Mission

NASA is targeting a launch for SPHEREx in late February 2025. Once in polar orbit around Earth, SPHEREx will begin a two-year mission to create the first all-sky spectroscopic survey in the near-infrared. Observing hundreds of millions of galaxies and a rich variety of astronomical phenomena, SPHEREx will investigate the origins of the universe, galaxies, and water and other life-sustaining molecules.

NASA’s SPHEREx mission will lift off from Space Launch Complex 4E at Vandenberg Space Force Base in California aboard a SpaceX Falcon 9 rocket, just as the Surface Water and Ocean Topography mission, shown here, did in December 2022. Credit: NASA | Full Image

Launch

SPHEREx has its first launch opportunity Feb. 27, 2025, and is targeted to lift off no later than April 2025. Each day within the launch period provides a single, nearly instantaneous launch window around 7:10 p.m. PST (10:10 p.m. EST).

The mission will launch aboard a SpaceX Falcon 9 rocket, procured by NASA’s Launch Services Program, from Space Launch Complex 4E at Vandenberg Space Force Base in California.

Launch Sequence

SpaceX’s Falcon 9 is a two-stage rocket that will launch SPHEREx in a south-southwest direction over the Pacific Ocean.

Key events after launch (times approximate):

• 2 minutes and 14 seconds after liftoff: Main engine cutoff (MECO), second stage separation, and second-engine start 1 (SES1) will occur in quick succession. The reusable Falcon 9 first stage will then begin its automated return to the launch site for a powered landing.
• 3 minutes and 5 seconds: After protecting the satellite as the rocket traveled through the atmosphere, the launch vehicle’s fairing, or nose cone, will separate into two halves and be jettisoned.
• 7 minutes and 9 seconds: Stage-II engine cutoff (SECO1) will take place, putting the launch vehicle and spacecraft in a coast phase.
• 39 minutes: Stage-II first restart (SES2) will occur with a roughly 40-second burn, followed by stage-II engine cutoff (SECO2).
• 42 minutes: The launch vehicle and spacecraft will separate.
• 43 minutes: Initial acquisition of signal from the spacecraft is expected via the TrollSat ground station in Antarctica.

Orbit

The SPHEREx spacecraft will orbit Earth about 404 miles (650 kilometers) overhead. Its polar orbit is also Sun-synchronous, which means its orientation relative to the Sun remains consistent throughout the year. By remaining over Earth’s day-night (or terminator) line for the entire mission, the observatory will keep the conical photon shields that surround its telescope pointed at least 91 degrees away from the Sun — an overwhelming source of light and heat. In addition, the telescope will point away from Earth and the bright infrared glow the planet produces. Each approximately 98-minute orbit allows the telescope to image a 360-degree strip of the celestial sky. As Earth’s orbit around the Sun progresses, that strip slowly advances, enabling SPHEREx to complete an all-sky map within six months.

SPHEREx will look outward from low Earth orbit, circling the planet along its day-night (or terminator) line. This illustration depicts the spacecraft's orbital plane in orange, and its field of view in green. Credit: NASA/JPL-Caltech | Full Image

In-Orbit Checkout

Once SPHEREx is safely in orbit, controlling its orientation, and communicating with ground stations, the mission will transition to the in-orbit checkout phase. During this 30-day period, the mission team will complete the activities to prepare SPHEREx for its survey operations:

1. Commissioning the spacecraft, including all necessary calibrations
2. Cooling the telescope to its designed operating temperature
3. Characterizing the telescope’s optical performance in space

Early in the commissioning phase, on the mission’s third day, the spacecraft is scheduled to eject the dust cover latched in place over the telescope’s primary instrument aperture. After the carefully orchestrated deployment — the mission’s sole mechanical deployment — the cover will float away and eventually burn up in Earth’s atmosphere.

The telescope will also begin cooling down passively to its desired operating temperature. Portions of the telescope, including some of its detectors, must be brought below minus 350 degrees Fahrenheit (about minus 210 degrees Celsius). (More information about cooling is available in the Spacecraft section.)

Survey Operations

Once SPHEREx has been fully commissioned, the mission will begin its survey operations phase. Circling Earth about 14.5 times per day, SPHEREx will complete more than 11,000 orbits over its 25 months of planned survey operations. The spacecraft will take up to about 600 exposures per day, allowing it to complete four all-sky spectroscopic surveys during its prime mission.

Prime Mission Duration

The baseline mission for SPHEREx covers 27 months, including launch, one month of in-orbit checkout, 25 months of survey operations, and one month of decommissioning activities.