The Parker Solar Probe (PSP; previously Solar Probe, Solar Probe Plus or Solar Probe+)[6] is a NASAspace probe launched in 2018 with the mission of making observations of the outer corona of the Sun. It will approach to within 9.86 solar radii (6.9 million km or 4.3 million miles)[7][8] from the center of the Sun, and by 2025 will travel, at its closest approach, as fast as 690,000km/h (430,000mph) or 191 km/s, which is 0.064% the speed of light.[7][9] It is the fastest object ever built on Earth.[10]
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.[13] The card also contains photos of Parker and a copy of his 1958 scientific paper predicting important aspects of solar physics.[14]
On 29 October 2018, at about 18:04 UTC, the spacecraft became the closest ever artificial object to the Sun. The previous record, 42.73million kilometres (26.55million miles) from the Sun's surface, was set by the Helios 2 spacecraft in April 1976.[15] At its perihelion on 27 September 2023, the PSP's closest approach was 7.26million kilometres (4.51million miles),[16] reaching this distance again on 29 March 2024.[17] This will be surpassed after the remaining flyby of Venus.
History
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,[18][19][20] 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".[21][22]
Studies in the 1970s and 1980s reaffirmed its importance,[21] 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.[23][24]
Evolution of PSP design
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 R☉, a perihelion of 4 R☉),[24] 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, 3+1⁄2 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.[25] 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".[25]
In the early 2010s, plans for the Solar Probe mission were incorporated into a lower-cost Solar Probe Plus.[26] 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,[27][28] who had proposed the existence of nanoflares as an explanation of coronal heating[29] as well as having developed a mathematical theory that predicted the existence of solar wind.[30] The solar probe cost NASA US$1.5 billion.[31][32] The launch rocket bore a dedication in memory of APL engineer Andrew A. Dantzler who had worked on the project.[33]
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 650kW/m2, or 475 times the intensity at Earth orbit.[1][34]:31 The solar shield is hexagonal, mounted on the Sun-facing side of the spacecraft, 2.3m (7ft 7in) in diameter,[35]11.4cm (4.5in) thick, and is made of two panels of reinforced carbon–carbon composite with a lightweight 11-centimeter-thick (4.5in) carbon foam core,[36] which is designed to withstand temperatures outside the spacecraft of about 1,370°C (2,500°F).[1] The shield weighs only 73 kilograms (160lb) and keeps the spacecraft's instruments at 29°C (85°F).[36]
A white reflective alumina surface layer minimizes absorption. The spacecraft systems and scientific instruments are located in the central portion of the shield's shadow, where direct radiation from the Sun is fully blocked. If the shield were not between the spacecraft and the Sun, the probe would be damaged and become inoperative within tens of seconds. As radio communication with Earth will take about eight minutes in each direction, the Parker Solar Probe has to act autonomously and rapidly to protect itself. This will be done using four light sensors to detect the first traces of direct sunlight coming from the shield limits and engaging movements from reaction wheels to reposition the spacecraft within the shadow again. According to project scientist Nicky Fox, the team describe it as "the most autonomous spacecraft that has ever flown".[6]
The primary power for the mission is a dual system of solar panels (photovoltaic arrays). A primary photovoltaic array, used for the portion of the mission outside 0.25au, is retracted behind the shadow shield during the close approach to the Sun, and a much smaller secondary array powers the spacecraft through closest approach. This secondary array uses pumped-fluid cooling to maintain operating temperature of the solar panels and instrumentation.[37][38]
A light bar testing in the Astrotech processing facility.
Parker Solar Probe mated to its third stage rocket motor
PSP during extensive environmental testing.
PSP encapsulated in fairing.
The launch of the probe.
Trajectory
An animation of the Parker Solar Probe's trajectory from August 7, 2018, to August 29, 2025: Parker Solar Probe·Sun·Mercury·Venus·Earth For more detailed animation, see this video.
