Learn about NOAA’s Mauna Loa Observatory on the Big Island of Hawaii, the location of the Exploratorium’s June 5, 2012, webcast of the transit of Venus. A leading atmospheric research facility, the observatory has been collecting and monitoring data relating to atmospheric change since the 1950s. Dr. John Barnes, the Station Chief for the observatory, describes the functions of the MLO, which provides valuable long-term and continuous recording of data.