Minimize ISS Utilization: TSIS

ISS Utilization: TSIS (Total and Spectral solar Irradiance Sensor)

Overview    Launch   Instrument   References

The TSIS instrument, first selected in 1998 for the NPOESS (National Polar-orbiting Operational Environmental Satellite System) mission, re-manifested in 2010 on the NOAA-NASA JPSS (Joint Polar Satellite System) mission, then on the NOAA Polar Free Flyer, is now (2015) scheduled to be implemented as part of the newly established SIDAR (Solar Irradiance, Data and Rescue) program with a launch planned in 2017 to the ISS (International Space Station). 1) 2)

The objective of TSIS is to acquire measurements of total and spectral solar irradiance (TSI and SSI, respectively). TSI (Total Solar Irradiance) is required for establishing Earth's total energy input while SSI (Solar Spectral Irradiance) 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 TIM (Total Irradiance Monitor) and the SIM (Spectral Irradiance Monitor), currently flying on the NASA SORCE (Solar Radiation and Climate Experiment) mission. 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.


Figure 1: Overview of Earth science instruments on the ISS (installed or planned) in the second decade of the 21st century (image credit: NASA) 3)


Launch: A launch of TSIS-1 on SpaceX-15 Falcon 9 vehicle in a Dragon trunk is planned for August 2017. The launch site is the Cape Canaveral Air Force Station.

Orbit: Near-circular orbit of the ISS, altitude of ~400 km, inclination = 51.6º, period = 93 minutes.

Robotic installation of TSIS-1 onto EXPRESS (Expedite the Processing of Experiments to Space Station) Logistics Carrier (ELC-3).

• NASA/GSFC (Goddard Space Flight Center), Greenbelt, Maryland:

- TSIS-1 project: project management, system engineering, safety and mission assurance, and engineering oversight for the TSIS-1 payload

- ESDIS (Earth Science Data and Information System) Project/GES DISC (Goddard Earth Sciences Data and Information Services Center): archive and distribution for TSIS-1 data

• University of Colorado CU/LASP (Laboratory for Atmospheric and Space Physics), Boulder, CO:

- Design, development and testing of TSIS-1, support for ISS integration, science operations of the TSIS-1 instrument, data processing, data evaluation and delivery to the GES DISC

- TSIS-1 Science Operations Center, TSIS-1 Science Data System

• International Space Station Program:

- Launch services and robotic installation of the TSIS-1 payload onto an ISS Express Logistics Carrier (ELC-3), mission operations, and communications

- ISS interface: ISS POIC (Payload Operations Integration Center), Huntsville Operations Support Center, AL.

Table 1: Overview of TSIS-1 mission responsibilities 4)

The TSIS-1 mission is planned for an operational period of 5 years with solar tracking during sunlit phases.

• TIM (Total Irradiance Monitor) provides 7 configurations. TIM measures TSI incident at outer boundaries of atmosphere.

• SIM (Spectral Irradiance Monitor) provides 13 configurations. SIM measures SSI from 200 – 2400 nm (96% of TSI).

Mounted on the ELC-3 (ExPRESS Logistics Carrier 3), 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.


Figure 2: Artist's rendition of the TSIS-1 instrument to be installed at ELC-3 of the ISS (image credit: NASA, LASP)

Legend to Figure 2: The TSIS TPS (Thermal Pointing System) is deployed above the ELC-3 location after installation in order to provide sufficient clearance to track the sun each orbit with a two-axis gimbal.



TSIS (Total and Spectral solar Irradiance Sensor) instrument

In early 2014, NOAA and NASA agreed to fly TSIS on the ISS (International Space Station). In the FY16 President's Budget, NASA assumes responsibility for the TSIS mission on ISS (Ref. 4).

The TSIS-1 TIM and SIM instruments are upgraded versions of the two instruments that are flying on the SORCE (Solar Radiation and Climate Experiment) mission.

TSIS-1 is needed on-orbit as soon as practical to provide total and spectral solar irradiance measurements needed to maintain 35+ year climate data record continuity:

- Solar irradiance data record is critical for determining solar influences on Earth climate

- SORCE (Solar Radiation and Climate Experiment), launched in 2003 with a 5-year design life, currently provides these measurements

- Total Solar Irradiance Calibration Transfer Experiment (TCTE), built from "spare parts" and launched November 2013 on Air Force Space Test Program Satellite (STPSat-3, 2-3 year design life), will provide calibration between SORCE and TSIS-1 total solar irradiance measurements.


Figure 3: The TSI Climate Data Record now spans 36 years. Instrument offsets are unresolved calibration differences, much of which are due to internal instrument scatter (image credit: CU/LASP)


Development status:

• University of Colorado is upgrading existing chamber for TSIS-1 thermal vacuum testing.

• NASA assumed responsibility for TSIS-1 as of October 1, 2015. The TSIS-1 project (and LASP contract) are funded.

• A TSIS-1 delta-Critical Design Review was successfully completed July 2015.

• A NASA decision to accommodate TSIS-1 on the ISS (International Space Station) was provided in April 2014.

• A portion of the TSIS-1 sensors were already fabricated over the years; they are in storage at CU/LASP (Figure 4).


Figure 4: Status of the TSIS elements in November 2015 (image credit: CU/LASP)

Science Objectives:

• Nominal five-year mission, provides continuation of TSI record from SORCE and USAF STPSat-3

• Quantify variability in incoming solar radiation, as the most precise indicator for changes in Sun's energy output

• Determine regions/layers of Earth's atmosphere that are affected by solar variability, in order to quantify solar forcing mechanisms causing changes in climate

• Determination of whether the Sun's spectral ultraviolet output is in- or out-of-phase with visible wavelength output

• Provision of TSI and SSI data to support community science in climate, atmosphere, solar physics, and radiative transfer modeling.


Figure 5: Total and spectral solar irradiance missions of NASA and NOAA (image credit: NOAA, NASA, Ref. 2)


1) "Quick Facts: Total and Spectral Solar Irradiance Sensor (TSIS)," CU/LASP (University of Colorado/ Laboratory for Atmospheric and Space Physics), 2015, URL:

2) Dan Mamula, "NOAA Solar Irradiance Data and Rescue (SIDAR) Program," NOAA, April 30, 2015, URL:

3) Julie A. Robinson, William L. Stefanov,"Earth Science Research on the International Space Station," Committee on Earth Science and Applications from Space (CESAS) Space Studies Board National Academies of Science, Engineering, Medicine, 29 March 2016, URL:

4) Candace Carlisle, "Total and Spectral solar Irradiance Sensor (TSIS-1) Project Overview, " 2015 Sun-Climate Symposium, Savannah, Georgia, USA, Nov. 10-13, 2015 URL:

The information compiled and edited in this article was provided by Herbert J. Kramer from his documentation of: "Observation of the Earth and Its Environment: Survey of Missions and Sensors" (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates (

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