The Parker Solar Probe mission design uses 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 6×10^6km (3.7×10^6mi; 0.040au).[35] The spacecraft trajectory will include seven Venus flybys over nearly seven years to gradually shrink its elliptical orbit around the Sun, for a total of 24 orbits.[1] The near Sun radiation environment is predicted to cause spacecraft charging effects, radiation damage in materials and electronics, and communication interruptions, so the orbit will be highly elliptical with short times spent near the Sun.[34]
The trajectory requires high launch energy, so the probe was launched on a Delta IV Heavylaunch vehicle and an upper stage based on the Star 48BV solid rocket motor.[34] Interplanetary gravity assists will provide further deceleration relative to its heliocentric orbit, which will result in a heliocentric speed record at perihelion.[4][39] As the probe passes around the Sun, it will achieve a velocity of up to 200km/s (120mi/s), which will temporarily make it the fastest human-made object, almost three times as fast as the previous record holder, Helios-2.[40][41][42]
Launch injection was very close to the modelled one, but nevertheless required path correction. Trajectory was re-optimized after the launch to save the fuel. The first Venus flyby was only 52 days after the launch; three trajectory correction maneuvers were performed in this window.[20]
On September 27, 2023, the spacecraft traveled at 394,736 miles per hour (176.5 km/s), fast enough to fly from New York to Tokyo in just over a minute.[16]Like every object in an orbit, due to gravity the spacecraft will accelerate as it nears perihelion, then slow down again afterward until it reaches its aphelion.
Science goals
An apparent size of the Sun as seen from the Parker Solar Probe at perihelion compared to its apparent size seen from Earth
How is energy from the lower solar atmosphere transferred to, and dissipated in, the corona and solar wind?
What processes shape the non-equilibrium velocity distributions observed throughout the heliosphere?
How do the processes in the corona affect the properties of the solar wind in the heliosphere?
Determine the structure and dynamics of the plasma and magnetic fields at the sources of the solar wind.
How does the magnetic field in the solar wind source regions connect to the photosphere and the heliosphere?
Are the sources of the solar wind steady or intermittent?
How do the observed structures in the corona evolve into the solar wind?
Explore mechanisms that accelerate and transport energetic particles.
What are the roles of shocks, reconnection, waves, and turbulence in the acceleration of energetic particles?
What are the source populations and physical conditions necessary for energetic particle acceleration?
How are energetic particles transported in the corona and heliosphere?[34]
Instruments
Schematic view of all PSP's instrumentsParker Solar Probe 3D model
Parker Solar Probe has four main instruments:[43][44]
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 2,500°F (1,370°C). The 2-meter-long (6ft 7in) 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.[43]
IS☉IS (Integrated Science Investigation of the Sun). The instrument uses two complementary instruments to measure particles across a wide range of energies. By measuring electrons, protons and ions, IS☉IS will understand the particles' lifecycles — where they came from, how they became accelerated and how they move out from the Sun through interplanetary space. The two energetic particle instruments on IS☉IS are called EPI-Lo and EPI-Hi (EPI stands for Energetic Particle Instrument). EPI-Lo measures the spectra of electrons and ions and identifies carbon, oxygen, neon, magnesium, silicon, iron and two isotopes of helium, He-3 and He-4. Distinguishing between helium isotopes will help determine which of several theorized mechanisms caused the particles' acceleration. The instrument has a design with an octagonal dome body supporting 80 viewfinders. Multiple viewfinders provide a wide field of view to observe low-energy particles. An ion that enters EPI-Lo through one of the viewfinders first passes through two carbon-polyimide-aluminum foils and then encounters a solid-state detector. Upon impact, the foils produce electrons, which are measured by a microchannel plate. Using the amount of energy left by the ion's impact on the detector and the time it takes the ions to pass through the sensor identifies the species of the particles. EPI-Hi uses three particle sensors composed of stacked layers of detectors to measure particles with energies higher than those measured by EPI-Lo. The front few layers are composed of ultra-thin silicon detectors made up of geometric segments, which allows for the determination of the particle's direction and helps reduce background noise. Charged particles are identified by measuring how deep they travel into the stack of detectors and how many electrons they pull off atoms in each detector, a process called ionization. At closest approach to the Sun, EPI-Hi will be able to detect up to 100,000 particles per second. The Principal Investigator is David McComas at Princeton University.[43][45]
