Illuminating First Light Data from Parker Solar Probe

Just over a month into its mission, Parker Solar Probe has returned first-light data from each of its four instrument suites. These early observations – while not yet examples of the key science observations Parker Solar Probe will take closer to the Sun – show that each of the instruments is working well. The instruments work in tandem to measure the Sun’s electric and magnetic fields, particles from the Sun and the solar wind, and capture images of the environment around the spacecraft.

“All instruments returned data that not only serves for calibration, but also captures glimpses of what we expect them to measure near the Sun to solve the mysteries of the solar atmosphere, the corona,” said Nour Raouafi, Parker Solar Probe project scientist at the Johns Hopkins University Applied Physics Lab in Laurel, Maryland.

The mission’s first close approach to the Sun will be in November 2018, but even now, the instruments are able to gather measurements of what’s happening in the solar wind closer to Earth. Let’s take a look at what they’ve seen so far.

WISPR (Wide-field Imager for Solar Probe)

As the only imager on Parker Solar Probe, WISPR will provide the clearest-yet glimpse of the solar wind from within the Sun’s corona. Comprising two telescopes, WISPR sits behind the heat shield between two antennae from the FIELDS instrument suite. The telescopes were covered by a protective door during launch to keep them safe.

WISPR was turned on in early September 2018 and took closed-door test images for calibration. On Sept. 9, WISPR’s door was opened, allowing the instrument to take the first images during its journey to the Sun.

A blue-toned, two-panel image of space with stars visible throughout. In the left panel, the Milky Way is also visible.
The right side of this image — from WISPR’s inner telescope — has a 40-degree field of view, with its right edge 58.5 degrees from the Sun’s center. The left side of the image is from WISPR’s outer telescope, which has a 58-degree field of view and extends to about 160 degrees from the Sun. There is a parallax of about 13 degrees in the apparent position of the Sun as viewed from Earth and from Parker Solar Probe. Credit: NASA/Naval Research Laboratory/Parker Solar Probe

Download these images in HD formats from NASA’s Scientific Visualization Studio. 

Russ Howard, WISPR principal investigator from the Naval Research Laboratory, studied the images to determine the instrument was pointing as expected, using celestial landmarks as a guide.

“There is a very distinctive cluster of stars on the overlap of the two images. The brightest is the star Antares-alpha, which is in the constellation Scorpius and is about 90 degrees from the Sun,” said Howard.

The Sun, not visible in the image, is far off to the right of the image’s right edge. The planet Jupiter is visible in the image captured by WISPR’s inner telescope — it’s the bright object slightly right of center in the right-hand panel of the image.

“The left side of the photo shows a beautiful image of the Milky Way, looking at the galactic center,” said Howard.

The exposure time – i.e. the length of time that light was gathered for this image, an interval which can be shortened or lengthened to make the image darker or brighter – is on the lower end, and there’s a reason: “We intentionally wanted to be on the low side in case there was something very bright when we first turned on, but it is primarily because we are looking so far from the Sun,” explains Howard.

As the spacecraft approaches the Sun, its orientation will change, and so will WISPR’s images. With each solar orbit, WISPR will capture images of the structures flowing out from the corona. While measurements have been made before by other instruments at a distance of 1 AU – or approximately 93 million miles – WISPR will get much closer, about 95% of the way to the Sun from Earth, dramatically increasing the ability to see what’s occurring in that region with a much finer scale than ever before and providing a more pristine picture of the solar corona.

ISʘIS (Integrated Science Investigation of the Sun)

Two side by side plots. On the left, EPI-Lo, with a diagonal streak of data near the center of the plot. On the right, EPI-Hi, with two nearly parallel streaks of data near the lower left.
Credit: NASA/Princeton University/Parker Solar Probe

ISʘIS (pronounced “ee-sis” and including the symbol for the Sun in its acronym) measures high-energy particles associated solar activity like flares and coronal mass ejections. (The mission’s other particle instrument suite, SWEAP, focuses on low-energy particles that make up the solar wind.) ISʘIS’ two Energetic Particle Instruments cover a range of energies for these activity-driven particles: EPI-Lo focuses on the lower end of the energy spectrum, while EPI-Hi measures the more energetic particles. Both instruments have gathered data under low voltage, making sure their detectors work as expected. As Parker Solar Probe approaches the Sun, they will be fully powered on to measure particles within the Sun’s corona.

