January 31, 2011

Applied Physics Lab tapped to provide solar probe instrument

Already on board to design and build NASA’s Solar Probe Plus spacecraft, APL has been tapped to provide an instrument for the sun-swooping probe that will measure key properties of the energetic particles blasted off the sun.

Set to launch by 2018, Solar Probe Plus will venture into the sun’s outer atmosphere—called the corona—and gather data to answer two of the biggest mysteries in heliophysics: why the sun’s corona is so much hotter than its inner regions, and how these particles, known as the solar wind, are accelerated.

Last month NASA selected five science instrument suites to fly on the probe. APL will contribute a detector to the Integrated Science Investigation of the Sun, or ISIS, a two-part energetic-particle instrument suite headed by Southwest Research Institute in San Antonio.

APL will build EPI-Lo, a time-of-flight-based spectrometer that will measure the makeup and intensities of protons and heavy elements, as well as energetic electrons at lower energies where this acceleration begins. “These measurements are important for exploring ‘shocks’ and other processes that blast material out of the corona, and for identifying seed populations for energetic particles,” said Ralph McNutt of APL’s Space Department, who is a co-investigator on the Solar Probe Plus science team.

ISIS’ other half, a high-energy detector from a team that includes the Jet Propulsion Laboratory, Caltech and NASA’s Goddard Space Flight Center, will provide similar data on protons, heavy elements and electrons at higher energies.

McNutt said that the mission’s direct measurements of activity near the sun will add data that are critical to understanding the relationship between sun and Earth, as well as the impact of solar activity on humans and technologies in space and on the ground.

NASA’s selection of the science instrument payload to compile this information—looking at the structure and dynamics of the sun’s magnetic field, investigating how the solar atmosphere is heated and accelerated to produce the solar wind, and exploring mechanisms that accelerate and transport high-energy solar particles all the way to the edge of the solar system—is a significant mission development step, added Andy Dantzler, Space Department programs manager.

After launch, Solar Probe Plus will use seven gravity assists at Venus to shape its approach to the sun. The compact solar-powered spacecraft will weigh about 1,350 pounds; designs include an 8-foot-diameter, 4.5-inch-thick, carbon foam–filled solar shield atop the spacecraft body. At its closest passes, the spacecraft must survive solar intensity 500 times stronger than spacecraft experience while orbiting Earth.

Work at APL is well under way on the solar shield designs and other systems to deliver this payload to the sun.