A physicist at the National Institute of Standards and Technology (NIST) has helped NASA scientists observe a “hidden” layer of the Sun where violent space weather can originate, by positioning a crucial UV sensor inside a space-borne instrument.

The Sun releases particles and electromagnetic fields into space and when these particles pass through the Sun’s “transition region,” 5,000 kilometres above the surface, they can gather considerable steam, resulting in violent episodes of “space weather”.

The space weather can damage Earth-orbiting satellites and disrupt electronic communications.

To avoid this, a team at NASA Marshall Space Flight Center in Huntsville constructed a rocket-borne instrument, known as the Solar Ultraviolet Magnetograph Investigation (SUMI), designed to take pictures of these magnetic fields from space.

The optics in SUMI break down the incoming UV light into a spectrum of individual wavelengths and fans them out, much as a prism fans out white light into a rainbow.

“The problem is that SUMI’s detectors are small, so they don’t capture a wide range of wavelengths,” said NIST physicist Joseph Reader.

The solution is to get a light source that can produce these same lines in the laboratory,” he said, and use them to properly adjust the instrument’s sensors.

That’s where NIST’s unique “sliding spark source comes into the picture.

It consists of a pair of graphite electrodes with a quartz surface in between. A spark from these electrodes glides along the quartz surface, controllably producing the desired wavelengths of UV light from ionized carbon. Inside a clean room in Huntsville, UV radiation from the spark source entered SUMI, enabling its sensors to be accurately positioned before deployment.

On July 30, 2010, SUMI was successfully launched from White Sands, N.M. It rocketed 320 km in space and observed sunspot 11092 for about 6 minutes before parachuting back to earth. The Huntsville team is analyzing the data it obtained.