NOAA-11(1988–2004) was the fourth operational satellite in the Advanced TIROS-N series. The satellite carried the AVHRR and TOVS which were present on previous NOAA satellites, the solar proton monitor, and the SARSAT system. In addition, the ERBE instruments, which consisted of short wave and long wave radiometers, were used to study the Earth's albedo in attempt to recognize and interpret seasonal and annual climate variations. The SBUV radiometer was flown on this satellite since the satellite was intended to replace NOAA-9. NOAA-11 was operational for the period 24 September 1988 to March 1995.