Matching its own records for speed and distance to the Sun, NASA’s Parker Solar Probe completed its 12th close approach to the Sun on June 1, coming within 5.3 million miles (8.5 million kilometers) of the solar surface.
The close approach (known as perihelion) occurred at 6:50 p.m. EDT (10:50 p.m. UTC), with Parker Solar Probe moving about 364,660 miles per hour (586,860 kilometers per hour) – fast enough to cover the distance between Los Angeles and London in under a minute. The milestone also marked the midway point in the mission’s 12th solar encounter, which began May 27 and continues through June 7.
The spacecraft entered the encounter in good health, with all systems operating normally. Parker Solar Probe is scheduled to check back in with mission operators at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland – where it was also designed and built – on June 4.
In 2018, NASA launched Parker Solar Probe on an unprecedented mission to study the Sun up close. The mission was defined with three key scientific goals:
To trace the flow of energy that heats the Sun’s outer atmosphere.
To shed light on the sources of the solar wind, the constant flow of solar material escaping from the Sun.
To explore how solar energetic particles – which can make the 93-million mile (150 million kilometer) journey to Earth in under an hour – are transported and accelerated.
Now four years after launch, the mission has officially met its MissionSuccess criteria, making inroads towards achieving these key goals and more. As Parker Solar Probe continues its mission, it continues to break records and capture first-of-its-kind measurements of the Sun.
Here are the need-to-know facts about NASA’s historic mission to touch the Sun.
1.Parker Solar Probe was the first NASA mission named for a living person.
In honor of Eugene Parker, eminent physicist who first predicted the solar wind, NASA announced in May 2017, that it would rename the Solar Probe Plus mission to Parker Solar Probe. Parker witnessed the spacecraft’s launch in person and the discoveries made in the mission’s few years. He passed away on March 15, 2022, at age 94.
2. The spacecraft carries revolutionary technology.
The mission was conceived in 1958, but it took 60 years to develop the technology to make it happen. Designed and built at the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland, Parker Solar Probe carries a heat shield, autonomous onboard “smarts” to keep the spacecraft facing the Sun, and an efficient cooling system.
3. It’s a repeated record-breaker.
Just a few months after launch, Parker Solar Probe became the closest human-made object to the Sun, passing within 26.55 million miles (42.72 million kilometers) from the Sun’s surface, and became the fastest human-made object, reaching speeds of 153,454 miles per hour. Since then, it has repeatedly broken both of those records, and will reach a top speed of about 430,000 miles per hour (700,000 kilometers per hour) as it flies to within 3.9 million miles (6.2 million kilometers) of the Sun’s surface in 2024. See where Parker Solar Probe is in real time here.
4. Parker Solar Probe has officially sampled the Sun.
In December 2021, NASA announced that Parker Solar Probe had achieved its cornerstone objective: making the first measurements from within the atmosphere of a star.
5. It’s made game-changing discoveries.
Parker Solar Probe carries four instrument suites, and each is now credited with several groundbreaking discoveries. A small sample of them is described below.
The Solar Wind Electrons Alphas and Protons investigation (SWEAP) Surveying where Sun becomes solar wind
When Parker Solar Probe entered the solar atmosphere, it made the first-ever crossing of what’s known as the Alfvén critical surface – the boundary where solar material anchored to the Sun first escapes and becomes the solar wind.
Until this crossing, no one knew what that boundary would look like. During its first pass close enough to cross the boundary, Parker Solar Probe passed into and out of the corona several times. This revealed key information about the boundary’s shape, revealing that the Alfvén critical surface wasn’t shaped like a smooth ball. Rather, it has spikes and valleys that wrinkle the surface.
The SWEAP instrument established that the wrinkles were due to coronal streamers – giant plumes of solar material rising through the Sun’s atmosphere. Streamers have long been observed by Sun-watching spacecraft near Earth, but never before measured directly. The results are reshaping what we know about the Sun’s atmosphere and how it transforms into the solar wind.
The Wide-Field Imager for Parker Solar Probe (WISPR) The first hints of a dust-free zone
Dust is just about everywhere in our solar system — the remnants of collisions that formed planets, asteroids, comets and other celestial bodies billions of years ago. Almost a century ago, astronomer Henry Norris Russell predicted that there should be a region around the Sun where dust particles should get hot enough to sublimate and thus disappear, creating a dust-free zone. People looked for evidence of the sublimation zone for decades but there was no consistent evidence for its existence whatsoever.
