A NASA mission to map 450 million galaxies is currently under construction

A NASA mission to map 450 million galaxies is currently under construction

Essential elements are coming together for NASA’s SPHEREx mission, a space telescope that will create a never-before-seen map of the universe.

NASA’s SPHEREx space telescope is starting to look a lot like when it reaches Earth orbit and begins mapping the entire sky. Short for Specto-photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer, SPHEREx resembles a trumpet, although it is about 8.5 feet (2.6 meters) tall and about 10.5 feet (3.2 meters) wide. What gives the observatory its distinctive shape are its cone-shaped photon shields, which are assembled in a clean room at NASA’s Jet Propulsion Laboratory in Southern California.

Three cones, each inside the other, will surround the SPHEREx telescope to protect it from the light and heat of the Sun and Earth. The spacecraft will sweep every part of the sky, such as scanning the interior of the Earth, to complete two maps of the entire sky each year.

“SPHEREx has to be very flexible because the spacecraft has to move relatively quickly as it scans the sky,” said Sarah Soska, deputy payload manager and payload systems engineer for the mission. “It doesn’t look that way, but the armor is actually very light and made of layers of materials like a sandwich. The outside has aluminum sheets, and the inside is a honeycomb-shaped aluminum structure that looks like cardboard—light but sturdy.”

NASA SPHEREx will create a map of the sky like no other. Check out some of the special equipment the expedition is using to conduct cutting-edge science. Image source: NASA/JPL-Caltech

When launched – no later than April 2025 – SPHEREx will help scientists better understand where water and other key components necessary for life originate. To do this, the mission will measure the abundance of water ice in interstellar clouds of gas and dust, where new stars are born and from which planets eventually form. It will study the cosmic history of galaxies by measuring the collective light they produce. These measurements will help figure out when galaxies started forming and how their composition changed over time. Finally, by mapping the positions of millions of galaxies relative to each other, SPHEREx will search for new clues about how the rapid expansion, or inflation, of the universe occurred a fraction of a second after the big bang.

Cool and stable

SPHEREx will do all this by detecting infrared light, a range of wavelengths longer than visible light that the human eye can see. Infrared light is sometimes called thermal radiation because all warm objects emit it. Even a telescope can create infrared light. Because this light may interfere with detectors, the telescope must be kept cool — below 350 degrees Fahrenheit (about minus 210 degrees Celsius).

An outer photon shield will block light and heat from the Sun and Earth, and gaps between the cones will prevent heat from making its way inward toward the telescope. But to ensure SPHEREx reaches its ultra-cold operating temperature, it also needs something called a V-groove radiator: three conical mirrors, each like an upside-down umbrella, stacked on top of each other. Located beneath the photon shields, each consists of a series of wedges that redirect infrared light so that it bounces through the gaps between the shields and out into space. This removes heat transferred through the struts from the spacecraft’s room-temperature bus containing the computer and electronics.

“We are not only interested in how cool SPHEREx is, but also whether its temperature stays the same,” said Konstantin Pinanin, the mission’s payload manager from JPL. “If the temperature changes, the sensitivity of the detector may change, which could be interpreted as a false signal.”

Eye on the sky

The heart of SPHEREx is of course its telescope, which collects infrared light from distant sources using three mirrors and six detectors. The telescope is tilted on its base so it can see as much of the sky as possible while remaining within the protection of the photon shields.
The telescope, built by Ball Aerospace in Boulder, Colorado, arrived in May at the California Institute of Technology in Pasadena, California, where it was integrated with detectors and a V-groove radiator. Then, at JPL, engineers mounted it on a shaking table that simulated the vibration the telescope would endure during the rocket’s journey into space. It then returned to Caltech, where scientists confirmed that its mirrors were still in focus after a vibration test.

SPHEREx’s infrared “vision.”

Mirrors inside the SPHEREx telescope collect light from distant objects, but it is the detectors that can “see” the infrared wavelengths that the mission is trying to observe.

A star like our Sun emits the full range of visible wavelengths, so it is white (although Earth’s atmosphere makes it appear more yellow to our eyes). A prism can break this light into its component wavelengths – the rainbow. This is called spectroscopy.

SPHEREx will use filters mounted on top of its detectors to perform the spectroscopy. Each approximately cookie-sized filter appears iridescent to the naked eye and contains multiple parts to block all but one specific wavelength of infrared radiation. Each object observed by SPHEREx will be imaged through each piece, enabling scientists to see the specific wavelengths of infrared light emitted by that object, whether it is a star or a galaxy. In total, the telescope can observe more than 100 different wavelengths.

From this, SPHEREx will create maps of the universe unlike any seen before.

More about the mission

SPHEREx is managed by the Jet Propulsion Laboratory (JPL) for NASA’s Astrophysics Division within the Science Mission Directorate in Washington. Ball Aerospace built the telescope and will supply the spacecraft bus. Scientific analysis of the SPHEREx data will be conducted by a team of scientists based at 10 institutions across the United States and South Korea. The data will be processed and archived at IPAC at Caltech. The SPHEREx dataset will be publicly available.

For more information about the SPHEREx mission visit:


News Media Contact

Calla Coffield
Jet Propulsion Laboratory, Pasadena, California.


(Tags for translation)Department of Astrophysics

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