Comedian Sacha Baron Cohen, in character as his alter ego Ali G, asked Buzz Aldrin if astronauts had ever gone to the sun. "It's too hot," Aldrin replied sardonically. "What if we were to go during the winter?" Cohen persisted.
Though we have hurtled spacecraft into the frigid frontiers of the solar system, where water would freeze rock solid in seconds, we have never ventured closer to the seething sun than the distance of the planet Mercury.
The European Space Agency has now signed a contract with the aerospace company Astrium UK to build a $400 million spacecraft to fly closer to the sun than has ever before been attempted. It's called, simply, Solar Orbiter, or SolO — maybe the Star Wars character Hans Solo should be part of its mission patch.
Over the past several decades an armada of sun-watching spacecraft, notably SOHO, SDO and STEREO missions, have been monitoring our nearest star from afar. SolO, on the other hand, will take a close-up look at the region where the "rubber hits the road" — that is, where the solar wind is born from the roiling activity deep inside the sun's atmosphere. This means perusing sunspots, active regions, coronal holes and other solar phenomenon from closer than ever before.
Large storms on the sun interfere with communications, and they can even do damage to power lines and satellite electronics. The hurricane blast of radiation from the sun affects all the planets sequentially, lighting up aurorae on Earth to as far as Neptune.
The joint ESA/NASA mission will be launched in 2017. Once lofted into solar orbit, SolO will burn propellant to "hit the brakes" and reduce its orbital speed (which is the same as Earth's) so that it can fall deeper into the sun's gravitational well. The spacecraft will have the ability for part of its 186-day highly elliptical orbit to match the sun's rotational speed. This will allow SolO essentially to hover above an interesting active region on the sun and continuously monitor changes in its magnetohydrodynamic fireworks.
With a gravity assist from Venus, SolO will ratchet its orbital plane at a steeper inclination to the sun so that it can provide a close-up look at the relatively uncharted polar regions.
At its closest approach, the spacecraft will be hot enough to cook hot dogs. "Heat will be a huge problem," Ralph Cordey, the head of science at Astrium UK, was reported as saying in a BBC article.
Like a moth flitting near a flame, on its elliptical orbit, the spacecraft will skirt by the sun at an altitude of just 26 million miles above the sun's seething surface.
The sunward side of the heat shield will roast at oven temperatures of 500 degrees Fahrenheit (260 degrees Celsius). The spacecraft's suite of instruments will need to peek at the broiling sun through shuttered slits like a knight in battle armor peering at an adversary.
Ironically, the solar arrays will be flooded with so much light, they must be designed to withstand the heat. They will be tilted obliquely to the incoming glare of sunlight.
SolO will measure the sun's twisted magnetic fields and do a chemical analysis. But it will no doubt enthrall the public with spectacular pictures of the fantasy solar landscapes of magnetically sculpted structures, where glowing gas dances and forms loops. Details as small as 100 miles across will be discernible.
The seven-year mission is a big step toward the day solar astrophysicists will be able to give us precise weather predictions for upcoming solar storms.
Image credits: ESA, NASA