Parker Solar Probe


The Parker Solar Probe is a NASA robotic spacecraft 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 from the center of the Sun, and by 2025 will travel, at closest approach, as fast as, or 0.064% the speed of light.
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 Newman 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 October 29, 2018, at about 18:04 UTC, the spacecraft became the closest ever artificial object to the Sun. The previous record, from the Sun's surface, was set by the Helios 2 spacecraft in April 1976. As of its perihelion on January 29, 2020, the Parker Solar Probe's closest approach is. This will be surpassed after each successive flyby of Venus.

History

The Parker Solar Probe concept originates in the 1958 report by the Fields and Particles Group 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 80s 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 eponymous Outer Planet/Solar Probe 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 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, 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.
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 Newman Parker, who coined 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.

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 reinforced carbon–carbon composite, which is designed to withstand temperatures outside the spacecraft of about.
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 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 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".
The primary power for the mission is a dual system of solar panels. 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 operating temperature of the solar panels and instrumentation.

Trajectory

The Parker Solar Probe mission design uses repeated gravity assists at Venus to incrementally decrease its orbital perihelion to achieve a final altitude of approximately 8.5 solar radii, or about. 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, which will temporarily make it the fastest human-made object, almost three times as fast as the previous record holder, Helios-2. 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.

Mission

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. 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.
Much of the rest of each orbit will be devoted to transmitting data from the science phase. But during this part of each orbit, there will still be periods when communication is 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. Second, even when the probe is not particularly near the Sun, when the angle between the probe and the Sun is too small, the Sun's radiation will overwhelm the communication link.

Science goals

The goals of the mission are:
To achieve these goals, the mission will perform five major experiments or investigations:
After the first Venus flyby, the probe will be in an elliptical orbit with a period of 150 days, making three orbits while Venus makes two. On the second flyby, the period shortens to 130 days. After less than two orbits 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 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.
YearDateEventDistance
from Sun 		Speed
Orbital period
Notes
YearDateEventFlyby altitude
over Venus 		Leg of
Parker's orbit 		Inside/Outside
orbit of Venus 		Notes
2018August 12
07:31 UTC		Launch151.6–174
2018October 3
08:44 UTC		Venus flyby #12548 kmInboundInsideFlybys 1 and 2 occur at the
same point in Venus's orbit
2018November 6
03:27 UTC		Perihelion #195150Solar encounter phase
October 31 – November 11
2019April 4
22:40 UTC		Perihelion #295150Solar encounter phase
March 30 – April 10
2019September 1
17:50 UTC		Perihelion #395150Solar encounter phase
August 16 – September 20
2019December 26
18:14 UTC		Venus flyby #23023 kmInboundInsideFlybys 1 and 2 occur at the
same point in Venus's orbit
2020January 29
09:37 UTC		Perihelion #4109130Solar encounter phase
January 23 – February 29
2020June 7
08:23 UTC		Perihelion #5109130Solar encounter phase
May 9 – June 28
2020July 11
03:22 UTC		Venus flyby #3834 kmOutboundOutside Flybys 3 and 4 occur at the
same point in Venus's orbit
2020September 27Perihelion #6129112.5
2021January 17Perihelion #7129112.5
2021February 20Venus flyby #42392 kmOutboundOutsideFlybys 3 and 4 occur at the
same point in Venus's orbit
2021April 29Perihelion #8147102
2021August 9Perihelion #9147102
2021October 16Venus flyby #53786 kmInboundInsideFlybys 5 and 6 occur at the
same point in Venus's orbit
2021November 21Perihelion #1016396
2022February 25Perihelion #1116396
2022June 1Perihelion #1216396
2022September 6Perihelion #1316396
2022December 11Perihelion #1416396
2023March 17Perihelion #1516396
2023June 22Perihelion #1616396
2023August 21Venus flyby #63939 kmInboundInsideFlybys 5 and 6 occur at the
same point in Venus's orbit
2023September 27Perihelion #1717692
2023December 29Perihelion #1817692
2024March 30Perihelion #1917692
2024June 30Perihelion #2017692
2024September 30Perihelion #2117692
2024November 6Venus flyby #7317 kmOutboundOutside
2024December 24Perihelion #2219288
2025March 22Perihelion #2319288
2025June 19Perihelion #2419288
2025September 15Perihelion #2519288
2025December 12Perihelion #2619288

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.

Operational history

On December 4, 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 winds 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 researchers found a "surprisingly large azimuthal component of the plasma velocity. 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".
Parker discovered evidence of a cosmic dust free zone of 3.5 million miles radius from the Sun, due to vaporisation of cosmic dust particles by the Sun's radiation.