“…Several successful field campaigns and long-term deployments have demonstrated that the Bruker EM27/SUN FTIR spectrometer is an excellent instrument with good quality, robustness and reliability and its performance offers the potential to support TCCON (Frey et al, 2015 andKlappenbach et al, 2015;Chen et al, 2016;Butz et al, 2017;Sha et al, 2019;Jacobs et al, 2020;Tu et al, 2020a and2020b;Dietrich et al, 2021). The Bruker EM27/SUN spectrometers have become commercially available from April 2014 onwards and currently about 70 spectrometers are operated by different working groups in Germany, France, Spain, Finland, Romania, USA, Canada, UK, India, Korea, Botswana, Japan, China, Mexico, Brazil, Australia and New Zealand.…”