TOKYO ― Japan successfully launched its latest Information Gathering Satellite (IGS) reconnaissance satellite Feb. 1 aboard the 27th flight of its H-2A rocket, which blasted off from the Tanegashima Space Center at 10:21 local time.

The radar surveillance satellite is designed as an on-orbit backup to support the nominal constellation of four IGS satellites, comprising two optical and two radar satellites, Koshi Nitta, an official at the Cabinet Satellite Intelligence Center, which operates the IGS, told SpaceNews.

The launch continues a good run for the IGS, a top-priority national security space program that has been steadily replenished after a difficult start. The latest satellite is the sixth radar satellite launched for the constellation and 13th overall.

The Japanese government initiated the IGS program to give Japan an independent means to monitor North Korea following an August 1998 missile test that overflew Japan. The program has seen its troubles, however, including early on orbit failures and the 2003 H-2A rocket failure that destroyed a pair of replenishment satellites.

Mitsubishi Electric Corp. is the prime contractor on the IGS satellites, and the H-2A, which flew in its basic 202 configuration Feb. 1, is built by Mitsubishi Heavy Industries Corp.

Despite the failure of the IGS-Radar 2 satellite in summer 2010, just three and a half years into its mission, the current constellation now has four working satellites – two optical and two radar – with the latest launch offering some on-orbit insurance, Nitta said. The current fleet is the IGS-Optical 3 launched in November 2009, IGS-Optical 4 launched in September 2011, IGS-Radar 3 launched in December 2011 and IGS-Radar 4 launched in January 2013.

While the Japanese government does not disclose the IGS satellite capabilities, the optical and radar satellites now in orbit are believed to be able to resolve objects about 60 centimeters across and 1 meter across, respectively.

The constellation may still include a third-generation optical test satellite with 41-centimeter resolution that launched with IGS-Radar 4. A similar but operational version of that higher-resolution satellite is expected to launch in March or April.

Japan’s latest long-term space policy has funded steady replenishment of the constellation with increasingly capable satellites, which have a nominal five-year lifespan. Commitment to the program has been underscored by steady budget increases.

According to Japan’s third Basic Plan for space activity, released Jan. 9 by the Office of National Space Policy, Japan may expand the constellation to six or even eight satellites, although details have yet to be announced.

Currently the plan calls for launching optical satellites in 2016, 2019, 2021 and 2024 and additional radar satellites in calendar 2016, 2017, and 2021. In addition, at least one dedicated data relay satellite will be launched in 2019 to handle the data expected from the new satellites.

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...