NASA develops new tool to measure total solar irradiance


The instrument, the Total and Spectral Solar Irradiance Sensor (TSIS-1), is said to be capable of precisely measuring what researchers call “total solar irradiance”.

According to NASA, which has spent the past 40 years measuring solar irradiance, the new data will provide a more accurate understanding of what constitutes the earth’s primary energy source, and help scientists simulate better models of the earth’s climate.

“You can look at the Earth and Sun connection as a simple energy balance. If you have more energy absorbed by the Earth than leaving it, its temperature increases and vice versa,” said Peter Pilewskie, TSIS-1 lead scientist at the Laboratory for Atmospheric Physics (LASP) in Boulder, Colorado.

Under NASA’s direction, LASP is providing and distributing the instrument’s measurements to the scientific community. “We’re measuring all the radiant energy that is coming to Earth,” continued Pilewskie.

However, the sun’s output energy is not constant, usually fluctuating over a course the 11 years, from a relatively quiet state to a peak in intensity, with explosions of light and solar material. The peak in intensity is referred to as a solar maximum. Periods where the sun has fewer sunspots and dark areas, which can be the source of higher solar activity and in which there are fewer solar explosions, are referred to as solar minimums.

Scientists expect the sun to enter a solar minimum within the next three years, and TSIS-1 will be configured to take measurements.

“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 Centre in Greenbelt, Maryland.

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The new data is also expected to help scientists better understand the causes of solar irradiance fluctuations and how they are connected to the sun’s behavior over the last decades and centuries.

According to Doug Rabin, the deputy project scientist at Goddard, at this time, scientists do not have enough data or forecasting skill to predict whether total solar irradiance has any long-term trends, but the TSIS-1 has the potential to answer these questions.

An understanding of earth’s climate through models, is another expected benefit of the new data. Scientists use computer models to analyze change in the sun’s energy input.

The earth’s atmosphere can be simulated more accurately with the data, predicting how it will affect the atmosphere, oceans, weather and seasons. The simulations also take into account the effect on the earth’s climate of greenhouse gases, clouds, scattering light and small particles in the atmosphere called aerosols.

TSIS-1 will use two sensors to study the total amount of solar radiation emitted by the sun. The first being the Total Irradiance Monitor, while the second is called the Spectral Irradiance Monitor, which measures how the sun’s energy is distributed over the ultraviolet, visible and infrared regions of light.

NASA has said that TSIS-1 spectral irradiance measurements of the sun's ultraviolet radiation are critical to understanding the ozone layer.

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