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TSI Calibration Transfer Experiment (TCTE)

The Total solar irradiance Calibration Transfer Experiment (TCTE), is funded by NOAA's next-generation Joint Polar Satellite System (JPSS) and designed to continue measurements of the total energy output of the sun. These measurements are used to measure light from the sun at all wavelengths, which is the primary energy source that drives climate on Earth, and determines if solar changes influence Earth's climate.

TCTE is one of six payloads on the STPSat-3 satellite, which was built by Ball Aerospace & Technologies Corp. in Boulder, Colo. TCTE was launched on November 19, 2013 aboard a Minotaur I rocket from NASA's Wallops Flight Facility in Wallops Island, Va.

TCTE in development TCTE shown here as it was being built at Ball Aerospace. (Courtesy Ball Aerospace)

"The TCTE instrument is a creative, fast and low cost solution that will maintain and extend the solar energy data record until the launch of the next such instrument," said Harry Cikanek, JPSS director. "The U.S. Air Force, NOAA and NASA, along with our industry and academic partners, went from idea to development in a matter of months, much faster than usualwhich is notable given the challenges of integrating a new payload on an already designed mission."

The instrument was assembled by the Laboratory for Atmospheric and Space Physics (LASP), at the University of Colorado working with the TCTE program office at NASA's Goddard Space Flight Center in Greenbelt, Md., with a quick turnaround to get the instrument ready to fly on the Air Force satellite. "The resourcefulness and ingenuity of the LASP, NASA and NOAA team in building and integrating the TCTE in such a short period demonstrates responsive engineering at its finest," said Kevin Carmack, Polar Free-Flyer project manager at NASA Goddard.

A key factor in the rapid development was the availability of an existing instrument developed by NASA for a mission launched in 2003. The TCTE instrument is one of three nearly identical instruments built as part of NASA's investment in the Total Irradiance Monitor deployed in 2003 on the Solar Radiation and Climate Experiment (SORCE) mission. Because the instrument was already built, it was able to be quickly integrated onto the Air Force satellite with short notice, due to a cancellation of another instrument.

The solar irradiance record from space that began in 1978 is currently measured by the SORCE mission. While SORCE was designed to last for five years, it is still recording data more than 10 years later, but the aging satellite is nearing the end of its battery life. TCTE is intended as an interim solution to maintain and extend the data record until the launch of next measurement mission, the Total Solar Irradiance Sensor (TSIS), which does not yet have a launch date.

"TCTE is a scientific mission that supports the national interest in understanding the solar influence on the Earth climate system. It was great how the importance of this scientific goal was recognized and supported by the governmental organizations NOAA, NASA and the Department of Defense, and implemented by the University of Colorado through LASP and industry by Ball Aerospace in such a cost effective and efficient way,f said Thomas Sparn, TCTE program manager at LASP.

NOAA's mission is to understand and predict changes in Earth's environment, from the depths of the ocean to the surface of the sun, and to conserve and manage our coastal and marine resources.

For more information about TCTE please visit:

The TIM Instrument

The TIM instrument will measure TSI, the spatially and spectrally integrated solar radiation incident--the Sun's net energy output--at the top of the Earth's atmosphere. TIM continues 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 refined TIM for improved accuracy since its first launch on the Solar Radiation and Climate Experiment (SORCE). TIM will monitor 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, the TIM measures TSI to an estimated absolute accuracy of 350 ppm, or 0.035%. Relative changes in solar irradiance are measured to less than 10 ppm/yr (0.001%/yr), allowing determination of possible long-term variations in the Sun's output.

For more information on the Total Irradiance Monitor please visit:

TCTE in development TIM measures the total light coming from the Sun at all wavelengths. It will be integrated in the TCTE payload. (Courtesy LASP)

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