Quick Facts: Total Solar Irradiance Calibration Transfer Experiment (TCTE)

The TCTE launched onboard a U.S. Air Force spacecraft, shown here as it was being built at Ball Aerospace. (Courtesy Ball Aerospace)

Mission Introduction

The Total Solar Irradiance Calibration Transfer Experiment (TCTE) operated from November 2013 until June 2019, and monitored incoming solar energy to help scientists understand the causes of climate change on our planet. Incident sunlight—the sunlight that falls directly on a surface—is the primary energy source that drives Earth’s climate. TCTE measured total solar irradiance (TSI), or the total light coming from the Sun at all wavelengths, in order to monitor changes in the incident sunlight at the top of Earth’s atmosphere. The mission assisted in maintaining measurement continuity of the four-decade-long TSI climate data record following the loss of the NASA Glory mission in 2011.

TCTE launched on November 19, 2013, as a payload onboard the U.S. Air Force Space Test Program spacecraft known as STPSat-3, which was developed and built by Ball Aerospace.

LASP Roles

LASP provided:

  • The Total Solar Irradiance Monitor (TIM)
  • TIM Principal Investigator, Greg Kopp

LASP Instrument

The LASP built and designed Total Irradiance Monitor (TIM) measured the total light coming from the Sun at all wavelengths. (Courtesy LASP)

The TIM instrument measured TSI, the spatially and spectrally integrated solar radiation incident—the Sun’s net energy output—at the top of the Earth’s atmosphere. TIM helped continue a solar climate data record that has been compiled by NASA and NOAA since 1978 and is used to determine the sensitivity of the Earth’s climate to the natural effects of solar forcing. LASP has continued to refine TIM for improved accuracy since its first launch on the Solar Radiation and Climate Experiment (SORCE).

The TCTE TIM monitored the incident sunlight to the Earth’s atmosphere using an ambient temperature active cavity radiometer. Using electrical substitution radiometers (ESRs) and taking advantage of new materials and modern electronics, TCTE measured TSI to an estimated absolute accuracy of 350 ppm, or 0.035%. TCTE measured relative changes in solar irradiance to less than 10 ppm/yr (0.001%/yr), which assisted in the determination of possible long-term variations in the Sun’s output.

For more information about the Total Irradiance Calibration Transfer Experiment (TCTE), see: https://lasp.colorado.edu/home/tcte.

Quick Facts

Launch date: November 19, 2013
Launch location: Wallops Island, Virginia
Launch vehicle: Minotaur I
Mission target: Low-Earth orbit
Mission duration: 5 and 1/2 years
End of mission: June 30, 2019
Other organizations involved:

  • NASA
  • Ball Aerospace
  • U.S. Air Force
  • NOAA

(863 KB PDF)

Click on image to view a PDF of TCTE-TIM FAQs