NASA’s Parker Solar Probe depends on the Sun, not just as an object of scientific investigation, but also for the power that drives its instruments and systems. On Thursday, May 31, 2018, the spacecraft’s solar arrays were installed and tested. These arrays will power all of the spacecraft’s systems, including the suites of scientific instruments studying the solar wind and the Sun’s corona as well as the Solar Array Cooling System (SACS) that will protect the arrays from the extreme heat at the Sun.
“Unlike solar-powered missions that operate far from the Sun and are focused only on generating power from it, we need to manage the power generated along with the substantial heat that comes from being so close to the Sun,” said Andy Driesman, project manager from the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland. “When we’re out around the orbit of Venus, we fully extend the arrays to get the power we need. But when we’re near the Sun, we tuck the arrays back until only a small wing is exposed, and that portion is enough to provide needed electrical power.”
The solar arrays are cooled by a gallon of water that circulates through tubes in the arrays and into large radiators at the top of the spacecraft. They are just over three and a half feet (1.12 meters) long and nearly two and a half feet (0.69 meters) wide. Mounted on motorized arms, the arrays will retract almost all of their surface behind the Thermal Protection System – the heat shield – when the spacecraft is close to the Sun. The solar array installation marks some of the final preparation and testing of Parker Solar Probe leading up to the mission’s July 31 launch date.
Throughout its seven-year mission, NASA’s Parker Solar Probe will swoop through the Sun’s atmosphere 24 times, getting closer to our star than any spacecraft has gone before. The spacecraft will carry more than scientific instruments on this historic journey — it will also hold more than 1.1 million names submitted by the public to go to the Sun.
“Parker Solar Probe is going to revolutionize our understanding of the Sun, the only star we can study up close,” said Nicola Fox, project scientist for Parker Solar Probe at the Johns Hopkins Applied Physics Lab in Laurel, Maryland. “It’s fitting that as the mission undertakes one of the most extreme journeys of exploration ever tackled by a human-made object, the spacecraft will also carry along the names of so many people who are cheering it on its way.”
NASA’s Parker Solar Probe gets its power from the Sun, so the solar arrays that collect energy from our star need to be in perfect working order. This month, members of the mission team tested the arrays at Astrotech Space Operations in Titusville, Florida, to ensure the system performs as designed and provides power to the spacecraft during its historic mission to the Sun.
Parker Solar Probe is powered by two solar arrays, totaling just under 17 square feet (1.55 square meters) in area. They are mounted to motorized arms that will retract almost all of their surface behind the Thermal Protection System – the heat shield – when the spacecraft is close to the Sun.
You don’t get to swim in the Sun’s atmosphere unless you can prove you belong there. And Parker Solar Probe’s Faraday cup, a key sensor on the spacecraft, earned its stripes on April 19 by enduring testing in a homemade contraption designed to simulate the Sun.
The cup will scoop up and examine the solar wind as the probe passes closer to the Sun than any previous human-made object. In order to confirm the cup will survive the extreme heat and light of the Sun’s corona, researchers previously tortured a model of the Faraday cup at temperatures exceeding 3,000 degrees Fahrenheit, courtesy of the Oak Ridge National Laboratory’s Plasma Arc Lamp. The cup, built from refractory metals and sapphire crystal insulators, exceeded expectations.
But the final test took place on April 19, in a homemade contraption Kasper and his research team call the Solar Environment Simulator. While being blasted with roughly 10 kilowatts of light on its surface—enough to heat a sheet of metal to 1,800 degrees Fahrenheit in seconds—the Faraday cup model ran through its paces, successfully scanning a simulated stream of solar wind.
Justin Kasper, University of Michigan associate professor of climate and space sciences and engineering, is principal investigator for Parker Solar Probe’s Solar Wind Electrons Alphas and Protons (SWEAP) investigation.
NASA’s Parker Solar Probe will carry 1,137,202 submitted and confirmed names on its journey to the Sun. Submissions opened on March 6, 2018, and closed on April 27 at 11:59 p.m. EDT. A chip containing the names will be installed onto the spacecraft before launch.
