NASA's SPHEREx space telescope has been tucked inside a custom-built chamber on and off for the past two months undergoing tests to prepare it for its two-year mission in space. SPHEREx, which stands for Spectro-Photometer for the History of the Universe, Epoch of Reionization and Ices Explorer, is set to launch into orbit around Earth no later than April 2025. It will map the entire sky in infrared wavelengths of light, capturing not only images of hundreds of millions of stars and galaxies but spectra for these objects as well. Spectra are created by instruments that break apart light into a rainbow of wavelengths, revealing new details about a cosmic object's composition, distance, and more.
"It's a small telescope, but it gathers an enormous amount of light thanks to its very wide field of view," explains Stephen Padin, a research professor of physics at Caltech and member of the SPHEREx team. "This will be the first all-sky near-infrared spectroscopic survey."
To ready SPHEREx for its journey, scientists and engineers at Caltech and the Jet Propulsion Laboratory (JPL), which is managed by Caltech for NASA, have been busy testing SPHEREx's detectors and optics in a basement lab at Caltech's Cahill Center for Astronomy and Astrophysics. Because performing these tests requires simulating the extremely cold vacuum of space, the SPHEREx team enlisted colleagues at the Korean Astronomy and Space Science Institute (KASI) to build a specialized chamber for this purpose. The SUV-sized chamber cools the telescope to about minus 350 degrees Fahrenheit (about minus 200 degrees Celsius).
"A series of measurements inside the chamber will test that the telescope is in focus and stays in focus through the shaking of launch," says Jamie Bock, the principal investigator of the mission, professor of physics at Caltech, and senior research scientist at JPL. "The chamber will later be used to characterize SPHEREx's spectrometer, which will capture detailed spectral information for every point on the sky."
Last year, the custom chamber was lowered into the basement of Cahill with the help of a 30-ton crane, as seen here in this timelapse video. The telescope was then carefully prepared to be placed in the chamber, a process that included wrapping parts of the telescope in a foil material to block out stray light and to keep the telescope cool. A second timelapse video shows team members loading the telescope into the chamber.