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.[43]
SWEAP (Solar Wind Electrons Alphas and Protons). This investigation will count the electrons, protons and helium ions, and measure their properties such as velocity, density, and temperature. Its main instruments are the Solar Probe Analyzers (SPAN, two electrostatic analyzers) and the Solar Probe Cup (SPC). SPC is a Faraday cup, a metal device that can catch charged particles in a vacuum. Peeking over the heat shield to measure how electrons and ions are moving, the cup is exposed to the full light, heat and energy of the Sun. The cup is composed of a series of highly transparent grids — one of which uses variable high voltages to sort the particles — above several collector plates, which measure the particles' properties. The variable voltage grid also helps sort out background noise, such as cosmic rays and photoionized electrons, which could otherwise bias the measurements. The grids, located near the front of the instrument, can reach temperatures of 3,000°F (1,650°C), glowing red while the instrument makes measurements. The instrument uses pieces of sapphire to electrically isolate different components within the cup. As it passes close to the Sun, SPC takes up to 146 measurements per second to accurately determine the velocity, density and temperature of the Sun's plasma. SPAN is composed of two instruments, SPAN-A and SPAN-B, which have wide fields of view to allow them to see the parts of space not observed by SPC. Particles encountering the detectors enter a maze that sends the particles through a series of deflectors and voltages to sort the particles based on their mass and charge. While SPAN-A has two components to measure both electrons and ions, SPAN-B looks only at electrons. The Principal Investigator is Justin Kasper at the University of Michigan and the Smithsonian Astrophysical Observatory.[43]
An additional theoretical investigation named Heliospheric origins with Solar Probe Plus (HeliOSPP) starting from 2010 and ending in 2024 has the role of providing theoretical input and independent assessment of scientific performance to the Science Working Group (SWG) and the SPP Project to maximize the scientific return from the mission. The Principal Investigator is Marco Velli at the University of California, Los Angeles and the Jet Propulsion Laboratory; he also serves as the Observatory Scientist for the mission.[34]
Mission
Launch of the Parker Solar Probe in 2018Artist's rendition of the Parker Solar Probe approaching the Sun
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.[46] 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 63,569 kilometres per hour (39,500mph)[47]
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.[48]
The probe successfully performed the first of the seven planned Venus flybys on 3 October 2018, where it came within about 2,400 kilometres (1,500mi) of Venus in order to reduce the probe's speed and orbit closer to the Sun.[49]
The second flyby of Venus on December 26, 2019. The velocity decreases by 2.9 km/s to 26 km/s (red circle), shifting the spacecraft to a new orbit closer to the Sun.
Within each orbit of the Parker Solar Probe around the Sun, the portion within 0.25 AU is the Science Phase, in which the probe is actively and autonomously making observations. Communication with the probe is largely cut off in that phase.[50]:4 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.[50]:8
Much of the rest of each orbit is devoted to transmitting data from the science phase. But during this part of each orbit, there are still periods when communication is not possible. First, the requirement that the heat shield of the probe be pointed towards the Sun sometimes puts the heat shield between the antenna and Earth. Second, even when the probe is not particularly near the Sun, when the angle between the probe and the Sun, as seen from Earth, is too small, the Sun's radiation can overwhelm the communication link.[50]:11–14
After the first Venusflyby, the probe was in an elliptical orbit with a period of 150 days (two-thirds the period of Venus), making three orbits while Venus makes two. After the second flyby, the period shortened to 130 days. After less than two orbits, only 198 days later, it encountered Venus a third time at a point earlier in the orbit of Venus. This encounter shortened its period to half of that of Venus, or about 112.5 days. After two orbits it met Venus a fourth time at about the same place, shortening its period to about 102 days.[51]
After 237 days, it met Venus for the fifth time and its period was shortened to about 96 days, three-sevenths that of Venus. It then made seven orbits while Venus made three. The sixth encounter, almost two years after the fifth, shortened its period down to 92 days, two-fifths that of Venus. After five more orbits (two orbits of Venus), it will meet Venus for the seventh and last time, decreasing its period to 88 or 89 days and allowing it to approach closer to the Sun.[51]
Timeline
The speed of the probe and distance from the Sun, from launch until 2026
Flybys 3 and 4 occur at the same point in Venus's orbit.
