Total and Spectral Solar Irradiance Sensor

Total and Spectral Solar Irradiance Sensor is a suite of scientific instruments designed to make precise, long-term measurements of the Sun's energy output. It is a critical component of the National Aeronautics and Space Administration's Earth observation fleet, continuing a multi-decade record essential for climate science. The sensor operates from the International Space Station, providing data on both total solar irradiance and its spectral distribution. This information is fundamental for understanding the Sun's influence on Earth's climate system and atmospheric chemistry.

Overview and Mission Objectives

The primary mission of the Total and Spectral Solar Irradiance Sensor is to extend the uninterrupted, four-decade climate data record of solar irradiance initiated by missions like the Solar Radiation and Climate Experiment. Its key objectives are to measure Total Solar Irradiance with high accuracy and to observe Spectral Solar Irradiance from the ultraviolet to the infrared wavelengths. These measurements are vital for detecting long-term trends in the Sun's behavior and for separating natural solar variability from anthropogenic forcing in climate change studies. The project is managed by the Goddard Space Flight Center with the University of Colorado Boulder's Laboratory for Atmospheric and Space Physics providing the core instrumentation.

Instrument Design and Operation

The sensor suite consists of two primary instruments: the Total Irradiance Monitor and the Spectral Irradiance Monitor. The Total Irradiance Monitor is an electrically self-calibrating radiometer that captures the full spectrum of the Sun's power reaching Earth. The Spectral Irradiance Monitor uses a prism spectrometer to break sunlight into its constituent wavelengths, monitoring variations in specific spectral bands. The instruments were launched aboard a SpaceX Falcon 9 rocket as part of the Space Test Program Satellite-6 payload and were subsequently installed on the International Space Station's ExPRESS Logistics Carrier. This external platform provides a stable, sun-pointing vantage for continuous observation.

Scientific Data and Contributions

Data from the Total and Spectral Solar Irradiance Sensor are processed and archived by the Goddard Space Flight Center's Solar Radiation and Climate Experiment project team and distributed through the NASA Langley Research Center's Atmospheric Science Data Center. The measurements have refined the absolute value of the solar constant and provided detailed records of spectral changes during the declining phase of Solar cycle 24 and the onset of Solar cycle 25. This spectral data is crucial for modeling the response of the Earth's ozone layer to ultraviolet flux and for improving the accuracy of climate model simulations conducted by institutions like the National Center for Atmospheric Research.

Historical Context and Development

The development of the Total and Spectral Solar Irradiance Sensor was driven by the need to continue the solar irradiance record following the end of the Solar Radiation and Climate Experiment mission. Its heritage traces directly to instruments flown on Solar Radiation and Climate Experiment and the Solar Ultraviolet Spectral Irradiance Monitor on the Solar Radiation and Climate Experiment satellite. The project faced significant challenges, including a launch delay following the failure of the Orbital Sciences Cygnus CRS Orb-3 mission. Funding and oversight were provided by the United States Department of Defense's Space Test Program, with NASA assuming responsibility for mission operations and science data processing post-launch.

Integration and Impact on Climate Models

The long-term, precise data from the Total and Spectral Solar Irradiance Sensor are integrated into major climate assessment reports, such as those by the Intergovernmental Panel on Climate Change. By quantifying the Sun's radiative forcing, the data help constrain key parameters in general circulation models used by the National Oceanic and Atmospheric Administration and the European Centre for Medium-Range Weather Forecasts. This integration improves predictions of global temperature trends, sea level rise, and regional climate impacts, thereby informing international policy discussions under frameworks like the United Nations Framework Convention on Climate Change.

Category:NASA programs Category:Earth observation satellites Category:Spacecraft launched in 2018