The WISPR instrument made the first detection of dust depleting close to the Sun, observing the light reflected from dust dimming at about 19 solar radii (8.2 million miles, or 13.2 million kilometers, away from the Sun). Models of the results suggest that a dust-free zone should exist starting at about 5 solar radii (2.2 million miles, or 3.5 million kilometers, from the Sun).
FIELDS Tracking down the Sun’s magnetic reversals
When Parker Solar Probe sent back the first observations from its voyage to the Sun, scientists found their magnetic field measurements spiked with what became known as switchbacks: rapid flips in the Sun’s magnetic field that reversed direction like a zig-zagging mountain road.
FIELDS has since helped narrow down their origins. During Parker Solar Probe’s 6th flyby of the Sun, FIELDS data revealed that the switchbacks aligned with magnetic “funnels” in the solar surface. These funnels emerge from between structures called supergranules – giant bubbles on the Sun in which hot plasma from the solar interior rises up, spreads out across the surface, cools and then sinks back down. The magnetic geometry of these regions suggests that magnetic reconnection powers the solar wind.
While the new findings locate where switchbacks are made, the question of how they’re formed is still a matter of active research.
The Integrated Science Investigation of the Sun (ISʘIS) Rewriting the book on solar energetic particles
ISʘIS, pronounced “ee-sis” and including the symbol for the Sun in its acronym, measures solar energetic particles, the most energetic particles that escape the Sun. Measured near Earth, solar energetic particles events are relatively rare and hard to predict. But detecting SEPs close to the Sun, ISʘIS has changed just about everything we know about these speedy particles. ISʘIS has found that SEPs are much more common than expected, that they contain a wider range of types of particles than expected, and that their paths from the Sun are not as direct as previously thought – they can be disrupted by the switchbacks detected by fields and can at times follow a path twice as long as expected. By measuring these events so close to the Sun, ISʘIS is detecting events so small that all trace of them is lost before they reach Earth, helping scientists develop a fuller picture of where they come from and how they’re accelerated away from the Sun.
As NASA’s Parker Solar Probe completes its latest swing around the Sun, it’s doing so in full view of dozens of other spacecraft and ground-based telescopes.
These powerful instruments can’t actually see Parker itself – the van-sized spacecraft is far too small for visible detection – but they offer from a distance what the probe is sensing close-up, as it samples and analyzes the solar wind and magnetic fields from as close as 5.3 million miles (8.5 million kilometers) from the Sun’s surface.
Occurring at 10:36 a.m. EST (15:36 UTC) on Feb. 25, this was the 11th close approach – or perihelion in the spacecraft’s orbit around the Sun – of 24 planned for Parker Solar Probe’s primary mission. Most of these passes occur while the Sun is between the spacecraft and Earth, blocking any direct lines of sight from home. But every few orbits, the dynamics work out to put the spacecraft in Earth’s view – and the Parker mission team seizes these opportunities to organize broad observation campaigns that not only include telescopes on Earth, but several spacecraft as well.
More than 40 observatories around the globe, including the recently commissioned Daniel K. Inouye Solar Telescope in Hawaii, among other major installations in the southwestern United States, Europe and Asia, are training their visible, infrared and radio telescopes on the Sun over the several weeks around the perihelion. About a dozen spacecraft, including NASA’s STEREO, Solar Dynamics Observatory, TIMED and Magnetospheric Multiscale missions, ESA’s and NASA’s Solar Orbiter, ESA’s BepiColombo, the JAXA-led Hinode, and even NASA’s MAVEN at Mars are making simultaneous observations of activity stretching from the Sun to Earth and beyond.
The pass also marked the midway point in the mission’s 11th solar encounter, which began Feb. 20 and continues through March 2. The spacecraft checked in with mission operators at APL – where Parker Solar Probe was designed and built – on Feb. 28 to report that it was healthy and operating as expected.
Most of the data from this encounter will stream back to Earth from March 30 through May 1, though the team will get a glimpse of some readings when the spacecraft sends a limited amount of data this week.
