SPHEREx’s Concentric Cones Unveiled
Pasadena, Calif. (Jan. 30, 2025) – NASA’s SPHEREx mission, scheduled to launch in 2025, is a revolutionary astrophysics mission that will map the entire sky in near-infrared light and study the history of cosmic expansion and the evolution of galaxies. To capture as much information as possible, SPHEREx employs a unique telescope design with four concentric mirrors.
The SPHEREx telescope, known as the Three-Mirror Anastigmat (TMA), consists of three concentric mirrors that shape light into a diffraction-limited spot, resulting in sharp images over a wide field of view. The fourth mirror, known as the focal plane mask, is located inside the instrument’s focal plane and acts as a special filter, dividing the light into different wavelengths.
“The TMA design is a crucial aspect of SPHEREx’s mission,” said James Bock, SPHEREx principal investigator at the California Institute of Technology in Pasadena. “It allows us to collect a significant amount of light from each part of the sky, enabling us to probe the distant universe with unprecedented detail.”
The four concentric mirrors, made of lightweight beryllium, are arranged as follows:
- Primary mirror: A 70-centimeter-diameter concave mirror that collects light from the scene and directs it to the secondary mirror.
- Secondary mirror: A 35-centimeter-diameter concave mirror that focuses the light onto the tertiary mirror.
- Tertiary mirror: A 17.5-centimeter-diameter convex mirror that collimates the light, directing it towards the focal plane.
- Focal plane mask: Located inside the instrument’s focal plane, the focal plane mask contains an array of precisely positioned holes and slits that divide the light into different wavelengths.
The focal plane mask is a key component of the SPHEREx instrument, enabling the mission to obtain information about the composition, age, and evolution of galaxies. By splitting the light into different wavelengths, SPHEREx can study how the abundance of elements in galaxies has changed over time.
“The focal plane mask is essentially a ‘science filter’ that allows us to separate different types of light,” said Mike Werner, SPHEREx project scientist at NASA’s Jet Propulsion Laboratory in Southern California. “This information will provide valuable insights into the chemical processes occurring within galaxies.”
SPHEREx is designed to map the entire sky twice every six months, providing a comprehensive view of the universe. The mission’s observations are expected to yield a wealth of data, including information on more than 300 million galaxies, the black holes in their centers, and the evolution of the universe over the last 13 billion years.
The SPHEREx mission is funded by NASA’s Astrophysics Division. JPL, a division of Caltech, manages the mission for NASA’s Science Mission Directorate in Washington. The SPHEREx science team includes researchers from Caltech, JPL, NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and the University of Arizona in Tucson.
SPHEREx’s Concentric Cones
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