Parker Solar Probe: To Touch The Sun

During the late summer of 2018, the Parker Solar Probe will launch from Cape Canaveral aboard a Delta IV rocket, an expendable heavy lift launch vehicle that’s currently the world’s highest capacity rocket. The Earth-shaking rocket will carry a payload many decades in the making to the beginning of a remarkable seven-year journey.

Parker Solar Probe is on a mission to touch the sun – coming closer than any spacecraft in human history. The probe will face intense heat and radiation to gather a trove of new data about our star from a vantage point that was considered to be science fiction just 50 years ago.

The solar array cooling system for the Parker Solar Probe spacecraft undergoing thermal testing at NASA Goddard Space Flight Center in Greenbelt, Maryland. Credit: NASA/JHUAPL The University of Michigan is a part of this historic mission. Climate & Space professor Justin Kasper joins four other researchers leading teams in flying instruments aboard the probe. Professor Kasper’s Solar Wind Electrons Alphas and Protons (SWEAP) Investigation will examine the most abundant particles in the solar wind: electrons, helium and hydrogen ions.

FIFTY YEARS IN THE MAKING

In 1958, astrophysicist Eugene Parker was a young professor at the University of Chicago’s Fermi Institute. That year, he published an article in the Astrophysical Journal called “Dynamics of the interplanetary gas and magnetic fields” in which he theorized that highly energized matter were continuously emanating from stars – including our own sun. Prior to this point, space was thought to be empty.

Parker described a complex stream of magnetic fields, plasmas, and energized particles flowing outward from the sun’s surface. He called this energetic torrent the “solar wind.” He further proposed an explanation for the superheated solar atmosphere, called the corona, which, in apparent contradiction to the laws of physics, is actually hotter than the surface of the sun. Parker’s paper was received with great interest, resulting in the first concepts for a solar probe being discussed at the “Simpson’s Committee” of the Space Science Board (National Academy of Sciences, Oct. 24, 1958). In the years since, researchers have continued to focus on the space environment surrounding our star, a field of study now known as heliophysics.

Earlier this year, the mission (previously known as Solar Probe Plus) was renamed in honor of Professor Parker in acknowledgement of his enormous contributions to the field of heliophysics and space science.

“This is the first time NASA has named a spacecraft for a living individual,” said Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate in Washington. “It’s a testament to the importance of his body of work, founding a new field of science that also inspired my own research and many important science questions NASA continues to study and further understand every day.”

REACHING OUT

Parker Solar Probe’s proximity to the Sun will provide researchers with an unprecedented bird’s-eye view of the workings of our star, critical information that will aid in our ability to forecast significant space-weather events. The historic mission will visit a previously unexplored area of our solar system, providing answers to scientific questions waiting for over five decades.

“The solar probe is going to a region of space that has never been explored before. It’s very exciting that we’ll finally get a look,” says Professor Parker. “One would like to have some more detailed measurements of what’s going on in the solar wind. I’m sure that there will be some surprises. There always are.”

But unlocking the mysteries of the solar corona isn’t the only motivating factor for the mission. The fundamentally unstable corona is the source of the solar wind, and other phenomena such as solar flares and coronal mass ejections. During these events, billions of tons of highly magnetized material can erupt from the sun at speeds of several million miles per hour. When the material reaches Earth, it interacts with (or “shakes”) our protective magnetic field. Shaking Earth’s magnetic field can cause surges in power lines that destroy equipment and knock out power over large areas. A solar event can also change the orbits of satellites and shorten their lifetimes. Until we can explain what is going on up close to the sun, we will not be able to accurately predict space weather effects that can cause havoc at Earth.

A recent National Academy of Sciences study estimates that a huge solar event could cost the U.S. $2 trillion in damage without sufficient advance warning. The result of such an event could potentially leave the eastern seaboard of the U.S. without power for a year.

As our society becomes ever more dependent on technology, the threat of global systemic disruption becomes exponentially greater. Parker Solar Probe will be the first spacecraft to penetrate the sun’s corona, and the invaluable data it collects on the ebb and flow of the solar environment will help us better plan and protect against solar weather events in the future.

THE MISSION

In order to get close to its objective, Parker Solar Probe will leverage the gravitational field of the planet Venus, performing seven flybys during its nearly seven-year mission to gradually shrink its orbit around the sun. During its final three orbits, the probe will fly to within 9.86 solar radii (the sun’s radius), or about 3.7 million miles of the sun. This is about seven times closer than the Helios-A spacecraft’s record-setting pass in February of 1975.

At its closest passes to the sun, the probe will be traveling at over 400,000 miles per hour – faster than any previous spacecraft. At that distance, the temperature outside the spacecraft will reach nearly 2,500 degrees Fahrenheit (1,377 degrees Celsius). The spacecraft and most instruments will be protected from the Sun’s heat by a 4.5-inch-thick carbon-composite shield. The lone exception will be Professor Kasper’s SWEAP investigation, a special component of which is a small instrument called a Faraday Cup that will peer around the protective heat shield of the spacecraft directly at the sun. SWEAP will pull in a sample of the solar atmosphere and touch the sun for the first time in human history.

The primary science goals for the mission are to trace the flow of energy and understand the heating of the solar corona, and to explore the physical mechanisms that accelerate the solar wind and energetic particles.

To meet those objectives, Parker Solar Probe will carry four instrument suites into the corona and study the solar wind and energetic particles as they blast off the surface of the sun. These instrument suites will study magnetic fields, plasma, and energetic particles, and will image the solar wind.

The instruments are: the Fields Experiment from the University of California Space Sciences Laboratory, Berkeley, California (Prof. Stuart Bale, Principal Investigator); the Integrated Science Investigation of the Sun from Princeton University (Dr. David McComas, Principal Investigator); the Solar Wind Electrons Alphas and Protons Investigation from the University of Michigan/Smithsonian Astrophysical Observatory, Cambridge, Massachusetts (Prof. Justin Kasper, Principal Investigator); and the Wide Field Imager for Solar Probe Plus from the Naval Research Laboratory, Washington, D.C. (Dr. Russell Howard, Principal Investigator).

“Parker Solar Probe is going to answer questions about solar physics that we’ve puzzled over for more than six decades,” said Parker Solar Probe Project Scientist Nicola Fox, of the Johns Hopkins University Applied Physics Laboratory. “It’s a spacecraft loaded with technological breakthroughs that will solve many of the largest mysteries about our star, including finding out why the sun’s corona is so much hotter than its surface. And we’re very proud to be able to carry Gene’s (Parker) name with us on this amazing voyage of discovery.”

Parker Solar Probe is scheduled to launch between July 31 – August 19, 2018. ​

- EJ Olsen