When a sun-gazing NASA satellite designed and built by the University of Colorado Boulder launched into space on Jan. 25, 2003, solar storms were raging.
A decade later, the four instruments onboard the Solar Radiation and Climate Experiment, or SORCE, have given scientists an unprecedented look at some of the most intense solar eruptions ever witnessed 鈥� including the notorious Halloween storms in October and November 2003 鈥� as well as the anomalously quiet solar minimum that hushed the sun鈥檚 surface beginning in 2008 and, now, a new solar maximum that appears to be the least active in a century.
鈥淲e were there to see it transform from a fairly normal solar cycle to a very low-activity solar cycle,鈥� said Tom Woods, associate director of CU-Boulder鈥檚 Laboratory for Atmospheric and Space Physics, known as LASP, and principal investigator for SORCE. 鈥淥f course we couldn鈥檛 predict or know that, but it鈥檚 very exciting.鈥�
The data generated by SORCE鈥檚 instruments, which were originally designed to operate for just five years, are downloaded twice a day with the help of CU-Boulder undergraduates working at LASP mission control. Scientists are now using that data to better understand how energy from the sun affects Earth鈥檚 climate. While human-produced greenhouse gases have been the dominant driver of climate change over the last several decades, the activity of the sun can either enhance or offset the resulting global warming.
鈥淎bout 10 to 15 percent of the climate warming since 1970 is due to the sun,鈥� Woods said. 鈥淭hat鈥檚 going to change now. Now that solar activity is low, the global warming trend could slow down some, but not nearly enough to offset the anthropogenic effects on global warming.鈥�
The current, lackluster solar maximum is being compared to periods when astronomers observed very few sunspots in the early 19th century known as the Dalton Minimum and in the last half of the 17th century known as the Maunder Minimum. During the Maunder Minimum, which coincided with an era known as the Little Ice Age, temperatures in Europe were especially cool, with rivers and canals freezing during the winter across the continent and rapidly advancing glaciers destroying villages in the Swiss Alps.
The SORCE mission is also a critical contributor to the long-term record of total solar irradiance 鈥� the magnitude of the sun鈥檚 energy when it reaches the top of the Earth鈥檚 atmosphere 鈥� which stretches back to 1978, when the Nimbus-7 satellite was launched. The Total Irradiance Monitor, or TIM, instrument onboard SORCE is taking the most accurate and most precise measurements of total solar irradiance ever collected.
鈥淭he total solar irradiance provides nearly all the energy powering the Earth鈥檚 climate system, exceeding all other energy sources combined by 2,500 times,鈥� said Greg Kopp, LASP senior research scientist and co-investigator responsible for the TIM instrument. 鈥淎ny change in total irradiance can thus have large effects on our climate.鈥�
Data from the SORCE mission have also begun a new record for measurements of visible and near-infrared light emitted from the sun. The solar spectral irradiance measurements are being made for the first time by the Spectral Irradiance Monitor, or SIM. Combined with other instruments onboard SORCE, scientists can now see all the wavelengths, including those in the ultraviolet range, emitted by the sun at once. This new way of seeing the sun has led to interesting discoveries, including that the energy emitted in some wavelengths of light vary out of phase with the sun鈥檚 overall activity, actually increasing as the number of sunspots decreases.
Now that SORCE has doubled its original life expectancy, LASP scientists are building new instruments to take over when SORCE gives out. A new TIM built at LASP launched on NASA鈥檚 Glory mission in 2011, but the satellite failed to make orbit. After the loss of Glory, CU-Boulder scientists, determined to avoid a gap in the record of total solar irradiance measurements, came up with a creative solution, repurposing a ground-based TIM to quickly make it space-worthy and then integrating it onto a U.S. Air Force satellite built by Ball Aerospace that is set to launch in August of this year.
