Fastest spacecraft ever built to break its own speed record

On September 30, 2024, the Parker Solar Probe reached its 21st perihelion: its closest approach to the Sun.

The science questions that are being answered by the Parker Solar Probe are fundamental to understanding the Sun, its corona, and the phenomenon of space weather. By the end of its mission, the Parker Solar Probe will have set a number of records and scientific firsts, including becoming the closest and fastest spacecraft ever with respect to the Sun.

Presently, perihelion is only 7.87 million km (4.89 million miles) from the Sun’s surface.

This image and plot shows the Parker Solar Probe’s path and distance, with respect to the Sun, from its August 12, 2018 launch until its 21st perihelion, which it reached on September 30, 2024.

Its novel heat shield enables science operations under these extreme conditions.

The heat shield for the Parker Solar Probe, visible as the topmost structure here with a white alumina coating on the outer surface, is absolutely necessary for protecting the vital instruments inside from the otherwise catastrophic heat from the Sun. Once the heat shield fails, the entire probe is destined to fail within seconds.

From closest approach, the Sun appears 28 times larger than terrestrial views.

From Earth, the Sun subtends an angle of roughly half a degree on the sky. From the vantage point of the Parker Solar Probe at perihelion, the Sun will appear approximately 28 times larger in diameter and more than 750 times larger in terms of angular area.

The naked-eye planets have been glimpsed in perfect alignment.

During its 5th perihelion, on June 7, 2020, the Parker Solar Probe looked back toward Earth and was able to spot the Solar System’s innermost six planets all in one frame off to the same side of the limb of the Sun: Mars, Saturn, Jupiter, Venus, Earth, and Mercury, as shown from left-to-right.

Parker currently achieves maximum speeds of 176 km/s (109 mi/sec): the fastest spacecraft of all-time.

It’s also observed novel phenomena never seen before.

Discovered for the first time by the Parker Solar Probe, the solar wind exhibits magnetic switchbacks, where the magnetic field bends back on itself as particles stream away from the Sun. This discovery has yet to be fully explained, but particles emanating from the Sun impact all of the planets, and cause similar mass loss rates for the atmospheres of Venus, Earth, and Mars.

Magnetic switchbacks have been discovered in the solar wind.

As Parker Solar Probe passed through the corona on encounter nine, the spacecraft flew by structures called coronal streamers. These structures can be seen as bright features moving upward in the upper images and angled downward in the lower row. Such a view is only possible because the spacecraft flew above and below the streamers inside the corona. Until now, streamers have only been seen from afar, such as during total solar eclipses.

It’s flown through coronal streamers, only witnessed previously from afar.

And the clouds of Venus have been witnessed parting, revealing the Venusian surface.

As Parker Solar Probe flew by Venus on its fourth flyby, its WISPR instrument captured these images, strung into an animation, which show the nightside surface of the planet. Dark features, poking through the temporarily thin layer of clouds, do indeed correspond to the Venusian surface.

Parker’s spaceborne views match Magellan’s infrared maps spectacularly.

The WISPR data from the Parker Solar Probe, in monochrome, clearly matches the surface features seen by the significantly longer-than-optical wavelengths of the orbiter Magellan, shown in assigned color. The view of Venus from the Parker Solar Probe represents the first time the clouds of Venus have ever been seen parting, revealing the surface below.

But Parker’s next trick will be its greatest: the closest gravity assist ever.

By passing outside of Venus’s orbit while plunging toward the Sun, or passing interior to Venus’s orbit while moving outward away from the Sun, the Parker Solar Probe can receive a negative gravity assist, causing it to lose energy and, subsequently, to achieve a closer perihelion than its prior orbits. A seventh and final gravity assist with Venus will occur on November 6, 2024.

On November 6th, it comes within 317 km (197 miles) of Venus, which steals its kinetic energy.

By either passing inside of Venus’s orbit while plunging toward the Sun (as shown), or outside of Venus’s orbit while moving away from the Sun, the spacecraft can get de-boosted via the gravity assist/gravitational slingshot mechanism. The two other allowable maneuvers would increase the spacecraft’s speed, resulting in a velocity boost, rather than a de-boost.

As a result, it will plunge closer to the Sun, subsequently, than ever before.

This animation shows the trajectory of the Parker Solar Probe from its 2018 launch through its expected disabling in 2025. A total of seven gravity assists from Venus are planned, all of the de-boosting variety, with the seventh and final encounter scheduled for November 6, 2024.

On December 24, 2024, it will set new speed (192 km/s) and solar distance (6.9 million km) records.

This graph shows the speed of the Parker Solar Probe and its distance, both with respect to the Sun. Its various perihelia and Venus flybys are shown in red and green numbered points, respectively. It is unknown whether the Parker Solar Probe will survive beyond its 24th perihelion pass.

Next year, the Sun’s heat should finally disable this record-setting spacecraft.

Solar coronal loops, such as those observed by NASA’s Solar Dynamics Observatory (SDO) satellite here in 2014, follow the path of the magnetic field on the Sun. When these loops ‘break’ in just the right way, they can emit coronal mass ejections, which have the potential to impact Earth. The connection between the solar corona just above the photosphere and the outer phenomena that pervade the rest of the Solar System relies on in situ missions like the Parker Solar Probe to fill in the gaps between the Sun itself and Earth-based observations. After 24-25 orbits, the Parker Solar Probe is expected to succumb to the heat of the Sun.

Mostly Mute Monday tells an astronomical story in images, visuals, and no more than 200 words.