TOKYO — Japan is planning to expand its fleet of reconnaissance satellites as part of an effort to improve the nation’s monitoring of North Korea and the Chinese navy. The move comes as Japan strengthens its military ties with the United States.

A Nov. 11 report by the Space Policy Commission, Japan’s top decision-making body for space matters, recommends doubling the number of Intelligence Gathering Satellites (IGS) to eight satellites and launching two relay satellites to support the expanded constellation. Prime Minister Shinzo Abe’s government is expected to adopt the recommendations in December.

Japan established the IGS program following the 1998 flyover of a North Korean Taepodong missile that North Korea claimed was a satellite launch. Fourteen Mitsubishi Electric Corp.-built IGS satellites have been launched since 2003.

The constellation originally was designed to include two optical and two radar satellites with one on-orbit spare. The current IGS fleets consists of four optical and three radar satellites, one of which is serving as a spare.

The so-called Revised Basic Plan released Nov. 11 updates a plan announced in February recommending Japan “strengthen” its orbital surveillance and reconnaissance capabilities for land and maritime observation but the Space Policy Commission — which reports to Abe — had left the number of IGS satellites open for discussion.

The Revised Basic Plan confirms the increased importance of space assets in Japan’s national security, said Christopher W. Hughes, professor of international politics and Japanese studies, and an expert on Japan’s military, at England’s University of Warwick.

“We need to [view] Japan increasingly seriously as an important player in military space in East Asia,” he said.

Japan’s posture has evolved rapidly since Abe became prime minister in December 2012. A National Security Strategy released in December 2013 called for Japan’s space policy to be integrated into the nation’s military defense strategy and closely coordinated with the United States. In April, Japan and the U.S. updated joint defense guidelines for the first time in 17 years, agreeing to promote “seamless” cooperation while boosting Japan’s use of space in support of the U.S.-Japan Security Alliance. In July, Japan ended its ban on collective self-defense, freeing Japan to more readily support the United States if the U.S. comes under attack in a conflict in East Asia.

“Japan’s ambition to in essence double the number of its Information Gathering Satellites demonstrates its increasing seriousness about outer space as a key dimension of its overall reform and strengthening of its security stance,” Hughes said.

“The IGSs are…military in nature and will serve an important function of developing Japan’s [Intelligence Surveillance and Reconnaissance] capabilities to respond to Chinese activities in and around the disputed Senkaku/Diaoyu islands, and further reinforce Japan’s ability to offer space capabilities in the service of the U.S.-Japan alliance as pledged in the revised U.S.-Japan Defense Guidelines in April this year and made possible through the collective self-defense legislation in the early autumn,” he said.

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...