The Japanese have launched the centrepiece of the Global Precipitation Measurement constellation, an international partnership aimed at providing a worldwide map of precipitation levels. The GPM Core satellite will serve to provide a reference point with which the rest of the constellation’s data can be calibrated. The launch of the H-IIA rocket took place at 18:37 UTC from the Tanegashima Space Centre.
The Global Precipitation Measurement constellation is a joint venture between NASA and the Japan Aerospace Exploration Agency (JAXA), the Indian Space Research Organisation (ISRO), the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT), France’s Centre National d’Études Spatiales (CNES) and the United States National Oceanic and Atmospheric Administration (NOAA).
In addition to the GPM Core spacecraft, the GPM constellation consists of nine other spacecraft with four more awaiting launch. The operational fleet consists of satellites from all of the participating organisations.
The NOAA’s three most recently launched civilian low-orbit weather satellites; NOAA-18, NOAA-19 and Suomi NPP, form part of the GPM constellation. The NOAA also contributes data from two Defense Meteorological Satellite Program (DMSP) satellites, USA-191 and USA-210, which they operate on behalf of the Department of Defense.
NOAA-18, which was named NOAA-N at the time of launch, was launched in May 2005. NOAA-19, formerly NOAA-N’, followed it into orbit in February 2009 despite an accident which required the spacecraft to be rebuilt after falling off a tilt platform during ground testing.
The final two TIROS satellites in the NOAA’s Polar-orbiting Operational Environmental Satellite (POES) system, both spacecraft are based around the TIROS-N bus and are the primary vehicles in the NOAA’s low-orbit civilian weather forecasting fleet.
The Suomi satellite was deployed into orbit in October 2011; built as a technology demonstrator for the National Polar orbiting Operational Environmental Satellite System (NPOESS) programme, the spacecraft was placed into service as a gapfiller after NPOESS was cancelled in 2010. All three satellites were launched from Vandenberg Air Force Base by Delta II rockets.
Suomi will be followed by the Joint Polar Satellite System (JPSS), of which the first satellite is scheduled for launch in 2016 or 2017. JPSS-1, which is based on Suomi, will join the GPM constellation upon its entry into service.
The two DMSP satellites were deployed by larger rockets; USA-191 – which is also known as DMSP-5D3 F-17 – was orbited by a Delta IV Medium in November 2006 and USA-210, or DMSP-5D3 F-18, flew atop an Atlas V 401 in October 2009. Two further DMSP satellites will join the constellation once they are launched; DMSP-5D3 F-19 will ride an Atlas V into orbit later this year, while F-20 is slated to launch in 2020.
CNES and ISRO contribute their joint Megha-Tropiques satellite, launched by a PSLV in October 2011, while the pan-European EUMETSAT provides data from its MetOp-B satellite which was launched aboard a Soyuz rocket in September 2012. MetOp-C, slated for a 2017 launch from Kourou, will also form part of the Global Precipitation Mission.
The GPM Core spacecraft itself is a joint venture between JAXA and NASA; the two agencies have previously collaborated on several other space missions, including the Tropical Rainfall Measuring Mission (TRMM). After over sixteen years in orbit TRMM remains operational and continues to return useful scientific data.
The satellite, which was launched on the last successful flight of the original H-II in 1997, also forms part of the GPM constellation.
The final GPM satellite is JAXA’s Shizuki, or GCOM-W1, satellite; launched in May 2012 atop an H-IIA. Such a large fleet of satellites allows measurements to be taken at every point on the Earth several times in one day; NASA aims to produce global precipitation maps updated every three hours.
The GPM Core Observatory carries two instruments which will add to the suite already carried by the other GPM satellites. The GPM Microwave Imager (GMI), a microwave radiometer, was manufactured by Ball Aerospace and consists of a 1.2 metre (3.9-foot) antenna with sensors to measure radiation flux at thirteen different wavelengths.
Following on from the TRMM Microwave Imager (TMI) aboard the Tropical Rainfall Measuring Mission, itself derived from the Special Sensor Microwave Imagers (SSM/I) flown aboard several DMSP satellites, GMI will cover a greater range of frequencies, extending much further towards the higher-frequency end of the spectrum.
The Dual-frequency Precipitation Radar (DPR) is GPM Core’s JAXA-sponsored instrument. Built by NEC Toshiba Space Systems, DPR will transmit pulses at two wavelengths and measure how much of each pulse is reflected back. By studying the difference in reflection at the two different wavelengths, JAXA hope to be able to characterise the size and nature of the particles of precipitation.