Solar Activity Picks Up
Parker Solar Probe is expected to dip back into the Sun’s outer atmosphere – the corona – continuing the solar wind and magnetic field readings it has taken since before it first “touched the Sun” last year.
Along with that data, scientists eagerly anticipate a look at what Parker Solar Probe recorded from the large solar prominence on Feb. 15 that blasted tons of charged particles in the spacecraft’s direction. Project Scientist Nour Raouafi of the Space Exploration Sector, said it was the largest event Parker Solar Probe has experienced during its first three-and-a-half years in flight.
“The shock from the event hit Parker Solar Probe head-on, but the spacecraft was built to withstand activity just like this – to get data in the most extreme conditions,” he said. “And with the Sun getting more and more active, we can’t wait to see the data that Parker Solar Probe gathers as it gets closer and closer.”
Assisted by a pair of orbit-shaping Venus flybys in August 2023 and November 2024, Parker Solar Probe will eventually come within 4 million miles (6.2 million kilometers) of the solar surface in December 2024 at speeds topping 430,000 miles per hour. Follow the probe’s trek through the inner solar system.
Blazing along at space-record speeds that would get it from Earth to the Moon in under an hour, NASA’s Parker Solar Probe completed its 10th close approach to the Sun on Nov. 21, coming within 5.3 million miles (8.5 million kilometers) of the solar surface.
The close approach (known as perihelion), also at a record distance, occurred at 4:25 a.m. EST (8:25 UTC), with Parker Solar Probe moving 364,660 miles per hour (586,864 kilometers per hour). The milestone also marked the midway point in the mission’s 10th solar encounter, which began Nov. 16 and continues through Nov. 26.
The spacecraft entered the encounter in good health, with all systems operating normally. Parker Solar Probe is scheduled to check back in with mission operators at the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland – where it was also designed and built – on Nov 24.
The spacecraft will transmit science data from the encounter – largely covering the properties and structure of the solar wind as well as the dust environment near the Sun – back to Earth from Dec. 23-Jan. 9.
Parker Solar Probe will break its own distance and speed records on that approach – the 10th of 24 planned, progressively closer trips around the Sun – when it comes about 5.3 million miles (8.5 million kilometers) from the Sun’s surface, while reaching top speeds of 101 miles (163 kilometers) per second, or 364,621 miles per hour. The probe’s science instruments are already queued up to measure the properties of the solar wind near its source, but the spacecraft is also making other critical, if not unexpected, discoveries.
“We’re observing higher than expected amounts of dust near the Sun,” said Nour Raouafi, Parker Solar Probe project scientist at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland. “What’s exciting about this is it’s greatly improving our understanding of the innermost regions of our heliosphere, giving us insight into an environment that, until now, was a total mystery.”
Parker Solar Probe designed, built and now operated at APL, does not carry a dust detector. But as dust grains pelt the spacecraft along its path, the high-velocity impacts create clouds of plasma. These clouds produce unique electrical charges that are picked up by several sensors on the probe’s FIELDS instrument, which is designed to measure the electric and magnetic fields near the Sun. Mission scientists have used this data, for example, to construct comprehensive pictures of the structure and behavior of the large cloud of dust that swirls through the innermost solar system.
The visible imaging camera, WISPR, also picks up bits of material expelled from the spacecraft’s structures after impact with those dust grains. But it also images dust structures far away from the spacecraft, such as the dust ring that shares Venus’ orbit. While learning about space dust isn’t a prime mission science goal, the WISPR and FIELDS have planned for specifically investigating near-Sun dust – in a region of the solar system where no mission has ever operated.
The Parker Solar Probe team did prepare for the spacecraft’s precarious trek through this potentially hazardous environment – as early as the initial mission concept phase – at least as well as our scientific community understood it before the probe’s 2018 launch.
“We designed materials and components that survive hypervelocity dust impacts and the effects of the even smaller particles created in these impacts,” said Jim Kinnison, Parker Solar Probe mission systems engineer at APL. “We modeled the makeup and effects of the dust environment, tested how materials react to the dust particles, and installed fault-tolerant onboard systems that are keeping Parker Solar Probe safe in this unexplored region.”
