Summary of TCTE Observations

The TCTE Total Irradiance Monitor (TIM) measures the total solar irradiance (TSI), the spatially and spectrally integrated absolute intensity of solar radiation, at the top of the Earth’s atmosphere. The TCTE TSI data are produced both as daily and 6-hourly mean irradiances reported at a solar distance of 1 astronomical unit (AU) and zero relative line-of-sight velocity with respect to the Sun, as well as at the Earth’s center (intended for climate modelers). Both TSI products contain science results for the entire TCTE mission and are updated daily seven days in arrears of data acquisition to include new measurements as available.

Commissioning – Daily Observations (Dec. 2013 – May 2014): Early in the mission, the TCTE acquired daily measurements to establish good overlap with the SORCE/TIM.

Weekly Observations (May 2014 – 31 Dec. 2014): To save costs, NOAA and NASA Project Management required the TCTE measurements be reduced to weekly. That observation cadence commenced in May 2014. The data during these weekly measurements greatly subsample the true solar variability, so have little value for solar research but nevertheless enable the calibration transfer of the TSI record from the SORCE era forward in time, as was the TCTE’s original intent.

Daily Observations Resume (1 Jan. 2015 – 1 July 2019): At the beginning of 2015 daily observations resumed. These data provide the highest quality TCTE measurements, as they are frequent enough to sample solar variability and as the instrument better maintains thermal stability with frequent solar observations.

Completed Science Mission (1 July 2019): TCTE completed its science mission and was permanently turned off on July 1, 2019. TSI data is available between 2013-12-16 and 2019-05-16.

Learn more about TCTE TSI data products via the SORCE website.

TCTE Instrument TIM
Temporal Cadence Daily and 6-Hourly
Detector Active Cavity Radiometer (ambient temperature)
Accuracy 1000 ppm (1 σ) for V.1

350 ppm (1 σ) eventual expectation

Long-Term Repeatability 10 ppm per year (1 σ)
Data Level 3


TIM TSI Data Product Release Notes