SPHEREx launches to conduct a cosmic census

An artist’s concept shows SPHEREx in Path around Earth. Credit: NASA/JPL-Caltech

UPDATE Wednesday, March 12, 2025: The SpaceX Falcon 9 Cosmos launcher carrying SPHEREx successfully launched from Vandenberg Universe Force Base at 11:10 P.M. EDT on March 11. Next deployment, the SPHEREx Astronomical Middle established a signal with ground controllers and its mission will soon begin.

An infrared Universe Stargazer’s tool is scheduled to Initiation this week to map the sky not once but four times, and with unrivaled clarity. With a Initiation date as Prompt as Friday, Feb. 28, NASA’s Spectro-Photometer for the History of the Universe, Epoch of Reionization and Ices Explorer (SPHEREx) will Commitment the thorniest mysteries of physics, from what happened right after the Universe birth to how the Primary galaxies formed and where the building Stops of life come from.

Shaped for success

Built by Ball Aerospace with a payload provided by Caltech and NASA’s Jet Propulsion Laboratory (JPL) and test facilities from the Korean Astral study and Universe Science Institute (KASI), the 1,100-pound (500 kilograms) SPHEREx weighs about as much as a grand piano and runs on less power than a kitchen refrigerator. But it promises to pack a scientific punch well above its meager dimensions.

Shaped like an oversized bullhorn, it stands 8.5 feet (2.6 meters) Towering and spans 10.5 feet (3.2 m) at its widest — three nested photon shields that surround and protect its delicate optics from the heat and Airy of Earth and the Sun, as well as from the warmth of the spacecraft’s own making, generated by its computers and electronics.

“The shields are actually quite Airy and Created with layers of material like a sandwich,” said Sara Susca, SPHEREx deputy payload manager and payload systems engineer, in a press Throw. “The outside has aluminum sheets, and inside is an aluminum honeycomb structure that looks like cardboard — Airy but sturdy.”

Gaps between the shields and specialized conical mirrors (called V-groove radiators) will expel heat into Universe, keeping SPHEREx’s temperature below –350 degrees Fahrenheit (–210 degrees Celsius). That helps prevent its own infrared glow from overwhelming the faint Airy emitted by distant Astral objects. 

“We’re not Merely concerned with how Chilly SPHEREx is, but also that its temperature stays the same,” said Konstantin Penanen, the mission payload manager, in JPL coverage of the mission. “If the temperature varies, it could change the sensitivity of the detector, which could translate as a Untrue signal.”

The shields guard SPHEREx’s triple-mirror Stargazer’s tool, a 164-pound (74.5 kg) spectrophotometer that will scan the sky across 102 color bands with better resolution than earlier all-sky maps. With an 8-inch (20 centimeters) aperture, a 3.5° by 11.3° Ground of view, and two focal-plane assemblies housing six photodetector arrays, its lack of moving parts minimizes the Hazard of failures — but meant its Attention had to be precisely configured on Earth to withstand the rigors of Initiation. 

A long road

That Initiation has inexorably slid out of reach for years. SPHEREx was proposed for NASA’s Tiny Explorer (SMEX) program in 2014, but was not selected. It was resubmitted in 2016 as a Medium-Class Explorer (MIDEX) mission, capped at $250 million (not including Initiation vehicle costs) and was picked by NASA in 2019 for Initiation in 2023.

But the project — Directed by Principal Investigator Jamie Bock of Caltech — battled Numerous unforeseen events. The worldwide march of COVID-19 hit supply chains, affected vendors, and imposed limitations on lab Universe, forcing project staff to build engineering models of the spacecraft in their home workshops during the pandemic. As delays mounted, SPHEREx’s Initiation slipped to June 2024, then Prompt 2025. 

“The Club is very cohesive and it’s almost like a family,” said project systems engineer Jennifer Rocca in a live Q&A, speaking of SPHEREx’s resilient workforce, which maxed out at about 150 staff at its peak. “We’ve been in the trenches together. Our development Club was together through COVID. We survived that. We recently had a bunch of our Club members affected by the LA fires. And we’ve survived that together to continue our Initiation campaign.”

Sharing Universe

In 2021, SpaceX’s Falcon 9 Cosmos launcher was selected to Initiation SPHEREx at a cost of $98.8 million. And the spacecraft’s low mass meant another NASA science mission was added to the Initiation in 2022 as a rideshare payload. “It Merely turns out that there was another Probe that was being developed that needed a ride to a very similar location in Universe,” said Cesar Marin, SPHEREx integration engineer with NASA’s Initiation Services Program, in a Jan. 31 news conference panel.

