The flight Ocean Color Instrument (OCI) is connected to flex lines and other alignment calibration hardware in a thermal vacuum chamber as it is prepared for thermal testing in a clean tent at Goddard Space Flight Center in Greenbelt, MD. OCI is a highly advanced optical spectrometer that will be used to measure properties of light over portions of the electromagnetic spectrum. It will enable continuous measurement of light at finer wavelength resolution than previous NASA satellite sensors, extending key system ocean color data records for climate studies. OCI is PACE's (Plankton, Aerosol, Cloud, ocean Ecosystem) primary sensor built at Goddard Space Flight Center in Greenbelt, MD.