The Sun pushed three satellites down from Earth’s orbit

When operating in low Earth orbit (at an altitude of 2,000 km or less), satellites will go through a process of reducing orbit, gradually lowering altitude and eventually burning up in the atmosphere. However, three small satellites Binar-2, 3 and 4 belonging to the Binar Space program of Curtin University, Australia, fell into the atmosphere much earlier than expected.

Binar-2, 3 and 4 have only been operational for two months, while the expected time is 6 months. This early termination affects the scientific research and testing of new systems they are carrying out. The reason is that the Sun has increased activity and the Binar satellite is not the only victim. A sharp increase in solar activity has caused difficulties for satellite operators over the past few years.

Solar activity includes phenomena such as sunspots, solar flares and solar wind – a stream of charged particles directed towards Earth. This is a result of the star’s magnetic field constantly changing, and about every 11 years, it completely reverses. At the midpoint of the cycle, solar activity will peak.

Although scientists know about the solar cycle, specific activities are still difficult to predict. The dynamics are complex while space weather forecasting is still in its infancy.

Over the past few months, solar activity indicators have been 1.5 times higher than predicted. Increased activity means more solar flares and stronger solar wind. The enhanced flow of charged particles could damage or disrupt electronic components on the satellite.

Excess energy from solar activity is 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 is the force that disrupts their orbits and causes them to fall towards the Earth’s surface.

Binar Space is a satellite research program aimed at improving understanding of the solar system and reducing barriers to space activity. The program began deployment with the first satellite, Binar-1, in September 2021, when solar activity was relatively low. This box-shaped satellite with a 10 cm edge starts at an altitude of 420 km and remains in orbit for 364 days.

The program’s next satellites, Binar-2, 3 and 4, are expected to last about 6 months due to increased solar cell area and stronger solar activity. But instead, they only lasted two months and then burned out.

Although small cube satellites are relatively cheap, ending a mission prematurely is always costly. This is even more true with commercial satellites, highlighting the need for more accurate space weather forecasts.

Luckily the Sun will calm down. Although it is stronger than expected, solar activity could slow down by 2026 and return to a minimum by 2030.