University of Colorado at Boulder University of Colorado CU Home Search A to Z Index Map

Quick Facts: Total and Spectral Solar Irradiance Sensor (TSIS)

A close-up view of TSIS as deployed on the International Space Station ExPRESS logistics carrier (ELC)-3. The TSIS Thermal Pointing System (TPS) is deployed above the ELC after installation in order to provide sufficient clearance to track the sun each orbit with a two-axis gimbal. (Courtesy NASA/LASP)

A close-up view of TSIS as deployed on the International Space Station ExPRESS logistics carrier (ELC)-3. The TSIS Thermal Pointing System (TPS) is deployed above the ELC after installation in order to provide sufficient clearance to track the sun each orbit with a two-axis gimbal. (Courtesy NASA/LASP)

Mission Introduction

The Total and Spectral Solar Irradiance Sensor (TSIS), first selected in 1998 for the National Polar-orbiting Operational Environmental Satellite System (NPOESS), re-manifested in 2010 on the NOAA-NASA Joint Polar Satellite System (JPSS), then the NOAA Polar Free Flyer, is now scheduled to be implemented as part of the newly established Solar Irradiance, Data and Rescue (SIDAR) program with a launch in 2017 to the International Space Station.

The TSIS will acquire measurements of total and spectral solar irradiance (TSI and SSI, respectively). TSI is required for establishing Earth’s total energy input while SSI is needed to understand how the atmosphere responds to changes in the sun’s output. Solar irradiance is one of the longest and most fundamental of all climate data records derived from space-based observations.

TSIS provides continuation of the Total Irradiance Monitor (TIM) and the Spectral Irradiance Monitor (SIM), currently flying on the NASA Solar Radiation and Climate Experiment (SORCE). Launched in 2003, SORCE is now more than six years beyond its prime-mission lifetime. The launch failure of the NASA Glory mission in 2011, coupled with diminished battery capacity on SORCE and delays in the launch of TSIS have put the continuous 36-year TSI record at risk. In 2012, a plan to maintain continuity of the TSI calibration scale between SORCE and TSIS was rapidly implemented through the USAF Space Test Program STPSat-3 that launched in late 2013. The shorter SSI record faces a likely gap between SORCE and TSIS.

Highly accurate, stable, and continuous observations of solar irradiance are critical to understanding the present climate epoch and for predicting future climate.

The Total Irradiance Monitor

TIM measures the total light coming from the sun at all wavelengths. (Courtesy LASP)

LASP Roles

LASP provides:

  • The Total Irradiance Monitor (TIM) instrument
  • The Spectral Irradiance Monitor (SIM) instrument
  • TSIS Principal Investigator, Peter Pilewskie
  • Mission operations for TSIS

LASP Instruments

TSIS is a dual-instrument package that will acquire solar irradiance measurements from the International Space Station over a nominal period of five years. TSIS has been identified as providing critical data in determining the natural forcings of the climate system and the current collaboration with the National Oceanic and Atmospheric Administration (NOAA) will insure the continuity of the solar irradiance Climate Data Record (CDR) through TSIS.

The Spectral Irradiance Monitor (SIM) instrument

SIM will measure how the light from the sun is distributed by wavelength. (Courtesy LASP)

TSIS is comprised of the Total Irradiance Monitor, or TIM, which measures the total solar irradiance (TSI) that is incident at the outer boundaries of the atmosphere; and the Spectral Irradiance Monitor, or SIM, which measures solar spectral irradiance (SSI) from 200 nm to 2400 nm (96 percent of the TSI). The TSIS TIM and SIM are heritage instruments to those currently flying on the SORCE satellite. Both were selected as part of the TSIS because of their unprecedented measurement accuracy and stability, and because both measurements are essential to constraining the energy input to the climate system and interpreting the response of climate to external forcing. TSIS is required in order to continue the 36-year record of TSI, extend the newer 12-year record of SSI, and insure the stewardship of the solar irradiance Climate Data Record into the future.

Quick Facts

Launch date: Delivery to ISS in April 2017; Launch and deployment in August 2017
Launch location: Cape Canaveral Air Force Station
Launch vehicle: Space X Falcon 9 and Dragon capsule
Mission target: Low Earth orbit
Mission duration: 5 years
Other key dates:
Other organizations involved:

  • NASA’s Goddard Space Flight Center (GSFC)
  • National Oceanic and Atmospheric Administration