NASA set to launch SPHEREx space telescope to scan entire sky

The latest addition to NASA’s fleet of space telescopes will launch this weekend and quickly set to work scanning the entire sky in a range of near-infrared wavelengths, collecting rich data on more than 450 million galaxies.

The Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer (SPHEREx) is due to launch on 2 March atop a SpaceX Falcon 9 rocket from Vandenberg Space Force Base in California at 10.09pm local time.

It carries a camera with a filter that splits incoming light like a prism and beams different portions of the spectrum onto 102 separate colour sensors. As the telescope pans around the sky, it slowly pieces together a complete image pixel by pixel. This strategy allows a relatively small and simple camera with no moving parts to do what might otherwise require a heavy and costly suite of sensors.

“If you scan the sky slowly by moving the telescope incrementally, then after enough time, every pixel in the sky will have been observed over a very wide wavelength range, giving you a crude spectrum of every bit of the sky, which has never been done before,” says Richard Ellis at University College London. “It’s a very small space telescope, but it’s got some very unique features.”

Ellis says this rich dataset will allow serendipitous discoveries. “It’s likely to find the unexpected,” he says.

The infrared data, outside the range of human vision, will allow scientists to determine how far away objects are and learn about how galaxies form and evolve. It can also be used to determine the chemical make-up of objects, potentially revealing the presence of water and other key ingredients for life.

Anything interesting thrown up by SPHEREx can then be investigated in a more focused way using NASA’s existing space telescope fleet, including the ageing but powerful Hubble Space Telescope and the newer James Webb Space Telescope (JWST).

Christopher Conselice at the University of Manchester, UK, says SPHEREx won’t match the resolution of JWST or produce similarly awe-inspiring images, but it will be a “workhorse” for scientific discovery.

“JWST has the potential to point at one part of the sky, take some big pictures [and reveal] something completely new. And SPHEREx won’t be able to really do the same thing,” he says. “It’s going to be an analysis that’s going to take years and it’s going to cover the sky many, many times.”

SPHEREx will orbit Earth 14.5 times a day, facing away from the planet’s surface, and complete 11,000 orbits in its two-year lifespan. Three cone-shaped shields will protect its instruments against interference from the radiant heat of Earth and the sun.

Launching on the same rocket will be another NASA mission, Polarimeter to Unify the Corona and Heliosphere (PUNCH), which will study the sun’s solar wind.