NASA’s Parker Solar Probe is rotated down to a horizontal position during pre-launch processing and testing on April 10, 2018, at Astrotech Space Operations in Titusville, Florida, just outside Kennedy Space Center. Once horizontal, the integration and testing team will measure the alignment of the heat shield mounting points with respect to the spacecraft structure. This is done to assure that the umbra (or shadow) cast by the heat shield – called the Thermal Protection System – protects the spacecraft and instruments.
On the morning of Tuesday, April 17, 2018, crews from United Launch Alliance raised the 170-foot tall Delta IV Heavy launch vehicle – the largest and most powerful rocket currently used by NASA – at Launch Complex 37 at Cape Canaveral Air Force Station in Florida. This Delta IV Heavy will carry Parker Solar Probe, humanity’s first mission to the Sun’s corona, on its journey to explore the Sun’s atmosphere and the solar wind. Launch is scheduled for approximately 4 a.m. EDT on July 31, 2018.
The launch vehicle consists of three Common Booster Cores, with a second stage on the center core; the encapsulated spacecraft, is scheduled to arrive in early July for integration onto the rocket. The spacecraft is now at Astrotech Space Operations in nearby Titusville undergoing final integration and testing. Parker Solar Probe will be the fastest human-made object in the solar system, traveling at speeds of up to 430,000 miles per hour (700,000 kilometers per hour).
The Thermal Protection System — also known as the heat shield — for NASA’s Parker Solar Probe arrived in Titusville, Florida, on April 18, 2018, bringing it one step closer to reuniting with the spacecraft that will be the first to “touch” the Sun.
The Parker Solar Probe spacecraft arrived at Astrotech Space Operations two weeks prior, on April 3, to complete final testing. Though the spacecraft was flown by the Air Force’s 436th Airlift Wing, the Thermal Protection System, or TPS, traveled on a flatbed truck, securely encased in a metal shipping container during its road trip to the Sunshine State. After setting off on a rainy Monday morning from Maryland, it was greeted with Florida’s balmy heat on Wednesday afternoon at Astrotech, where it will eventually be reattached to the spacecraft before launch in late July.
The innovative TPS will be the one barrier shielding the spacecraft and its instruments from the intense heat of the Sun. Made of carbon-carbon composite and stretching approximately eight feet wide, the TPS will withstand temperatures of up to 2,500 degrees Fahrenheit while keeping the spacecraft and instruments at a comparatively comfortable 85 degrees Fahrenheit. The heat shield has a plasma-sprayed white surface that will reflect the intense heat energy of the Sun’s corona away from the spacecraft.
Parker Solar Probe has completed its space environment testing at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and was lifted out of the thermal vacuum chamber on March 24, 2018, after just over two months inside.
Since January, Parker Solar Probe underwent a series of tests inside NASA Goddard’s large thermal vacuum chamber – officially called the Space Environment Simulator – that mimicked the conditions the spacecraft will face in space throughout its seven-year mission. After initially testing the spacecraft’s functions under hot and cold extremes, engineers have spent the past month slowly cycling the temperatures in the thermal vacuum chamber back and forth between hot and cold, making sure Parker Solar Probe’s systems and components operate properly. This thermal cycling is similar to the conditions the spacecraft will experience as it completes 24 close approaches to the Sun over its seven-year mission.
“Successfully completing this final round of space environment testing is critical, and the team has created an exceptional spacecraft,” said Andy Driesman, Parker Solar Probe program manager from the Johns Hopkins Applied Physics Lab in Laurel, Maryland, which designed, built, and will manage the mission for NASA. “We now know the spacecraft and systems are able to operate in space, and that Parker Solar Probe is ready to embark on this historic mission.”
After undergoing final preparations, the spacecraft will leave NASA Goddard and travel to Florida this spring. Once in Florida, Parker Solar Probe will go through its final integration and testing at Astrotech Space Operations in Titusville before launching from NASA’s Kennedy Space Center in Florida this summer. Parker Solar Probe’s launch window opens on July 31, 2018.