In early November, three Australian satellites plunged and burned up in the Earth’s atmosphere due to increased solar activity.
When operating in low Earth orbit (below 2,000 km), satellites undergo a process of orbital decay, gradually lowering their altitude before ultimately burning up in the atmosphere. However, the small satellites Binar-2, 3, and 4 from the Binar Space program at Curtin University, Australia, fell into the atmosphere much earlier than expected.
Binar-2, 3, and 4 had only been operational for two months, while their expected lifespan was six months. This premature end affects the scientific research and new system testing they were conducting. The cause is the increased activity of the Sun, and the Binar satellites are not the only victims. The heightened solar activity has posed challenges for satellite operators over the past few years.
Simulation of Binar satellites operating in orbit. (Photo: Spaceanddefense).
Solar activity includes phenomena such as sunspots, solar flares, and solar winds—streams of charged particles directed toward Earth. This is a result of the star’s magnetic field constantly changing and reversing approximately every 11 years. At the midpoint of the cycle, solar activity peaks.
Although scientists are aware of the solar cycle, the specific activity remains challenging to predict. The dynamics are very complex, while space weather forecasting is still in its early stages.
In recent months, indicators of solar activity have been 1.5 times higher than predicted. Increased activity means more solar flares and stronger solar winds. Enhanced streams of charged particles can damage or disrupt electronic components on satellites.
The excess energy from solar activity gets absorbed into the outer atmosphere, causing it to expand. As a result, all satellites at altitudes below 1,000 km experience significantly greater atmospheric drag. This force disrupts their orbits and causes them to fall toward the Earth’s surface.
Binar Space is a satellite research program aimed at enhancing understanding of the solar system and reducing barriers for space operations. The program began deployment with its first satellite, Binar-1, in September 2021, during a period of relatively low solar activity. This cubic satellite, with edges of 10 cm, started at an altitude of 420 km and survived 364 days in orbit.
The subsequent satellites in the program, Binar-2, 3, and 4, were expected to last around six months due to increased solar panel surface area and stronger solar activity. However, they only lasted two months before burning up.
Although these small cubic satellites are relatively inexpensive, the early termination of missions always incurs losses. This is particularly true for commercial satellites, emphasizing the need for more accurate space weather forecasting.
Fortunately, the Sun is expected to calm down. Despite its unexpectedly strong activity, solar activity may slow down by 2026 and return to minimum levels by 2030.