27 September
Perihelion #6
14.2
129
112.5
2021
17 January
Perihelion #7
20 February
Venus flyby #4
2392 km
Outbound
Outside
Flybys 3 and 4 occur at the same point in Venus's orbit.
28 April
Perihelion #8
11.1
147
102
First perihelion to enter the solar corona
9 August
Perihelion #9
16 October
Venus flyby #5
3786 km
Inbound
Inside
Flybys 5 and 6 occur at the same point in Venus's orbit.
21 November
Perihelion #10
9.2
163
96
2022
25 February
Perihelion #11
1 June
Perihelion #12
6 September
Perihelion #13
11 December
Perihelion #14
2023
17 March
Perihelion #15
22 June
Perihelion #16
21 August
Venus flyby #6
3939 km
Inbound
Inside
Flybys 5 and 6 occur at the same point in Venus's orbit.
27 September
Perihelion #17
7.9
176
92
29 December
Perihelion #18
2024
30 March
Perihelion #19
30 June
Perihelion #20
30 September
Perihelion #21
6 November
Venus flyby #7
317 km
Outbound
Outside
24 December
Perihelion #22
6.9
192
88
2025
22 March
Perihelion #23
19 June
Perihelion #24
15 September
Perihelion #25
12 December
Perihelion #26
↑ For altitude above the surface, subtract one solar radius ≈0.7 Gm. (A Gm (gigametre) is a million km or about 621371 mi.)
↑ Details on Venus flybys from Guo et al.[50]:6 This was published in 2014, four years before the mission began. For a variety of reasons, including the fact that the launch had to be delayed at the last minute, actual details could differ from the ones presented in the work.
↑ Inbound indicates that the Venus flyby will take place after Parker's aphelion (in the case of the first flyby, after its launch), on its way to perihelion. Outbound indicates that the Venus flyby will take place after Parker's perihelion, on its way to aphelion.
↑ Inside indicates that the probe will pass in between Venus and the Sun. Outside indicates that the probe will pass beyond Venus from the Sun; the probe will briefly pass through Venus's shadow in those instances.
↑ The first orbital period of 174 days was the orbit established by the launch and course adjustments, and was the orbit the probe would have taken had nothing further happened to change it. That orbit was, per mission plan, never completed. On the probe's first inbound course towards the Sun, it made its first planned encounter with Venus, which shortened its orbit considerably.
↑ The altitude is from the source cited,[50]:6 dated 2014. 2548 km comes to 1583 mi. NASA's [53] and Johns Hopkins's [54] press releases (identical), say "...came within about 1500 miles of Venus' surface..." A NASA blog,[49] says, "...completed its flyby of Venus at a distance of about 1500 miles..." Other news reports, presumably taking that information, also provide a figure of 2414 km. But neither the NASA/Hopkins press release nor the blog gives a figure in kilometers. Both the NASA and Hopkins press releases say that the flyby reduced the speed of the Parker Solar Probe (relative to the Sun) by about 10%, or 7000 mph. This altered the orbit, bringing perihelion about 4 million miles closer to the Sun than it would have been without the gravity assist.
↑ By way of comparison, the planet Mercury orbits the Sun at a distance varying from about 46.0 Gm (46,001,200 km) at its closest to about 69.8 Gm (69,816,900 km) at its farthest.
