Sun-Watching Satellite Endures Double Eclipse Day

Earth and Moon Briefly Obscure Solar Observatory

An orbiting spacecraft dedicated to observing the sun experienced a rare celestial event on July 25, simultaneously facing a lunar transit and an Earth eclipse. NASA’s Solar Dynamics Observatory (SDO) had its view of the sun obscured by both the moon and Earth on the same day, an unusual occurrence driven by its orbit.

A Day of Celestial Obstructions

The SDO, launched in 2010, maintains a geosynchronous orbit around Earth to provide continuous solar monitoring. This orbit is designed to keep Earth out of its observational path, but twice a year, the planet itself blocks the sun for several weeks. On this particular day, the moon also passed between the SDO and the sun.

Lunar Transit Deepest Yet

The moon’s passage, a lunar transit, began around 2:45 UTC. This event was the SDO’s fourth partial solar eclipse by the moon since April, and notably, the deepest one observed. It obscured up to 62% of the sun’s visible disk and lasted approximately 50 minutes, as detailed on the SDO’s blog.

Earth’s Shadow Falls

Following the lunar transit, Earth then entered the picture. Beginning around 6:30 UTC, approximately three hours after the moon’s obscuration ended, Earth completely blocked the SDO’s view of the sun. This terrestrial eclipse concluded shortly before 8:00 UTC, according to SDO’s blog.

The visual difference between the two eclipses is distinct in the SDO’s imagery. Earth’s atmosphere creates a soft-edged shadow, while the moon, lacking an atmosphere, casts a sharp, circular silhouette against the sun. This phenomenon is not unprecedented; similar “double eclipses” were witnessed by the SDO in 2015 and 2016.

Upcoming Eclipses for Earthbound Observers

While the SDO experienced these simultaneous events, Earth-bound skywatchers must wait longer for their next solar eclipse. A partial solar eclipse will be visible over New Zealand and parts of Australia on September 21. The next total solar eclipse, offering a more dramatic view, is scheduled for August 12, 2026, and will be visible across Greenland, Iceland, Russia, Spain, and Portugal.

The SDO is currently within its 31st eclipse season, which commenced on July 10 and is slated to conclude on August 7. This period is a regular occurrence that interrupts the spacecraft’s solar observations due to Earth’s position in its orbit.

In 2023, scientists continued to analyze solar activity, with the sun experiencing a notable increase in sunspot activity as it heads towards solar maximum, the peak of its 11-year cycle. This heightened activity can lead to more frequent solar flares and coronal mass ejections, phenomena that the SDO diligently monitors for their potential impact on Earth’s technology and atmosphere.