Solar Radiation and Climate Experiment

Solar Radiation and Climate Experiment was a NASA-sponsored satellite mission that provided state-of-the-art measurements of incoming X-ray and ultraviolet radiation from the Sun. The mission's primary goal was to measure the Total Solar Irradiance and Spectral Solar Irradiance with unprecedented accuracy and long-term precision. These critical data were essential for studying the Sun's influence on Earth's atmosphere and climate system, informing models of climate change and atmospheric chemistry. Operated by the University of Colorado Boulder's Laboratory for Atmospheric and Space Physics, the satellite far exceeded its planned lifespan.

Mission and objectives

The core scientific objective was to acquire a continuous, precise record of the Sun's energy output across a broad spectrum. This involved measuring the Total Solar Irradiance, the total power integrated across all wavelengths, and the Spectral Solar Irradiance, its distribution at individual wavelengths from the X-ray to the infrared. These measurements were designed to determine the Sun's variability over an 11-year solar cycle and to understand how these changes in solar irradiance affect Earth's climate and the chemical composition of the upper atmosphere, particularly the stratosphere and thermosphere. The data were crucial for testing and refining climate models used by institutions like the Intergovernmental Panel on Climate Change.

Spacecraft and instruments

The satellite was based on the LEOStar-2 bus built by Orbital Sciences Corporation and launched via a Pegasus XL rocket from the Stargazer carrier aircraft. It carried a suite of four primary instruments. The Total Irradiance Monitor was the flagship instrument, continuing the precise TSI record started by missions like ERBS and ACRIMSAT. The Spectral Irradiance Monitor measured ultraviolet and visible light, while the Solar Stellar Irradiance Comparison Experiment covered ultraviolet to near-infrared. The XUV Photometer System monitored extreme ultraviolet radiation. The spacecraft operated in a sun-synchronous orbit with an inclination of 40 degrees, optimized for continuous solar viewing.

Scientific findings

The mission provided definitive data confirming that Total Solar Irradiance varies by approximately 0.1% over a solar cycle, a variation too small to account for recent global warming. It precisely quantified the much larger variability in the ultraviolet spectrum, which has a disproportionate impact on ozone production and the heating of the stratosphere. These measurements were critical for understanding events like the January 2005 solar storm and its impact on the ionosphere. The data revealed complex relationships between different spectral bands during solar flares and helped disentangle solar influences from anthropogenic forcings in climate records.

Mission timeline and operations

Launched on January 25, 2003, from Cape Canaveral, the mission began its nominal five-year science phase. Operations were managed by the Laboratory for Atmospheric and Space Physics in Boulder, Colorado. The mission was extended multiple times due to the continued health of its instruments and the critical importance of its long-term dataset. In 2013, a battery anomaly began to limit operations, requiring periodic shutdowns. It continued to collect data in a reduced capacity until its final decommissioning command was sent on February 25, 2020, after over 17 years of operation.

Data products and legacy

The mission produced a continuous, 17-year climate data record of solar irradiance that is publicly archived through the Goddard Space Flight Center's Goddard Earth Sciences Data and Information Services Center. This dataset is a foundational component of climate research and was directly used by projects like the Climate Absolute Radiance and Refractivity Observatory. Its measurements bridged the gap between earlier missions like UARS and the follow-on Total and Spectral Solar Irradiance Sensor on the Joint Polar Satellite System. The precision of its data set a new standard for the field and remains a critical benchmark for understanding natural climate variability.

Category:NASA satellites Category:Earth observation satellites Category:Spacecraft launched in 2003