NASA to launch instrument developed at MSU to study sun
courtesy photo
Montana State University alumnus Jake Davis, left, Professor Charles Kankelborg, and doctoral students Catharine “Cappy” Bunn and Suman Panda, pose at White Sands Missile Range in New Mexico, where they are preparing for the launch of the FURST rocket mission to observe the sun in far ultraviolet.
courtesy photo
The payload for a NASA sounding rocket mission undergoes testing at White Sands Missile Range in New Mexico in preparation for an Aug. 11, 2024, launch. An instrument designed and built at Montana State University to observe the sun in far ultraviolet is installed in the wide part of the payload.
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BOZEMAN – An instrument designed and built at Montana State University to capture the first high-resolution, far-ultraviolet spectrum of the entire sun was launched into space aboard a NASA rocket on Sunday, Aug. 11.
The launch, scheduled for 1:05 p.m. Mountain time from the White Sands Missile Range in New Mexico, will be livestreamed at https://video.ibm.com/wstf-wsmr.
The unnarrated video will be “pretty spartan,” according to Charles Kankelborg, MSU professor of physics and principal investigator for the scientific mission, but viewers should be able to visually follow the rocket’s trajectory, watch its first and second stages separate, and see the second stage fire as it catapults the Full-sun Ultraviolet Rocket Spectrometer, or FURST, into space for its roughly five-minute mission.
Kankelborg, a member of MSU’s internationally known Solar Physics Group, has built several scientific instruments to study the sun. He began developing FURST in 2018, after the idea was suggested to him by Phil Judge, a senior scientist at the High Altitude Observatory at the National Center for Atmospheric Research.
“He said nobody has ever measured a high-resolution, far-ultraviolet spectrum of the sun-as-a-star – it hadn’t been done,” said Kankelborg.
The sun emits light from across the electromagnetic spectrum, including near, middle, far and extreme ultraviolet light, whose wavelengths are shorter than visible light. The MSU team’s instrument is designed to measure far ultraviolet light, with wavelengths ranging from 120 to 180 nanometers. Those wavelengths are absorbed high in Earth’s atmosphere, which is why the readings need to be taken from space.
Kankelborg explained that scientists routinely collect high-resolution spectral data from little sections of the sun at a time, but nobody has ever taken a high-resolution, far ultraviolet reading from the entire solar orb at once – and because of the extreme variability in activity and presentation between the sun’s center and edges, as well as the various features like sunspots and plages, it’s impossible to use those slices of data to make accurate conclusions about the sun as a whole.
“When trying to assemble or guesstimate a whole-sun spectrum from little pieces, there’s no way to be sure you’ve done it right,” he said.
By contrast, the Hubble telescope has captured far-ultraviolet spectra of many entire, far-away stars. Those data helped scientists determine the stars’ characteristics, such as temperature, density, chemical composition and velocity.
“The main purpose of this mission is to really understand the solar spectrum and compare it with other stars,” Kankelborg said. “We don’t yet have the data we need to put the sun in context with all of those.”
Being able to make those direct comparisons may help scientists better understand how ultraviolet radiation emitted by the sun affects comets, moons and planets, including Earth, he added. The new data also may help answer how the common, small explosions of plasma in the sun’s transition region – the area between the solar surface and the outermost part of the sun’s atmosphere, called the corona – influence the spectrum of the sun as a whole. Kankelborg said such explosions, which are about the size of Earth, change the frequency of light emitted by the sun.
MSU doctoral student of physics Catharine Bunn, who is part of the FURST launch team, has been studying magnetic reconnections in the sun by analyzing data collected by NASA’s Interface Region Imaging Spectrograph, or IRIS, satellite, which scans the sun every month to produce a high-resolution, full-disk image. Kankelborg explained that by comparing IRIS and FURST data, scientists will be able to see for the first time how those events affect the spectrum of the star as a whole.
Typically, far-ultraviolet spectra are collected by directing light through a tiny slit in a spectrograph and using diffraction grating – a tool that splits light into its different colors – to reimage the beams. When he started to design FURST, Kankelborg said he didn’t know how he would focus light from the entire sun through a tiny slit.
“We needed to squeeze the whole width of the sun down to 15 microns,” Kankelborg said. “The idea came to us to just use little glass cylinders – stirring rods like you use in chemistry class.”
Unable to find an optics manufacturer to make the cylinders, the team instead bought commercial glass cylinders and “diced them up,” Kankelborg said. MSU electrical engineering doctoral student Suman Panda built a digital microscope to examine their optical quality and selected the cylinders best suited for the mission. Those were given a reflective coating so that when sunlight hits their convex surfaces, it is reflected and directed so it can be split and analyzed.
NASA’s sounding rocket won’t deliver FURST into orbit, but it will take it high enough to escape Earth’s atmosphere – about 300 kilometers, or 186 miles, above the ground.
“We’ll have about 300 seconds, or five minutes, and will take an exposure every 10 seconds. As we’re doing that, we’re rotating between channels – each glass stirring rod takes a different channel, so we’ll be able to observe in each of those channels over and over again,” Kankelborg said.
The instrument will return to Earth via parachute for retrieval.
Kankelborg has been in New Mexico since mid-July preparing for the mission with Bunn, Panda, and MSU mechanical engineering alumnus Jake Davis, who works for MSU’s Space Science and Engineering Lab (SSEL). MSU electrical engineering alumnus James Joseph, who designed the electronics and software for the FURST shutter controller in the SSEL, spent 10 days with the team at White Sands in July. Roy Smart, a doctoral student in physics who created the detailed optical design for the instrument, will join the team for the launch.
Kankelborg said sounding rocket missions provide an excellent learning opportunity for students.
“They have serious responsibilities and will be hands-on with instrument hardware and operationally on launch day,” he said. “They learn experimental space science from the inside out.”
Because the project was delayed by the COVID-19 pandemic, it wasn’t originally scheduled to take place during the current high point in the sun’s 11-year solar activity cycle.
“We had no intention of waiting until solar maximum, but we’ll take it – it’s exciting to measure the sun when it’s active,” Kankelborg said. “I think we have a really versatile experiment. It will be informative for heliophysicists like me, but also for atmospheric scientists, stellar astronomers and people interested in the atmospheres of other solar system bodies.”