EPI-Lo’s initial data, on the left, shows background cosmic rays, particles that were energized and came rocketing into our solar system from elsewhere in the galaxy. As EPI-Lo’s high voltage is turned on and Parker Solar Probe gets closer to the Sun, the particles measured will shift toward solar energetic particles, which are accelerated in bursts and come streaming out from the Sun and corona.

On the right, data from EPI-Hi shows detections of both hydrogen and helium particles from its lower-energy telescopes. Nearer to the Sun, scientists expect to see many more of these particles — along with heavier elements — as well as some particles with much higher energies, especially during solar energetic particle events.

“The ISʘIS team is delighted with instrument turn-on so far,” said David McComas, Professor of Astrophysical Sciences at Princeton University and principal investigator of the ISʘIS instrument suite. “There are a few more steps to go, but so far everything looks great!”


The FIELDS instrument suite aboard Parker Solar Probe captures the scale and shape of electric and magnetic fields in the Sun’s atmosphere. These are key measurements to understanding why the Sun’s corona is hundreds of times hotter than its surface below.

A plot of three data streams, all high and steady at the beginning, then with a rapid drop to lower and more unsteady values.
Credit: NASA/UC Berkeley/Parker Solar Probe

FIELDS’ sensors include four two-meter electric field antennas — mounted at the front of the spacecraft, extending beyond the heat shield and exposed to the full brunt of the solar environment — as well as three magnetometers and a fifth, shorter electric field antenna mounted on a boom that extends from the back of the spacecraft.

The data above, gathered during the boom deployment shortly after the spacecraft’s launch in August, shows how the magnetic field changes as the boom swung away from Parker Solar Probe. The early data is the magnetic field of the spacecraft itself, and the instruments measured a sharp drop in the magnetic field as the boom extended away from the spacecraft. Post-deployment, the instruments are measuring the magnetic field in the solar wind — illustrating the very reason such sensors need to be held out far from the spacecraft.

A three panel plot showing similar streaks of data near the middle. The bottom two plots, from Parker Solar Probe, are clearer than the top plot, from Wind.
This plot was updated on Sept. 21, 2018, to better illustrate the comparison between Parker Solar Probe’s data (center and bottom) and the data from the Wind mission (top). Both versions are available from NASA’s Scientific Visualization Studio. Credit: NASA/UC Berkeley/Parker Solar Probe/Wind

In early September, the four electric field antennas on the front of the spacecraft were successfully deployed — and almost immediately observed the signatures of a solar flare.

“During its commissioning time, FIELDS measured its first radio burst from a solar flare,” said principal investigator Stuart Bale, of the Space Sciences Laboratory at the University of California, Berkeley. Such bursts of radio waves can be detected during solar flares — enormous eruptions of energy and light — and are associated with the energetic electrons that flares release. This radio burst was captured by the FIELDS electric field antennas, shown above with measurements from NASA’s Wind spacecraft (on the top) for comparison.

“FIELDS is one of the most comprehensive fields and waves suites ever flown in space, and it is performing beautifully,” said Bale.

SWEAP (Solar Wind Electrons Alphas and Protons)

A plot with mostly blue background and a red (stronger) feature near the bottom.
Credit: NASA/University of Michigan/Parker Solar Probe

The SWEAP suite includes three instruments: Two Solar Probe Analyzers measure electrons and ions in the solar wind, while the Solar Probe Cup sticks out from behind Parker Solar Probe’s heat shield to measure the solar wind directly as it streams off the Sun. After opening covers, turning on high voltages and running internal diagnostics, all three instruments caught glimpses of the solar wind itself.

Because of Parker Solar Probe’s position and orientation, the science team expected that Solar Probe Cup would mostly measure background noise at first, without picking up the solar wind. But just after the instrument was powered on, a sudden, intense gust of solar wind blew into the cup, visible in the data as the red streak. As the spacecraft approaches the Sun, such observations will be Solar Probe Cup’s bread and butter — and will hopefully reveal new information about the processes that heat and accelerate the solar wind.

