Parker Solar Probe
Parker Solar Probe (previously Solar Probe, Solar Probe Plus, or Solar Probe+, abbreviated PSP) is a NASA robotic spacecraft en route to probe the outer corona of the Sun. It will approach to within 9.86 solar radii (6.9 million kilometers or 4.3 million miles) from the center of the Sun and will travel, at closest approach, as fast as 690,000 km/h (430,000 mph).
Artistic rendition of the Parker Solar Probe.
|Names||Solar Probe (before 2002) |
Solar Probe Plus (2010–17)
Parker Solar Probe (since 2017)
|Operator||NASA · Applied Physics Laboratory|
|Mission duration||Planned: 6 years, 321 days |
Elapsed: 4 months and 6 days
|Manufacturer||Applied Physics Laboratory|
|Launch mass||685 kg (1,510 lb)|
|Dry mass||555 kg (1,224 lb)|
|Payload mass||50 kg (110 lb)|
|Dimensions||1.0 m × 3.0 m × 2.3 m (3.3 ft × 9.8 ft × 7.5 ft)|
|Power||343 W (at closest approach)|
|Start of mission|
|Launch date||August 12, 2018, 07:31 UTC|
|Rocket||Delta IV Heavy / Star-48BV|
|Launch site||Cape Canaveral SLC-37|
|Contractor||United Launch Alliance|
|Semi-major axis||0.388 AU (58.0 million km; 36.1 million mi)|
|Perihelion||0.046 AU (6.9 million km; 4.3 million mi; 9.86 R☉)[note 1]|
|Aphelion||0.73 AU (109 million km; 68 million mi)|
|Band||Ka band |
Official insignia for the Parker Solar Probe mission
The project was announced in the fiscal 2009 budget year. The cost of the project is US$1.5 billion. Johns Hopkins University Applied Physics Laboratory designed and built the spacecraft, which was launched on August 12, 2018. It became the first NASA spacecraft named after a living person, honoring physicist Eugene Parker, professor emeritus at the University of Chicago.
A memory card containing the names of over 1.1 million people was mounted on a plaque and installed below the spacecraft's high-gain antenna on May 18, 2018. The card also contains photos of Parker and a copy of his 1958 scientific paper predicting important aspects of solar physics.
On 29 October 2018, the spacecraft surpassed the current record of 26.55 million miles from the Sun's surface at about 1:04 p.m. EDT. The previous record was set in April 1976 by the Helios 2 spacecraft.
The Parker Solar Probe concept originates from a predecessor Solar Orbiter project conceived in the 1990s. Similar in design and objectives, the Solar Probe mission served as one of the centerpieces of the eponymous Outer Planet/Solar Probe (OPSP) program formulated by NASA. The first three missions of the program were planned to be: the Solar Orbiter, the Pluto and Kuiper belt reconnaissance mission Pluto Kuiper Express, 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 R☉, a perihelion of 4 R☉), 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. 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 cancellation of the program also resulted in the initial cancellation of New Horizons, the mission that eventually won the competition to replace Pluto Kuiper Express in the former OPSP program. That mission, which would eventually be launched as the first mission of the New Frontiers program, a conceptual successor to the OPSP program, would undergo a lengthy political battle to secure funding for its launch, which occurred in 2006.
In the early 2010s, plans for the Solar Probe mission were incorporated into a lower-cost Solar Probe Plus. The redesigned mission uses multiple Venus gravity assists for a more direct flight path, which can be powered by solar panels. It also has a higher perihelion, reducing the demands on the thermal protection system.
In May 2017, the spacecraft was renamed Parker Solar Probe in honor of astrophysicist Eugene Parker, coiner of the term "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.
The Parker Solar Probe will be 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 650 kW/m2intensity at Earth orbit.:31 The solar shield is hexagonal, mounted on the Sun-facing side of the spacecraft, 2.3 m (7.5 ft) in diameter, 11.4 cm (4.5 in) thick, and is made of reinforced carbon–carbon composite, which is designed to withstand temperatures outside the spacecraft of about 1,370 °C (2,500 °F). 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, the Parker Solar Probe will have to act autonomously and rapidly to protect itself. This will be done using four light sensors to detect the first traces of direct sun light coming from the shield limits and engaging movements from fly 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".
