Deep space satellite tracking faces mounting pressure as requests overwhelm NASA’s Deep Space Network. A new preprint paper on arXiv proposes a no-cost tracking solution by using spacecraft solar array data gathered during eclipses.
Spacecraft already track solar panel output using Maximum Power Point Tracking algorithms to maximize incoming solar radiation. Eclipses occur when a spacecraft positions itself so that an orbiting body sits between the craft and the Sun. Engineers typically avoid these events because solar arrays stop generating electricity, batteries drain, and onboard temperatures drop sharply.
Precise timing of blackouts traveling across solar panels holds valuable navigation data, Universe Today reported. Astronomers know the exact positions of the Sun, Earth, and the Moon years in advance. Shadows cast into space feature two nested cones: the penumbra, where the Sun is partially blocked, and the umbra, where it is completely cut off.
When a spacecraft enters one of these cones, solar radiation drops sharply while electronics run on onboard batteries. Recording timestamps for voltage drops and recovery allows a navigation algorithm to determine three-dimensional space location without cameras or radio signals, according to researchers Ian Down, James McElreath, and Manoranjan Majji.
Gathering precise measurements is difficult. The Moon lacks an atmosphere, creating a jagged shadow that tracks surface mountains and craters. Each feature shifts eclipse timing by a few seconds. Earth features a squished shape at the poles, while its atmosphere blurs the Sun and enlarges its shadow.
Researchers turned to a dataset of over 22,000 historical observations of lunar craters covered by Earth’s shadow, collected by astronomers between 1842 and 2011. The algorithm mapped Earth shadow parts to specific ground features to pinpoint spacecraft location. Testing the system involved flight telemetry from CAPSTONE, a CubeSat mission operated by Advanced Space where lead author Down works.
CAPSTONE completed its mission in July 2026. On January 11, 2026, the spacecraft traveled through the Moon’s shadow. Solar panel voltage dropped from 23V near zero and recovered to 31V in sunlight, Universe Today reported.
Researchers timed entry and exit to the lunar shadow within 15 seconds of CAPSTONE’s actual path. Simulating a scenario where a spacecraft missed ground station check-ins cut position uncertainty by more than 60 percent. The system requires no additional hardware, functioning as zero-Size Weight and Power for spacecraft.
Recording timestamps when solar panel voltage drops and recovers inside Earth or Moon shadow cones allows navigation algorithms to calculate three-dimensional position.
Earth’s squished polar shape and atmosphere blur the Sun and enlarge its shadow, requiring historical datasets of lunar crater observations from 1842 to 2011 to map ground features.
CAPSTONE provided flight telemetry when it traveled through the Moon’s shadow on January 11, 2026, dropping voltage from 23V to near zero before recovering to 31V.
The system does not entirely replace ground-based radio tracking, but provides a safety net as spacecraft venture beyond low Earth orbit, as detailed in Eclipse Observables for Navigation in Cislunar Space.
Worth a look