When North Korea sent what it claims was a rocket carrying a satellite over the Tohoku region Sunday, the Self-Defense Forces units deployed to possibly intercept it held their fire because the craft apparently posed no threat to Japan's territory.

This leaves unanswered the question of how effective the country's ¥800 billion missile defense system is and what may be required to cope with future threats.

Following are questions and answers on how Japan responded to what it called a provocative missile test: