The Compact TIM (CTIM) Instrument

The long-term balance between Earth’s absorption of solar radiative energy and emission of radiation to space is a fundamental climate measurement. Total solar irradiance (TSI) has been measured from space by a 40-year uninterrupted sequence of instruments. The Compact Total Irradiance Monitor (CTIM) is a CubeSat instrument that will demonstrate next-generation technology for monitoring total solar irradiance. It includes novel silicon-substrate room-temperature vertically aligned carbon nanotube (VACNT) bolometers. The CTIM, an eight-channel 6U CubeSat instrument, is currently in the development phase. The basic design is similar to the SORCE, TCTE and TSIS TIM instruments. Like TSIS TIM it will measure the total irradiance of the sun with an uncertainty of <0.01% and a stability of <0.001%/year. The underlying technology, including the silicon VACNT bolometers, has been demonstrated at the prototype-level. In late 2018 and early 2019 we will build, test, and environmentally qualify a CTIM prototype. A flight instrument will then be built, integrated with a CubeSat bus, and tested in preparation for a target launch date in late 2020.