Mr Viral
A filter for the Universe
“SPHEREx is going to produce an enormous three-dimensional map of the entire night sky.”
NASA’s SPHEREx observatory after completion of environmental testing at BAE Systems in Boulder, Colorado, last year.
Credit:
NASA/JPL-Caltech/BAE Systems
Satellites come in all shapes and sizes, but there aren’t any that look quite like SPHEREx, an infrared observatory NASA launched Tuesday night in search of answers to simmering questions about how the Universe, and ultimately life, came to be.
The mission launched aboard a SpaceX Falcon 9 rocket from Vandenberg Space Force Base in California at 8:10 pm local time (11:10 pm EDT) Tuesday. Less than 45 minutes later, the Falcon 9’s upper stage released SPHEREx into a polar orbit at an altitude of roughly 420 miles (675 kilometers). Ground controllers received the first signals from the spacecraft, confirming its health after reaching space.
As soon as next month, once engineers verify the observatory is ready, SPHEREx will begin a two-year science mission surveying the sky in 102 colors invisible to the human eye. The observatory’s infrared detectors will collect data on the chemical composition of asteroids, hazy star-forming clouds, and faraway galaxies.
A Falcon 9 rocket lifted SPHEREx into orbit.
Credit:
NASA/Jim Ross
“SPHEREx is going to produce an enormous three-dimensional map of the entire night sky, and with this immense and novel dataset, we’re going to address some of the most fundamental questions in astrophysics,” said Phil Korngut, the mission’s instrument scientist at Caltech.
“Using a technique called linear variable filter spectroscopy, we’re going to produce 102 maps in 102 wavelengths every six months, and our baseline mission is to do this four time over the course of two years,” Korngut said.
Boiling it down
The acronym for the SPHEREx mission is a mouthful—it stands for the Spectro-Photometer for the History of the Universe, Epoch of Reionization and Ices Explorer. Scientists sum up the $488 million mission by saying it seeks answers to three basic questions:
• How did the Universe begin?
• How did galaxies begin?
• What are the conditions for life outside the Solar System?
While it’s possible to sum up these objectives in an elevator pitch, the details touch on esoteric topics like cosmic inflation, quantum physics, and the flatness of spacetime. Philosophically, these questions are existential. SPHEREx will try to punch above its weight.
Built by BAE Systems, SPHEREx is about the size of a subcompact car, and it lacks the power and resolution of a flagship observatory like the James Webb Space Telescope. Webb’s primary mirror spans more than 21 feet (6.5 meters) across, while SPHEREx’s primary mirror has an effective diameter of just 7.9 inches (20 centimeters), comparable to a consumer-grade backyard telescope.
SPHEREx will test the inflationary model, a theory to explain the unimaginably violent moments after the Big Bang.
Credit:
NASA
But NASA’s newest space telescope has a few advantages. While Webb is designed to peer deep into small slivers of the sky, SPHEREx’s wider field of view will observe the sky in all directions. Like its name might suggest, SPHEREx will capture a spherical view of the cosmos. Color filters overlay the instrument’s detector array to separate light coming into the telescope into its component wavelengths, a process known as spectroscopy. NASA says SPHEREx’s unique design allows it to conduct infrared spectroscopy on hundreds of thousands of objects simultaneously, and more than 600 exposures per day.
“SPHEREx is a testament to doing big science with a small telescope,” said Beth Fabinsky, the mission’s project manager at NASA’s Jet Propulsion Laboratory in California.
Because SPHEREx orbits hundreds of miles above the Earth, the telescope flies above the discernible atmosphere, which can absorb faint thermal energy coming from distant astronomical sources. Its detectors must be cold, below minus 360 degrees Fahrenheit, or 55 Kelvin, or the the telescope would be blinded by its own light. This is the reason the spacecraft has such an unusual look.
Many past infrared telescopes used cryogenic coolant to chill their detectors, but this is a finite resource that gradually boils off in space, limiting mission lifetimes. Webb uses a complicated tennis court-sized sunshield to block heat and light from the Sun from its infrared instruments. Engineers came up with a simpler solution for SPHEREx.
Three concentric photon shields extend from the top of the spacecraft to insulate the telescope’s optics and detectors from light from the Sun and the Earth. This design requires no moving parts, boosting the mission’s reliability and longevity. The photon shields look like an Elizabethan collar. Pet owners may know it as the “cone of shame” given to animals after surgeries.
Like NASA’s new half-billion-dollar space telescope, this cheery canine wears his collar with pride.
Credit:
Michael Macor/San Francisco Chronicle via Getty Images
For SPHEREx, this cone is an enabler, allowing astronomers to map hundreds of millions of galaxies to study inflation, a cosmological theory that suggests the Universe underwent a mind-boggling expansion just after the Big Bang nearly 13.8 billion years ago. Through the process of inflation, the Universe grew a “trillion-trillion-fold” in a fraction of a second, Korngut said.
The theory suggests inflation left behind the blueprint for the largest-scale structures of the Universe, called the cosmic web. Inflation “expanded tiny fluctuations, smaller than an atom, to enormous cosmological scales that we see today, traced out by galaxies and clusters of galaxies,” said Jamie Bock, a cosmologist at Caltech who leads the SPHEREx science team.
“Even though inflation (theory) was invented in the 1980s, it’s been tested over the intervening decades and has been consistent with the data,” Bock said. “While we have this general picture, we still don’t know what drove inflation, why it happened. So what SPHEREx will do will test certain models of inflation by tracing out the three dimensions, hundreds of millions of galaxies, over the entire sky. And those galaxies trace out the initial fluctuations set up by inflation.”