DPR will broadcast 1.67 microsecond pulses at a frequency of 13.6 gigahertz via its 1.013 kilowatt Ku-band transmitter. The 146 watt Ka-band transmitter will operate at a frequency of 35.5 gigahertz, broadcasting pulses 1.67 and 3.23 microseconds in duration.
Both instruments will be able to provide data with a resolution of five kilometres (3 miles); the Ku-band payload will cover a 245 kilometre (152 mile) swath of land, while Ka-band will cover a swath of 120 kilometres (75 miles). By comparison, GMI covers a swath of 885 kilometres (550 miles).
In total, the GPM Core satellite has a mass of 3,850 kilograms, or 8,500 pounds. Designed for a minimum of three years’ service, it has been fuelled to ensure that it can remain operational until at least 2019. Twin solar arrays power the spacecraft, providing it with around 1.9 kilowatts.
NASA’s Goddard Space Flight Center was responsible for the construction of the satellite, which was built in-house. Goddard will also operate the satellite and manage its mission.
In addition to GPM-Core, seven smaller satellites were carried aboard the H-IIA as secondary payloads.
Ginrei, also known as ShindaiSat, is a 35 kilogram (77 lb) spacecraft developed by Shinshu University to demonstrate bidirectional optical communications. The spacecraft will use light-emitting diodes amplified by parabolic mirrors to transmit signals optically, while an 80 millimetre (3.2 inch) lens will be used to receive signals from the ground. As a backup, the satellite carries a radio communications system.
Ginrei has a cuboid shape, measuring 40 centimetres in two axes and 45 centimetres in the third (16 by 18 inches). It is solar powered, with body-mounted panels generating up to 24 watts each. At peak consumption, the spacecraft requires 126 watts of power to operate. To ensure the correct orientation for visual communications, the satellite is three-axis stabilised.
The Interactive Satellite for Art and Design Experimental Research (INVADAR) was built by Tama Art University. It is the first satellite to launch as part of Tama University’s ArtSat programme, aimed at using satellites for artistic projects. The satellite is equipped with a 22.5 kilopixel camera for Earth imaging and sensors to return telemetry which the spacecraft’s operators claim will be useful for art projects.
INVADAR is slightly larger than a single-unit CubeSat – with two sides of 10 centimetres and one of 12 cm (3.9 and 4.7 in) – and has a mass of a 1.8 kilograms (4.0 pounds). It is expected to operate for 190 days, returning data via amateur radio transmissions.
Kagoshima University’s KSAT-2 is a single unit CubeSat aimed at conducting basic weather research, studying the locations of rainfall and tornadoes in the atmosphere and conducting radar imagery with a Ku-band system. The spacecraft is also to be used for a series of tracking and orbit-determination experiments, and will demonstrate deployment of a miniaturised boom for CubeSat experiments.
KSAT-2 is a replacement for the original KSAT satellite, also known as Hayato. Carried as a secondary payload on the May 2010 launch of Akatsuki, Hayato failed to establish communications with its controllers after separation. It decayed from orbit in July 2010, having never been heard from. Kagoshima University are hopeful that the reflight will be more successful.
Osaka Prefecture University Satellite (OPUSAT), built by the Osaka Prefecture University, is a technology demonstration satellite. Built to the single-unit CubeSat standard, OPUSAT will be used to test the use of a lithium-ion capacitor in addition to its battery, a move which is hoped to provide more power to the spacecraft’s systems and allow the batteries to drain more thoroughly.
The Space Tethered Autonomous Robotic Satellite II, or STARS-II, follows on from the STARS-I satellite launched in 2009. Consisting of two separate spacecraft units joined by a tether, STARS will test deployment of its tether in space. The daughter satellite, which is slightly smaller than the parent satellite, will produce images of the tether deployment.
Undeployed, STARS measures 16 by 16 by 41 centimetres (6 by 6 by 16 in). The mother satellite is 25 centimetres (9.8 inches) in length with a mass of 5 kilograms (11 pounds) while the daughter satellite measures 16 cm (6 in) long and has a mass of 4 kg (9 lb). The satellite will be operated by Kagawa University.
Teikyou University’s bioscience satellite, TeikyoSat-3, has a mass of 20 kilograms (44 lb), and is intended to study mould growth in space. A sample of dictyostelium discoideum will be grown and scientists at the university hope to be able to study how microgravity and radiation levels in low earth orbit affect the mould throughout its lifecycle.
Yui, also known as Imagine The Future 1 (ITF-1), is a single-unit CubeSat from the University of Tsukuba. The primary goal of the mission is to establish a worldwide network of amateur radio operators returning telemetry from the satellite.
