Parker Solar Probe

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Parker Solar Probe.jpg

Parker Solar Probe (previously Solar Probe, Solar Probe Plus, or Solar Probe+, abbreviated PSP[1]) is a NASA robotic spacecraft en route to probe the outer corona of the Sun.[2][3][4] It will approach to within 8.86 solar radii (6.2 million kilometers or 3.85 million miles) from the "surface" (photosphere) of the Sun[5] and will travel, at closest approach, as fast as 700,000 km/h (430,000 mph).[6]

The project was announced in the fiscal 2009 budget year. Johns Hopkins University Applied Physics Laboratory designed and built the spacecraft, which was originally scheduled to launch in 2015,[7] but was launched on August 12, 2018.[8] This was the first time a NASA spacecraft was named after a living person, honoring physicist Eugene Parker, professor emeritus at the University of Chicago.[9]

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.[10] The card also contains photos of Parker and a copy of his 1958 scientific paper predicting important aspects of solar physics.

History

Light bar testing in the Astrotech processing facility

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.[11][12]

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 D, a perihelion of 4 D),[12] 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 12 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 cancelled as part of President George W. Bush's request for the 2003 United States federal budget.[13] 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."[13]

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.[14] 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.[15]

In the early 2010s, plans for the Solar Probe mission were incorporated into a lower-cost Solar Probe Plus.[16] 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,[17][18] coiner of the term "solar wind".

Mission profile

NASA's Parker Solar Probe during extensive environmental testing

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 Parker Solar Probe mission design uses repeated gravity assists at Venus to incrementally decrease its orbital perihelion to achieve multiple passes of the Sun at approximately 8.5 solar radii, or about 6 million km (3.7 million mi; 0.040 AU).[19]

The spacecraft's systems are protected from the extreme heat near the Sun by a solar shadow-shield. Due to the inverse-square law, incident solar radiation at perihelion is approximately 650 kW/m2, or 475 times the intensity at Earth orbit.[20][21]:31 The solar shield is hexagonal, mounted on the Sun-facing side of the spacecraft, 2.3 m (7.5 ft) in diameter,[19] 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).[20] 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. According to project scientist Nicky Fox, the team describe it as "the most autonomous spacecraft that has ever flown".[1]

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 0.25 AU, 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.[22]

Trajectory

Animation of Parker Solar Probe's trajectory from August 7, 2018 to August 29, 2025
  Parker Solar Probe ·   Sun ·   Mercury ·   Venus ·   Earth
Second flyby of Venus on December 22, 2019. The velocity decreases by 2.9 km/s to 26 km/s on December 26 (red circle), then the spacecraft enters a new orbit closer to the Sun.

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.[20] The science phase will take place during those 7 years, focusing on the periods when the spacecraft is closest to the Sun. 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.[21]

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.[21] Interplanetary gravity assists will provide further deceleration relative to its heliocentric orbit, which may result in a heliocentric speed record at perihelion.[23][24] 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.[25][26][27] Like every object in an orbit, due to gravity the spacecraft will accelerate as it nears perihelion, then slow down again afterwards until it reaches its aphelion.

Scientific goals

Apparent size of the Sun as seen from the orbit of the Parker Solar Probe compared to its apparent size seen from Earth.

The goals of the mission are:[21]

  • 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.

Investigations

In order to achieve these goals, the mission will perform five major experiments or investigations:[21]

  • 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 is comprised of 2 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).

Timeline

After the first Venus fly-by, 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 fly-by, 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.[28]

Perihelion means the point in the PSP's orbit closest to the Sun

Completed events are shown in bold
Year Events
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
2018 Aug 12
Launch
Sep 28
First flyby of Venus
(period 150 days)
Nov 1
Perihelion #1
2019 Mar 31
Perihelion #2
Aug 28
Perihelion #3
Dec 21
Second flyby of Venus
(period 130 days)
2020 Jan 24
Perihelion #4
Jun 2
Perihelion #5
Sep 22
Perihelion #6
Jul 6
Third flyby of Venus
(period 112.5 days)
2021 Jan 13
Perihelion #7
Apr 24
Perihelion #8
Aug 5
Perihelion #9
Nov 16
Perihelion #10
Feb 16
Fourth flyby of Venus
(period 102 days)
Oct 11
Fifth flyby of Venus
(period 96 days)
2022 Feb 21
Perihelion #11
May 28
Perihelion #12
Sep 1
Perihelion #13
Dec 6
Perihelion #14
2023 Mar 13
Perihelion #15
Jun 17
Perihelion #16
Sep 23
Perihelion #17
Dec 24
Perihelion #18
Aug 16
Sixth flyby of Venus
(period 92 days)
2024 Mar 25
Perihelion #19
Jun 25
Perihelion #20
Sep 25
Perihelion #21
Dec 19
Perihelion #22
First close approach to the Sun
Nov 2
Seventh flyby of Venus
(period 88 days)
2025 Mar 18
Perihelion #23
Jun 14
Perihelion #24
Sep 10
Perihelion #25
Dec 7
Perihelion #26
A graph of the velocity and distance from the sun of the probe from launch date until 2026. Legend: -: Perihelion; -: Flyby

Mission status

Launch occurred on August 12, 2018, at 3:31 a.m. EDT, 7:31 a.m. GMT. The spacecraft is operating nominally, and during its first week in space it will deploy its high-gain antenna, magnetometer boom, and its electric field antennas. Instrument testing will begin in early September, and its first science observations will start in December 2018.[29]

See also

Sun observation spacecraft
Spacecraft design

References

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  4. Applied Physics Laboratory (November 19, 2008) (.PDF). Feasible Mission Designs for Solar Probe Plus to Launch in 2015, 2016, 2017, or 2018. Johns Hopkins University. Archived from the original on April 18, 2016. https://web.archive.org/web/20160418160052/http://solarprobe.jhuapl.edu/common/content/SolarProbePlusFactSheet.pdf. Retrieved February 27, 2010.
  5. Lua error in Module:Citation/CS1 at line 379: attempt to call method 'match' (a nil value).
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  20. 20.0 20.1 20.2 Cite error: Invalid <ref> tag; no text was provided for refs named extreme
  21. 21.0 21.1 21.2 21.3 21.4 Fox, N.J.; Velli, M.C.; Bale, S.D.; Decker, R.; Driesman, A.; Howard, R.A.; Kasper, J.C.; Kinnison, J. et al. (November 11, 2015). "The Solar Probe Plus Mission: Humanity's First Visit to Our Star" (in en). Space Science Reviews 204 (1–4): 7–48. doi:10.1007/s11214-015-0211-6. ISSN 0038-6308. http://link.springer.com/10.1007/s11214-015-0211-6.
  22. Lua error in Module:Citation/CS1 at line 379: attempt to call method 'match' (a nil value).
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  27. (in en) Parker Solar Probe – Check123, Video Encyclopedia, https://www.check123.com/videos/13450-parker-solar-probe, retrieved June 1, 2017
  28. See data and figure at Lua error in Module:Citation/CS1 at line 379: attempt to call method 'match' (a nil value).
  29. Lua error in Module:Citation/CS1 at line 379: attempt to call method 'match' (a nil value).


External links

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