Ohsumi or Ōsumi, named after an old province of Japan in the area that is today the eastern part of Kagoshima Prefecture, is the first Japanese artificial satellite. It was launched on February 11, 1970 by a Lambda 4S rocket from the Uchinoura Space Center.
Japan became the fourth nation after the USSR, the United States of America and France to launch an artificial satellite into successful Low Earth Orbit (LEO) on its own.
The Japanese space program
Many aeronautical engineers lost their jobs after World War II as aircraft development was banned under the U.S. Occupation of Japan. This changed after the signing of the San Francisco Peace Treaty in 1951, which once again allowed the development of aviation technology.
Japan’s space exploration originated in the mid-1950s as a research group led by Hideo Itokawa at the University of Tokyo (abbreviated as Todai, it is a public research university located in Tokyo, Japan; it was established in 1877 as the first imperial university and is one of Japan’s most prestigious universities). Hideo Itokawa (July 20, 1912 – February 21, 1999) was a pioneer of Japanese rocketry, popularly known as “Dr. Rocket”, and described in the media as the father of the Japanese space program.
The 23-centimetre long Pencil Rocket (first launched on April 12, 1955) was the first experiment of its kind in Japan. This rocket was initially associated with the development of rocket aircraft and not with space exploration. However, with Japan’s participation in the International Geophysical Year, the focus of the rocket project shifted towards space engineering. Rocket sizes increased gradually from less than thirty centimetres at the start of the program to over fifteen metres in the mid-1960s. The aim of the original research program was to launch a man-made satellite.
By the 1960s, two organizations, the Institute of Space and Astronautical Science (ISAS) and the National Space Development Agency of Japan (NASDA), were developing their own rockets. In 1963, the Science and Technology Agency established the National Aerospace Laboratory (NAL) where basic research on space technology was to be conducted. After experiencing numerous failures in the 1990s and 2000s, ISAS and NASDA merged – along with the National Aerospace Laboratory of Japan (NAL) – to form the unified Japan Aerospace Exploration Agency (JAXA) in 2003.
The Lambda 4S
The Lambda 4S or “L-4S” was an experimental Japanese expendable carrier rocket (an expendable launch vehicle or ELV is a launch system or launch vehicle stage that is used only once to carry a payload into outer space; historically, satellites and human spacecraft were launched mainly using expendable launchers which’ advantages include cost savings through mass production, and a greater payload fraction).
It was produced by Nissan and the Institute of Space and Astronautical Science (a Japanese national research organization of astrophysics using rockets, astronomical satellites and interplanetary probes which played a major role in Japan’s space development) and launched five times between 1966 and 1970 with Ohsumi technology demonstration satellites. The first four launches failed, however the fifth, launched on February 11, 1970, successfully placed Ohsumi, the first Japanese satellite, into Low Earth Orbit (LEO).
The Lambda 4S, with its payload capacity of twenty-six kilograms, consisted of four stages, with two booster rockets augmenting the first stage. SB-310 rockets were used as boosters, with an L735 first stage. The second stage was a reduced length derivative of the L735, whilst an L500 was used as the third stage. The fourth stage was an L480S. All of the stages burned solid fuel.
Following its retirement in 1970, a sounding rocket derived from it flew three times in order to test technologies for the Mu rockets (a series of Japanese solid-fuelled carrier rockets, which were launched from the Uchinoura Space Center between 1966 and 2006) to follow. The Mu rockets replaced the Lambda 4S for orbital launches.
Ohsumi, the first Japanese satellite
The Ohsumi satellite was a small observatory carrying five experiments designed to make ionospheric observations of temperature and density, measurements of solar emission, and measurements of energetic particles. A 500-kilometre circular orbit was intended, but an elliptical orbit was achieved. The satellite was a regular 26-sided polygonal prism with a circumscribed radius of seventy-five centimetres. The batteries were powered by more than five thousand solar cells mounted on the satellite body. Among the scientific instruments were a longitudinal precise accelerometer, a longitudinal accelerometer, a strain gauge-type thermometer, a telemetry transmitter, a beacon transmitter, and a pilot transmitter.
About two and a half hours after the launch, a radio signal from Ohsumi was received at Uchinoura to confirm its first revolution around the Earth. The radio signal level gradually fell and the next day, February 12, during its 6th revolution, it became very faint. The signal could no longer be detected during the 7th revolution. It is believed that the signal of Ohsumi was lost fourteen to fifteen hours after launch, probably caused by rapid reduction of power capacity because of higher than expected temperatures. The satellite continued to orbit the Earth, and on August 2, 2003, it re-entered the atmosphere and was melted. The re-entry location was around North Africa (border between Egypt and Libya).
The Uchinoura Space Center
The Uchinoura Space Center, which used to be called before the establishment of the Japan Aerospace Exploration Agency (JAXA) in 2003 the Kagoshima Space Center, is a space launch facility close to the Japanese town of Kimotsuki, Kagoshima Prefecture, Japan. All Japan’s scientific satellites were launched from Uchinoura. It continues to be used for suborbital launches, and has also been used for the Epsilon orbital launch vehicle (a Japanese solid-fuel rocket designed to launch scientific satellites capable of placing a 600-kilogram payload into Sun-synchronous orbit, a follow-on project to the larger and more expensive M-V rocket which was retired in 2006). Additionally, the centre has antennas for communication with interplanetary space probes.
Established in February 1962, the then-called Kagoshima Space Center (KSC) was constructed on the Pacific coast of Kagoshima Prefecture for the purpose of launching large rockets with probe payloads. Prior to establishment of KSC, test launches of the 23-centimetre long Pencil Rocket (first launched on April 12, 1955), the 120-centimetre-high Baby Rocket (which finally reached an altitude of six kilometres), and the 270-centimetre-high Kappa Rocket had been performed at the Noshiro Rocket Testing Center (established in 1962) from the mid-1950s to the 1960s.
However, progress in rocket development and larger launch vehicles required a site with more expansive down range than the narrow Sea of Japan: the Uchinoura Space Center was created. Situated in hilly terrain, the site at first glance does not appear to be exceptional; however, landscape engineering resulted in a launch facility which maximizes the unique terrain features of the site.