↑ After the second solar encounter phase, Parker Solar Probe was able to download much more data than NASA had expected. So NASA announced a substantial extension of the third solar encounter phase from 11 days to about 35 days. The observational instruments were turned on when Parker Solar Probe came within 0.45 au on the inbound trip, and are planned to run until the probe reaches about 0.50 au outbound.[58]
↑ The third flyby of Venus was the first to pass behind Venus from the point of view of the Sun. The probe was in Venus's shadow, obscured from the Sun, for about 11 minutes, and passed through a so-called "tail" of Venus – a trail of charged particles from the atmosphere of Venus. The probe's instruments were to be turned on to make observations.[64]
Findings
PSP observed switchbacks — traveling disturbances in the solar wind that caused the magnetic field to bend back on itself.NASA animation of the Probe passing through the Sun's stellar corona. 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 magnetic field of the solar wind.[65] They were first observed by the NASA-ESA mission Ulysses, the first spacecraft to fly over the Sun's poles.[66][67] The switchbacks generate heat that warms solar corona.[68]
On 4 December 2019, the first four research papers were published describing findings during the spacecraft's first two dives near the Sun.[69][70][71][72][73] 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.[70][74] The probe observed approximately a thousand "rogue" magnetic waves in the solar atmosphere that instantly increase solar winds by as much as 300,000 miles per hour (480,000km/h) and in some cases completely reverse the local magnetic field.[70][71][75][76]
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".[70][71]
PSP discovered evidence of a cosmic dust-free zone of 3.5 million miles (5.6 million kilometres) radius from the Sun, due to vaporisation of cosmic dust particles by the Sun's radiation.[77]
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;[78][79] the probe measured the solar wind plasma environment with its FIELDS and SWEAP instruments.[80] This event was described by NASA as "touching the Sun".[78]
On 25 September 2022, the first discovery of a comet was made in images from the Parker Solar Probe. The comet is named PSP-001. It was found by Peter Berrett, who participates in the NASA funded Sungrazer project.[81] 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 sungrazer comets have been discovered in the images taken by the Parker Solar Probe, including two non-group comets.
PSP and ESA-NASA's Solar Orbiter (SolO) missions cooperated to trace solar wind and transients from their sources on the Sun to the inner interplanetary space.[85]
In 2022, PSP and SolO 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.[86][87]
In March 2024, both space probes were at their closest approach 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 solar wind, that allowed scientists to compare data from both probes.[88]
Gallery
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.[89]
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[90]
Photo from the WISPR shows a coronal streamer, seen over the east limb of the Sun on Nov. 8, 2018, at 1:12a.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.[91]
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[92]
Photo taken by the probe during its second Venus flyby, July 2020
As Parker Solar Probe flew by Venus on its fourth flyby, its WISPR instrument captured these images, showing the nightside surface of the planet[93][94]
As the probe passed through the Sun's corona in early 2021, it flew by structures called coronal streamers
STEREO– Solar observation mission (2006–present), launched 2006
TRACE– NASA satellite of the Explorer program, launched 1998
WIND– NASA probe to study solar wind, at L1 since 1995, launched 1994
Ulysses– 1990 robotic space probe; studied the Sun from a near-polar orbit
Spacecraft thermal control– Process of keeping all parts of a spacecraft within acceptable temperature ranges
MESSENGER, Mercury orbiter (2011–2015) with sun shield
Solar Orbiter, Sun-observing space probe developed by the European Space Agency (ESA) launched on 10 February 2020
Notes
↑ Mission planning used a perihelion of 9.5R☉ (6.6Gm; 4.1×10^6mi), or 8.5R☉ (5.9Gm; 3.7×10^6mi) altitude above the surface,[5] but later documents all say 9.86R☉. The exact value will not be finalized until the seventh Venus gravity assist in 2024. Mission planners might decide to alter it slightly before then.
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The Solar Orbiter (SolO) is a Sun-observing probe developed by the European Space Agency (ESA) with a National Aeronautics and Space Administration (NASA) contribution. Solar Orbiter, designed to obtain detailed measurements of the inner heliosphere and the nascent solar wind, will also perform close observations of the polar regions of the Sun which is difficult to do from Earth. These observations are important in investigating how the Sun creates and controls its heliosphere.