The spacecraft team has noticed that occasionally, the star tracking cameras used as part of the guidance and control system see reflected light from dust and shattering particles that can momentarily disrupt their ability to see stars. Kinnison noted, however, that this doesn’t compromise the safety of spacecraft or instrument operations, and the star trackers aren’t the spacecraft’s only method of controlling where it points. The guidance and control software uses data from the star trackers in tandem with an inertial measurement unit and solar-limb sensors to keep the Thermal Protection System – the heat shield – pointed toward the Sun.
“Because the system was built to be robust and highly autonomous, loss of data from any one source doesn’t affect the ability to control the spacecraft attitude, and in a worst-case situation, can work indefinitely with just the Solar Limb Sensors that watch for unexpected solar illumination on the spacecraft due to attitude errors,” he said. “With PSP now in its 10th orbit around the Sun, the spacecraft is proving it can handle this unexpected dust environment.”
And that’s good news, he added, with Parker Solar Probe only set to move closer to – and faster around – the Sun. Assisted by two more Venus flybys, in August 2023 and November 2024, Parker Solar Probe will eventually come within 4 million miles (6.2 million kilometers) of the solar surface in December 2024, at speeds topping 430,000 miles per hour.
NASA’s Parker Solar Probe is speeding in toward the Sun after a swing past Venus on Oct. 16, successfully using the planet’s gravity to shape its path for its next closest approach to our star.
At just after 5:30 a.m. EDT, moving about 15 miles (24 kilometers) per second, the spacecraft swooped 2,370 miles (3,814 kilometers) above Venus’ surface. Such gravity assists are essential to the mission to bring Parker Solar Probe progressively closer to the Sun; the spacecraft counts on the planet to reduce its orbital energy, which in turn allows it to travel closer to the Sun and measure the properties of the solar wind near its source.
This was the fifth of seven planned Venus gravity assists. The flyby reduced Parker Solar Probe’s orbital speed by about 6,040 miles per hour (9,720 kilometers per hour), and set it up for its 10th close pass (or perihelion) by the Sun, on Nov. 21.
Parker Solar Probe will break its own distance and speed records on that closest approach, when it comes approximately 5.3 million miles (8.5 million kilometers) from the Sun’s surface — some 1.2 million miles (1.9 million kilometers) closer than the previous perihelion on Aug. 13 – while reaching 101 miles (163 kilometers) per second, or 364,621 miles per hour. Assisted by two more Venus flybys, in August 2023 and November 2024, Parker Solar Probe will eventually come within 4 million miles (6.2 million kilometers) of the solar surface in December 2024.
Parker Solar Probe, which was designed and built at the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland, is healthy and its systems are operating normally after the Oct. 16 Venus flyby. The flyby operation was monitored by the spacecraft and mission operations teams at APL, through NASA’s Deep Space Network.
By Mike Buckley Johns Hopkins University Applied Physics Lab
On Sept. 29, NASA’s Parker Solar Probe completed a quick maneuver that positioned the spacecraft for a flyby of Venus next month.
The maneuver, monitored from the mission operations center at the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland, lasted just five seconds and trimmed the spacecraft’s velocity by 9.7 centimeters per second, or less than a third of a mile per hour. But it was critical for keeping Parker Solar Probe on pace for its next pass by Venus on Oct. 16, when it will use the planet’s gravity to swing toward its tenth close approach to the Sun.
Parker Solar Probe, which was designed and built at APL, is healthy and its systems are operating normally. The spacecraft completed its ninth solar encounter on Aug. 15, at closest approach coming within 6.5 million miles (10.4 million kilometers) of the Sun’s surface. The upcoming Venus gravity assist will send the spacecraft even closer to the Sun’s blazing surface – about 5.6 million miles (9 million kilometers) – on Nov. 21.
Assisted by two additional Venus flybys, Parker Solar Probe will eventually come within 4 million miles (6.4 million kilometers) of the solar surface in late 2024.
On Aug. 13, 2021, at 5:50 a.m. EDT, mission controllers at the Johns Hopkins University Applied Physics Laboratory, in Laurel, Maryland, received a “tone one” beacon from Parker Solar Probe, indicating that all systems were healthy and operating normally after the spacecraft’s ninth close approach to the Sun on Aug. 9.
During this close pass by the Sun — called perihelion — Parker Solar Probe matched its own records for spacecraft distance from the Sun and speed, coming to within about 6.5 million miles (10.4 million kilometers) of the Sun’s surface, while moving faster than 330,000 miles per hour (532,000 kilometers per hour).
