Utah State University has been developing the Filter Incidence Narrow-band Infrared Spectrometer (FINIS) as a compact instrument for observing atmospheric methane from CubeSats. This instrument will be tested on the upcoming ACMES mission for use as a methane detector. The ACMES mission was selected in 2021 as part of the NASA In-space Validation of Earth Science Technologies (InVEST) program with an expected launch in 2024. Methane is the second most important greenhouse gas and one for which a reduction in emissions could have a significant impact on the near-term rate of global warming. As part of the effort to measure tropospheric methane concentration from space, point source leaks have shown to be challenging to be detected and measured using historic satellite sensors due to their low spatial resolution. In this context, Utah State University has been developing FINIS to be suitable for CH4 leak detection using the differential absorption technique in the 1.6 um band of methane. This paper presents the FINIS design for ACMES, including the instrument review, the concept of operation along with lessons learned from previous air-based testing of the FINIS prototype
