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Japan Investigates The Moon

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the Moon
The Moon
More than a third of a century has passed since the Apollo Program carried Americans to the Moon in 1969-1972. While those flights and the few subsequent unmanned probes have brought back much scientific data, they have not come close to answering all of the questions humans have about Earth's natural satellite.

Recently, the Moon has regained the attention of space engineers and scientists. They suggest that understanding the evolution of the Moon would help resolve important mysteries about Earth itself.

It is said that the Japanese people traditionally have felt very close to the Moon. Learning about its mysteries makes exploration an important challenge. Japanese space scientists want to revisit the Moon.

In recent years, Japan has developed a heavy-lifting rocket that will enable the island nation to conduct its own explorations of the Moon, planets and Sun.

The nation has sent a spacecraft that passed Mars and another that is on its way to an asteroid. Next, Japan will send two robot exploration missions to the Moon – LUNAR-A and SELENE. It also wants to send a probe to the planet Venus.

The Japanese daily newspaper Mainichi Shimbun said on February 28, 2005, that Japan Aerospace Exploration Agency (JAXA) is preparing a long-term space plan that would include constructing a research base on the Moon starting around 2025.


Artist concept of LUNAR-A over the Moon
Japan's LUNAR-A mooncraft
ISAS artist concept
The Japanese lunar penetrator mission, LUNAR-A, will be launched on an Mu-5 three-stage solid-fuel rocket from Kagoshima Space Center in an attempt to explore inside the Moon.

The launch has been delayed for technical and financial reasons until no earlier than 2006.

The 1,200-lb. craft will use seismometers and heat-flow probes installed in ground penetrators to study the lunar interior. Two penetrators will be deployed on the lunar surface – one on the nearside of the Moon and one on the farside.

LUNAR-A will fly into an elliptical orbit around the Moon with a low point 25 miles above the lunar surface. The penetrators will separate from the orbiter at the low points. It will take about two weeks to deploy correctly the two penetrators at the widely spaced sites.

The nearside penetrator will be located near the old Apollo 12 site or Apollo 14 site, allowing comparisons between LUNAR-A data and Apollo data. The farside penetrator will be positioned opposite that site on the back of the Moon.

Each penetrator is expected to penetrate to a depth of 3-6 feet, depending on the hardness of the surface they strike. From that depth in the lunar soil, the penetrators will transmit data on the strength and travel times of deep moonquakes reverberating from the nearside to the farside. That should reveal the size of the Moon's core, if it has one. Understanding the properties of the core is necessary to understanding the Moon's origins.

Data will be stored in a recorder in the penetrator to be transmitted up to the orbiter when it flies over every 15 days. The orbiter then will forward the data to Earth.

After releasing the penetrators, the orbiter will maneuver into a low circular path 125 miles above the lunar surface. From there, it will use its 100-ft. resolution, monochromatic camera to snap shots of subtle variations in the topography on the lunar surface near the terminator.

LUNAR-A is the first step in Japan's long-range plan to study seismology on all of the so-called terrestrial planets in the inner Solar System. Similar penetrators will be used to deploy seismometers on all of the terrestrial planets and their moons – Mercury, Venus and Mars.

Seismology on future lunar flights will be designed to bring a better understanding of the structure of the Moon's mantle and crust and what geologists call the "lunar dichotomy." Next up is the lunar surveyor SELENE.


Artist concept of SELENE in space
Japan's SELENE mooncraft
Tsukuba University artist concept
click to enlarge
SELENE is a lunar surveyor that Japan hopes to launch in 2008. The name is short for SELenological and ENgineering Explorer.

Larger and more complex than the earlier Japanese Moon probes, SELENE will be designed to:
  • explore the origin and evolution of the Moon
  • obtain data across the entire lunar surface to find ways of utilizing the Moon's resources
  • develop lunar orbital systems in preparation for continuous exploration of the Moon
The SELENE orbiter will have thirteen instruments including imagers, a radar sounder, laser altimeter, X-ray fluorescence spectrometer and gamma-ray spectrometer to study the origin, evolution, and tectonics of the Moon.

One of Japan's H-2A rockets will carry the 4,400-lb. spacecraft to space from the Tanegashima Space Center.

Three sats in one. SELENE actually will consist of three separate lunar satellites – the main orbiter, a small relay satellite, and a small Very Long Baseline Interferometry (VLBI) astronomy satellite called VRAD.
  • The orbiter is a rectangular box of scientific instruments. It is about 7 ft. by 14 ft. and weighs about 3,500 lbs. This main orbiter will travel around the Moon carrying out observations of the surface.

  • The relay satellite is shaped as a small octagonal prism and used to relay communications from the orbiter to Earth when the orbiter is out of sight on the far side of the Moon.

  • VRAD, the astronomy satellite, is shaped like the relay satellite and used to measure precisely the position, precession and shape of the Moon using the Very Long Baseline Interferometry technique.
SELENE will fly five days to reach the Moon. There, it will fly a long elliptical path around the Moon ranging from 75 miles out to 8,000 miles.

The relay satellite will be dropped off in a 62 x 1,500 mile orbit. The VLBI satellite will be released into a 62 x 500 mile orbit.

