Parker Solar Probe

The Parker Solar Probe concept originates in the 1958 report by the Fields and Particles Group, Committee 8 of the National Academy of Sciences' Space Science Board, which proposed several space missions including "a solar probe to pass inside the orbit of Mercury to study the particles and fields in the vicinity of the Sun". Studies in the 1970s and 1980s reaffirmed its importance, but it was always postponed due to cost. A cost-reduced Solar Orbiter mission was studied in the 1990s, and a more capable Solar Probe mission served as one of the centerpieces of the Outer Planet/Solar Probe (OPSP) program formulated by NASA in the late 1990s. The first three missions of the program were planned to be: the Solar Orbiter, the Pluto and Kuiper belt reconnaissance Pluto Kuiper Express mission, and the Europa Orbiter astrobiology mission focused on Europa. The original Solar Probe design used a gravity assist from Jupiter to enter a polar orbit which dropped almost directly toward the Sun. While this explored the important solar poles and came even closer to the surface (3 , a perihelion of 4 ), the extreme variation in solar irradiance made for an expensive mission and required a radioisotope thermal generator for power. The trip to Jupiter also made for a long mission, years to first solar perihelion, 8 years to second. Following the appointment of Sean O'Keefe as Administrator of NASA, the entirety of the OPSP program was canceled as part of President George W. Bush's request for the 2003 United States federal budget. Administrator O'Keefe cited a need for a restructuring of NASA and its projects, falling in line with the Bush Administration's wish for NASA to refocus on "research and development, and addressing management shortcomings". The redesigned mission uses multiple Venus gravity assists for a more direct flight path, which can be powered by solar panels. It has a higher perihelion, reducing the demands on the thermal protection system. In May 2017, the spacecraft was renamed the Parker Solar Probe in honor of astrophysicist Eugene Newman Parker, who had proposed the existence of nanoflares as an explanation of coronal heating as well as having developed a mathematical theory that predicted the existence of solar wind. The solar probe cost NASA US$1.5 billion. The launch rocket bore a dedication in memory of APL engineer Andrew A. Dantzler who had worked on the project. A memory card containing names submitted by over 1.1 million people was mounted on a plaque and installed below the spacecraft's high-gain antenna. The card also contains photos of Parker and a copy of his 1958 scientific paper predicting important aspects of solar physics. == Spacecraft ==

The Parker Solar Probe is the first spacecraft to fly into the low solar corona. It will assess the structure and dynamics of the Sun's coronal plasma and magnetic field, the energy flow that heats the solar corona and impels the solar wind, and the mechanisms that accelerate energetic particles. The spacecraft's systems are protected from the extreme heat and radiation near the Sun by a solar shield. Incident solar radiation at perihelion is approximately , or 475 times the intensity at Earth orbit. The solar shield is hexagonal, mounted on the Sun-facing side of the spacecraft, in diameter, thick, and is made of two panels of reinforced carbon–carbon composite with a lightweight carbon foam core, which is designed to withstand temperatures outside the spacecraft of about . File:KSC-20180605-PH GEB01 0116 (41073463690).jpg|A light bar testing in the Astrotech processing facility. File:Parker Solar Probe mated.jpg|Parker Solar Probe mated to its third stage rocket motor File:Parker Solar Probe.webm|PSP during extensive environmental testing. File:Parker fairing.jpg|PSP encapsulated in fairing. File:NASA's Parker Solar Probe Mission Launches to Touch the Sun.webm|The launch of the probe. == Trajectory ==

