小型衛星群で探知能力向上　ミサイル防衛、米国と連携―防衛省

　防衛省は、日本や同盟国に向かうミサイルの探知・追尾など早期警戒能力向上のため、小型人工衛星群（コンステレーション）の導入検討に着手する。月内にも閣議決定する宇宙基本計画改定案に「米国との連携を踏まえ、必要な措置を講じる」と明示。小型衛星の打ち上げや地上局の整備を検討する。
　コンステレーションは多数の衛星が同じ軌道を周回する運用方式で、監視精度が高い。大型衛星に比べコストが低い上、１機が機能を失っても他の衛星が補完できることから、「対衛星兵器の攻撃からの脆弱（ぜいじゃく）性を克服する」（防衛省）メリットもある。
　ただ、実用化には先行する米国の協力が前提となるため、導入時期は未定だ。（2020/06/04-17:24）

The Defense Ministry plans to introduce a satellite constellation system to strengthen Japan's capabilities of detecting and tracking missiles heading for the country or the United States, its sole ally, it was learned Thursday.
   The plan is specified in a draft revision to the government's basic space policy plan. The draft was approved by the ruling Liberal Democratic Party the same day and is expected to gain cabinet approval later this month, informed sources said.
   The constellation system, in which many small missile warning satellites go around the same orbit, can track projectiles more accurately and is much less vulnerable to anti-satellite weapons attacks than a single satellite system, a ministry official said, adding that launching small satellites in a bundle is cheaper than sending a large one into orbit.
   Although the ministry is starting discussions on launching small satellites and setting up ground facilities, Japan cannot decide when to introduce the constellation satellite system until it obtains cooperation from the United States, which leads in the practical use of the system, people familiar with the matter said.
   The draft revision to the 10-year basic policy plan underscores the importance of enhancing space security and promoting Japan's space exploration with other countries.