Japan conducted its second launch of the year on Saturday, with an H-IIA rocket orbiting the second Advanced Land Observation Satellite, Daichi-2 – better known as ALOS-2. Liftoff from the iconic Tanegashima Space Centre was on schedule at 12:05 local time (03:05 UTC).
Daichi-2 (ALOS-2) is a radar imaging spacecraft which will be operated by the Japan Aerospace Exploration Agency (JAXA). Bound for sun-synchronous orbit, it is expected to be used for land and resource studies, disaster monitoring and environmental research.
The ALOS-2 mission follows on from the original ALOS, which was launched in 2006 and operated for five years until mid-May 2011. Unlike its predecessor, which carried both optical and radar imagery payloads, Daichi-2 will be used only for radar imaging.
An ALOS-3 spacecraft, which would have carried a suite of optical instruments, was proposed for a 2015 or 2016 launch, however the mission has not been funded.
Although the first ALOS mission operated for five years, exceeding both its three-year design life and the planned two-year extension to its mission, its primary optical imager was found to be defective and many of the images it produced were of lower quality than had been expected.
ALOS-2 is a 2,120 kilogram (4,670 lb) spacecraft, which is designed for five years of operation although JAXA hope to be able to extend this to seven years. The satellite is equipped with a pair of solar arrays, capable of generating at least 5.2 kilowatts of power – more earlier in the mission.
Two antennae will be used to return data to Earth; an X-band antenna for direct communications and a Ka-band transceiver which will relay data via the Kodama Data Relay Test Satellite, which was launched in 2002.
The primary instrument of Daichi-2 is the Phased Array L-band Synthetic Aperture Radar 2, or PALSAR-2.
An improved version of the PALSAR instrument on the original Daichi satellite, PALSAR-2 is a synthetic aperture radar operating in the l-band of the electromagnetic spectrum with a wavelength of 22.9 centimetres (9.02 in).
A carrier wave with a frequency between 1.24 and 1.28 gigahertz will be used, with the radar emitting between 1,500 and 3000 pulses per second.
The antenna, which measures 9.9 by 2.9 metres (32 by 9.5 feet), can provide strip mapping or a higher-resolution steerable spotlight beam which can be pointed to either side at an angle of up to 30 degrees. The instrument has a mass of 656.8 kilograms (1,448 lb), and can emit up to 6,100 watts of power.
In spotlight mode the satellite can produce images with an azimuthal resolution of 1 metre and a radial resolution of 3 metres (3 by 10 ft), while strip mapping can produce resolutions of between 3 and 10 metres (10-33 feet). In scanning mode the instrument can observe a 350 kilometre (217 mile) swath at a resolution of 100 metres (330 feet).
In addition to PALSAR, Daichi-2- is carrying the Compact Infrared Camera (CIRC). A technology demonstration payload, CIRC was built by Mitsubishi Electric using off-the-shelf components. Using an infrared microbolometer, the instrument will be used to detect wildfires.
A second, identical, instrument is planned for delivery to the International Space Station in the next year, for operation on the outside of Japan’s Kibo module.
The Space-Based Automatic Identification System Experiment 2 (SPAISE-2) payload consists of an Automatic Identification System (AIS) receiver, which will be used to collect and relay automated signals from ships at sea. The instrument, which follows on from the SPAISE experiment aboard Japan’s Small Demonstration Satellite 4 – which launched in 2012 – is capable of receiving four AIS messages simultaneously.
Four other satellites joined with ALOS-2 atop the H-IIA for its ride into orbit. The Space Research On Unique Technology (SPROUT) spacecraft is a 7.1 kilogram (16 lb) nanosatellite measuring 20 centimetres (7.9 in) along each side, built and operated by Nihon University.
The satellite carries the Inflatable Membrane Structure System, a triangular deployable structure measuring 1.5 metres (5 feet) in length. The satellite’s primary objective is to deploy this structure and subsequently use it as a passive deorbit device.
SPROUT also carries an amateur radio payload and a small camera to verify deployment of the membrane and subsequently take pictures of the Earth.
Tohoku University’s Raijin-2, meaning ‘Rising’, is a reflight of the SpriteSat-1 mission which was launched in 2009. That spacecraft, which was also known as Raijin, was lost early in its 2009 mission after an onboard computer malfunction left it unable to start or operate its instruments.
The fifty-kilogram (110 lb) satellite has a similar configuration to its predecessor and will be used to study electrical discharges in the upper atmosphere associated with thunderstorms.
The University International Formation Mission (UNIFORM), for Wakayama University is another fifty-kilogram satellite. The mission aims to monitor the Earth’s surface for signs of wildfires, and to relay data on these fires to emergency services in near-real-time. The satellite will use a combination of infrared and visible-light images to identify potential fires, which will then be verified from the ground.
The Space Optical Communications Research Advanced Technology Satellite (SOCRATES) satellite carries a laser communications experiment for Japan’s National Institute of Information and Communications Technology.
A 48-kilogram (106 lb) spacecraft, SOCRATES was built by Advanced Engineering Services. The primary objective of the mission is to validate the satellite bus, with operation of its Small Optical Transponder (SOTA) payload considered a secondary objective.
