Since the Copernican revolution, we know that our world revolves around the Sun. The star is responsible for both our days and our seasons, but we know relatively little information about it. The idea to send a probe to the Sun and learn more was initially conceived in the 1990s, but budget cuts and restructuring resulted in the project being pushed aside until 2009. After nine years of development, production, and testing, the Parker Solar Probe (PSP) launched on August 12, 2018 and is now winging its way towards the Sun. The primary objective for PSP is to learn about the star’s corona and magnetic fields, so researchers can use this information to determine the causes of solar wind and flares1.
To gather these data, the probe will pass through the atmosphere of the Sun, getting as close as 3.8 million miles to the surface, closer than any manmade object has ever gotten. While 3.8 million miles may not seem very close, the Earth is, on average, 92.96 million miles away from the Sun2. In order to get within 4 million miles of the Sun, PSP will fly by Venus seven times, using the gravity of the planet to slow down and tighten its solar orbit3. On October 3, the probe got its first gravity assist as it zoomed past Venus. During some of these Venutian flybys, PSP will gather new data about the planet that also hasn’t had many exploratory missions. PSP will orbit the Sun 24 times, getting progressively closer with each revolution. At its closest orbit, it will take the spacecraft just 88 days to revolve around the star4.
The point at which the probe is closest to the Sun during each orbit is called a perihelion, and PSP’s first perihelion will occur on November 14. As it gets closer and closer to our star, the spacecraft will gather data using four research instruments: Electromagnetic Fields Investigation (FIELDS), Wide-Field Imager for Parker Solar Probe (WISPR), Solar Wind Electrons Alphas and Protons (SWEAP), and Integrated Science Investigation of the Sun (ISʘIS)5. Every time the probe passes by the Sun, it will take readings from a different area, allowing the same data to be captured from many different regions of our star over the seven year planned mission.
The FIELDS instrument will gather data about the magnetic and electric fields in the Sun’s atmosphere. Using two cameras specially designed to withstand solar radiation and space dust, WISPR will take images of the corona by using the probe’s heat shield to block the Sun’s light. SWEAP and ISʘIS use different instrumentation to count electrons, protons, and helium ions and measure velocity, density, and temperature of these particles. Together, information from these instruments will give us a better understanding of both solar wind and the plasma within the corona. Researchers are also hoping to use these data to predict solar storms before they happen, to protect satellites, astronauts, and the International Space Station from the harmful bursts of radiation that accompany these storms5.
In order for the probe to get this close to the Sun, it has to be capable of withstanding temperatures of up to 2500°F (1400°C)6. PSP is shielded from the Sun’s thermal energy by a special heat shield called the Thermal Protection System (TPS). The TPS is a 3-layer carbon-composite sandwich underneath a white ceramic coating that will reflect even more heat. In addition to the heat shield, the probe has a cooling system to keep the solar panels from overheating. The coolant for the system is plain deionized water, pressurized to keep the boiling point above 257°F (125°C). It has to withstand a temperature range of 50°F-257°F, and water is the best liquid to handle that range.
As the probe gathers data, it will not communicate with Earth because its limited energy will be tied up operating the research instruments. When it completes each pass of data collection, it will send large batches of information back to Earth via NASA’s Deep Space Network7. Once the data are received, researchers will learn new and exciting information about the star around which we revolve. The mission for PSP is officially scheduled through 2025, but if fuel remains in the spacecraft beyond that time, instruments could continue to gather data until the fuel runs out4. Without fuel, the probe won’t be able to position the heat shield to protect itself from the Sun, and the spacecraft will burn up from the intense heat.
If you’re interested in finding out more about our Solar System and the stars, the Cape Fear Astronomical Society holds meetings the first Sunday of every month (second Sunday, if the first is on a holiday weekend) at 7:00 pm in room 212 of DeLoach Hall at UNCW.