NASA is set to launch a sounding rocket that will take short journey to the Earth's atmosphere to catch a glimpse of the Sun with X-ray vision. The Focusing Optics X-ray Solar Imager (FOXSI) mission is set to take its third flight from the New Mexico on September 7. FOXSI is a sounding rocket mission. Derived from the nautical term 'to sound,' meaning to measure, sounding rockets make brief 15-minute journeys above Earth's atmosphere for a peek at space before falling back to the ground. Smaller, cheaper and faster to develop than large-scale satellite missions, sounding rockets offer a way for scientists to test their latest ideas and instruments Without special instrumentation, the Sun looks calm and inert. However, beneath that placid facade are countless miniature explosions called nanoflares. These small but intense eruptions are born when magnetic field lines in the Sun's atmosphere tangle up and stretch until they break like a rubber band. The energy they release accelerates particles to near lightspeed and according to some scientists, heats the solar atmosphere to its searing million-degree Fahrenheit temperature. FOXSI will travel above the shield of Earth's atmosphere, to stare directly at the Sun and search for nanoflares using its X-ray vision. "FOXSI is the first instrument built specially to image high-energy X-rays from the Sun by directly focusing them," said Lindsay Glesener, space physicist at the University of Minnesota in the US. "Other instruments have done this for other astronomical objects, but FOXSI is so far the only instrument to optimize especially for the Sun," said Glesener, principal investigator for the mission. The Sun tells its story in layers of light, each of which reveals what is happening at different temperatures. For example, the sunlight that our eyes can see is primarily from the Sun's photosphere, which is approximately 10,000 degrees Fahrenheit. However, there is much more going on outside the bounds of human vision. X-ray light, in particular, reveals processes that heat plasma to millions of degrees Fahrenheit, like the most violent explosions at the cores of nanoflares. Acquiring high-quality views of X-rays from the Sun is not easy. Unlike visible light, X-rays are hard to focus. They are largely unaffected by the lenses and mirrors used in conventional telescopes. Previous X-ray missions had to make do without focused light. To focus the X-rays, the FOXSI team used extremely hard, smooth surfaces tilted to a small angle (less than half a degree) that would gently corral incoming X-ray light to a point of focus. This will be FOXSI's third flight - its first was in 2012, during which it successfully viewed a small solar flare in progress, and its second in 2014, when it detected the best evidence at the time of X-ray emission from nanoflares. The third mission follows up on this discovery, but this time it includes a new telescope designed for imaging lower-energy, so-called soft X-rays as well.