 Landsat-9 successfully completed its underflight experiment with Landsat-8, demonstrating its ability to accurately measure surface temperatures and reflectance. Ground-based measurements were taken concurrently to compare results with those obtained from Landsat-9. The results showed that Landsat-9 is performing similarly to Landsat-8, with a maximum difference of 2K in the thermal infrared and 2-8% in the visible and near infrared bands. This indicates that Landsat-9 is operating as expected and will continue to provide accurate data throughout its mission. This article was authored by Raymond Ian, Erringer Race, Lucy Felton, and others.