Juno is a NASA space probe orbiting the planet Jupiter. It was built by Lockheed Martin and is operated by NASA's Jet Propulsion Laboratory. The spacecraft was launched from Cape Canaveral Air Force Station on August 5, 2011 UTC, as part of the New Frontiers program. Juno entered a polar orbit of Jupiter on July 5, 2016, UTC, to begin a scientific investigation of the planet. After completing its mission, Juno was originally planned to be intentionally deorbited into Jupiter's atmosphere, but has since been approved to continue orbiting until contact is lost with the spacecraft.
The International Cometary Explorer (ICE) spacecraft, designed and launched as the International Sun-Earth Explorer-3 (ISEE-3) satellite, was launched on 12 August 1978 into a heliocentric orbit. It was one of three spacecraft, along with the mother/daughter pair of ISEE-1 and ISEE-2, built for the International Sun-Earth Explorer (ISEE) program, a joint effort by NASA and ESRO/ESA to study the interaction between the Earth's magnetic field and the solar wind.
The Solar Dynamics Observatory (SDO) is a NASA mission which has been observing the Sun since 2010. Launched on 11 February 2010, the observatory is part of the Living With a Star (LWS) program.
Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission began in February 2007 as a constellation of five NASA satellites to study energy releases from Earth's magnetosphere known as substorms, magnetic phenomena that intensify auroras near Earth's poles. The name of the mission is an acronym alluding to the Titan Themis.
The exploration of Mercury has a minor role in the space interests of the world. It is the least explored inner planet. As of 2015, the Mariner 10 and MESSENGER missions have been the only missions that have made close observations of Mercury. MESSENGER made three flybys before entering orbit around Mercury. A third mission to Mercury, BepiColombo, a joint mission between the Japan Aerospace Exploration Agency (JAXA) and the European Space Agency, is to include two probes. MESSENGER and BepiColombo are intended to gather complementary data to help scientists understand many of the mysteries discovered by Mariner 10's flybys.
The Magnetospheric Multiscale (MMS) Mission is a NASA robotic space mission to study the Earth's magnetosphere, using four identical spacecraft flying in a tetrahedral formation. The spacecraft were launched on 13 March 2015 at 02:44 UTC. The mission is designed to gather information about the microphysics of magnetic reconnection, energetic particle acceleration, and turbulence — processes that occur in many astrophysical plasmas. As of March 2020, the MMS spacecraft has enough fuel to remain operational until 2040.
Europa Clipper is a space probe developed by NASA to study Europa, a Galilean moon of Jupiter. It was launched on October 14, 2024. The spacecraft will use gravity assists from Mars on March 1, 2025, and Earth on December 3, 2026, before arriving at Europa in April 2030. The spacecraft will then perform a series of flybys of Europa while in orbit around Jupiter.
The Interstellar Mapping and Acceleration Probe(IMAP) is a heliophysics mission that will simultaneously investigate two important and coupled science topics in the heliosphere: the acceleration of energetic particles and interaction of the solar wind with the local interstellar medium. These science topics are coupled because particles accelerated in the inner heliosphere play crucial roles in the outer heliospheric interaction. In 2018, NASA selected a team led by David J. McComas of Princeton University to implement the mission, which is currently scheduled to launch on 29 April 2025. IMAP will be a Sun-tracking spin-stabilized satellite in orbit about the Sun–Earth L1 Lagrange point with a science payload of ten instruments. IMAP will also continuously broadcast real-time in-situ data that can be used for space weather prediction.
FIELDS is a science instrument on the Parker Solar Probe (PSP), designed to measure magnetic fields in the solar corona during its mission to study the Sun. It is one of four major investigations on board PSP, along with WISPR, ISOIS, and SWEAP. It features three magnetometers. FIELDS is planned to help answer an enduring questions about the Sun, such as why the solar corona is so hot compared to the surface of the Sun and why the solar wind is so fast.
