A Japanese reconnaissance satellite rode to orbit Tuesday aboard the country’s H-IIA carrier rocket. Liftoff, from the Tanegashima Space Centre, occurred at the opening of a fourteen-minute window at 12:34 local time (04:34 UTC).
Tuesday’s launch deployed IGS Optical 6, part of the optical imaging component of Japan’s Joho Shushu Eisei (JSE) – or Information Gathering Satellites (IGS) constellation.
The IGS system consists of both optical and radar imaging satellites, with the programme led by Japan’s Cabinet Satellite Intelligence Centre. The project began in the late 1990s, after North Korea attempted to launch its first satellite – Kwangmyŏngsŏng-1 – with the rocket overflying Japan during its ascent. Although Kwangmyŏngsŏng-1 failed to achieve orbit, the launch demonstrated that North Korean missiles could reach Japan and prompted the Japanese government to step up monitoring of potential threats.
IGS Optical 6 is the fifteenth Information Gathering Satellite to launch – a number which includes two prototype optical imaging satellites, and a pair of spacecraft which were lost in a November 2003 launch failure. As of late last year, the operational IGS constellation was reported to consist of two optical satellites – launched in 2011 and 2015 – and four radar-imaging spacecraft.
The first two IGS satellites – Optical 1 and Radar 1 – were successfully launched together in March 2003 aboard a single H-IIA rocket. A repeat of this launch eight months later ended in failure when once of the H-IIA’s solid rocket boosters failed to separate, and the rocket was subsequently destroyed by range safety.
A replacement optical satellite – IGS Optical 2 – was deployed in 2006. IGS Radar 2 was launched in February 2007, sharing the journey to orbit with IGS Optical 3V – a prototype for a second generation of optical imaging missions. Optical 2 and Radar 2 were the last first-generation IGS satellites to launch.
The operational second-generation optical component of IGS consisted of IGS Optical 3 and 4, which were launched in November 2009 and September 2011 respectively. Radar satellites, Radar 3 and 4, were deployed in December 2011 and January 2013. These were joined by an on-orbit spare, launched in February 2015, to allow the system to continue operating should one of its satellites fail.
The optical constellation entered its third generation with the launch of IGS Optical 5 in March 2015 – following a prototype, IGS Optical 5V, which launched along with Radar 4 in 2013. The Optical 6 satellite that will launch Tuesday is the second operational third-generation satellite.
While the optical-imaging part of the IGS system has entered its third generation, the second-generation radar imaging satellites are still in use. An additional spacecraft, Radar 5, was deployed last March. All four second-generation radar satellites remain in service, as do the Optical 4 and Optical 5 spacecraft.
The IGS Optical 6 mission will provide Japan with high-resolution images to support both national security and civil government applications, including disaster monitoring. The third-generation optical satellites are reported to have an imaging resolution of around 40 centimeters (16 inches).
The Optical 6 spacecraft was constructed, like all IGS satellites, by Mitsubishi Electric. Its launch will be undertaken by Mitsubishi Heavy Industries, using an H-IIA rocket.
The H-IIA, which has been used for all IGS launches to date, is Japan’s workhorse rocket for deploying a varied array of missions into Earth orbit and beyond. First flown in 2001, the H-IIA was derived from the earlier H-II, with modifications intended to decrease its cost and improve its reliability.
H-IIA is a two-stage rocket, with both stages burning cryogenic propellant: liquid hydrogen oxidized by liquid oxygen. Depending on the payload and target orbit, two or four SRB-A3 solid rocket motors are used to provide additional thrust during the early stages of flight. On early launches a combination of SRB-A and Castor-4AXL motors were used. However, the upgrade from SRB-A to SRB-A3 rendered these obsolete.
The vehicle which performed Tuesday’s launch, H-IIA F38, flew in the 202 configuration, which uses two SRB-A3s. It was H-IIA’s thirty-eighth flight: 36 of the previous 37 launches have been successful. The only failure came on the rocket’s sixth flight – the dual-satellite IGS launch at the end of 2003 upon which one of the SRB-A motors failed to separate.
The launch took place from Pad 1 of the Yoshinobu Launch Complex at Japan’s Tanegashima Space Centre. The launch pad, which was originally built for the H-II, has supported all of the H-IIA’s launches. A second pad at the complex, which was built as a backup for the H-IIA, has been used instead by the larger H-IIB rocket.
H-IIA’s LE-7A first-stage engine ignited two or three seconds before the zero mark in Tuesday’s countdown – or X-0, as it is designated for Japanese launches. Once X-0 was reached, the two SRB-A3 boosters ignited, and H-IIA F38 began the climb to orbit.
The SRB-A3 motors burned for about 99 seconds. As they approached burnout, their thrust tailed off to the point that they no longer provided enough thrust to be useful to the mission. Nine seconds after burning out, the spent boosters were jettisoned by hydraulic actuators.
Late in first stage flight, H-IIA’s payload fairing separated from around the satellite at the nose of the vehicle. The first stage continued to burn until around the six-minute and fifty-second mark, by which point it will have exhausted its fuel supply and shut down its engine.
The first stage separates about eight seconds after cutoff. The second stage’s LE-5B engine ignites six seconds later, taking over powering the rocket towards orbit. This will make either a single burn – lasting around eight minutes – or two shorter burns, injecting the IGS Optical 6 spacecraft into sun-synchronous orbit. It appears the single burn option was taken, IGS Optical 6 then separated from the H-IIA.
Tuesday’s launch was the first of the year for the H-IIA. However, Japan has already conducted two launches in 2018 using its other rockets. An Epsilon vehicle deployed ASNARO-2 – another radar-imaging mission – in mid-January. At the beginning of February, a modified SS-520 sounding rocket was used to deploy a CubeSat – TRICOM-1R (since renamed Tasuki) – in a demonstration of small satellite launch capability.
It is not clear when Japan’s next orbital launch will take place. The next launch with a confirmed timeframe is that of Kounotori 7, or HTV-7, aboard an H-IIB rocket. A resupply mission to the International Space Station, this is currently targeting August.
Other launches that are expected to take place in 2018 using the H-IIA rocket include the deployments of the GOSAT-2 climate research satellite and of another IGS spacecraft – with a radar-imaging payload.