Japan Exploring Our Solar System . . .

MUSES-A Hiten and Hagoromo at the Moon

Satellites     Rockets     Surveying the Moon     Exploring Planets

Japan's interplanetary probe Nozomi arrives at Mars in 2004 in a NASDA artist's view. Japan's lunar satellite MUSES-A orbited the Moon in 1990.
Japan sent the Muses-A science explorer, later renamed Hiten, around the Moon in 1990, dropping off the miniature lunar satellite Hagoromo as it swung by. At the time, the dual satellite was said to be practice for future interplanetary spaceflights.

Japan, the fourth nation ever to send a satellite to Earth orbit, became the third nation 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 robot science explorer 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.

Japan fired the Muses-A dual satellite to practice for future interplanetary spaceflights including probes to Mars and asteroids. [see: MUSES-C]

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.

Nissan 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 dated to 1953 and 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.

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.

Snowy night. 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.

Lunar distance. The Moon orbits Earth 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 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.

Traveling at 2,237 mph on an oblong path around Earth, Hiten reached two goals: it did 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.

Gravity assist. A swing-by uses gravity to accelerate or decelerate a spacecraft's speed. The familiar technique has been employed by a number of American deep space probes.

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 will remain in orbit around the Moon. Neither Hiten nor Hagoromo were meant to land on the Moon.

Tiny craft. 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 allows 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.

ISAS. The Muses-A/Hiten/Hagoromo project was sponsored by Japan's government-funded Institute of Space and Astronautical Science (ISAS). Affiliated with the Education Ministry, ISAS focuses on science research in space.

Japan's other space agency, the National Space Development Agency (NASDA), focuses on applied uses of space. At the time, NASDA was developing a small space shuttle and a powerful all-Japanese H-2 rocket to lift payloads comparable to those carried by U.S., Soviet and European rockets. The H-2 was expected to lift two tons to orbit later in the 1990's. Japan's Science and Technology Agency, part of NASDA, developed communications and weather satellites.

The 1,210-lb. CS-3a and CS-3b communications satellites, launched in 1988, had been the largest satellites NASDA had sent to space so far.

Interplanetary future. Both ISAS and NASDA were preparing for future manned space flights and interplanetary travel. The Muses-A mission gave Japan valuable experience in targeting orbits and in the use of swing-bys to guide future spacecraft traveling to distant planets.

Japan had made a late start in space work under restrictions at the end of World War II and had been using technology from the U.S. It had low space budgets, spending only $1.06 billion for space projects the year before.

Building a respectable launch record, Japan enjoyed a 100 percent success rate with its smaller N-series rockets and nearly 100 percent success with its larger H-1 rockets. NASDA had its first failure in 20 launches in August 1989 when the first stage of an H-1 rocket failed to ignite.

Launch sites. The country also had a shortage of good launch sites. Kagoshima Space Center is at the southern tip of Japan. Rockets were fired toward space from a pad on small Tanegashima Island offshore. Japan had made two dozen launches since 1975 from Tanegashima Island.

The Uchinoura pad at Kagoshima Space Center and the pad on Tanagashima Island, Japan's two launch sites, were very small when compared with space centers in other nations. Because tuna fishermen near the center complained that blastoffs were dangerous, launches were permitted in a 90-day period each year — 45 days in January-February and 45 days in August.

Kagoshima. Kyushu, a mountainous island with famous peaks rising to 6,500 ft., is southernmost of the four main islands of Japan. One prefecture in Kyushu is Kagoshima whose two million people mostly are foresters and coastal fishermen.

The ancient seaport city of Kagoshima is a well-protected harbor on the the west coast of Kagoshima Bay, a deep inlet on the southern coast of Kyushu. For centuries, Kagoshima was the castle city of a powerful daimyo of the Satsuma clan.

The city was bombarded by British warships in 1863, destroyed by fire in 1877, damaged by eruption of the volcano On-take on an island in the bay in 1914, and bombed from June to August 1945 by planes of the Allies in World War II. Today the city, with a population of half a million, is best known for its Satsuma ware.

Ohsumi. 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.

Since then, Japan's space program has relied more on resourceful engineering than large budgets. 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." At that time, Japan had launched four dozen spacecraft since 1970 with one-third still in operation.

Competition. The likelihood of Japan challenging other nations for commercial space business was thought to be strong. U.S. President George Bush in May 1989 charged that space satellites were one of three areas in which Japan indulged in unfair trade practices. Wood products and supercomputers were the other two.

The U.S. trade representative claimed Japan favored buying satellites from its own companies, despite the availability of quality U.S. satellites. The trade representative said the idea was to enhance Japanese satellite builders at the expense of U.S. industry.

Swing-by. A swing-by 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 U.S. used it first when Mariner 10 flew by Venus in 1973 on its way to Mercury in 1974.

Launched successfully November 3, 1973, Mariner 10 was the first craft from Earth to visit two planets. It flew by Venus February 5, 1974, and went on to fly by Mercury three times. The first Mercury fly-by was March 29, 1974. The second, September 21, 1974. The third, March 16, 1975.

Mariner 10. Mariner 10 contained two TV cameras which transmitted the first close-ups of Mercury and Venus. It also had an infrared radiometer to sense the temperature of Mercury's surface, ultraviolet spectrometers to find atmosphere air glow and measure how the Sun's ultraviolet rays were absorbed, and magnetometers to sense changes in the magnetic field as Mariner 10 flew its course.

The craft flew by Venus at a distance of 3,579 miles, sending back 3,500 photos. Pictures in ultraviolet light showed cloud cover and circulation of the atmosphere clearly. The gravity of Venus then was used to slingshot Mariner 10 toward Mercury.

The first pass by Mercury was at a distance of 460 miles above the baked planet's surface. The second was at a distance of 29,827 miles. The third, at 205 miles. Altogether 10,000 photos of Mercury were transmitted to Earth. The planet's magnetic field was discovered. Mariner 10 now is in orbit around the Sun.

First since '76. 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. Most recent was the USSR's Luna 24 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.