SpaceX and NASA are set for the launch of the agency’s newest space telescope and solar research mission. A Falcon 9 will liftoff from California with the Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer (SPHEREx) near-infrared observatory, with the Polarimeter to Unify the Corona and Heliosphere (PUNCH) heliophysics mission flying as a rideshare.
During its mission, SPHEREx will complete surveys of the entire sky in optical and near-infrared light, observing over 450 million galaxies and more than 100 million stars in the Milky Way. From these surveys, scientists will identify the source of the early universe’s inflation and search for organic molecules throughout the universe. Meanwhile, PUNCH will utilize four small satellites to investigate the Sun’s inner heliosphere and how the corona becomes solar wind.
Falcon 9 was scheduled to liftoff from Space Launch Complex 4E (SLC-4E) at Vandenberg Space Force Base in California on Saturday, March 8, at 7:10 PM PST (03:10 UTC on March 9). SpaceX announced a delay due to vehicle checkouts, pending a new launch date.
That vehicle, Falcon booster B1088, will support this mission. Following liftoff and stage separation, the booster will return to the launch site and perform a landing at Landing Zone 4 (LZ-4), located just a couple hundred meters west of SLC-4E. This launch will serve as B1088’s third flight, having previously flown the Transporter 12 and NROL-126 missions from Vandenberg.
Falcon 9 will launch on a southwestern trajectory out of Vandenberg, flying SPHEREx and PUNCH to a Sun-synchronous orbit. In total, SPHEREx and PUNCH mass 256 kg. Assuming an on-time launch, this mission will mark the 445th Falcon 9 mission, the 27th SpaceX mission of 2025, and the 45th orbital launch attempt of 2025 worldwide.
SPHEREx
Designed as a medium-class mission within NASA’s Explorers program, SPHEREx was selected by NASA for funding and development in February 2019. The mission is managed by NASA’s Jet Propulsion Laboratory (JPL) in California, with James Bock of the California Institute of Technology (Caltech) serving as principal investigator.
SPHEREx’s first proposal was submitted to NASA in December 2014 and was subsequently selected for continued development as part of the Small Explorer Program (SMEX) in July 2015. However, SPHEREx’s proposal was ultimately not selected for funding as part of SMEX, and the SPHEREx team resubmitted an upgraded proposal for SPHEREx as a Medium-Class Explorer (MIDEX) mission in December 2016. The SPHEREx MIDEX proposal was selected as a finalist in August 2017 and was later announced as the winner in February 2019.
SPHEREx entered Phase C of NASA’s Project Life Cycle in January 2021, allowing mission teams to finalize the mission’s design and begin constructing and assembling spacecraft components. NASA selected SpaceX’s Falcon 9 to launch the mission in February 2021 and announced the addition of PUNCH as a rideshare payload in August 2022.
The observatory was fully assembled by April 22, 2024, and entered final testing soon after. These tests were conducted in late 2024 and, following completion, SPHEREx was shipped to Vandenberg for final integration with the Falcon 9 upper stage and payload fairing encapsulation.
Rather than relying on a suite of highly technical instruments, SPHEREx will utilize a single, wide-field aluminum telescope instrument designed for a single observing mode in either visible or near-infrared light. This telescope features three mirrors, an aperture diameter of 20 cm, and six mercury cadmium telluride photodetector arrays. These characteristics give the telescope an 11 degree by 3.5 degree field of view, with the telescope obtaining spectra through multiple exposures and placing an object at different positions within its field of view. Observing an object at different locations within the telescope will allow SPHEREx to measure the light from the object across multiple wavelengths.
SPHEREx also features six linear variable filters (LVF). These LVFs produce spectra, and do so by the telescope moving in the wavelength-varying directions of the LVFs — a method that was proven on NASA’s New Horizons mission to Pluto with the LEISA instrument.
Extending away from the telescope is SPHEREx’s three-stage V-groove system, which gives the observatory its recognizable conical shape and allows for the cooling of its optics and internal systems. This three-stage V-groove design consists of three nested photon shields that protect the spacecraft’s cooler and telescope optics from radiation emitted by the Sun, Earth, and the spacecraft. Like the James Webb Space Telescope, SPHEREx must be cooled to extremely low temperatures of less than 55 degrees Kelvin to ensure that any heat from the observatory doesn’t interfere with infrared observations, as a significant portion of infrared light is emitted as heat.
6154 lightning strikes in 6 hours! Unheard of in February for at least 10 years (new daily record since 2014). Electrical activity was remarkably intense for the season on February 25, and concentrated in the center-east.
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