H-IIA conducts IGS Optical 7 launch

by William Graham

Making its first flight in over a year, Mitsubishi Heavy Industries’ H-IIA rocket lifted off from the Tanegashima Space Centre on Sunday with a reconnaissance satellite for the Japanese government. Liftoff occurred at10:34 local time 01:34 UTC, during a five-minute launch window.

Sunday’s launch deployed the IGS Optical 7 satellite for the Cabinet Satellite Intelligence Centre, an agency of the Japanese government responsible for space-based surveillance. IGS Optical 7 is part of the Information Gathering Satellite (IGS) or Joho Shushu Eisei (JSE) system, consisting of spacecraft collecting optical and radar images of the Earth.

Japan began development of IGS in the late 1990s, following North Korea’s attempted satellite launch in 1998. Although the North Korean launch failed to reach orbit, the rocket carrying it crossed Japan during its ascent, sparking fears that North Korean missiles would be able to target the islands. With IGS, Japan aimed to develop an independent reconnaissance capability to monitor future threats. The constellation can also be used for disaster monitoring and other civilian applications by the Japanese government.

All of Japan’s IGS satellites have been launched on the country’s own H-IIA rocket. Optical 7 will be the eighteenth IGS spacecraft to launch – although this number includes two satellites that failed to reach orbit.

The first few satellites were launched in pairs, sharing a single rocket for their ride into orbit. The first pair, consisting of IGS Optical 1 and IGS Radar 1, were deployed in March 2003 during the fifth flight of the H-IIA. The rocket’s sixth flight, eight months later, ended in failure after one of the solid rocket motors failed to separate. The IGS Optical 2 and Radar 2 satellites were lost in the failure, however these designations were re-used for subsequent satellites.

The replacement IGS Optical 2 was launched on its own aboard the tenth H-IIA in September 2006, while its Radar counterpart flew as part of the penultimate IGS dual-launch the following February, accompanied by a prototype for the second generation of optical satellite. This was followed by two operational second-generation optical satellites, Optical 3 and 4, deployed on solo launches in November 2009 and September 2011. Five second-generation radar satellites – IGS Radar 3 to 6 plus an unnumbered spare, have launched between 2011 and 2018.

IGS Optical 7 is part of the third generation of IGS Optical satellites, the third such satellite to be launched. It follows on from the Optical 5 and 6 satellites, launched in March 2015 and February 2018 respectively, and the prototype – IGS Optical 5V – which preceded them.

IGS Radar Second Generation

IGS satellites are assembled by Mitsubishi Electric. Few details about the satellites have been made public, however the Optical component are believed to carry high-resolution imagers capable of producing pictures at resolutions of up to 40 centimetres (16 inches).

The IGS Optical 7 satellite rode to orbit aboard H-IIA F-41, the forty-first flight of Japan’s workhorse rocket, the H-IIA. Built and operated by Mitsubishi Heavy Industries, the H-IIA first flew in August 2001 and was developed as a more reliable and lower-cost successor to the earlier H-II. Instead of the two large solid rocket boosters that augmented the H-II, H-IIA uses two or four SRB-A3 motors to provide additional thrust depending on mission requirements. The rocket can operate in the 202 configuration – with two boosters – and the 204 configuration with four. The launch will use an H-IIA 202.

Two previous configurations, the 2022 and 2024, were intended to fill the gap in performance between the 202 and 204, respectively using two and four of the smaller Castor-4AXL boosters alongside a pair of SRB-A motors. With the introduction of the upgraded SRB-A3 motors in 2009 these configurations became obsolete and were retired.

The larger H-IIB was developed from the H-IIA using a widened version of the rocket’s first stage, with an additional engine, to allow heavier payloads such as the Kounotori H-II Transfer Vehicle (HTV) to be carried. Both rockets will be replaced by the new H-III currently under development, which is expected to make its maiden flight later this year or early next.

H-IIA launches take place from Pad 1 of the Yoshinobu Launch Complex, located at the Tanegashima Space Centre. The Yoshinobu complex consists of two launch pads – Pad 1 was originally built for the H-II and subsequently converted for use by H-IIA. The adjacent Pad 2 was built as a backup for the H-IIA but is instead used for H-IIB missions.

Tanegashima Space Centre – via JAXA

The launch complex also includes a vehicle assembly building (VAB) about 500 metres (550 yards) to the northwest where rockets are integrated atop a mobile launch platform. H-IIA F-41 was transported from the VAB to Pad 1 on Monday in preparation for a launch attempt on Tuesday, however a nitrogen leak in one of the umbilical lines connected to the rocket’s payload fairing led to a 24-hour delay.

Before liftoff, the two-stage H-IIA were loaded with liquid hydrogen and liquid oxygen – the cryogenic propellants that fuel its first and second stage engines.

The moment of launch for Japanese rockets is termed X-0 – equivalent to T-0 or H-0 in other countries. Two or three seconds before the countdown reaches this mark the LE-7A engine that powers H-IIA’s first stage ignited. AT X-0 the rocket’s two SRB-A3 motors ignited powering H-IIA F-41 away from its launch pad.

About 99 seconds after liftoff the two SRB-A3 boosters burned out, depleting their solid propellant. Nine seconds later their spent casings were jettisoned using hydraulic actuators at the base of the first stage. Under the power of its LE-7A engine the first stage burned for another five minutes after booster separation.

Shortly before the end of first stage flight, with H-IIA in space and above most of Earth’s atmosphere, the rocket’s payload fairing separated. This was the nose cone that encloses the IGS Optical 7 satellite during the first few minutes of the flight, protecting the satellite from aerodynamic forces as H-IIA ascended through the dense lower regions of the atmosphere. As soon as the fairing was no longer needed to protect the satellite, it was jettisoned to reduce the vehicle’s weight.

In all, H-IIA’s first stage burned for about six minutes and fifty seconds. After shutdown of its LE-7A engine the rocket coasted for about eight seconds before stage separation. Second stage ignition occurred about six seconds later, with the second stage firing its LE-5B engine for about eight minutes to place its payload into a sun-synchronous low Earth orbit.

H-IIA with IGS Radar 6 going through MaxQ

The launch marked the first launch of 2020 for Japan, and the first flight of an H-IIA since October 2018. Delays from the originally-scheduled date of 27 January have stretched this gap to just under 457 days, exceeding the previous longest gap between two H-IIA missions of 455 days, between the rocket’s November 2003 launch failure and its return to flight in February 2005.

Japan has not yet announced the next H-IIA launch – however several missions are on the books for 2020. These include a communications satellite intended to relay data from the IGS constellation, a replacement satellite for the QZSS navigation system, commercial launches of an Inmarsat-6 communications satellite and an Emirati Mars probe. The Mars launch is expected around the middle of the year when the relative positions of Earth and Mars facilitate optimal launch opportunities.

An H-IIB launch is slated for May, which will be the rocket’s last flight and will carry the Kounotori 9 resupply spacecraft bound for the International Space Station. JAXA aims to make the first launch of the new H-III rocket in the 2020 Financial Year, which runs from April until April 2021.

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