SPHEREx’s telescope will also collect the combined light emitted by all galaxies, all the way back to the cosmic dawn, when the first stars and galaxies shined through the foggy aftermath of the Big Bang. Scientists believe star formation peaked in the Universe some 10 billion years ago, but their understanding of cosmic history is based on observations of a relatively small population of galaxies.
“SPHEREx, with its small telescope, is going to address this subject in a novel way,” Bock said. “Instead of really counting, very deeply, individual galaxies, SPHEREx is going to look at the total glow produced by all galaxies. This cosmological glow captures all light emitted over cosmic history from galaxies, as well as anything else that emits light. So it’s a very different way of looking at the Universe, and in particular, that first stage of star and galaxy formation must also be in this cosmic glow.”
Bock and his science team will match the aggregate data from SPHEREx with what they know about the Universe’s early galaxies from missions like Webb and the Hubble Space Telescope. “We can compare to counts that have been built up with large telescopes and see if we’ve missed any sources of light,” Bock said.
Closer to home
In our own galaxy, SPHEREx will use its infrared sensitivity to investigate the origins and abundance of water and ice in molecular clouds, the precursors to alien solar systems where gas and dust collapse to form stars and planets.
“We think that most of the water and ice in the universe is in places like this,” said Rachel Akeson, SPHEREx science data center lead at Caltech. “It’s also likely that the water in Earth’s oceans originated in the molecular cloud. So how will SPHEREx map the ice in our galaxy? While other space telescopes have found reservoirs of water in hundreds of locations, SPHEREx observations of our galaxy will give us more than 9 million targets, a much bigger sample than we have now.”
As the telescope scans across these millions of targets, its detectors will make measurements of each point in the sky in 102 infrared wavelengths. With the help of spectroscopy, SPHEREx will measure how much water is bound up in these star-forming clouds.
“Knowing the water content around the galaxy is a clue to how many locations could potentially host life,” Akeson said.
The SPHEREx observatory (top) was joined on its ride to space by four small NASA satellites (bottom) setting out to study the solar wind.
Credit:
Benjamin Fry/BAE Systems
All-sky surveys like SPHEREx’s often turn up surprises because they ingest immense amounts of data. They leave behind enduring legacies by building up catalogs of galaxies and stars. Astronomers use these archives to plan follow-up observations by more powerful telescopes like Webb and Hubble, or with future observatories employing technologies unavailable today.
As it pans across the sky observing distant galaxies, SPHEREx’s telescope will also catch glimpses of targets within our own Solar System. These include planets and thousands of asteroids, comets, icy worlds beyond Pluto, and interstellar objects that occasionally transit through the Solar System. SPHEREx sill measure water, iron, carbon dioxide, and multiple types of ices (water, methane, nitrogen, ammonia, and others) on the surface of these worlds closer to home.
Finding savings where possible
A second NASA mission hitched a ride to space with SPHEREx, deploying into a similar orbit a few minutes after the Falcon 9 released its primary payload.
This secondary mission, called PUNCH, consists of four suitcase-sized satellites that will study the solar corona, or outer atmosphere, a volatile sheath of super-heated gas extending millions of miles from the Sun’s surface. NASA expects PUNCH’s $150 million mission will reveal information about how the corona generates the solar wind, a continuous stream of charged particles streaming out in all directions from the Sun.
There are tangible reasons to study the solar wind. These particles travel through space at speeds close to 1 million mph, and upon reaching Earth, interact with our planet’s magnetic field. Bursts of energy erupting from the Sun, like solar flares, can generate shocks in the solar wind current, leading to higher risks for geomagnetic storms. These have a range of effects on the Earth, ranging from colorful but benign auroras to disruptions to satellite operations, navigation, and communication.
Other NASA spacecraft have zoomed in to observe second-by-second changes in the Sun’s atmosphere, and a fleet of sentinels closer to Earth measure the solar wind after it has traveled through space for three days. PUNCH will combine the imaging capacities of four small satellites to create a single “virtual instrument” with a view broad enough to monitor the solar wind as it leaves the Sun and courses farther into the Solar System.
Hailing a ride to space is not as simple as opening up Uber on your phone, but sharing rides offers a more cost-effective way to launch small satellites like PUNCH. SpaceX regularly launches rideshare flights, called Transporter missions, on its Falcon 9 rocket, sometimes with more than 100 satellites on a single launch going to a standard orbit. Missions like SPHEREx and PUNCH aren’t usually a good fit for SpaceX’s Transporter missions because they have more stringent demands for cleanliness and must launch into bespoke orbits to achieve their science goals.
Matching SPHEREx and PUNCH to the same rocket required both missions to go to the same orbit, and be ready for launch at the same time. That’s a luxury not often available to NASA’s mission planners, but where possible, the agency wants to take advantage of rideshare opportunities.
Launching the PUNCH mission on its own dedicated rocket would have likely cost at least $15 million. This is the approximate price of a mission on Firefly Aerospace’s Alpha rocket, the cheapest US launcher with the muscle to lift the PUNCH satellites into orbit.
“This is a real change in how we do business,” said Mark Clampin, the acting deputy administrator for NASA’s Science Mission Directorate, or SMD. “It’s a new strategy that SMD is working where we can maximize the efficiency of launches by flying two payloads at once, so we maximize the science return.”
Stephen Clark is a space reporter at Ars Technica, covering private space companies and the world’s space agencies. Stephen writes about the nexus of technology, science, policy, and business on and off the planet.
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