A pair of plots, the top with only a little bit of data and bottom with a consistent background measurement.
Credit: NASA/University of Michigan/Parker Solar Probe

The two Solar Probe Analyzers (SPAN) also caught early peeks of the solar wind. During commissioning, the team turned the spacecraft so that SPAN-A — one of the two SPAN instruments — was exposed to the solar wind directly. It captured about 20 minutes’ worth of data (right), including measurements of solar wind ions (top) and electrons (bottom). While SPAN-A and its sister instrument, SPAN-B, will measure solar wind electrons throughout the mission, the spacecraft’s orientation now means that SPAN-A will likely go several more years before it captures such ion measurements again. This is because solar wind electrons can be measured from any direction, as their low mass and high temperature make their motion much more random, while the much heavier solar wind ions follow a relatively direct path out from the Sun.

“SWEAP’s solar wind and corona plasma instrument performance has been very promising,” said Justin Kasper, principal investigator of the SWEAP instrument suite at University of Michigan.  “Our preliminary results just after turn-on suggest we have a set of highly sensitive instruments that will allow us to do amazing science close to the Sun.”

Download these images in HD formats from NASA’s Scientific Visualization Studio. 

By Sarah Frazier (NASA) & Justyna Surowiec (APL)

NASA’s Goddard Space Flight Center, Greenbelt, Md.

Johns Hopkins University Applied Physics Lab, Laurel, Md.

Parker Solar Probe’s Solar Array Cooling System Fully Activated

On Sept. 13, Parker Solar Probe’s first-of-its-kind water-cooled Solar Array Cooling System (or SACS) was made fully operational. The SACS will protect Parker Solar Probe’s solar arrays — responsible for powering the spacecraft — from the intense heat of the Sun.

Though the solar arrays rely on the Sun’s energy to create electrical power for the spacecraft, they’re also very sensitive to overheating, and Parker Solar Probe is the first scientific mission to use a water-cooled solar array thermal management system. Water flows through mini-channels embedded in the solar arrays to absorb heat, then flows into four radiators to release that heat into space. This keeps the solar panels cool while near the Sun, allowing them to efficiently generate power for the spacecraft.

Though the Sun-facing side of Parker Solar Probe’s heat shield will reach temperatures as high as 2,500 degrees Fahrenheit when the spacecraft is close to the Sun, the SACS will keep the solar arrays — partially exposed to the Sun’s direct radiation — at less than 302 degrees.

NASA’s Parker Solar Probe is shown here mated to its third stage rocket motor on July 16, 2018, at Astrotech Space Operations in Titusville, Florida. The Solar Array Cooling System uses large black radiators, at the top of the spacecraft, to cool water that flows through portions of the solar arrays, bottom left.
NASA’s Parker Solar Probe is shown here mated to its third stage rocket motor on July 16, 2018, at Astrotech Space Operations in Titusville, Florida. The Solar Array Cooling System uses large black radiators, at the top of the spacecraft, to cool water that flows through portions of the solar arrays, bottom left. Credit: NASA/Johns Hopkins APL/Ed Whitman


As planned, the cooling system came partially online shortly after launch on Aug. 12. Roughly one hour after Parker Solar Probe’s 3:31 a.m. EDT launch, the spacecraft autonomously released the launch locks on its two solar arrays and deployed the panels. The spacecraft then released approximately two-thirds of a gallon of deionized water from a heated tank into two of four large radiators, mounted just below the spacecraft’s heat shield.

Then on Sept. 13, at around 11 p.m. EDT — when the spacecraft had reached a distance of about 84 million miles (135 million kilometers) from the Sun — the remaining one-third of a gallon of water was released, activating the last two radiators and making the SACS fully operational. These events were controlled by the mission operations team at the Johns Hopkins Applied Physics Lab in Laurel, Maryland.

“There are a number of technological breakthroughs on Parker Solar Probe that make the mission possible,” said APL’s Andy Driesman, project manager for mission. “The Solar Array Cooling System is really the heart and circulatory system of the spacecraft. Without it, the solar arrays would not survive the heat from the Sun, and we would not be able to operate the instruments that will explore the Sun’s corona and the systems that protect the spacecraft from the intense solar environment.”

