PUNCH Instruments

NASA’s Polarimeter to Unify the Corona and Heliosphere, or PUNCH mission, is a constellation of four small satellites in low Earth orbit that will make global, 3D observations of the Sun's corona to better understand how the mass and energy there becomes the solar wind that fills the solar system. By imaging the Sun’s corona and the solar wind together, scientists hope to better understand the entire inner heliosphere – Sun, solar wind, and Earth – as a single connected system.

Three of the PUNCH satellites will carry a Wide Field Imager (WFI), and the fourth will carry the Narrow Field Imager (NFI).

The Narrow Field Imager (NFI)
The Narrow Field Image (NFI) is a coronagraph, a type of device that blocks out the bright light from the Sun to better see details in the Sun's outer atmosphere, or corona. The coronagraph will have a similar field of view as the SOHO (Solar and Heliospheric Observatory) Large Angle and Spectrometric Coronagraph (LASCO) C3 field, from 6 to 32 solar radii on the sky, and it will view the corona in both polarized and unpolarized light.

Wide Field Imager (WFI)
The Wide Field Imager (WFI) is a heliospheric imager, a device that provides views from 18 to 180 solar radii (45 degrees) away from the Sun in the sky. Heliospheric imagers use an artificial “horizon” and deep baffles to view the very faint outermost portion of the solar corona and the solar wind itself. The instrument reduces direct sunlight by over 16 orders of magnitude, which is like the ratio between the mass of a human and the mass of a cold virus. The wide-field imaging optics are based on the design of the famous Nagler eyepieces, which are known among observational astronomers for their clarity, low distortion, wide field, and achromatic focus. Three of the PUNCH spacecraft will carry a WFI instrument.

See https://science.nasa.gov/mission/punch/