NASA’s latest space telescope has taken the first science observations of its two-year mission to study the universe in dozens of colors. The Spectro-Photometer for the History of the Universe, Epoch of Reionization and Ices Explorer (SPHEREx) telescope maps the entire sky in 102 infrared wavelengths — or colors — to study galaxy formation, cosmic inflation, and the origins of water and organic molecules in planetary systems.
SPHEREx launched atop a Falcon 9 in March, sharing its ride with the four spacecraft of NASA’s Polarimeter to Unify the Corona and Heliosphere (PUNCH) mission. With the PUNCH satellites also having sent back their first images, the spacecraft are now being readied to study the solar corona and solar wind.
SPHEREx begins its science mission
On March 27 — 15 days after its launch — SPHEREx saw its first light, proving its instruments performed as designed. This milestone was then followed by calibration and checkouts, culminating in the start of SPHEREx’s science operations on May 1.
“Some of us have been working toward this goal for 12 years,” said SPHEREx principal investigator Jamie Bock of Caltech and NASA’s Jet Propulsion Laboratory (JPL). “The performance of the instrument is as good as we hoped. That means we’re going to be able to do all the amazing science we planned on and perhaps even get some unexpected discoveries.”
Zoom on the dust cloud in SPHEREx’s image, using different color filters. (Credit: NASA/JPL-Caltech)
As NASA announced SPHEREx had begun its science mission, the agency also released some of the telescope’s first images, taken in April. The images show a collection of dust in a nearby dwarf galaxy known as the Large Magellanic Cloud, which SPHEREx captured in different wavelengths of infrared light. As the molecules that make up the dust absorb and emit only specific wavelengths, the dust cloud’s appearance differs in each image.
As different chemical compounds and elements impart a unique signature on the spectrum of light that reaches the telescope, astronomers use these properties to study the chemical composition of astronomical objects. SPHEREx’s design allows it to perform these spectroscopy studies at a large scale across the entire sky, capturing a total of 102 wavelengths.
To capture this range of wavelengths, SPHEREx is fitted with six detectors, each featuring a linear variable filter. Each filter has a gradient of 17 segments, each letting through only a single wavelength of light. After taking an image, or exposure, with all detectors, SPHEREx slightly shifts its position to capture each part of the sky at a different wavelength.
Through the 25 months of its planned mission, SPHEREx is set to take 600 exposures every day, for a total of 3,600 images across all detectors. From its position in Sun-synchronous orbit around Earth, the telescope will see the entire sky in six months. This allows NASA to create four maps of the universe by the end of SPHEREx’s mission.
“Thanks to the hard work of teams across NASA, industry, and academia that built this mission, SPHEREx is operating just as we’d expected and will produce maps of the full sky unlike any we’ve had before,” said Shawn Domagal-Goldman, acting director of the Astrophysics Division at NASA Headquarters in Washington. “This new observatory is adding to the suite of space-based astrophysics survey missions leading up to the launch of NASA’s Nancy Grace Roman Space Telescope. Together with these other missions, SPHEREx will play a key role in answering the big questions about the universe we tackle at NASA every day.”
In addition to analyzing its chemical composition, studying a galaxy’s spectrum also allows astronomers to determine its distance. As a result of the universe’s expansion, all distant galaxies move away from us, with farther galaxies moving faster. This shifts the galaxy’s light spectrum to longer wavelengths in an effect known as redshift. Measuring the magnitude of this redshift allows astronomers to determine the galaxy’s relative velocity, and thus its distance.
Using information, SPHEREx will map the positions of galaxies in three dimensions, allowing astronomers to study the structure of the universe known as the cosmic web.
Galaxies are not distributed evenly throughout the universe but appear in clusters along filaments of gas and other matter. Scientists believe that this cosmic web is an imprint of tiny ripples that appeared moments after the Big Bang. By studying these large-scale structures, SPHEREx’s team hopes to unveil the process that drove the inflation of the early universe.
“We’re going to study what happened on the smallest size scales in the universe’s earliest moments by looking at the modern universe on the largest scales,” said Jim Fanson, the mission’s project manager at NASA’s Jet Propulsion Laboratory in Southern California. “I think there’s a poetic arc to that.”
Schematic overview of SPHEREx using KSAT’s antenna and network to transmit data to NASA. (Credit: NASA/Dave Ryan)
SPHEREx sends down roughly 20 gigabytes of data each day through NASA’s Near Space Network. However, to optimally support the new telescope, NASA needed to upgrade one of the network’s ground stations in Antarctica. Under its Space Communications and Navigation (SCaN) program, NASA contracted a commercial partner to implement the upgrade.
The Norwegian company Kongsberg Satellite Services (KSAT) upgraded its antenna at the Troll research station in Antarctica. As SPHEREx flies within range of this antenna, it transmits to the ground station, which then sends the data to KSAT’s relay satellite network. From there, SPHEREx’s observations end up in NASA’s Data Acquisition Process and Handling Environment (DAPHNE+).
“By connecting the Troll antenna to DAPHNE+, we eliminated the need for large, undersea fiberoptic cables by virtually connecting private and government-owned cloud systems, reducing the project’s cost and complexity,” said Matt Vincent, SPHEREx mission manager for the Near Space Network at NASA’s Goddard Space Flight Center. “We were able to find a networking solution with KSAT that did not require us to put additional hardware in Antarctica. Now we are operating with the highest data rate we have ever downlinked from that location.”
PUNCH commissioning continues
SPHEREx shared its ride into space with NASA’s PUNCH mission, which is planned to investigate space weather. Together, the four satellites in the constellation will make 3D observations of the inner solar system and the outer layers of the Sun’s atmosphere, or solar corona. Studying the corona in polarized light, PUNCH will help scientists figure out how the corona’s mass and energy become the solar wind.
The first image from PUNCH’s Narrow Field Imager (left) and one of the mission’s Wide Field Imagers (right). (Credit: NASA/SwRI/NRL)
One of the PUNCH satellites carries the Narrow Field Imager (NFI), which took its first image on April 14. The other three satellites are outfitted with Wide Field Imagers (WFI), which all captured their first light in the following days. These inaugural images proved that all cameras are in focus and function as designed.
Following this, teams will start calibrating the instruments to improve image quality. Meanwhile, the satellites are moving to the correct alignment in their orbits, which will allow the WFI images to be stitched together for a wider view of the solar wind and corona.
(Lead image: The collection of dust in the Large Magellanic Cloud as observed by SPHEREx at a wavelength of 3.29 microns. Credit: NASA/JPL-Caltech)
