Last week, a NASA spacecraft placed a large film solar sail into orbit around Earth after a failed attempt a few days earlier. However, subsequent observations of the spacecraft showed it “rolling or yawing” in space, which may have also affected its orbit around our planet.

New observations suggest that a NASA spacecraft that recently deployed a state-of-the-art solar sail into Earth orbit is “tipping or rocking” in space as it orbits our planet. NASA officials told Live Science that the unusual motion was expected, but did not say exactly what it was.

The Advanced Composite Solar Sail System (ACS3) mission aims to test the effectiveness of a new type of solar sail, a device that has the potential to propel spacecraft at higher speeds than currently available by using radiation pressure generated by sunlight. Researchers hope that such technology could one day help carry humans to the edge of the solar system and beyond.

The ACS3 spacecraft consists of a foil sail of about 860 square feet (80 square meters) tightly wrapped inside a microwave-oven-sized satellite, known until recently as a CubeSat. The sail is deployed from a small box using a new set of folding booms made of a new composite material that is 75 percent lighter and more resistant to sunlight than the frames used in previous solar sails used by Russia, Japan, NASA and other private companies.

ACS3 was successfully launched into space on a Rocket Labs Electron Rocket, which launched from a dedicated launch pad in New Zealand on April 23. The CubeSat was placed in low Earth orbit, about 600 miles (965 kilometers) above our planet’s surface, and remained there until scientists made preparations to deploy the sail.

The ACS3 team first attempted to deploy the sail on Aug. 26, but abandoned the roughly 25-minute procedure after “the onboard power monitor detected higher-than-expected motor currents.” After the problem was resolved, the sail was fully deployed on Aug. 29, mission scientists at NASA’s Ames Research Center in California’s Silicon Valley said in a statement.

The spacecraft’s first photos from Earth, including a time-lapse of the sail streaking across the night sky over the Netherlands by interdisciplinary scientist Marco Langbroek, confirmed that the sail was deploying properly. But soon observers began to notice something unusual.

Langbroek, who is currently a lecturer in space situational awareness at Delft University of Technology in the Netherlands, shared images of ACS3 steadily dimming and brightening as it flew over a satellite tracking station near Leiden on Sunday, September 1. In a related blog post , the researcher explained that the object became as bright as some of the brightest stars in the sky, to the point where it was barely visible.

User “mickeywzk” also posted a video of a solar sail brightening significantly over the X for 30 seconds on September 1.

Changes in brightness indicate that [космічний корабель] It is now slowly tumbling, or oscillating, over a period of minutes, Langbroek told Live Science in an email on Monday, Sept. 2. He added that the spacecraft’s orbital eccentricity, or path around our planet, has also changed slightly since Aug. 30, potentially related to the tumbling.

Employees at satellite tracking company s2a Systems also noticed a discrepancy in the ACS3 light curve taken by a telescope at the company’s Swiss base on Aug. 29 that suggested a possible “slow return” by the spacecraft. But at this early stage, there wasn’t enough evidence to fully support the shaky hypothesis.

“We cannot directly confirm Dr. Langbroek’s observation, but we find his conclusion quite plausible,” s2a systems general manager Roger Spinner told Live Science on Tuesday (September 3).

On Wednesday, Sept. 4, NASA officials confirmed to Live Science that the spacecraft had indeed rotated. “The spacecraft is currently inverting as part of the planned sail deployment sequence,” Jasmine Hopkins, public affairs specialist for NASA’s Space Technology Mission Office, told Live Science via email.

NASA officials have not released any additional information about the rollover or deployment sequence, but Hopkins noted that the spacecraft’s Attitude Control System (ACS) — the device that controls the spacecraft’s orientation relative to an inertial reference frame — is not currently functioning.

Hopkins added that the ACS will be reengaged once the mission team is “satisfied with the sail tension.” But there was no indication of when that might be. The solar sail will be visible to the naked eye as it passes across the night sky over the next few weeks, depending on how bright it is at the time.