Parker Solar Probe

The Parker Solar Probe (Parker Solar Probe) is an unmanned spacecraft developed by NASA and launched on 12 August 2018 to directly study the Sun’s atmosphere. The mission aims to elucidate the dynamics magnetic structures and energy transport processes of solar wind by observing the Sun’s outer atmosphere, the corona, with high resolution. This mission represents a turning point in astrophysics and heliophysics research because it is the first human-made vehicle to make direct contact with the Sun’s interior.

^{Parker Solar Probe (}NASA⁾

The probe is constructed from specially developed high-temperature-resistant materials, as it approaches within just a few million kilometers of the Sun’s surface. One of its most remarkable features is a carbon-composite heat shield approximately 11.43 centimeters thick. This shield maintains the spacecraft’s main body at around 30°C even under conditions where surface temperatures reach 1370°C (2500°F). The front surface of the shield is made of carbon-carbon material while the rear surface is coated with a special white ceramic layer. This design both reflects radiation and disperses heat without significant absorption.

The solar panel system has also been engineered with special thermal protection. Only a small portion extends beyond the shield and is supported by active liquid cooling circulation systems that enable operation even under extreme heat conditions.

^{Structure of the Parker Solar Probe’s heat shield (Generated by Artificial Intelligence)}

The Parker Solar Probe carries four main scientific instrument suites designed to measure the Sun’s magnetic fields plasma waves energetic particles and electrical environment:

1. FIELDS: Measures electric and magnetic fields radio waves and plasma waves. This instrument provides direct data on the structure of the Sun’s magnetosphere.
2. SWEAP (Solar Wind Electrons Alphas and Protons): Measures the temperature velocity density and distribution of key particles in the plasma. It includes two instruments: the Faraday Cup and the Solar Probe Cup.
3. ISʘIS (Integrated Science Investigation of the Sun): Analyzes acceleration processes in solar wind by measuring low- and high-energy particles.
4. WISPR (Wide-Field Imager for Solar Probe): Used to image the corona and solar wind structures. This instrument enables observation of coronal mass ejections (CMEs) in the region close to the Sun.

The Parker Solar Probe’s mission comprises a total of 24 close passes. To progressively reduce its distance from the Sun on each orbit seven gravity assist maneuvers using Venus’s gravitational pull are planned. Starting in 2024 the probe’s closest approach to the Sun will be approximately 6.2 million kilometers — just nine times the Sun’s diameter.

When launched in 2018 the probe was about 25 million kilometers from the Sun. Over time this distance has decreased and during a flyby in 2021 the probe entered for the first time the Alfvén critical surface — the boundary beyond which the Sun’s magnetic influence no longer controls plasma particles. On 18 April 2021 observations showed the probe crossing this boundary three times and spending approximately five hours within the solar corona. This event has been described in human history as “touching the Sun.”

^{Photograph taken by the Parker Solar Probe on 8 November 2018 from approximately 27 million kilometers beyond the Sun’s surface (within the solar plasma) (}NASA⁾

Plasma particles emitted from the Sun reach a critical speed known as the Alfvén speed at which the Sun’s magnetic field can no longer control them. This boundary is defined as the Alfvén critical surface. Particles beyond this boundary break free from the Sun and form the solar wind. Previous remote observations suggested this surface lies between 10 and 20 solar radii from the Sun’s surface (approximately 6.9 to 13.8 million kilometers). The Parker Solar Probe has revealed that this boundary extends much farther inward in certain regions prompting a reevaluation of heliophysical models.

The greatest challenge during the probe’s flight is operating under extreme thermal radiation high-velocity plasma particles and intense magnetic fields. The spacecraft’s orbital velocity reaches up to approximately 192000 kilometers per second — among the highest speeds ever achieved by a spacecraft. Any hardware outside the heat shield would vaporize within seconds so every component and sensor is precisely aligned to remain in the shield’s shadow.

^{Visual representing the Parker Solar Probe entering the solar corona (}NASA⁾

The Parker Solar Probe has a unique mission not only because of its proximity to the Sun but also because it performs direct measurements. Previous missions (SOHO STEREO Ulysses) were limited to remote sensing data. With Parker however direct measurements of temperature density velocity and magnetic fields within the Sun’s dynamic structure have been obtained. These data are critical for space weather forecasting and enable the development of predictive models to protect Earth’s power grids and communication infrastructure.

The Parker Solar Probe is a groundbreaking project in both engineering and science. It provides a robust data foundation for humanity to better understand its most powerful energy source and to advance future technologies operating in space. The mission will continue until 2025 and the data collected during its final passes are expected to significantly advance the field of heliophysics.