In a fascinating turn of events, two powerful rocket launches from East Asia within a span of 24 hours have given scientists a unique opportunity to study the effects of man-made space weather. The maiden voyage of China’s Gravity-1, touted as the most powerful all-solid propellant rocket to date, took off from an offshore platform in the Yellow Sea on January 11, 2024, around 0530 UT. Hot on its heels, Japan’s H-IIA rocket launched from the Tanegashima Space Center the very next day at 0444 UT.
These back-to-back launches, as reported in a recent study published in the journal ‘Space Weather’ (translated from English), have left a significant mark on the ionosphere, the layer of the Earth’s atmosphere that is ionized by solar and cosmic radiation. The study, led by P. K. Rajesh from the Department of Earth Sciences at National Cheng Kung University in Tainan, Taiwan, reveals that both launches induced concentric traveling ionospheric disturbances (CTIDs) and caused a significant depletion in total electron content (TEC) by 50%–70%.
So, what does this mean in simple terms? Well, imagine the ionosphere as a vast sea of electrons. When a powerful rocket launches, it’s like dropping a stone into that sea. The ripples that follow are the CTIDs, and the temporary reduction in the number of electrons is the TEC depletion. In this case, the ripples had periods of 9–11 minutes and wavelengths of 300–720 km, traveling at speeds of 300–1,100 m/s. The depletions covered a region of 3.5–4.5 degrees and lasted for 60–90 minutes before the ionosphere recovered.
The study also found that the Gravity-1 rocket emitted only 5%–7% of the water content in the H-IIA’s exhaust, but its steeper trajectory led to a more rapid and widespread TEC depletion. “The observations indicate a delay gradient of up to 60 mm/km, which is too small to threaten ground-based augmentation systems (GBAS),” Rajesh explained. GBAS are systems used to enhance the integrity and availability of Global Navigation Satellite Systems (GNSS) for aviation and maritime applications.
For the maritime sector, understanding these ionospheric disturbances is crucial. GNSS systems are widely used for navigation and positioning at sea. While the delay gradients observed in this study are not significant enough to disrupt these systems, it’s essential to monitor and study these events to ensure the reliability of GNSS signals.
Moreover, the study opens up opportunities for further research into the effects of rocket launches on the ionosphere. As space tourism and commercial space launches become more common, understanding and mitigating these man-made space weather events will be increasingly important.
In the words of Rajesh, “The results show that Gravity‐1 emitted only 5%–7% of the H2O contained in H‐IIA exhaust, while the rapid occurrence of TEC depletion covering a wider spatial area indicates its steeper vertical (closer to zenith) trajectory.” This finding underscores the need for careful consideration of launch trajectories and their potential impacts on the ionosphere.
In conclusion, while these findings may not have immediate commercial impacts, they highlight the importance of ongoing research and monitoring of man-made space weather events. For maritime professionals, staying informed about these developments can help ensure the continued reliability of GNSS systems and the safety of navigation at sea.