SoftBank Demonstrates Ground‑Laser Tracking of a Stratospheric HAPS

In late August 2026, a modest‑sized laser sitting on a concrete pad in Japan managed something that most people would consider sci‑fi: it stared up at a flying platform perched 20 km above the Earth, sent out a burst of light, and then caught the faint echo that bounced right back.

The platform, a long‑duration‑aircraft‑type HAPS operated by U.S. company Sceye, carried nothing more than a corner‑cube reflector (CCR). That little glassy prism is clever – it reflects any incoming beam straight back toward its source, no matter the angle. By mounting it on the HAPS, the team could test the hardest part of a future optical‑communication link: can a ground station actually find, point at, and keep tracking a fast‑moving object high in the stratosphere?

SoftBank, together with Hitotsubashi University and Japan’s National Institute of Polar Research, built a portable laser‑ranging system that fired short, low‑power pulses upward. The system didn’t just fire once; it continuously chased the HAPS over two days, adjusting its aim in real time as the aircraft drifted over the sea off Cape Muroto, Kochi Prefecture.

Why use a passive reflector instead of a full‑blown optical transceiver? Simplicity. The CCR lets researchers isolate the “point‑acquire‑track” (PAT) challenge without the added complexity of data‑laden communication hardware. In other words, they could ask: can we keep a needle‑thin laser spot on a moving target that’s swaying with wind and changing orientation? The answer, at least for this test, was a cautious “yes.”

The experiment also gathered valuable atmospheric data. As the laser beam traversed roughly 20 km of air, it experienced attenuation – a measure of how much the signal weakens. Knowing exactly how the stratospheric environment mutes a beam helps engineers size future optical terminals, choose wavelengths, and set power budgets for real‑world deployments.

It’s worth noting that the laser used was deliberately low‑power, and the system automatically shut off whenever a crewed aircraft crossed the line of fire. Safety first, even in a proof‑of‑concept.

SoftBank’s test builds on a lineage of stratospheric optics. Back in 2005, the German Aerospace Center’s STROPEX project sent a 1.25 Gbit/s data stream down from a balloon at 22 km. The U.S. Navy’s SOLD program later demonstrated optical links with high‑altitude balloons to de‑risk future tech. What sets SoftBank apart is the round‑trip laser path – ground → HAPS → ground – using a purely passive reflector, which isolates the tracking problem from data transmission.

Looking ahead, the plan is to replace the CCR with an active optical transceiver that can both send and receive data, turning the HAPS into a true node in a three‑dimensional communications mesh. Imagine a network where smartphones on the ground talk to a HAPS, which in turn beams information to low‑Earth‑orbit satellites, all via high‑capacity laser links.

SoftBank says the software driving the laser‑ranging system will be the backbone of its future optical‑communications terminal. In practice, the same code that kept the laser locked on the reflector will help lock a data‑bearing beam onto a moving aircraft. If the tech scales, commercial HAPS services – from high‑speed internet to emergency backhaul – could start appearing as early as 2027.

In short, the demo tackled one of the toughest hurdles for any stratospheric laser network: reliably finding and staying glued to a target that’s constantly shifting high above the ground. It’s a modest step, but a necessary one on the road to a truly layered, laser‑linked sky.