We received a question about the Solar Probe Plus, a new NASA mission that will study the sun's atmosphere and a wind that blows out from the sun across the solar system, called the solar wind. To learn more about the Solar Probe Plus, go to http://www.jpl.nasa.gov/news/news.cfm?release=2010-284 .
The questions come from Anthony, a middle school student working on physics homework. The answers were provided by NASA/JPL senior research scientist Marco Velli. Velli is also the mission's observatory scientist.
1. How is it possible to get such accurate information for the experiments when the probe is so far away from the sun's corona?
The Solar Probe Plus will study the sun from a distance that is 9.5 times the sun's radius. The sun has a diameter of roughly 1,392,000 kilometers (or 865,000 miles). At 9.5 solar radii, the sun's magnetic field still controls the dynamics of the coronal plasma (the sun's atmosphere) so we can discover how magnetic energy is released into the plasma. This will also allow us to study how the wind that comes from the sun, called the solar wind, accelerates. The solar wind extends into space about 100 Astronomical Units (AU), which is 100 times the sun to Earth distance. (The sun to Earth distance is one AU.)
In addition, the probe's orbit path will slowly work its way in from perihelions (closest approach to the sun) at 40 solar radii down to 9.5 solar radii. We have never explored the region inside 70 solar radii so there are many important measurements that will be made for the first time.
2. Why does this mission need to be done in 2018, why not any sooner?
This is an extremely challenging mission. Studies about spacecraft design have been carried out for a long time but the mission's goals or concept have only recently become mature enough to actually get done. A launch in 2015 or 2017 had been previously discussed but the funding for the experiments is being released as we speak, and 2018 is the fastest possible time compatible with all the checks and necessary steps that need to be taken to ensure mission success.
It sounds like a very long time, but it really is not when you consider the work the mission still requires.