ACS3

ACS3 stands for Advanced Composite Solar Sail System. This is NASA’s newest attempt at demonstrating a solar sail.

ACS3 launched on April 23, 2024. It is currently orbiting the earth and is undergoing a 1-to-2-month commissioning period, after which it will deploy its solar sail, which is expected sometime in June.

Because of its large, reflective sail, once it is fully operational, ACS3 is expected to be brighter than Sirius, the brightest star in the night sky. There isn’t a lot of details about this, however, it seems likely that this visibility may be in the form of flares similar to have seen with other satellites with large reflective surfaces; (see Satellite flare – Wikipedia). Heavens-Above, which is already tracking the satellite, will likely provide info on when and where the satellite will be visible once the sail is deployed.

Fortunately, the mission is only expected to last until December, 2024. After it has demonstrated the ability to adjust its orbit using only sunlight, the satellite will be decommissioned and directed into the earth’s atmosphere where it will burn up.

This YouTube video from NASA describes in basic details what the spacecraft looks like and how it operates.

The references below provide more detail. In particular, the Wilkie pdf is a detailed description of its construction and operation.

References:

• Advanced Composite Solar Sail System (ACS3) – NASA
• Advanced Composite Solar Sail System: Using Sunlight to Power Deep Space Exploration (ACS3) – NASA
• Wilkie_ACS3_mission_update_ISSS_2023_20230530_rev_a.pdf (nasa.gov)
• ACS3, NASA’s Advanced Composite Solar Sail… | The Planetary Society