Science data collection for this solar encounter continues through Aug. 15.
NASA’s Parker Solar Probe is speeding busily through its ninth science-gathering solar encounter, heading toward a close approach of the Sun on Aug. 9 that will take it to within about 6.5 million miles (10.4 million kilometers, or 14.97 solar radii) of the solar surface.
That matches the record-distance of its last closest approach (called perihelion) on April 29; at the same time, the probe will also equal its record-setting flyby speed of 330,000 miles per hour (532,000 kilometers per hour). And, it’s only 2.6 million miles from the ultimate closest approach of 3.8 million miles from the Sun’s surface, which Parker Solar Probe will reach will reach in December 2024.
Designed, built and operated at the Johns Hopkins Applied Physics Laboratory in Maryland, Parker Solar Probe is operating normally heading into perihelion. Using its four onboard instrument suites, the spacecraft will continue collecting data on the solar environment and solar wind for this encounter through Aug. 15, with much of the data from the encounter expected back on Earth by Aug. 18.
“We are getting into the critical phase of the Parker mission and we’re focused on quite a few things during this encounter,” said Nour E. Raouafi, Parker Solar Probe project scientist from APL. “We expect the spacecraft to be flying through the acceleration zone of the perpetual flow of charged particles that make up the solar wind. Solar activity is also picking up, which is promising for studying larger-scale solar wind structures, like coronal mass ejections, and the energetic particles associated with them.
“But you never know what else you’ll find exploring this close to the Sun,” he added, “and that’s always exciting.”
Three years into its seven-year primary mission, Parker Solar Probe remains healthy while traversing a path that will take it directly through the Sun’s outer atmosphere, known as the corona. The Thermal Protection System shielding the spacecraft is already facing temperatures above 1,200 degrees Fahrenheit (650 degrees Celsius). At Parker Solar Probe’s closest approaches, the TPS must withstand temperatures of 2,500 F while keeping the spacecraft and instruments in its shadow operating at about 85 F.
Preparations are underway for the mission’s fifth flyby of Venus, on Oct. 16, which will direct Parker Solar Probe even closer to the Sun for its 10th science orbit, which culminates with its fourth and final perihelion of the year on Nov. 21.
By Mike Buckley Johns Hopkins University Applied Physics Lab
The latest articles include data analysis, theory, and modeling. Among the major topics covered are magnetic switchbacks first discovered by Parker Solar Probe, the role of waves in heating solar plasma, solar angular momentum, the near-Sun dust environment, and the diversity of small energetic-particle events. Highlights include:
The enigma of magnetic switchbacks in the “young” solar wind. The switchbacks are more prominent, and play a larger role in the structure of the solar wind, closer to the Sun. Their origin, evolution and contribution to the heating and acceleration of the solar wind plasma is highly debated. Several papers in this issue discuss different aspects of this mysterious feature.
Clear evidence of the dust-free zone around the Sun, supporting the initial hints of such a zone published in the 2019 Nature papers.
Diverse kinetic and magnetohydrodynamic aspects of plasma — such as wave-particle interactions, magnetic field reconnection, and turbulence — pertinent to the heating and acceleration of the solar wind.
New results about large-scale solar wind structures, such as coronal mass ejections and stream interaction regions, and the often-associated solar energetic particles.
Designed, built, and operated by the Johns Hopkins Applied Physics Laboratory, or APL, in Laurel, Maryland, Parker Solar Probe recently completed its eighth solar encounter, breaking its own records for speed and proximity to the Sun. It will reach its top speed and closest point to our star — coming within 4 million miles of its surface, moving some 430,000 miles per hour — by December 2024. The Parker Solar Probe project is managed by the Heliophysics Division of NASA’s Science Mission Directorate in Washington, D.C.
“All of the results we’ve reported so far, since Parker Solar Probe began its mission in August 2018, depict conditions of a ‘quiet’ Sun during the solar minimum, or its least active period,” said Nour Raouafi, the Parker Solar Probe project scientist from APL. “Many more discoveries await us as the Sun becomes more active and as the spacecraft reaches deeper into the Sun’s corona.”
By Mike Buckley
Johns Hopkins University Applied Physics Lab