The rocket used to launch Daichi-2 and its secondary payloads was the H-IIA F24. The twenty-fourth H-IIA to fly, and the thirty-fifth overall mission for the H-II series, Saturday’s launch was conducted by Mitsubishi Heavy Industries, who also constructed the H-IIA.
The rocket flew in the 202 configuration, which is the most-flown version of the H-IIA. The core stages of the rocket use cryogenic propellant; liquid hydrogen oxidised by liquid oxygen.
The first stage is powered by an LE-7A engine, while an LE-5B is fitted to the second stage. A pair of SRB-A3 solid rocket motors will augment the first stage’s thrust at liftoff, before separating during the early stages of the mission.
The H-IIA was introduced in 2001, and has become the main rocket in Japan’s launch fleet. In addition to carrying payloads for JAXA and the Japanese military, in recent years it has begun to capture commercial launch contracts including one to carry Canada’s Telstar-12V next year and JSAT Corporation’s DSN-2 in 2017.
The H-IIA is able to fly in different configurations depending on payload requirements. Originally four configurations were available, differing in terms of the boosters attached to the first stage.
The 202 configuration uses a pair of SRB-A motors, with the 204 configuration featuring four SRB-As. The 2022 and 2024 variants also used two SRB-As while adding two or four Castor-4AXLs. The two versions using the American Castor motors have been retired, with only the 202 and 204 now available.
Since the last flight of the H-IIA 2024, which carried the Kizuna communications satellite in 2008, all H-IIA launches have used the 202 configuration – the only flight of the 204 to date was the December 2006 launch of Kiku 8. It is expected that the 204 will be used for the Telstar launch next year.
Like all H-IIA missions, F24 lifted off from Pad 1 of the Yoshinobu Launch Complex at Japan’s Tanegashima Space Centre. Constructed in the early 1990s to replace the nearby Osaka Launch Complex, Yoshinobu has been used by the entire H-II family of rockets, and is the only complex that these rockets have used.
The H-II made its maiden flight from Pad 1, then the only pad at the complex, in February 1992, beginning a series of seven launches over five years – the last of which used the H-IIS configuration with an improved second stage.
Due to cost and reliability concerns the H-II was retired from service in 1999, with its successor – the H-IIA – taking its place two years later. Around this time a second pad was added to the complex, however this remained unused until the maiden flight of the more powerful H-IIB in 2009.
Since then Pad 1 has been used exclusively by the H-IIA and Pad 2 exclusively by the H-IIB, although in theory the H-IIA can launch from either pad.
Rockets are assembled vertically in an integration building a few hundred metres northwest of the pads. The same facility is used for launches from both Pad 1 and Pad 2.
For Saturday’s launch, the rocket was transported to the launch pad Friday night, with approval being given at around 19:35 JST (10:35 UTC).
The H-IIA left its assembly facility at around 23:00 local time (14:00 UTC), with the rollout lasting around twenty five minutes. The terminal countdown began shortly after 02:30 local time (17:30 UTC on Friday).
The launch began with the first stage’s LE-7A engine igniting, followed shortly afterwards by the two solid rocket motors.
H-IIA F24 launched and climbed away from its pad, making a series of manoeuvres to attain the proper trajectory for its ascent towards sun-synchronous orbit.
First stage flight lasted six minutes and thirty-six seconds. Burnout of the two solid rocket motors occurred around 115 seconds into the flight, with the spent motors separating nine or ten seconds later leaving the first stage flying under its own power.
The payload fairing was jettisoned about four and a half minutes after liftoff.
Following the shutdown of the LE-7A at the end of first stage flight, the rocket coasted for twelve seconds, after which the depleted stage separated. Six seconds later the second stage fired its LE-5B engine for a single eight minute and twenty-four second burn.
Fifty seconds later Daichi-2 separated into its planned circular sun-synchronous orbit at an altitude of 628 kilometres (390 statute miles, 339 nautical miles).
A little under nine minutes after Daichi separated, deployment of the secondary payloads began. Raijin was the first to separate, about twenty five minutes after liftoff, with UNIFORM, SOCRATES and SPROUT following at four minute, ten second intervals.
Around thirty minutes after launch, Daichi-2 stabilised its attitude, deploy its solar arrays and orient itself towards the Sun. It remained in this configuration for around eight hours, after which the spacecraft reoriented itself towards the Earth. About thirteen hours after launch the process of deploying the PALSAR-2 instrument’s antennae will begin, lasting over twenty hours.
The two communications antennae will be deployed 37 and 47 hours into the mission, with the spacecraft entering its normal operational mode, under the control of its reaction wheels, around 51 hours after liftoff. Checkout and testing of the spacecraft and its instruments will then begin.
Saturday’s launch was the thirtieth orbital launch attempt of the year, after Friday’s surprise launch of three Russian Strela-3M communications satellites by a Rokot rocket.
That launch, which had been expected to occur no earlier than Sunday, appears to have been successful, with the three payloads taking on the designations Kosmos 2496 to 2498.
Japan’s launch was their second of 2014, following the launch of the GPM Core Observatory, also on an H-IIA 202, in late February.
It is unclear whether Japan plans to make any further launches this year; details of rumoured H-IIA missions carrying either a Himawari weather satellite or a military reconnaissance spacecraft have not yet materialised.
Japan’s next Kounotori mission to resupply the International Space Station is not scheduled to occur until next year.