As of 12 p.m. EDT on Sept. 14, Parker Solar Probe was 21 million miles (34 million km) from Earth, traveling at about 51,000 miles per hour (82,000 kph). Track the spacecraft’s progress online.

By Geoff Brown

Johns Hopkins University Applied Physics Lab

Where’s Parker Solar Probe? Track the Spacecraft Online

You can now track the position and speed of Parker Solar Probe on the web:

The plots showing the spacecraft’s heliocentric velocity, distances from the Sun and Earth, and round-trip light time to Earth update every hour.

A plot showing Parker Solar Probe's position relative to the Sun, Earth and its mission trajectory.

As of 11 a.m. EDT on Sept. 6, Parker Solar Probe is 16.27 million miles from Earth, traveling at 45,860 miles per hour.

Parker Solar Probe Continues Successful Commissioning Operations

Parker Solar Probe continues to bring its instruments and secondary systems online — slightly ahead of schedule — as it speeds away from Earth.

On Friday, Aug. 31, flight controllers at the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland performed a second planned Trajectory Correction Maneuver (TCM-2), a thruster burn which lasted for 35.2 seconds. This maneuver, which was executed with a high degree of precision, adjusted the direction of the spacecraft to position it for its Venus flyby on Oct. 3, when it will use Venus’ gravity to shed speed and draw its orbit closer to the Sun in preparation for its first solar approach.

On Sept. 2, four two-meter electric field antennas, part of the FIELDS instrument suite, were deployed. These antennas (as well as a fifth, which is mounted on the long boom at the other end of Parker Solar Probe) need to be extended away from the spacecraft to accurately measure the electric fields of the corona. These four antennas are not protected by Parker Solar Probe’s Thermal Protection System, or heat shield, so they are made of niobium C-103, a high-temperature alloy that can withstand the intense solar heat.

Illustration of Parker Solar Probe in space, with four antennas, two solar panels, and the Solar Probe Cup visible extending from behind the heat shield.
An artist’s concept of Parker Solar Probe in space. The FIELDS antennas extend out from behind the heat shield, and the Solar Probe Cup is visible on the right. Credit: NASA/JHUAPL

Just a few hours after the FIELDS antennas were deployed, the Solar Wind Electrons Alphas and Protons (SWEAP) investigation team successfully opened the covers of two instruments, the Solar Probe Analyzer (SPAN) instruments. The SPAN instruments are used to measure the solar wind when it is coming in at an angle relative to the spacecraft.

Before opening the SPAN instrument doors, the team ramped up high voltages on the Solar Probe Cup (SPC) instrument, also part of SWEAP. Solar Probe Cup measures the thermal solar wind plasma flowing radially from the Sun — requiring this instrument to be mounted outside the heat shield and pointed directly at the Sun. Like the FIELDS antennas, Solar Probe Cup’s heat shield is constructed of niobium C-103.

Other systems and instruments have completed checkouts as well. The spacecraft’s high gain antenna — which will be used to send high-rate science data to Earth — has been moved through its full range of motion.

EPI-Lo and EPI-Hi, the two Energetic Particle Instruments that make up the IS☉IS  suite (pronounced “ee-sis” and short for Integrated Science Investigation of the Sun), have been turned on and have completed low voltage checks.

The Wide-field Imager for Solar Probe (WISPR) instrument has been turned on and has taken closed-door test images to calibrate the systems and imagers.

“The spacecraft continues to perform as designed, and thanks to the team’s careful planning and execution, we’re commissioning instruments slightly ahead of schedule,” said APL’s Andy Driesman, Parker Solar Probe project manager.

“The science team is excited to begin the investigation phase of the mission,” said Nour Raouafi of APL, Parker Solar Probe project scientist. “We’re looking forward to seeing this initial science data and getting our first look at what we know will be many discoveries that Parker Solar Probe will make.”

As of 12 p.m. EDT on Sept. 4, Parker Solar Probe was more than 15 million miles from Earth, travelling at about 44,700 miles per hour (72,000 kilometers per hour).

Editor’s note: The original version of this post misstated the length of the TCM-2 thruster burn. This version has been updated with the correct figure. 

By Geoff Brown

Johns Hopkins University Applied Physics Lab