Carruthers observatory returns first ultraviolet views of Earth and Moon

by Clarence Oxford
Los Angeles CA (SPX) Dec 17, 2025

NASA's Carruthers Geocorona Observatory has captured its first images from space, providing ultraviolet views of Earth and the Moon and confirming that the spacecraft and its instruments are operating as intended. Taken on Nov. 17, months before the start of routine science observations, these first light images also preview the type of data the mission will collect on Earth's outer atmosphere.

The observatory's Wide Field Imager and Narrow Field Imager each obtained two views: one using a broad far-ultraviolet filter and another tuned to light from Earth's geocorona. In each image, Earth appears as the larger bright circle near the center of the frame, while the Moon shows up as a smaller circle positioned below and to the left.

The geocorona images isolate the specific ultraviolet wavelength emitted by atomic hydrogen, known as Lyman-alpha, which traces the exosphere, or the outermost layer of Earth's atmosphere. In these views, a diffuse halo of emission surrounds Earth, marking regions where hydrogen scatters sunlight and outlining the structure of the geocorona.

The Moon remains visible in Lyman-alpha because its rocky surface reflects sunlight across many wavelengths, including this narrow hydrogen line. Comparing these hydrogen-line images with the broad far-ultraviolet views will help scientists separate true geocoronal emission from reflected sunlight and refine measurements of hydrogen density in near-Earth space.

For this first test, Carruthers used five-minute exposure times, which were sufficient to verify instrument health and basic performance. During the main science phase, the observatory will extend exposures to about 30 minutes to reveal fainter structures in the geocorona and to follow how Earth's outer atmosphere reacts to changes in solar radiation and space weather.

The Narrow Field Imager's far-ultraviolet images also recorded two background stars whose estimated surface temperatures are roughly twice that of the Sun, making them bright at short wavelengths. These stars serve as early calibration targets for the observatory's detectors and optics.

Carruthers acquired the first light data from a position near the Sun-Earth Lagrange point 1, where the combined gravity of Earth and the Sun provides a stable observing location. From this vantage point, the spacecraft can maintain an uninterrupted view of the Sun-facing side of Earth, enabling long-duration monitoring without frequent eclipses or rapid changes in viewing geometry.

Mission teams will continue commissioning activities and instrument checks before transitioning to routine science operations. Over time, Carruthers will assemble a sequence of ultraviolet observations that tracks how the geocorona evolves with solar activity, improving understanding of how the Sun interacts with Earth's upper atmosphere and near-Earth space environment.