NASA sets launch date for SPHEREx telescope with PUNCH

NASA’s latest space telescope, SPHEREx, scheduled for launch on 28 February in tandem with another mission called PUNCH, has been hailed for both the colour range of the images it will produce and its ability to “peer back” to the first second after the Big Bang.

What the telescope will actually do, however, is somewhat more complex than might be inferred from either of these descriptions, according to technical details revealed today at a NASA science briefing.

No telescope can look directly at objects formed even close to that far back in the history of the Universe, and SPHEREx is not big enough, or powerful enough, to come close to matching the best existing telescopes. Instead, it is the latest in a growing array of relatively small wide-field telescopes capable of mapping the entire visible sky—in its case, once every six months. And, it will do that in 102 colors, far exceeding the color resolution of any prior all-sky map.

Shawn Domagal-Goldman, acting director of NASA’s Astrophysics Division, compares its mission to that of the James Webb Space Telescope.

“Imagine you’re a photographer who wants to capture wildlife in a forest,” he says. “You may take a camera designed to zoom in on a tree, or maybe even a nest and the eggs inside a nest. That’s what the James Webb does. SPHEREx is the panoramic lens. It’s going to give us not that egg in a nest in a tree; it’s going to give us the forest and all the trees within it.”

For astronomers, he adds, “the trees are galaxies or other celestial objects, and the forest is the known Universe.”

It is from studying that forest, he says, that astrophysicists will be able to reconstruct what happened farther back in time.

Partly, this will be done simply from mapping the 450 million or so galaxies that will be visible to SPHEREx. “Imagine an explosion [i.e., the Big Bang] happening and bits and pieces flying out,” Domagal-Goldman says. If you can map that well enough, “you might get information about the explosion that happened at the center. SPHEREx is going to do that.” I.e., it’s not going to actually see the first second of the Universe, “but it’s going to get reverberations that echoed into eras SPHEREx is going to directly observe,” Domagal-Goodman says.

Also important will be studying the large-scale clumping of galaxies and other matter.

“The distribution is not random,” says Phil Korngut, SPHEREx’s instrument scientist, from California Institute of Technology (Caltech). “It’s clumped together and it has filaments and voids. The origins of those fluctuations can tell us about the early Universe. If we can understand that structure, we can tie it back to those original moments just after the Big Bang.”

Equally interesting, he says, is to look at what is called the extra-galactic background light, a diffuse glow not created by any specific object we can see, but which instead goes far back through cosmic time. “It contains a wealth of information from every light source that’s ever existed,” Korngut says.

Closer to hand, the telescope’s enormous number of color channels, some in the visible, some in the infrared, give it spectroscopic capabilities that allow it to seek out the spectral signatures of important molecules throughout our own galaxy, says Rachel Akeson, SPHEREx science data center lead at Caltech. These include water and carbon dioxide, much of which is believed to lie in large gas and dust fields called molecular clouds.

“We think that most of the water and ice in the Universe is in places like this,” she says. “It’s also likely that the water in the Earth’s oceans originated in a molecular cloud.”

More on SPHEREx

PUNCH is a smaller mission, focused on things closer to home. Comprised of four suitcase-sized satellites, it will be inserted into low Earth orbit, from which it will continuously monitor, in three dimensions, the solar corona, the solar wind, and the impact of the solar wind on Earth.

From that, and data from other spacecraft studying the Sun and the heliosphere (the region of space surrounding the Sun), scientists hope to increase their understanding both of normal space weather and dangerous coronal mass ejections, which can create radiation that endangers both spacecraft and astronauts, says Nicholeen Viall, PUNCH mission scientist at NASA’s Goddard Space Flight Center.

The fact that both can be launched at once is an added bonus. “This basically two for the price of one,” Domagal-Goldman says.

Joe Westlake, director of NASA’s Heliophysics Division, agrees: “ride share capitalizes on every kilogram of launch capability,” he says. “

Attend the Launch Virtually

Members of the public can register to attend this launch virtually. NASA’s virtual guest program for this mission also includes curated launch resources, notifications about related opportunities or changes, and a stamp for the NASA virtual guest passport following launch.