New solar sensor will help monitor sun-to-climate link with greater accuracy
NASA has powered on its latest space payload to continue long-term measurements of the Sun’s incoming energy. Total and Spectral solar Irradiance Sensor (TSIS-1), installed on the International Space Station, became fully operational with all instruments collecting science data as of this March.
“TSIS-1 extends a long data record that helps us understand the Sun’s influence on Earth’s radiation budget, ozone layer, atmospheric circulation, and ecosystems, and the effects that solar variability has on the Earth system and climate change,” said Dong Wu, TSIS-1 project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
The instrument was launched from Space Launch Complex 40 at Cape Canaveral Air Force Station in Florida aboard a SpaceX Falcon 9 rocket on Dec. 15, 2017. After a two-week pause, TSIS-1 was extracted from the trunk of the SpaceX Dragon capsule and integrated onto its permanent home on the space station.
For over two months, the operations team at the University of Colorado Laboratory for Atmospheric and Space Physics (LASP) in Boulder, Colorado have been testing TSIS-1. First, the team tested the all-important pointing platform that directs the solar instruments at the Sun.
Next came testing of the solar instruments. TSIS-1 studies the total amount of light energy emitted by the Sun using the Total Irradiance Monitor, one of two sensors onboard. This sensor’s data will give us a better understanding of Earth’s primary energy supply and provide information to help improve models simulating the planet’s climate. The monitor first started collecting science data – called “first light”— on January 11th after its doors were opened to fully view the Sun. The sensor extends a 40-year measurement of the Sun’s total energy to Earth.
The second onboard sensor, called the Spectral Irradiance Monitor, measures how the Sun’s energy is distributed over the ultraviolet, visible and infrared regions of light. Measuring the distribution of the Sun’s energy is important because each wavelength of light interacts with Earth’s atmosphere differently.
For instance, spectral irradiance measurements of the Sun’s ultraviolet radiation are critical to understanding the ozone layer — Earth’s natural sunscreen that protects life from harmful radiation. The sensor experienced first light on March 4th when full science data collection began. TSIS-1’s Spectral Irradiance Monitor extends a 15-year record of spectral irradiance measurements.
“All systems are operating within their expected ranges,” said Peter Pilewskie, TSIS-1 lead scientist LASP. “A lot of hard work remains for the team to interpret and validate the TSIS-1 data.”
In addition to those 11-year changes, entire solar cycles can vary from decade to decade. Scientists have observed unusually quiet magnetic activity from the Sun for the past two decades with previous satellites. During the last prolonged solar minimum in 2008-2009, our Sun was as quiet it has been observed since 1978. Scientists expect the Sun to enter a solar minimum within the next three years, and TSIS-1 will be primed to take measurements of the next minimum.
“We don’t know what the next solar cycle is going to bring, but we’ve had a couple of solar cycles that have been weaker than we’ve had in quite a while so who knows. It’s a pretty exciting time to be studying the Sun,” said Dong Wu, the TSIS-1 project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Goddard is responsible for the overall development and operation of TSIS-1 on the International Space Station.
TSIS-1 data are particularly important for helping scientists understand the causes of total solar irradiance fluctuations and how they are connected with the Sun’s behavior over decades or centuries. Today, scientists have neither enough data nor the forecasting skill to predict whether total solar irradiance has any long-term trend, said Doug Rabin, deputy project scientist at Goddard. TSIS-1 will continue a data sequence that is vital to answering that question.
These data are also important for understanding Earth’s climate through models. Scientists use computer models to interpret changes in the Sun’s energy input. If less solar energy is available, scientists can gauge how that will affect Earth’s atmosphere, oceans, weather and seasons by using computer simulations. The input from the Sun is just one of many factors scientists used to model Earth’s climate. Earth’s climate is also affected by other factors such as greenhouse gases, clouds scattering light and small particles in the atmosphere called aerosols — all of which are taken into account in comprehensive climate models.
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