鈥淚t鈥檚 important to have continuous measurements of solar irradiance since we鈥檙e looking for small changes in the sun鈥檚 output over decades and even centuries,鈥� said Kopp. 鈥淒etecting such small changes using measurements disconnected in time would make this even more difficult.鈥�
A new SIM instrument, also built at LASP, is scheduled to launch in 2016 on a National Oceanic and Atmospheric Administration satellite. But while SORCE is expected to continue functioning for at least another year, allowing for overlapping measurements with the TIM instrument launching in August, it鈥檚 uncertain if SORCE鈥檚 SIM instrument will still be running when its successor makes it to space in 2016.
鈥淲e鈥檙e definitely hoping and planning that SORCE lasts through this year,鈥� Woods said. 鈥淏ut 2016 鈥� I don鈥檛 think SORCE鈥檚 battery is going to last that long.鈥�
During SORCE鈥檚 10-year foray in space, the satellite also witnessed two rare transits of the planet Venus in front of the sun and another two less-infrequent transits by Mercury. When Venus, the larger of the two planets and the closer to Earth, blocked out part of the sun鈥檚 light, SORCE鈥檚 TIM instrument measured a corresponding drop in the amount of total solar irradiance. The measurements are now useful reference tools for astronomers hoping to discover planets around other stars by measuring a dip in a star鈥檚 light from a planetary transit.
In all, CU-Boulder has received about $120 million from NASA for the construction and operation of SORCE. But in 2008, LASP took the unusual step of returning $3 million in cost savings from the SORCE mission to NASA that resulted from the program鈥檚 efficient operations.
Researchers at LASP are planning to celebrate SORCE鈥檚 10th birthday with cake, a science seminar and a write-up of the satellite鈥檚 top-10 accomplishments in NASA鈥檚 The Earth Observer magazine.
But while the decade mark is typically an important milestone for celebration here on Earth, the more appropriate milestone for SORCE may come in 2014 at the 11-year mark, the average length of a complete solar cycle.
鈥淓leven years is special to us,鈥� Woods said. 鈥淚nstead of having a big science conference this year, we鈥檙e planning it for next January.鈥�
For more information, visit LASP鈥檚 SORCE website at .
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SORCE Fact Sheet
- The 640-pound SORCE satellite was launched into space on Jan. 25, 2003, on a Pegasus XL launch vehicle from Florida鈥檚 Kennedy Space Center.
- SORCE has four instruments onboard, all of which were designed and built at the University of Colorado Boulder鈥檚 Laboratory for Atmospheric and Space Physics: the Total Irradiance Monitor (TIM), the Spectral Irradiance Monitor (SIM), the X-ray ultraviolet Photometer System (XPS) and the Solar and Stellar Irradiance Comparison Experiment (SOLSTICE).
- CU-Boulder has received about $120 million from NASA to design, build and operate SORCE. In 2008, LASP returned about $3 million in cost savings to NASA.
- SORCE is controlled by CU-Boulder staff and students at LASP鈥檚 mission operations center in the CU Research Park.
- Measurements taken by SORCE extend the record of Total Solar Irradiance, or the amount of the sun鈥檚 energy that reaches the top of Earth鈥檚 atmosphere and drives the Earth鈥檚 climate system. During its 10 years in space, SORCE鈥檚 TIM instrument established a new baseline for TSI that is 4.6 watts per square meter lower than previously measured.
- SORCE鈥檚 SIM and SOLSTICE instruments have allowed scientists for the first time to look at most of the wavelengths of light emitted from the sun.
- SORCE鈥檚 instruments observed two transits of Venus (June 2004 and June 2012) and two transits of Mercury (May 2003 and November 2006)
- The original principal investigator on the SORCE mission was LASP鈥檚 Gary Rottman, who retired in 2005. The current principal investigator is LASP鈥檚 Tom Woods.
- The SORCE website is at .
Contact:
Tom Woods, 303-492-422
Tom.Woods@lasp.colorado.edu
Greg Kopp, 303-735-0934
Greg.Kopp@lasp.colorado.edu
Laura Snider, CU media relations, 303-735-0528
Laura.Snider@colorado.edu