The main orbiter then will maneuver to a 62 mile circular orbit, from where it will observe the surface for a year.

JAXA project

LUNAR-A and SELENE have been projects of the Institute of Space and Astronautical Science (ISAS) and National Space Development Agency of Japan (NASDA). They now are projects of the Japan Aerospace Exploration Agency (JAXA), which was created in 2003 by the merger of ISAS, NASDA, and the National Aerospace Laboratory of Japan (NAL).

Japan's Institute of Space and Astronautical Science (ISAS) is a government-funded agency that focuses on science research in space. It has been affiliated with the Ministry of Education, Culture, Sports, Science and Technology, and now is part of JAXA.

NASDA focuses on applied uses of space. It has developed the series of powerful H-2 rockets that can lift payloads comparable to those carried by U.S., Soviet and European rockets. NASDA also is developing a small space shuttle. Japan's Science and Technology Agency, part of NASDA, develops communications and weather satellites. NASDA now is part of JAXA.

Both ISAS and NASDA have been carrying out interplanetary explorations and preparing for future manned space flights.


Japan's Hiten Moon probe
Japan's HITEN mooncraft
NASDA photo
In 1990, Japan sent its Muses-A robot science explorer into an Earth-Moon orbit. Later renamed Hiten, the unmanned explorer dropped off a miniature satellite called Hagoromo into lunar orbit as Hiten swung around the Moon.

The Hiten-Hagoromo dual satellite project was a practice operation for future interplanetary spaceflights. Its success led Japan to plan launches of a large satellite to orbit the Moon and flights to other planets of the Solar System.

Japan had been the fourth nation ever to send a satellite to Earth orbit. The Asian nation became the third country ever to send a spacecraft to the Moon when its Muses-A probe blasted off from Japan's Kagoshima Space Center on the southern island of Kyushu January 24, 1990.

After the spectacular night launch, the Muses-A spacecraft was renamed Hiten. It looped out from Earth and around the Moon. The 430-lb. mothership dropped off a miniature 26-lb. lunar satellite, Hagoromo, as it swung by the Moon in March 1990.

Hiten. The main spacecraft Hiten was a 430-lb., 5-ft.-diameter, 3-ft.-tall cylinder. Detachable from one end was the 26-lb. 1-ft.-tall miniature satellite Hagoromo.

Aboard the mothership was a West German micrometeorite counter from the Munich Technical University which recorded the weight, speed and direction of dust particles striking the craft. Both the large and small orbiters were built by NEC Corp., a major Japanese computer company, with government funding.

MU-3S-2 rocket. Muses-A rode to space atop an MU-3S-2 rocket built with government funds by car-maker Nissan Motor Co., Japan's second-largest automobile maker.

Nissan's aerospace division dates to 1953 and has had an important role in developing Japan's solid-fuel rocket engines. Development of the 92 ft. long, 5.5 ft. wide MU-3S-2 rocket began in 1980. It first flew in 1985. The three-stage, 62-ton MU-3S-2, not a particularly powerful rocket, was just strong enough to lift the 430-pound Muses-A payload.

Launch. There wasn't much publicity in Japan – the seemingly-momentous countdown wasn't live on television – however reporters flocked to a hillside some miles from the oceanside launch site to watch the blast off from Kagoshima Space Center.

Unfortunately, the countdown stopped at T-minus-18 seconds when an electrical switching problem cut off power to a hydraulic pump aiming the nozzle of an auxiliary booster rocket. It was the first time in five launches of the slender solid-fuel MU-3S-2 a countdown had to be stopped in the last 60 seconds.

Volcano dust. Winds had blown volcanic dust from the 3,668-ft. mountain, On-take, a nearby live volcano also known as Sakurajima. The grit blanketed much of the launch area, but engineers said the dust didn't cause the electrical problem.

Technicians, rushing that night to fix the red-and-silver solid-fuel space booster on Kagoshima's only launch pad, shivered as heaters in sheds and blockhouses were turned off to save electricity for launch equipment. Volunteers from nearby towns stood watch in red-and-black firefighter uniforms. Overcast skies blanketed the remote site and snow fell nearby as the rocket was ready to fly again. Amidst billowing clouds of smoke, it bounded into the night sky over the Pacific from its oceanside pad nestled between mountains.

Minutes later, the satellite separated from the rocket and was in a 250-mi.-high Earth orbit on an eight-week rendezvous with the Moon. After two circuits around the globe, solid-fuel rockets pushed the renamed Hiten out into a long oval orbit. NASA's Deep Space Network antennas at Tidbinbilla, Australia, and Goldstone, California helped the Japanese track Muses-A. They showed the satellite on its first day in space orbiting Earth out to a distance of 186,000 miles.

Navigating to the Moon. Earth's natural satellite orbits our planet every 27.322 days at an average distance of 238,861 miles. To navigate its course, the spacecraft looked at bright stars and the Moon's edge.

Hiten was in an elliptical orbit swinging farther out from Earth, coming closer to the Moon as time passed. The mothership arrived at the Moon on schedule on March 19, 1990, initiating Japan into the exclusive club of nations having spacecraft circling Earth's natural satellite. Only the U.S. and the USSR had done it before.

