "Uragan," was developed by the Altair design bureau under the direction of chief designer G.N. Volgin. The 3S90 used the same 9M38 missile as the 9K37, though the launcher and associated guidance radars were exchanged for naval variants. After the 9S90 system was tested, between 1974 and 1976 on the Kashin-class destroyer "Provorny", it was accepted into service in 1983 on the Project 956 Sovremenny-class destroyers. No sooner had the 9K37 "Buk" entered service than the Central Committee of the CPSU authorised the development of a modernised 9K37 which would become the 9K37M1 Buk-M1, adopted into service in 1983. The modernisation improved the performance of the system radars, its "probability of kill" and its resistance to electronic countermeasures (ECM). Additionally a non-cooperative threat classification system was installed, relying on analysis of returned radar signals to purportedly identify and clearly distinguish civilian aircraft from potential military targets in the absence of IFF. Another modification to the Buk missile system was started in 1992 with work carried out between 1994 and 1997 to produce the 9K37M1-2 Buk-M1-2, which entered service in 1998. This modification introduced a new missile, the 9M317, which offered greater kinematic performance over the previous 9M38, which could still be used by the Buk-M1-2.