The Japan Aerospace Exploration Agency (JAXA) conducted the scientific balloon flight B25-03, as part of the 2025 scientific balloon campaign, at the Taiki Aerospace Research Field. The balloon was launched on 20 June 2025, at 4:02 am JST for the purpose of testing the performance of an alignment monitor system. The balloon had a fully inflated volume of 30,000 m3 (diameter 42m) and ascended at a rate of approximately 230 m per minute.

2 hours and 10 minutes after launch, the balloon reached its floating altitude of 30 km over the Pacific Ocean, approximately 30 km south-east from the Taiki Aerospace Research Field. At 6:20 am JST, the balloon and the onboard equipment were separated by tele-command and slowly descended onto the sea, landing approximately 30 km south-east from the Taiki Aerospace Research Field, where they were recovered by recovery boats at 7:13 am JST.

Regarding the DemonstRation Experiment of Alignment Monitor (DREAM) 4, further research will now be conducted through the thorough analysis of the data obtained in this flight.

At the time of launch, the ground weather conditions were: weather: cloudy, wind speed: 1 m/s, and temperature: 15 degrees Celsius.

※ Research overview
To enhance the performance of scientific observations utilising large-scale structures such as large telescopes, a fundamental technology for high-precision measurement of structural deformations has been developed. This displacement measurement technology, which employs lasers, offers significant advantages over conventional displacement sensors, including longer working distance and the ability to be directly mounted on structural components. Additionally, the system features a simple configuration, enabling high reliability, reduced cost, and broader applicability to diverse experimental scenarios. Since 2021, three balloon experiments have been conducted to verify various aspects of the technology. These include the accuracy over various working distances, the performance under sunlight exposure, and the mitigation of thermal stresses at the instrument interfaces. In this flight, these individually validated technologies will be integrated to conduct a comprehensive evaluation test aimed at practical implementation.
DREAM: DemonstRation Experiment of Alignment Monitor

A balloon being inflated in a large hangar for its scientific flight B25-03. (credit: JAXA)

The balloon just before the launch of B25-03. (credit: JAXA)