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 , 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 0.25 AUoperating temperature of the solar panels and instrumentation.
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 6×106 km (3.7×106 mi; 0.040 AU). 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. 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.
The trajectory requires high launch energy, so the probe was launched on a Delta IV Heavy class launch vehicle and an upper stage based on the STAR 48BV solid rocket motor. Interplanetary gravity assists will provide further deceleration relative to its heliocentric orbit, which will result in a heliocentric speed record at perihelion. As the probe passes around the Sun, it will achieve a velocity of up to 200 km/s (120 mi/s), which will temporarily make it the fastest manmade object, almost three times as fast as the current record holder, Helios-B. 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.
Within each orbit of the Parker Solar Probe around the Sun, the portion within 0.25 AU will be the Science Phase, in which the probe will be actively and autonomously making observations. Communication with the probe will be largely cut off in that phase.:4 These science phases will run for a few days both before and after each perihelion. They will last 11.6 days for the earliest perihelion, and drop to 9.6 days for the final, closest perihelion.:8
Much of the rest of each orbit will be devoted to transmitting data from the science (observation and measurement) phase. But during this part of each orbit, there will still be periods when communication is impeded or not possible. First, the heat shield of the probe must be pointed towards the Sun; there will be times when that will put the heat shield between the antenna and Earth. Secondly, 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 will overwhelm the communication link.:11–14
The goals of the mission are:
- Trace the flow of energy that heats the corona and accelerates the solar wind.
- Determine the structure and dynamics of the magnetic fields at the sources of solar wind.
- Determine what mechanisms accelerate and transport energetic particles.
To achieve these goals, the mission will perform five major experiments or investigations:
- Electromagnetic Fields Investigation (FIELDS) – This investigation will make direct measurements of electric and magnetic fields, radio waves, Poynting flux, absolute plasma density, and electron temperature. It consists of two flux-gate magnetometers, a search-coil magnetometer, and 5 plasma voltage sensors. The Principal investigator is Stuart Bale, at the University of California, Berkeley.
- Integrated Science Investigation of the Sun (IS☉IS) – This investigation will measure energetic electrons, protons and heavy ions. The instrument suite is composed of two independent instruments, EPI-Hi and EPI-Lo. The Principal investigator is David McComas, at the Princeton University.
- Wide-field Imager for Solar Probe (WISPR) – These optical telescopes will acquire images of the corona and inner heliosphere. The Principal Investigator is Russell Howard, at the Naval Research Laboratory.
- Solar Wind Electrons Alphas and Protons (SWEAP) – 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, a Faraday cup). The Principal Investigator is Justin Kasper at the University of Michigan and the Smithsonian Astrophysical Observatory.
- Heliospheric Origins with Solar Probe Plus (HeliOSPP) – A theory and modeling investigation to maximize the scientific return from the mission. The Principal Investigator is Marco Velli at UCLA and the Jet Propulsion Laboratory (JPL).
After the first Venus flyby, the probe will be in an elliptical orbit with a period of 150 days (two-thirds the period of Venus), making three orbits while Venus makes two. On the second flyby, the period shortens to 130 days. After less than two orbits (only 198 days later) it encounters Venus a third time at a point earlier in the orbit of Venus. This encounter shortens its period to half of that of Venus, or about 112.5 days. After two orbits it meets Venus a fourth time at about the same place, shortening its period to about 102 days. After 237 days it meets Venus for the fifth time and its period is shortened to about 96 days, three-sevenths that of Venus. It then makes seven orbits while Venus makes three. The sixth encounter, almost two years after the fifth, brings its period down to 92 days, two-fifths that of Venus. After five more orbits (two orbits of Venus) it meets Venus for the seventh and last time, decreasing its period to 88 or 89 days and allowing it to approach closer to the Sun.
