The Compact Spectral Irradiance Monitor (CSIM) is a 6U CubeSat that will launch on the SpaceFlight SSO-A mission in late 2018. It will demonstrate next-generation technology for monitoring spectral solar irradiance. CSIM is a two-channel 6U CubeSat instrument similar in design to the SORCE and TSIS SIM instruments. It is designed to measure the solar spectral irradiance from 200-2600nm twice a day with a goal accuracy of <0.25%. The key detector that enables this level of accuracy, a vertically-aligned carbon nanotube electrical substitution radiometer, was developed jointly with the Sources and Detectors Group at NIST Boulder. TSIS SIM will have been performing solar observations for approximately nine months, so the direct comparison of initial solar observations of CSIM to the concurrent TSIS SIM observations will allow us to independently validate the degradation-correction scheme in place on TSIS SIM. During the 2-year CSIM mission, the CSIM measurements can supplement the TSIS SIM measurements. Additionally, we can use TSIS SIM as a reference to independently test the on-orbit degradation correction scheme of CSIM.