Normally, the first images of a spacecraft confirm that the instruments are working.
Washington DC .:
The first images of ESA / NASA’s Solar Orbiter, a new sun observation mission, are now available to the public, including the closest photos ever taken of the sun.
Solar Orbiter is an international collaboration between the European Space Agency or ESA and NASA, to study our nearest star, the Sun. Launched on February 9, 2020 (EST), the spacecraft completed its first close pass to the Sun in mid-June.
“These unprecedented images of the Sun are the closest we have ever obtained,” said Holly Gilbert, NASA project scientist for the mission at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
“These amazing images will help scientists reconstruct the atmospheric layers of the Sun, which is important for understanding how it determines space weather near Earth and throughout the solar system,” added Gilbert.
“We weren’t expecting such good results so soon. These images show that Solar Orbiter is on a good start,” said Daniel Muller, ESA Solar Orbiter project scientist.
Getting to this point was no small task. The new coronavirus has forced mission control of the European Space Operations Center, or ESOC, in Darmstadt, Germany, to shut down completely for more than a week.
During commissioning, the period during which each instrument is extensively tested, the staff of ESOC was reduced to a skeleton crew. All but essential staff worked from home.
“The pandemic has forced us to perform critical remote operations – the first time we have done so,” said Russell Howard, principal investigator for one of the Solar Orbiter imagers.
But the team adapted, even preparing for an unexpected encounter with the tails of ions and dust of comet ATLAS on June 1 and 6, respectively.
The spacecraft completed commissioning just in time for its first close solar pass on June 15. As it flew within 48 million miles of the Sun, the 10 instruments turned on and Solar Orbiter took the closest photos to the Sun to date. (Other spacecraft were closer, but none carried sun-facing imagers.)
Solar Orbiter carries six imaging instruments, each studying a different aspect of the Sun. Normally, the first images of a spacecraft confirm that the instruments are working; scientists do not expect new discoveries from them. But the extreme ultraviolet imager, or EUI, on Solar Orbiter returned data hinting at solar characteristics never observed in such detail.
Principal investigator David Berghmans, astrophysicist at the Royal Observatory of Belgium in Brussels, points out what he calls “campfires” dotting the Sun in EUI images.
“The campfires we are talking about here are the little nephews of solar flares, at least a million, maybe a billion times smaller. Looking at the new high resolution EUI images, they are literally everywhere we look”, said Berghmans.
It is not yet known what these campfires are or how they correspond to the solar lightings observed by other spacecraft. But it’s possible that these are mini-explosions known as nanoflares – tiny but ubiquitous sparks theorized to help heat the outer atmosphere of the Sun, or corona, to its temperature 300 times hotter than the sun’s surface.
To be sure, scientists need a more accurate measurement of the temperature of campfires. Fortunately, spectral imagery of the coronal environment, or SPICE instrument, also on Solar Orbiter, does just that.
“So we look forward to our next set of data. The hope is to detect nanoflares with certainty and to quantify their role in coronal heating,” said Frédéric Auchere, principal researcher for SPICE operations at the Institute for space astrophysics in Orsay, France.
Other images of the spacecraft offer additional promise for later in the mission when the Solar Orbiter is closer to the Sun.
The solar and heliospheric imager, or SoloHI, led by Russell Howard of the Naval Research Laboratory in Washington, DC, revealed the so-called zodiacal light, the sunlight reflecting off the interplanetary dust – a light so dim that the face shining from the Sun normally obscures it. To see this, SoloHI had to reduce the sunlight to a trillionth of its original brightness.
“The images produced such a perfect, clean zodiacal light pattern. It gives us a lot of confidence that we will be able to see the structures of the solar wind as we get closer to the Sun,” said Howard.
Images of the polar and helioseismic imager, or PHI, have shown that it is also primed for later observations. PHI maps the Sun’s magnetic field, with special emphasis on its poles.
It will have its climax later in the mission as the Solar Orbiter gradually tilts its orbit 24 degrees above the plane of the planets, giving it an unprecedented view of the poles of the Sun.
“The magnetic structures we see on the visible surface show that PHI is receiving higher quality data,” said Sami Solanki, PHI principal investigator at the Max Planck Institute for Solar System Research in Göttingen, Germany.
“We are ready for a great science as more and more solar poles appear,” added Solanki.
Today’s publication highlights the Solar Orbiter imagers, but the mission’s four in situ instruments also revealed early results.
In situ instruments measure the space environment immediately surrounding the spacecraft. The Solar Wind Analyzer, or SWA instrument, shared the first dedicated measurements of heavy ions (carbon, oxygen, silicon, iron and others) in the solar wind of the interior heliosphere.