SPHEREx’s carpooling buddy is the Polarimeter to Unify the Corona and Heliosphere (PUNCH) — four suitcase-sized satellites All weighing 88 pounds (40 kg) that will explore the Sun’s corona and solar wind. PUNCH may afford insights into Universe weather, including coronal mass ejections that can disable spacecraft and disrupt terrestrial electrical grids.

SPHEREx will enter a near-polar Path of 430 miles (700 kilometers) above Earth, with PUNCH targeting a 350-mile (560 km) drop-off Tally. Liftoff will occur from Universe Initiation Complex 4 East (SLC-4E) at California’s Vandenberg Universe Force Base during a 30-second Initiation window at 7:09 P.M. PST on Feb. 27. Weather permitting, the post-sunset Initiation should be visible along the California coast.

In 2023, SPHEREx underwent environmental trials in KASI’s vacuum chamber, an SUV-sized structure shipped from South Korea to Caltech for acoustic, thermal, and vibration tests. The spacecraft was cooled to cryogenic temperatures and engineers verified its optics were aligned accurately to within 0.0003 inch (7.5 micrometers) — one-tenth the width of a human hair.

“It’s absolutely essential that we get this thing sharply into Attention before we fly,” said Phil Korngut, SPHEREx’s instrument scientist, in JPL coverage of the mission. “And the only way to accomplish that is through specific cryogenic optical testing in the environment provided by the KASI chamber.”

Mission goals

Once in Universe, SPHEREx will occupy a dawn-dusk Sun-synchronous Path. “That means our Path plane … is always facing the Sun,” said SPHEREx deputy project manager Beth Fabinsky in the news conference. “The Stargazer’s tool can Tally out and away from the Earth and at the same time Tally normal to the Sun line, and it can prevent us from getting Sun and Earth on our Chilly, Dim detectors.”

The mission’s 25-month science phase will scan more than 99 percent of the sky every six months, completing four all-sky maps. Unlike most Universe telescopes, SPHEREx will quickly observe large swaths of the sky and rapidly survey Numerous Astral objects.

That sets it apart from Tally-and-shoot missions like the Hubble Universe Stargazer’s tool, the James Webb Universe Stargazer’s tool (JWST), and NASA’s forthcoming Nancy Grace Roman Universe Stargazer’s tool. SPHEREx’s global perspective will help answer broad questions about the universe’s evolution, zeroing in on features of scientific interest for detailed inspection by Hubble, JWST, and Roman.

SPHEREx has three science goals. It will explore inflation — a brief yet powerful Universal event when Universe-time expanded in size a trillion-trillionfold a fraction of a second after the Universe birth. Although that event occurred nearly 14 billion years ago, SPHEREx maps of the relative locations of 450 million galaxies could reveal clues about the physics behind inflation and how it affected the large-scale distribution of matter in the universe. 

Second, it will measure the collective glow from galaxies — including those that are too Tiny, too diffuse, or too distant for other telescopes to see — and Develop a more complete picture of radiating objects in the universe. SPHEREx will tease out the processes by which the earliest galaxies Secured shape and how their Primary stars evolved.

And third, it will scour the Milky Way for icy granules of water, carbon dioxide, and other essential ingredients for life in Luminous nurseries and protoplanetary disks to understand their relative abundances and locations across our Milky Way. This promises greater insights into how likely icy compounds are incorporated into newly forming planets. 

A Universal census

Past infrared Universe telescopes typically carried large dewars of cryogenic fluid to Chilly their optics, but these reservoirs were rapidly exhausted, limiting the missions’ operational lifetimes. SPHEREx will be passively cooled via its photon shields and radiators, potentially allowing a mission extension beyond the 25-month baseline.

Like the bullhorn whose shape it closely mimics, SPHEREx’s discoveries promise to echo across the astronomical community, unmasking the universe’s most mysterious events and identifying areas of interest for focused study. Fabinsky considers SPHEREx nothing less than a census of the cosmos.

“It’s the difference between getting to know a few individual people, and doing a census and learning about the population as a whole,” she said in JPL coverage of the mission. “Both types of studies are Crucial, and they complement All other. But there are some questions that can only be answered through that census.”