The Parker Solar Probe mission design used repeated gravity assists at Venus to incrementally decrease its orbital perihelion to achieve a final altitude (above the surface) of approximately 8.5 solar radii, or about . The spacecraft trajectory included seven Venus flybys over nearly seven years to gradually shrink its elliptical orbit around the Sun, for a total of 24 orbits. The near Sun radiation environment was predicted to cause spacecraft charging effects, radiation damage in materials and electronics, and communication interruptions, so the orbit is highly elliptical with short times spent near the Sun. The trajectory required high launch energy, so the probe was launched on a Delta IV Heavy launch vehicle and an upper stage based on the Star 48BV solid rocket motor. Interplanetary gravity assists provided further deceleration relative to its heliocentric orbit, which resulted in a heliocentric speed record at perihelion. As the probe passed around the Sun in December 2024, it achieved a velocity of or 191 km/s (118.7 mi/s) in the heliocentric ecliptic reference frame, which temporarily made it the fastest human-made object, almost three times as fast as the previous record holder, Helios-2. Launch injection was very close to predictions, but nevertheless required path correction. Trajectory was re-optimized after the launch to save fuel. The first Venus flyby was only 52 days after the launch; three trajectory correction maneuvers were performed in this window. Final orbit, possible extensions and end of mission The PSP performed its final gravity assist on November 6, 2024. It set the spacecraft on a new orbit passing 6.1 million kilometers (3.8 million miles) from the surface of the Sun. A beacon transmission was made and received successfully on December 20 to confirm that the craft was operating normally ahead of the perihelion. The exact time of closest approach was 11:53 UTC on December 24 but the craft was out of contact at this time. A further beacon transmission confirming successful passage was received on December 26. PSP's mission can be extended beyond main mission that will end in 2025. Currently discussed plan is "to complete the solar cycle at the 9.86 Rs perihelion distance". == Instruments ==

Parker Solar Probe has four main instruments: • FIELDS (Electromagnetic Fields Investigation). The instrument suite captures the scale and shape of electric and magnetic fields in the Sun's atmosphere. FIELDS measures waves and turbulence in the inner heliosphere with high time resolution to understand the fields associated with waves, shocks and magnetic reconnection, a process by which magnetic field lines explosively realign. FIELDS measures the electric field around the spacecraft with five antennas, four of which stick out beyond the spacecraft's heat shield and into the sunlight, where they experience temperatures of . The antennas are made of a niobium alloy, which can withstand extreme temperatures. FIELDS measures electric fields across a broad frequency range both directly and remotely. Operating in two modes, the four sunlit antennas measure the properties of the fast and slow solar wind — the flow of solar particles constantly streaming out from the Sun. The fifth antenna, which sticks out perpendicular to the others in the shade of the heat shield, helps make a three-dimensional picture of the electric field at higher frequencies. The suite also has three magnetometers to assess the magnetic field. A search coil magnetometer, or SCM, measures how the magnetic field changes over time. Two identical fluxgate magnetometers, MAGi and MAGo, measure the large-scale coronal magnetic field. The fluxgate magnetometers are specialized for measuring the magnetic field further from the Sun where it varies at a slower rate, while the search coil magnetometer is necessary closer to the Sun where the field changes quickly, as it can sample the magnetic field at a rate of two million times per second. The Principal Investigator is Stuart Bale at the University of California, Berkeley. • WISPR (Wide-field Imager for Solar Probe). These optical telescopes acquire images of the corona and inner heliosphere. WISPR uses two cameras with radiation-hardened Active Pixel Sensor CMOS detectors. The camera's lenses are made of a radiation hard BK7, a common type of glass used for space telescopes, which is also sufficiently hardened against the impacts of dust. The Principal Investigator is Russell Howard at the Naval Research Laboratory. == Mission ==

The Parker Solar Probe was launched on 12 August 2018, at 07:31 UTC. The spacecraft operated nominally after launching. During its first week in space it deployed its high-gain antenna, magnetometer boom, and electric field antennas. The spacecraft performed its first scheduled trajectory correction on 20 August 2018, while it was 8.8 million kilometers (5.5 million mi) from Earth, and travelling at Instrument activation and testing began in early September 2018. On 9 September 2018, the two WISPR telescopic cameras performed a successful first-light test, transmitting wide-angle images of the background sky towards the Galactic Center. The probe successfully performed the first of the seven planned Venus flybys on 3 October 2018, where it came within about of Venus in order to reduce the probe's speed and orbit closer to the Sun. Science phases run for a few days both before and after each perihelion. They lasted 11.6 days for the earliest perihelion, and will drop to 9.6 days for the final, closest perihelion. == Timeline ==

