One of the world’s most reliable launch vehicles—the Japanese H-IIA—has further cemented its credentials by delivering an ambitious mission into orbit to monitor Earth’s precipitation levels in unparalleled depth. The H-IIA lifted off at 3:37:00 a.m. JST Friday, 28 February (1:37:00 p.m. EST Thursday, 27 February) from the Tanegashima Space Centre, situated on the Pacific coastline of southeastern Tanegashima, one of the Ōsumi islands of southern Japan. Less than 24 minutes after launch, the Global Precipitation Measurement (GPM) Core Observatory had been inserted perfectly into an orbit of 253 miles (407 km), where it will observe the two-dimensional and three-dimensional structure of our planet’s precipitation patterns. It will produce a single, comprehensive data set every 2-3 hours and provide a new calibration standard for a “constellation” of international weather-watching missions. In doing so, it forms part of an effort to accurately measure rainfall and snowfall on a global scale and better understand the impact of extreme weather and provide more effective responses to natural disasters. Efforts to prepare for tonight’s mission have been ongoing at Tanegashima for several weeks. Last month, the components for the two-stage H-IIA vehicle arrived at the launch site for final processing, and on 13 February the GPM Core Observatory was encapsulated within its payload fairing, ahead of integration with the rocket. Final activities and checks were completed on 16 February, and the payload was transferred to the Vehicle Assembly Building (VAB) for attachment to the H-IIA on the 18th.
Built by Mitsubishi Heavy Industries, the H-IIA is one of the most reliable launch vehicles in the world. Its 95-percent success rate—with 21 successful flights and one failure since its maiden voyage in August 2001—positions it favorably in the same league as United Launch Alliance’s (ULA) Atlas V and Europe’s Ariane 5. Standing 173 feet (53 meters) tall, the two-stage rocket can deliver up to 33,000 pounds (15,000 kg) into low-Earth orbit and up to 13,227 pounds (6,000 kg) into geostationary transfer orbit. Over the last decade, it has lofted numerous payloads, most notably Japan’s Selenological and Engineering Explorer (SELENE) lunar orbiter in September 2007 and the Planet-C mission to Venus in May 2010.
About 12 hours ahead of tonight’s launch, the first of three major “Go/No-Go” decision polls were taken and the H-IIA was transferred 1,600 feet (500 meters) from the assembly building to the pad, arriving at its final Earthly destination at 9:32 p.m. JST (7:32 a.m. EST) Thursday. Technicians immediately began the process of loading liquid oxygen and hydrogen propellants into the rocket’s cryogenic first and second stages, and by 10:50 p.m. JST (8:50 a.m. EST) the stack was fully-fueled. In addition to the two stages, the rocket was powered uphill by two Solid Rocket Boosters (SRBs), which provided 81 percent of its propulsive yield. After fueling, radio frequency checks and attitude-control system tests were undertaken and at 2:38 a.m. JST Friday (12:38 p.m. EST Thursday), the X-60 minute poll produced a unanimous “Go” to press ahead with the Terminal Countdown. With weather and all stations declaring their status as “Green,” the countdown ran near-flawlessly, tracking a liftoff at 3:37 a.m. JST Friday (1:37 p.m. EST Thursday).
Nine minutes before launch, the GPM Core Observatory was transitioned to internal battery power, which would keep it alive until the deployment of its solar arrays in orbit. At 3:32:30 a.m. JST Friday (1:32:30 p.m. EST Thursday), with four minutes and 30 seconds remaining on the countdown clock, the “autosequencer” was activated and the final series of status checks were conducted, including verifying that the first and second stages were at their proper flight pressures and all systems were placed on internal power. At X-1 minute, the water deluge system flooded the launch pad in order to protect its infrastructure and provide acoustic dampening. At 30 seconds, the rocket’s on-board ordnance was armed and the guidance system transitioned to Flight Mode.
The launch sequence got underway with the ignition of the single LE-7A staged combustin engine of the H-IIA’s first stage, which roared to life at 3:36:55 a.m. JST Friday (1:36:55 p.m. EST Thursday). It subsequently progressed through five seconds of computer-controlled health checks, building up to full power. Then, at 3:37:00 a.m. JST Friday (1:37:00 p.m. EST Thursday), the two side-mounted SRBs were ignited and the H-IIA left the pad with a total propulsive yield of about 1.25 million pounds (570,840 kg). Shortly after clearing the tower, the rocket began a pitch, roll, and yaw program maneuver to establish itself onto the correct flight azimuth for the insertion of the GPM Core Observatory into orbit. Following a south-easterly course, heading out over the Pacific Ocean, the H-IIA burst through the sound barrier about 60 seconds after liftoff and experienced maximum aerodynamic pressure (colloquially dubbed “Max Q”) on its airframe.
By the time the SRBs burned out and separated, after 108 seconds, the vehicle was already at an altitude of about 29 miles (47 km). At this stage, it was traveling at 3,350 mph (5,400 km/h). The LE-7A continued the push toward space, finally burning out, as planned, at 396 seconds after launch, establishing the proper conditions for the ignition of the second stage’s restartable LE-5B engine. By this point, the H-IIA had attained an altitude of 143 miles (230 km) and a velocity of close to 11,200 mph (18,000 km/h). With a total thrust of 30,800 pounds (13,970 kg), the LE-7B picked up the baton and fired for more than eight minutes to complete the delivery of the GPM Core Observatory into orbit. The satellite was released into free flight at 3:52 a.m. JST Friday (1:52 p.m. EST Thursday), about 15 minutes after launch, and shortly thereafter ground stations confirmed receipt of data which indicated that it was healthy and running on battery power, ahead of the deployment of its solar arrays.
