They can release as much energy as tens of billions of hydrogen bombs exploding at the same time. They send protons and electrons rocketing at near the speed of light. They heat gas in the Sun’s atmosphere to tens of millions of degrees Celsius. They send a blast of gas and particles toward Earth, posing a danger to spacecraft and astronauts outside the planet’s magnetosphere, in rare cases even knocking out radio communications and power grids on the ground.
Because of the scientific mystery of how these solar eruptions are produced on the Sun with such scale and force, and also the major role they play in space weather that can impact life on Earth, NASA researchers have innovated new methods of gathering information about these violent events.
One NASA mission, the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) has significantly advanced understanding of solar flares since its launch in 2002. RHESSI scientists use the spacecraft’s imaging spectrometer to piece together pictures of solar flares from the high-energy X-ray and gamma-ray radiation they emit. While there is still much to be learned, data gathered by RHESSI has revealed how magnetic fields in the vast expanse of the solar atmosphere may be the force that drives the immense explosions. The instrument has imaged around 50,000 flares to date, providing information that may explain not only the workings of solar flares but also of much more massive energy releases from distant objects like black holes and quasars.
“We have been able to make images from X-rays with much finer resolution and greater sensitivity than have ever been made before,” says Brian Dennis, RHESSI Mission Scientist and astrophysicist in the Solar Physics Laboratory at Goddard Space Flight Center.
The key to RHESSI’s unprecedented capabilities lie in a set of essential components a NASA partner created for the mission. The manufacturing techniques developed to create the components have yielded innovations advancing medical imaging, transportation security, and even energy efficiency.
To gather its groundbreaking imagery, RHESSI’s spectrometer was outfitted with metal grids incorporated in devices called rotation modulation collimators (RMCs). As the spacecraft rotates, the grids block and unblock X-rays emanating from the Sun. The instrument’s detectors record the modulated radiation passing through the grids and transmit the information to the ground, where scientists generate images using computers. For this setup to function effectively, NASA needed the most finely crafted grids yet created. A number of attempts to create the technology failed until engineer Mike Appleby, working at a company called Thermo Electron Tecomet, was able to meet NASA’s requirement, producing grids using photoetched tungsten foils built up into precise stack laminations.
“Finding Mike Appleby was the real secret,” says Dennis. “Collaborating with him allowed us to do this mission.”
Appleby founded Mikro Systems Inc., based in Charlottesville, Virginia, in 2000 to build upon the unique lithography-based manufacturing platform he used to craft the RHESSI grids. Mikro partnered with NASA through the Small Business Innovation Research (SBIR) program to improve the company’s platform for producing even finer, more complex grids for future space imaging missions.