from Sun (Gm)
|Orbital period |
|Venus flyby #1||–||–||–|
|2019||Apr 4||Perihelion #2||24.8||95||150|
|Sep 1||Perihelion #3||24.8||95||150|
|Dec 26||Venus flyby #2||–||–||–|
|2020||Jan 29||Perihelion #4||19.4||109||130|
|Jun 7||Perihelion #5||19.4||109||130|
|Jul 11||Venus flyby #3||–||–||–|
|Sep 27||Perihelion #6||14.2||129||112.5|
|2021||Jan 17||Perihelion #7||14.2||129||112.5|
|Feb 20||Venus flyby #4||–||–||–|
|Apr 29||Perihelion #8||11.1||147||102|
|Aug 9||Perihelion #9||11.1||147||102|
|Oct 16||Venus flyby #5||–||–||–|
|Nov 21||Perihelion #10||9.2||163||96|
|2022||Feb 25||Perihelion #11||9.2||163||96|
|Jun 1||Perihelion #12||9.2||163||96|
|Sep 6||Perihelion #13||9.2||163||96|
|Dec 11||Perihelion #14||9.2||163||96|
|2023||Mar 17||Perihelion #15||9.2||163||96|
|Jun 22||Perihelion #16||9.2||163||96|
|Aug 21||Venus flyby #6||–||–||–|
|Sep 27||Perihelion #17||7.9||176||92|
|Dec 29||Perihelion #18||7.9||176||92|
|2024||Mar 30||Perihelion #19||7.9||176||92|
|Jun 30||Perihelion #20||7.9||176||92|
|Sep 30||Perihelion #21||7.9||176||92|
|Nov 6||Venus flyby #7||–||–||–|
|Dec 24||Perihelion #22||6.9||192||88|
|2025||Mar 22||Perihelion #23||6.9||192||88|
|Jun 19||Perihelion #24||6.9||192||88|
|Sep 15||Perihelion #25||6.9||192||88|
|Dec 12||Perihelion #26||6.9||192||88|
The perihelion distances above are from the center of the Sun. For altitude above the surface, subtract one solar radius ≈ 0.7 Gm.
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.
- Launch occurred on August 12, 2018, at 3:31 a.m. EDT, 7:31 a.m. GMT. The spacecraft operated nominally after launching. During its first week in space it deployed its high-gain antenna, magnetometer boom, and its electric field antennas. The spacecraft performed its first scheduled trajectory correction on 20 August 2018, while it was 5.5 million miles from Earth, and travelling at 63,569 km/h (39,500 mph).
- Instrument activation and testing began in early September 2018. On September 9, 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 October 3, 2018, where it came within about 1,500 miles (2,400 km) of Venus in order to reduce the probe's speed and orbit closer to the Sun.
- The first scientific observations are due to be transmitted in December 2018.
- Living With a Star
- Advanced Composition Explorer (ACE), launched 1997
- List of vehicle speed records
- MESSENGER, Mercury orbiter (2011–2015)
- Sun observation spacecraft
- Solar Dynamics Observatory SDO
- Helios, a pair of spacecraft launched in the 1970s to approach the Sun inside the orbit of Mercury, 63 R☉
- Solar Orbiter (planned for 2020), 60 R☉
- STEREO, launched 2006
- WIND, launched 1994
- Ulysses, solar polar orbiter (1990–2009)
- Spacecraft design
- Mission planning used a perihelion of 9.5 R☉ (6.6 Gm; 4.1×106 mi), or 8.5 R☉ (5.9 Gm; 3.7×106 mi) altitude above the surface, but later documents all say 9.86 R☉. 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.
- 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.
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|Wikimedia Commons has media related to Parker Solar Probe.|
- Parker Probe Plus at Johns Hopkins University Applied Physics Laboratory (JHUAPL)
- Solar Probe Plus (Mission Engineering Report; JHUAPL)
- Heliophysics Research (NASA)
- Explorers and Heliophysics Projects Division (EHPD; NASA)
- Parker Solar Probe (data and news; NASA)
- Parker Solar Probe (Video/3:45; NYT; August 12, 2018)
- Parker Solar Probe (Video-360°/3:27; NASA; September 6, 2018)