ORLANDO, Fla. — The U.S. Space Force is strengthening its partnership with Japan in a bid to counter China’s growing dominance in the space domain. The collaboration includes advancing shared capabilities in space object surveillance in order to track increasingly sophisticated Chinese satellites capable of dynamically altering their orbits.
Speaking at the Spacepower Conference on Dec. 10, Brig. Gen. Anthony Mastalir, commander of U.S. Space Forces Indo-Pacific, described the bilateral relationship as entering a transformative phase following the recent activation of U.S. Space Forces-Japan, a new command stationed at Yokota Air Base in Japan. Mastalir emphasized the strategic importance of alliances in the Indo-Pacific region 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 said.
The U.S. and Japan have agreed to include space within the scope of their mutual defense commitments. This means that attacks on satellites and other space-based infrastructure could trigger a collective defense response.
Collaboration on space domain awareness
At the core of the U.S.-Japan partnership is the enhancement of space domain awareness, or the capability for tracking and monitoring space objects. A joint initiative, the Quasi-Zenith Satellite System Hosted Payload (QZSS-HP) program, integrates U.S. optical sensor payloads, developed by MIT Lincoln Laboratory, into Japan’s QZSS infrastructure.
QZSS, often dubbed Japan’s version of GPS, employs geostationary satellites in inclined orbits to provide advanced navigation services across the Asia-Pacific region.
Two U.S. optical sensor payloads will be deployed aboard separate QZSS satellites, scheduled for launch in 2025 and 2026. These launches were delayed due to setbacks in Japan’s H3 rocket program.
Mastalir said these collaborations are likely to continue as China’s advanced satellite capabilities are a pressing concern for the U.S. and Japan. He highlighted the difficulties posed by Chinese spacecraft operating in non-Keplerian orbits, which deviate from classical orbital dynamics. Such orbits allow for continuous adjustments in trajectory, complicating traditional orbit determination and tracking methods.
“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 provide strategic advantages, enabling satellites to achieve precise positioning and adjust coverage dynamically. This flexibility is particularly valuable for surveillance and reconnaissance missions, allowing for enhanced monitoring of areas of strategic interest. By employing these techniques, China’s satellites gain the ability to evade tracking and improve their operational effectiveness.
Mastalir said Japan has been making substantial investments in both space-based and ground-based sensor systems to address these challenges.
The U.S.-Japan partnership is a critical element of the broader strategy to challenge what Mastalir referred to as “red” space — a term signifying the adversarial activities led by China.
“We must be prepared to ensure that we have the necessary awareness to counteract these threats,” Mastalir said.
