TOKYO — North Korea’s launch of a missile over Japanese territory for the second time in just over a decade put a spotlight on Japan’s emerging space policy and the possibility that Tokyo will seek to develop an independent space-based missile warning capability.

The April 5 test was described by North Korea as a successful satellite launch. However, U.S. government officials said the launch did not place anything into orbit and that the stages of the vehicle failed to separate as designed.

Just two days before the incident, Japan’s Strategic Headquarters for Space Policy (SHSP) issued a draft policy suggesting that national security will move to the top of the nation’s space agenda. Though the draft itself was vague, supporting documentation indicates a number of specific satellite capabilities are under discussion, including missile warning, improved surveillance and signals intelligence.

Both the creation of the cabinet-level SHSP and the finalizing of Japan’s so-called Fundamental Space Policy by the end of May 2009 were mandated by The Basic Law for Space Activities, passed by the Japanese parliament, or Diet, last May. That law lifted a longstanding Japanese ban on using space for military purposes.

Japanese Defense Minister Yasukazu Hamada, speaking at the Diet April 9, said Japan should consider developing an early warning satellite to monitor launches across its territory. Asked to clarify during a press conference the following day, Hamada hedged, saying talk of improving Japan’s nascent missile defense system is nothing new. “In terms of improving the credibility of Japan’s [missile defense system], early warning satellite capability is very important,” he said.

In an April 7 telephone interview, Kei Oguro, general affairs officer at the SHSP, declined to comment on any of the programs cited in the documents accompanying the draft policy. Decisions about whether and when to start them have yet to be made, he said. The draft policy will be superseded at the end of April by a more concrete set of proposals that will be opened for public comment, with the SHSP finalizing Japan’s Fundamental Space Policy by the end of May, he added.

Kazuto Suzuki, associate professor of international political economy at Hokkaido University and an expert on Japanese space policy, cautioned that the April 3 draft policy and supporting documents in no way represent the fixing of any programs or timetables. He said that while the release of the draft just before the missile launch was coincidental, the incident would “increase the rationale for early warning and strengthening missile defense.”

Planning documents accompanying the draft policy indicate Japan could launch two additional ground-surveillance satellites — one optical and one radar — as part of its Information Gathering Satellites (IGS) system currently on orbit. The new satellites would launch around 2016, the documents say. The infrared missile warning and signals intelligence satellites also would be launched around 2016.

The programs and timetables closely resemble those contained in national security space development guidelines issued in January by a high-level Ministry of Defense panel. Keiko Nakano, a ministry spokeswoman, declined to comment April 8.

An official with the Cabinet Satellite Intelligence Center, which manages the IGS system, urged caution regarding the possibility of launching additional IGS craft in 2016: “Please don’t even think of these as even at the proposal stage. They are only an image as yet,” the official said April 8.

The IGS system, approved following North Korea’s 1998 launch of a Taepodong-1 missile over Japanese territory, nominally consists of two optical and two radar imaging satellites. One of the radar satellites failed on orbit in 2007.

Constellation replenishment plans that have been confirmed by the Cabinet Satellite Intelligence Center include launches of additional optical satellites in 2009-2010, 2011 and 2014; and additional radar satellites in 2011 and 2012.

A satellite to test next-generation IGS technologies will be launched in 2012 but the official said he could not give details for security reasons.

A graduate of the Columbia Graduate School of Journalism, where he won the Horgan Prize for Excellence in Science Writing, Paul Kallender-Umezu is co-author of “In Defense of Japan: From the Market to the Military in Space Policy” (Stanford University...