Two technology demonstration payloads are also aboard Yui, testing a microprocessor which makes use of a new type of radiation-proofed memory and a tiny antenna printed on a circuit board measuring less than two by one centimetres (0.39 x 0.79 in).
The launch of GPM Core was conducted by Japan’s Mitsubishi Heavy Industries (MHI). Japan’s largest aerospace and defence contractor, MHI manufactures the H-II family of rockets for JAXA and has been responsible for conducting H-IIA launches since 2007 – taking over launches of the more powerful H-IIB as well last year. MHI’s first H-IIA launch was flight 13, which successfully deployed JAXA’s Kaguya spacecraft bound for the Moon.
Almost all of Mitsubishi’s launches to date have been for the Japanese government. Japan has never conducted a dedicated commercial launch, although a commercial payload – South Korea’s Arirang-3, was carried using excess capacity on the launch of GCOM-W1 in 2012.
Last year MHI signed a contract with Canada’s Telesat to deploy the Telstar 12V satellite using an H-IIA in 2015.
The H-IIA is Japan’s first successful indigenous liquid-fuelled rocket. Derived from the short-lived H-II, it was intended to provide cheaper and more reliable access to space over its predecessor. Prior to the H-II, Japan had relied on license-built American components combined with Japanese technology; the N-I and H-I consisted of Thor boosters with Japanese upper stages, while the N-II was essentially a Thor-Delta.
The H-IIA is a two-stage rocket, fuelled by cryogenic propellants: liquid hydrogen and liquid oxygen. The first stage is powered by a single LE-7A engine, while the second stage makes use of an LE-5B. Several solid rocket motors are attached to the first stage to augment its thrust at liftoff.
Four H-IIA configurations – differing in terms of the number and type of solid rocket boosters used – have flown. All four configurations feature at least two SRB-A motors, with more recent flights making use of the upgraded SRB-A3.
The 2022 and 2024 configurations each made use of two SRB-As, with an additional two or four Castor-4AXL motors respectively. The 202 configuration, which will be used for Friday’s launch, has just a pair of SRB-As, while the H-IIA 204 is the most powerful variant with four SRB-As. The Castor-powered variants are no longer in service.
The flightplan for Friday’s launch – which was designated flight number 23 or H-IIA F-23 – called for liftoff during a one-hour window, with the LE-7A engine igniting first followed by the solids. After liftoff, the rocket performed a series of manoeuvres to attain the necessary attitude for its ascent to orbit.
The two SRB-A3 motors burned for 99 seconds before their chamber pressure dropped below the point at which they are producing meaningful thrust. Nine seconds later the spent motors were jettisoned.
Four minutes and five seconds into flight, with the rocket at an altitude of 230 kilometres (143 miles, 124 nmi) the H-IIA’s payload fairing separated from around its passengers.
The first stage engine burned for six minutes and fifty seconds, propelling the rocket to a velocity of 5 kilometres per second (11,000 mph). Eight seconds after Main Engine Cutoff occurred, the second stage separated. Igniting six seconds after staging, the second stage made a single, eight minute and eight second, burn to place GPM Core into its planned deployment orbit.
Spacecraft separation occurred between 51 and 68 seconds after the end of powered flight. Ten minutes later GPM Core deployed its solar arrays. The satellite will operate in a circular orbit at an altitude of 407 kilometres (253 mi, 220 nmi), although the initial deployment orbit will be a little below this.
Friday’s launch took place from Pad 1 of the Yoshinobu Launch Complex at the Tanegashima Space Centre. The most northerly launch complex at Tanegashima, Yoshinobu is the only one which continues to be used for orbital launches.
Pad 1 was built for the H-II during the 1990s with a second pad being added as a backup for the H-IIA during the 2000s. Most of the H-II era hardware, including the pad’s tower, has since been removed from Pad 1; Pad 2 was built as a clean pad from the ground up. In practise, Pad 1 is used for all H-IIA launches, while Pad 2 serves the larger H-IIB.
The launch of H-IIA F-23 was the thirtieth launch from Pad 1, and the thirty-fourth overall from the Yoshinobu complex. It also marked the twenty-third flight of the H-IIA, and the first Japanese launch of 2014.
The next Japanese launch is scheduled for no earlier than April, with an H-IIA deploying the second Advanced Land Observing Satellite, Daichi-2.
An H-IIB launch carrying the fifth H-II Transfer Vehicle to the International Space Station is planned for July, with H-IIA launches later in the year expected to carry the Himawari-8 weather satellite, the Hayabusa-2 spacecraft bound for asteroid (162173) 1999 JU3, and potentially one or more reconnaissance satellites. No launches of Japan’s smaller Epsilon rocket are planned this year.