The first aerosol observing system (AOS) designed and mentored by the National Oceanic and Atmospheric Administration (NOAA) was located at the Southern Great Plains (SGP) megasite in Oklahoma and has been operational since the beginning of April 1996. In 2005, a second AOS, also designed and mentored by NOAA, joined the first ARM Mobile Facility (AMF1).
Brookhaven National Laboratory built two more basic and one enhancedAOSs. The two basic AOSs were deployed on Graciosa Island in the Azores and to the second ARM Mobile Facility (AMF2). In 2015 ARM built a fourth AOS for deployment at the third ARM Mobile facility (AMF3) in Oliktok, Alaska.
The enhanced AOS, which consists of two structures, can be deployed independently and were originally designated as the Mobile Aerosol Observing System, Aerosols (MAOS A) and Mobile Aerosol Observing System, Chemistry (MAOS C).
Although some commonalities exist, each AOS has a different complement of instruments. For a list of instruments included in the AOS, see Mobile AOS.