The Wide-Field Imager for Solar Probe (WISPR) is an imaging instrument of the Parker Solar Probe mission to the Sun, launched in August 2018. Imaging targets include visible light images of the corona, solar wind, shocks, solar ejecta, etc. Development of WISPR was led by the U.S. Naval Research Laboratory. The Parker Solar Probe with WISPR on board was launched by a Delta IV Heavy on 12 August 2018 from Cape Canaveral, Florida. WISPR is intended take advantage of the spacecraft's proximity to the Sun by taking coronagraph-style images of the solar corona and features like coronal streamers, plumes, and mass ejections. One of the goals is to better understand the structure of the solar corona near the Sun.
The Alfvén surface is the boundary separating a star's corona from the stellar wind defined as where the coronal plasma's Alfvén speed and the large-scale stellar wind speed are equal. It is named after Hannes Alfvén, and is also called Alfvén critical surface, Alfvén point, or Alfvén radius. In 2018, the Parker Solar Probe became the first spacecraft that crossed Alfvén surface of the Sun.
Magnetic switchbacks are sudden reversals in the magnetic field of the solar wind. They can also be described as traveling disturbances in the solar wind that caused the magnetic field to bend back on itself. They were first observed by the NASA-ESA mission Ulysses, the first spacecraft to fly over the Sun's poles. NASA's Parker Solar Probe and NASA/ESA Solar Orbiter both observed switchbacks.
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↑ Landis, Geoffrey A.; etal. (July 28–30, 2008). Solar Power System Design for the Solar Probe+ Mission(PDF). 6th International Energy Conversion Engineering Conference. Cleveland, Ohio. AIAA 2008-5712. Archived(PDF) from the original on November 11, 2020. Retrieved July 25, 2018. This article incorporates text from this source, which is in the public domain.
1 2 3 See data and figure at "Solar Probe Plus: The Mission". Johns Hopkins University Applied Physics Laboratory. 2017. Archived from the original on August 22, 2017. Retrieved June 17, 2017. This article incorporates text from this source, which is in the public domain.
↑ "HORIZONS System". Jet Propulsion Laboratory, NASA. Archived from the original on May 25, 2019. Retrieved August 16, 2018. Data file This article incorporates text from this source, which is in the public domain.
↑ "Parker Solar Probe Gets Extra Observation Time". parkersolarprobe.jhuapl.edu. Johns Hopkins University Applied Physics Laboratory. August 16, 2018. Archived from the original on October 4, 2019. Retrieved September 2, 2018. This article incorporates text from this source, which is in the public domain.
↑ "Parker Solar Probe Heads Toward Second Venus Flyby". Parker Solar Probe News Center. Johns Hopkins University Applied Physics Laboratory. November 20, 2018. Archived from the original on December 26, 2019. Retrieved December 23, 2019. Gives the time as "1:14 p.m. EST" and the distance of the flyby as "within 1870 miles". This article incorporates text from this source, which is in the public domain.
↑ "Welcome to Sungrazer". sungrazer.nrl.navy.mil. Retrieved July 18, 2023. This article incorporates text from this source, which is in the public domain.
↑ Biondo, Ruggero; etal. (December 2022). "Connecting Solar Orbiter remote-sensing observations and Parker Solar Probe in situ measurements with a numerical MHD reconstruction of the Parker spiral". Astronomy & Astrophysics. 668: A144. arXiv:2211.12994. Bibcode:2022A&A...668A.144B. doi:10.1051/0004-6361/202244535.This article incorporates textfrom this source, which is available under the CC BY 4.0 license.
Missions are ordered by launch date. † indicates failure en route or before any data returned. ‡ indicates use of the planet as a gravity assist en route to another destination.
Launches are separated by dots ( • ), payloads by commas ( , ), multiple names for the same satellite by slashes ( / ). Crewed flights are underlined. Launch failures are marked with the † sign. Payloads deployed from other spacecraft are (enclosed in parentheses).
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