The GPM Core Observatory is a joint venture between NASA—whose Goddard Space Flight Center of Greenbelt, Md., built the spacecraft—and the Japan Aerospace Exploration Agency (JAXA), which has supplied one of its two scientific instruments. It will also feature collaboration with the Department of Defense’s Defense Meteorological Satellite Program (DMSP), the National Oceanic and Atmospheric Administration (NOAA), the Indian Space Research Organisation (ISRO), the European Organisation for the Exploitation of Meteorological Satellites, and the Centre National d’Etudes Spatiales (the French National Space Centre, CNES). The GPM Core Observatory is an integral component of NASA’s Earth Systemic Missions program and will work as part of a network of satellites to provide full global coverage and assist with ongoing research into the processes of climate change, the forecasting of extreme weather events, and the addition of new capabilities to benefit society as a whole.
One of the satellites involved in the project is the highly successful Tropical Rainfall Monitoring Mission (TRMM), another joint NASA-JAXA venture, launched from Tanegashima in November 1997 to examine rainfall in the tropics. Still operational today, TRMM employs radar and visible, infrared, and microwave imaging sensors to monitor storm structures and lightning and provide data on the intensity and distribution of rainfall, together with energy levels in the atmosphere and at Earth’s surface. Working together with TRMM and several other missions—including the 2011-launched Suomi National Polar-Orbiting Partnership (NPP) satellite—the GPM Core Observatory will extend their capabilities by operating at much higher latitudes and with much higher resolution. It will operate at an orbital inclination of 65 degrees, which enables it to cover the globe from the Arctic to the Antarctic Circles. Consequently, it will study precipitation levels across this broad expanse of latitude and observe changing storm and weather systems by day and night.
In fact, TRMM research highlighted the importance of taking measurements at different times of day in order to improve the accuracy of weather systems and hurricane monitoring in real time. According to Michael Freilich, director of NASA’s Earth Sciences Division at the agency’s Washington, D.C., headquarters, the GPM mission is “vitally important for environmental research and weather forecasting.” Responding to natural disasters, added JAXA’s executive director, Shizuo Yamamato, could also aid Asian countries hit by devastating floods, through the provision of data for advanced alert systems. “Knowing rain and snow amounts accurately over the whole globe is critical to understanding how weather and climate impact agriculture, fresh water availability and responses to natural disasters,” Freilich explained.
Key to this capability is the GPM Core Observatory’s Dual-Frequency Precipitation Radar (DPR). Provided by JAXA, this instrument will produce three-dimensional maps of storm structures across its swath, including the intensity of rainfall and snowfall at the surface. Operating at two frequencies—Ku-band and Ka-band—it will allow meteorologists to estimate the size of precipitation particles and detect a wide range of rainfall and snowfall rates. The Ku-band element will cover a swath of 152 miles (245 km), whilst its Ka-band counterpart covers 74.5 miles (120 km). A second instrument, the GPM Microwave Imager (GMI), has been built by Ball Aerospace, under contract to NASA-Goddard, and will provide passive sensing of the microwave energy emitted by the atmosphere at 13 different frequency/polarization channels. This is expected to permit the construction of quantitative maps of precipitation across a 550-mile (885-km) swath.
The size of a small private jet, the GPM Core Observatory is the largest satellite ever built at NASA-Goddard. Following extensive thermal vacuum chamber tests and solar array deployment tests, it was transferred to Joint Base Andrews in Prince George’s County, Md., whereupon it was loaded aboard a U.S. Air Force C-5 transport aircraft for delivery to Japan. On 21 November 2013, the C-5 left Joint Base Andrews for the 7,300-mile (11,750-km) journey. Crossing the continental United States and performing a refueling stop in Anchorage, Alaska, the aircraft continued across the Pacific Ocean and touched down at Kitakyushu Airport, about 600 miles (960 km) southwest of Tokyo, on 24 November. The GPM Core Observatory was then delivered by cargo ship from the airport to the Tanegashima Space Centre. Shortly after its arrival at the launch site, the satellite underwent a Comprehensive Performance Test (CPT) in December 2013, which involved end-to-end testing of its 30 systems. Spacecraft alignments, including measurements of the GPM Core Observatory’s star trackers and thrusters, continued into January.
Following two months of inaugural checkout, the satellite will begin full science operations by the end of April. Its data will be downlinked through the Tracking and Data Relay Satellite System (TDRSS) to NASA-Goddard’s Precipitation Processing Center in Greenbelt, Md. This mission promises to pay huge dividends in our understanding of global precipitation, permitting improved knowledge of Earth’s water cycle and its link to climate change. Moreover, it will offer new insights into the monitoring and prediction of hurricanes and other extreme weather events, helping to respond to natural disasters, as well as offering a capability for better agricultural crop forecasting and freshwater resource monitoring.