SORCE had launched in 2003, and by 2013 switched to daytime-only observations due to battery degradation. TSIS-1, however, was not yet ready to launch. In order to contain a continuous record of TSI measurements, TCTE was assembled and launched in a span of five months. Although it was originally intended as an 18-month demonstration, TCTE's lifetime was extended and it continued to collect data through 2017, when TSIS-1 came online.
In addition to helping fill the gap between these missions and maintaining a continuous record of TSI observations, TCTE was used to help calibrate SORCE observations and lower uncertainties in total solar irradiance data. TCTE's quick construction was achieved partly by refurbishing SORCE's ground-based Total Irradiance Monitor (TIM) witness unit—a nearly identical instrument that had been kept for calibration and testing. The TCTE TIM, like its SORCE version, measured solar irradiance across the electromagnetic spectrum, detecting changes in irradiance as small as 0.001% per year.