The U.S. Space Force is bolstering its collaboration with Japan to counter China’s expanding influence in space. This involves improving joint capabilities in space object surveillance to monitor increasingly complex Chinese satellites capable of adjusting their orbits dynamically.
At the Spacepower Conference on December 10, Brig. Gen. Anthony Mastalir, commander of U.S. Space Forces Indo-Pacific, described the bilateral relationship as entering a pivotal stage after the recent launch of U.S. Space Forces-Japan, a new command located at Yokota Air Base in Japan. Mastalir emphasized the strategic value of alliances in the Indo-Pacific to “maintain peace and stability.”
“Our allies and partners recognize that a secure and accessible space domain is vital to collective defense, economic growth, and technological innovation,” Mastalir stated.
The U.S. and Japan have agreed to include space within their mutual defense agreements. This implies that attacks on satellites and other space-based infrastructure could trigger a collective defense response.
Central to the U.S.-Japan partnership is enhancing space domain awareness, or the ability to track and monitor space objects. A joint project, the Quasi-Zenith Satellite System Hosted Payload (QZSS-HP) program, integrates U.S. optical sensor payloads, created by MIT Lincoln Laboratory, into Japan’s QZSS infrastructure.
QZSS, often called Japan’s version of GPS, uses geostationary satellites in inclined orbits to offer advanced navigation services throughout the Asia-Pacific region.
Two U.S. optical sensor payloads will be deployed on separate QZSS satellites, set for launch in 2025 and 2026. These launches were delayed due to setbacks in Japan’s H3 rocket program.
Mastalir indicated that these collaborations will likely continue, as China’s advanced satellite capabilities are a significant worry for the U.S. and Japan. He highlighted the challenges presented by Chinese spacecraft operating in non-Keplerian orbits, which deviate from standard orbital patterns. These orbits allow for continuous trajectory adjustments, making traditional orbit determination and tracking more difficult.
“When we talk about space domain awareness, it’s important to get an orbit determination,” Mastalir explained. “But we also have to be prepared for spacecraft that are consistently maneuvering, making traditional tracking impossible.”
Non-Keplerian orbits offer strategic benefits, enabling satellites to achieve precise positioning and adjust coverage dynamically. This adaptability is especially valuable for surveillance and reconnaissance missions, enhancing monitoring of strategically important areas. By using these techniques, China’s satellites can evade tracking and improve their effectiveness.
Mastalir noted that Japan is investing heavily in both space-based and ground-based sensor systems to address these challenges.
The U.S.-Japan partnership is a key part of the broader strategy to counter what Mastalir referred to as “red” space — a term representing adversarial activities led by China.
“We must be prepared to ensure that we have the necessary awareness to counteract these threats,” Mastalir said.