. Inside the boundary at the corona's edge, its Alfvén critical surface, plasma connects to the Sun by waves traveling back and forth to the surface. On November 6, 2018, Parker Solar Probe observed its first magnetic switchbacks – sudden reversals in the direction of the magnetic field carried by the solar wind. They were first observed by the NASA-ESA mission Ulysses, the first spacecraft to fly over the Sun's poles. The switchbacks generate heat that warms solar corona. On 4 December 2019, the first four research papers were published describing findings during the spacecraft's first two dives near the Sun. They reported the direction and strength of the Sun's magnetic field, and described the unusually frequent and short-lived changes in the direction of the Sun's magnetic field. These measurements confirm the hypothesis that Alfvén waves are the leading candidates for understanding the mechanisms that underlie the coronal heating problem. The probe observed approximately a thousand "rogue" magnetic waves in the solar atmosphere that instantly increase solar wind speeds by as much as and in some cases completely reverse the local magnetic field. They also reported that, using the "beam of electrons that stream along the magnetic field", they were able to observe that "the reversals in the Sun's magnetic field are often associated with localized enhancements in the radial component of the plasma velocity (the velocity in the direction away from the Sun's center)". The researchers found a "surprisingly large azimuthal component of the plasma velocity (the velocity perpendicular to the radial direction). This component results from the force with which the Sun's rotation slingshots plasma out of the corona when the plasma is released from the coronal magnetic field". PSP discovered evidence of a cosmic dust-free zone of 3.5 million miles (5.6 million kilometers) radius from the Sun, due to vaporisation of cosmic dust particles by the Sun's radiation. On April 28, 2021, during its eighth flyby of the Sun, Parker Solar Probe encountered the specific magnetic and particle conditions at 18.8 solar radii that indicated that it penetrated the Alfvén surface; the probe measured the solar wind plasma environment with its FIELDS and SWEAP instruments. This event was described by NASA as "touching the Sun". PSP-001 was discovered in images from 29 May 2022, part of the spacecraft's 12th approach to the Sun. Since this discovery, a further 19 sungrazing comets have been discovered in the images taken by the Parker Solar Probe, including three non-group comets. In 2024, it was reported that the probe detected a Kelvin-Helmholtz instability (KHI) during an observed coronal mass ejection. It is the first spacecraft that detected this long theorized event. == Collaborations ==

The PSP and ESA-NASA Solar Orbiter (SolO) missions cooperated to trace solar wind and transients from their sources on the Sun to the inner interplanetary space. In 2022, PSP and SolO planners collaborated to study why the Sun's atmosphere is "150 times hotter" than its surface. SolO observed the Sun from 140 million kilometers, while PSP simultaneously observed the Sun's corona during flyby at a distance of nearly 9 million kilometers. In March 2024, both space probes were at their closest approaches to the Sun, PSP at 7.3 million km, and SolO at 45 million km. SolO observed the Sun, while PSP sampled the plasma of the solar wind, allowing scientists to compare data from both probes. Coordinated observations were also done with SOHO and STEREO-A spacecraft. == Gallery ==

File:WISPR first light image.png|WISPR first light image. The right portion of the image is from WISPR's inner telescope, which is a 40-degree field of view and begins 58.5 degrees from the Sun's center. The left portion is from the outer telescope, which is a 58-degree field of view and ends about 160 degrees from the Sun. File:Parker-view-of-earth.jpg|The view from the probe's WISPR instrument on Sept. 25, 2018, shows Earth, the bright sphere near the middle of the right-hand panel. The elongated mark toward the bottom of the panel is a lens reflection from the WISPR instrument File:Parker Solar Probe coronal stream wispr-big 1-st flyby.jpg|Photo from the WISPR shows a coronal streamer, seen over the east limb of the Sun on Nov. 8, 2018, at 1:12 a.m. EST. The fine structure of the streamer is very clear, with at least two rays visible. Parker Solar Probe was about 16.9 million miles (21.2 million km) from the Sun's surface when this image was taken. The bright object near the center of the image is Mercury, and the dark spots are a result of background correction. File:Wispr merged six planets.jpg|When Parker Solar Probe was making its closest approach to the Sun on June 7, 2020, WISPR captured the planets Mercury, Venus, Earth, Mars, Jupiter and Saturn in its field of view File:Venus-ParkerSolarProbe-July2020.jpg|Photo taken by the probe during its second Venus flyby, July 2020 File:Parker Solar Probe flew by Venus on its fourth flyby.gif|As Parker Solar Probe flew by Venus on its fourth flyby, its WISPR instrument captured these images, showing the nightside surface of the planet File:PSP "Touches the Sun".webm|As the probe passed through the Sun's corona in early 2021, it flew by structures called coronal streamers (timelapse encompassing 4 days) 14865 WISPR 12252025.webm|This video by WISPR during its record-breaking flyby of the Sun on Dec. 25, 2024, shows the solar wind racing out from the Sun's outer atmosphere, the corona. == See also ==