The Solar Orbiter Will Launch Monday on Its Journey to Peer Into the Sun

By Ryan F. Mandelbaum on at

Early Monday morning, the European Space Agency hopes to launch its Solar Orbiter in order to better understand a star we know far too little about: the Sun. The launch is scheduled for 4:03 am ET on 10 February (live stream from NASA TV is embedded below).

As its name suggests, the Solar Orbiter is a Sun-circling satellite, containing 10 instruments meant to take measurements otherwise hard to get from Earth-bound telescopes. The mission seeks to explain how the Sun generates the heliosphere, the region of plasma that surrounds the entire solar system, with an ultimate goal of being able to forecast the space weather that has the potential to damage many of the electronics we rely on today. This will also be the first mission to take a picture of the Sun’s poles.

The Solar Orbiter’s final 150-day elliptical orbit will take it as close as 26 million miles away from the Sun to nearly the same distance as Earth. The spacecraft will repeatedly return to Venus, each time using the planet’s gravity to slightly tilt its orbit in order to get a different view of the Sun, up to 17 degrees inclination from the plane in which the planets orbit. If the mission succeeds and is pushed into its extended phase, it will increase its orbital inclination to 33 degrees, the angle from which it will be able to image the Sun’s poles.

The Solar Orbiter being integrated into its rocket fairing. (Photo: ESA/S. Corvaja)

A suite of instruments will allow it to probe the various ways the Sun releases matter and energy. Four instruments will directly measure the Sun’s emissions: One detector will measure the energetic particles the Sun releases, looking to understand how these particles get accelerated; a magnetometer will measure the magnetic field close to the Sun; another detector will measure the radio and plasma waves; and a fourth will measure the solar wind’s density, velocity, temperature, and composition.

Meanwhile, six instruments aboard the Solar Orbiter will measure the Sun remotely. Two imagers will study the ultraviolet light from the Sun’s outer atmosphere, including its corona, in order to provide context for the solar wind measurements; a coronagraph will take high-resolution images of the corona from 1.7 to 4.1 solar radii; one imager will measure the magnetic field and visible light on the Sun’s surface; another imager will produce images of the solar wind; and a telescope will measure the properties of the x-rays the Sun emits.

The Solar Orbiter must survive both the extreme heat of the Sun and the extreme cold of empty space, Anne Pacros, the payload manager at the ESA’s European Space Research and Technology Centre, said in a NASA release. It will experience temperatures ranging from -184 to 520 Celsius. The mission comes equipped with a 10-by-8-foot, 324-pound heat shield made from super-reflective titanium foil atop aluminium, with gaps for heat to escape. A coating of calcium phosphate prevents the Sun’s radiation from degrading the shield. The mission’s controllers must ensure that the probe’s heat shield always points toward the Sun.

Though the Solar Orbiter won’t approach the Sun as closely as the Parker Solar Probe, which will come within a baffling 3.83 million miles, the two spacecraft function in tandem. The Parker Solar Probe will directly sample the Sun’s corona but does not have the same imaging capabilities as the Solar Orbiter. The Solar Orbiter therefore provides more context for the Parker Solar Probe’s measurements, according to an ESA fact sheet.

The Solar Orbiter is scheduled to launch from Cape Canaveral, Florida onboard an Atlas V 411 rocket. NASA TV’s live coverage will begin at 3:30 am GMT on Monday. If all goes according to plan, the probe will make its first pass of the Sun in June and its first close pass in March 2022.

Featured image: Solar Orbiter: ESA/ATG medialab; Parker Solar Probe: NASA/Johns Hopkins APL