How ISRO’s maiden satellite docking exercise was aided by favourable space weather

What is space weather? What was the SpaDeX mission? How did favourable space weather help the SpaDeX mission?

What is space weather?

The Sun is constantly spewing gases and particles into space in the form of solar wind. These particles come from the Sun’s hot outer atmosphere, known as the solar corona, and are electrically charged. Solar wind can travel at millions of kilometres per hour, and reach the farthest parts of the solar system.

These solar winds form space weather. Their frequency and intensity fluctuates based on the solar activity cycle, which refers to a periodic 11-year change in the Sun’s activity, measured based on sunspots observed. These spots are indicators of solar activity — the more the activity, the more hazardous the space weather.

The current solar cycle began in late 2019. The cycle entered its maximum phase in November 2023, and we are currently in the midst of an extended period of heightened solar activity.

How does space weather impact satellites and spacecraft?

“Precision docking is very challenging, even under normal circumstances. During severe space weather, when the space environment is disturbed, the task becomes even more difficult,” Dibyendu Nandi, solar physicist and head of the Center of Excellence in Space Sciences India (CESSI) at the Indian Institute of Science Education and Research (IISER), Kolkata, told The Indian Express.

While Earth’s atmosphere largely protects us from the vagaries of space weather, satellites and spacecraft are far more exposed.

“Enhanced high energy radiation associated with strong flares from the Sun can blind sensors and interfere with electronic control systems. Magnetic storms from the Sun, known as coronal mass ejections, or very high speed solar wind streams, can disturb the space environment resulting in loss of communication, and positional errors,” Nandi said.

Docking missions require two spacecraft to have negligible relative velocity between them, and their docking ports to be precisely aligned, to prevent collisions or damages. Any kind of inclement space weather, thus, introduces a whole new set of uncertainties which are challenging to handle.

“But the days leading up to the SpaDeX docking were surprisingly different. There were fewer sunspots and other magnetic structures on the Sun, and analysis by CESSI found that it was unlikely that solar activity could disrupt the near-Earth space environment [where the docking mission took place],” Nandi said. “The Sun certainly co-operated.”

What is SpaDeX? Why was the mission important?

ISRO on December 30 launched two small spacecraft — SDX01 (the ‘Chaser’) and SDX02 (the ‘Target’) — into a low-Earth circular orbit. It later set them apart at a distance of around 20 km in space.

After the initial inter-satellite separation, the ‘Chaser’ incrementally came closer to the ‘Target’ — at distances of 5 km, 1.5 km, 500 m, 225 m, 15 m, and 3 m — before the final docking or joining on Thursday.

Such a manoeuvre will be needed in future space missions like Chandrayaan-4 or to establish Bharatiya Antriksha Station, India’s very own space station. In these missions, multiple components will be sent to space separately (due to time, logistical, and payload capacity factors), before being brought together in space using docking manoeuvres.

According to Nandi, apart from demonstrating ISRO’s technological capabilities, the SpaDeX mission also underscores the need for investing in improved space weather forecasts. Just like improved weather forecasting on Earth has been vital to save human lives and infrastructure from severe weather events, having space weather forecasts in near real time is crucial especially when “critical space manoeuvres are being planned during this solar maximum phase,” Nandi said.