Swing-by. Traveling at 2,237 mph on an oblong path around Earth, Hiten reached two goals. It completed a swing-by of the Moon, using lunar gravity to boost its speed and enlarge its long elliptical orbit around Earth. And it disgorged the smaller basketball-sized satellite, Hagoromo, into orbit around the Moon.

A swing-by uses gravity to accelerate or decelerate a spacecraft's speed. It is a familiar technique used to boost a satellite's speed by taking advantage of the force of gravity from planets and the Sun. The method has been employed by a number of American deep space probes. The U.S. used it first when Mariner 10 flew by Venus in 1973 on its way to Mercury in 1974. The technique was used again by Japan in 1998 to send a probe toward Mars.

Bug's eyeball. Release of the 26-lb. satellite into orbit around the Moon showed great accuracy on the part of Japan's flight engineers. Kuninori Uesugi, chief scientist at Japan's Institute of Space and Astronautical Science, put it in baseball terms when he told reporters the success was like hitting the eyeball of a bug in the outfield from home base.

Hiten came within 9,100 miles of the Moon that day. It then continued to loop around the Moon and Earth eight times, four to speed up and four to slow down. Hiten means space flyer. The small satellite remains in orbit around the Moon. Neither Hiten nor Hagoromo were meant to land on the Moon.

The polyhedral-shaped tiny lunar orbiter is covered with solar cells to gather energy from the Sun and generate electricity. A tiny cross-shaped antenna allowed direct radio contact with controllers on Earth. The orbiter carried 11 of its 26 lbs. of weight in the "retro" motor it fired to move into orbit around the Moon. The small lunar satellite was designed to record temperatures and electrical fields around the Moon and radio the data to the mothership for relay to Earth.

Dead radio. A broken transistor radio caused Japan's space scientists to lose track of Hagoromo on March 19. Apparently Hagoromo's tiny rocket motor had fired on schedule to pull away from Hiten while the mothership was 12,500 miles from the Moon that day, but the small satellite's tracking transmitter failed immediately, leaving a record of rocket firing but no signal to track the location of the satellite. Fortunately, Japanese astronomers using large optical telescopes later were able to see Hagoromo orbiting the Moon.

Kuninori Uesugi, chief scientist at Japan's Institute of Space and Astronautical Science (ISAS), said a transistor in the satellite's radio must have failed.

Later on. Hiten continued on its long oval orbit, encompassing Earth and the Moon, collecting data on space dust and other phenomena. By its fifth fly-by of the Moon on August 6, 1990, Hiten was travelling out more than 600,000 miles from Earth.

Japanese scientists expected to maintain that 600,000-mi. apogee distance for the rest of the spacecraft's life. Among other jobs, Hiten was a test flight for a future mission called Geotail, part of an international Sun-Earth physics research project, that would fly a long elliptical orbit.

The Muses-A/Hiten/Hagoromo project, sponsored by ISAS, gave Japan valuable experience in targeting orbits and in the use of swing-bys to guide future spacecraft traveling to distant planets.

First since 1976. Muses-A Hiten added prestige to Japan's space program as it closed a 14-year era with no Moon missions from anywhere on Earth. Previously, only the U.S. and USSR had sent craft to the Moon. The last previous was the USSR's Luna 24 spacecraft with an unmanned rover which landed on the Moon in 1976.

From the earliest days of their space programs in the 1950's, the U.S. and the USSR had flung rockets at the Moon. Most memorable from those early days may have been the USSR's robot probe Luna 3 which radioed the first pictures of the dark side of the Moon in October 1959.

Later unmanned American probes, including a successful 1960's series of Surveyor automatic landers, led to six manned Apollo landings on the lunar surface from 1969 to 1972. Thirty USSR Luna and Zond spacecraft explored the Moon between 1959 and 1976 while Ranger, Surveyor and Lunar Orbiter probes explored the Moon for the U.S. in the 1960's.


Japan's first satellite was Ohsumi, launched February 11, 1970. Launch of Ohsumi made Japan the fourth nation capable of launching satellites to Earth orbit, after the USSR, the U.S. and France. Japan has launched dozens of spacecraft since 1970 with a third of the satellites still in operation.

Since then, Japan's space program has relied more on resourceful engineering than large budgets. At the time of his launch, Muses-A mission chief Hiroki Matsuo told reporters, "This time we are going to the Moon, but our objective is not the Moon itself. Our institute is getting into interplanetary missions in the 1990's and for that we need to refine our technology."

After the Muses-A success, Japan launched a spacecraft in 1998, called Planet-B or Nozomi, to carry out scientific studies at Mars. That launch made Japan the third nation ever to send a spacecraft to Mars.

Next, Japan launched MUSES-C in 2003, an interplanetary probe to fly 186 million miles across the Solar System to asteroid 1998-SF36 and return to Earth with a sample of the soil found there.
MUSES is short for Mu Space Engineering Spacecraft.
ISAS also launched a solar observation mission called Solar-B on September 22, 2006.

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