After passing all the necessary checks and calibrations, NASA says its SPHEREx space observatory is ready to embark on its expansive mission. As of May 1, the spacecraft has begun imaging a 3D map of the entire sky and its hundreds of millions of galaxies. But in order to complete such a massive objective, SPHEREx is going to need to take a lot of photos—about 3,600 per day over the next two years, to be more specific.
Pointed away from Earth about 404 miles overhead, the orbital observatory will circle the planet from north to south about 14.5 times each day as it images a single, circular strip of the sky. Given Earth’s own solar orbit, it will only take about six months for SPHEREx to have glimpsed space in every direction at least once.
Technically, each picture is a composite of images from six separate detectors designed for specific light wavelengths. This set of six images is referred to as an exposure, with about 600 exposures produced by SPHEREx per day. SPHEREx also alters its position after every exposure, but it does not use thrusters to shift. Instead, it uses a system of spinning reaction wheels inside the spacecraft.
While other projects like COBE have previously mapped the whole sky, SPHEREx is the first to do it across so many color spectrums. Using spectroscopy, the observatory splits light across 102 infrared wavelengths that are invisible to the human eye. This will allow the observatory to construct a better 3D map that includes distances between galaxies in all directions, as well as measure the collective glow from every galaxy that’s ever existed. The method also enables SPHEREx to provide information about a cosmic object’s composition, which can help search for key ingredients for life like water molecules.
Peering deep into the sky will additionally provide details about the first fraction of a second that followed the big bang, when cosmic inflation expanded the universe a “trillion-trillionfold,” according to NASA.
SPHEREx team members are already excited by what they’ve seen of the observatory.
“The performance of the instrument is as good as we hoped,” said principal investigator Jamie Bock. “That means we’re going to be able to do all the amazing science we planned on and perhaps even get some unexpected discoveries.”
“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. “I think there’s a poetic arc to that.”
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