Scientific Experiments and Interplanetary Missions

Japan is one state which has been involved in undertaking interplanetary missions for many years. These missions involve robotic trips to other planets. So far they have not attempted any manned 3 interplanetary missions.[126] Japan entered into the arena of deep space missions in mid-1980s. This was the period after the beginning of space age when for the first time spacefaring nations had an opportunity to study the characteristics of a comet of significant importance which was to make its presence felt in the inner solar system. It was the most famous Halley’s Comet.[127] Japan used this opportunity to organise its deep space mission by launching two probes for studying this comet: a path finder and a main probe (MS-T5 and Planet A). Very useful information was provided by this mission; however, these probes received very less publicity at global level.

Japan has focused on studying the characteristics of the Sun for the deeper understanding and also that of our planetary system. Studying Sun is technologically challenging and scientifically important endeavour. It is the only fixed star available for any study. The knowledge about its evolution and other properties is essential to know more about the mechanisms of various processes taking place in the universe. Japan puts a major emphasis on solar studies. Till date, they have launched two satellites to unravel some of the mysteries and mechanisms of the activities taking place in the solar corona. The first satellite was launched during end August 1991, and this was followed by second satellite during 2006. The second satellite is approximately at an altitude of 680 km. Countries like the US and UK have also contributed in these missions.[128]

Japan was the first country to launch a spacecraft towards the Moon since the erstwhile USSR (Luna 24—Aug 1976). Japan’s first Moon probe Muses A[129] (the mother craft was called Hiten) was launched on January 24, 1990. This experiment

had a major learning value for the Japanese scientists. The basic purpose behind launching this dual satellite was to practise for future interplanetary spaceflights (probes to mars and asteroids). Hiten was the Earth-Moon-orbiting spacecraft and had released a small orbiter called Hagoromo into lunar orbit. Hiten was not programmed for entering lunar orbit and was to act as a relay for Hagoromo. Both the crafts were not programmed for Moon landing. Unfortunately, Hagoromo developed a technical snag (probably radio failed), and its entry into Moon’s orbit was verified only based on the observations from the optical telescope.

Because of this failure, the Japanese scientists along with NASA scientists decided to salvage this mission. It was not possible to change the Hiten’s position form the Earth’s orbit to Moon’s orbit due to fuel shortages. Hence, the route to reach the moon’s orbit was changed, and low-energy lunar transfer was carried out (it took many months). To do this, first ever aerobraking manoeuvre in deep space was carried out. Finally, Hiten was made to hit the moon. The Muses-A[130] mission gave Japan precious experience in targeting orbits and in the use of swingbys[131] to guide future spacecraft travelling to distant planets. Japan’s Kaguya space mission (2007) has been discussed in detail in another chapter of this book.

Japan also had devised an ambitious deep space mission Akatsuki (Dawn/Venus Climate Orbiter) to Venus with the aim to analyse the planet’s atmosphere. This was the first interplanetary weather satellite with a lifetime of 2 years. This 1,058- lb robotic probe was launched aboard an H-2A rocket on May 21, 2010. It was expected to reach Venus by December 2010. It was to enter an equatorial orbit around Venus stretching from just above the planet’s blanketing atmosphere to an altitude of nearly 50,000 miles. Six experiments were planned to peer deep into the planet’s atmosphere and even study surface activity [16].

Unfortunately, this mission failed to reach Venus on December 7, 2010. It was to enter orbit around the planet (an elliptical orbit ranging from 300 to 80,000 km from Venus) but the planned attempt to initiate orbit insertion operations by igniting the orbital manoeuvring engine failed (the engines fired for 3 min only when they were required to fire for 12 min period). Now, JAXA is developing plans to attempt another orbital insertion burn when the probe returns to Venus in 6 years by keeping the probe into hibernation for the time in-between [17, 18].

This was Japan’s second interplanetary mission after the Nozomi spacecraft that twice missed entering orbit around Mars after launching in 1998. Nozomi was launched during 1998 to understand more about the atmosphere around the Mars; however, the mission failed because it could not gain sufficient velocity and achieve the required orbit.

Japan also has a significant interest in asteroid mining. They had launched Hayabusa (MUSES-C) capsule on May 9, 2003 which rendezvoused with a near­Earth asteroid[132] called 25143 Itokawa in mid-September 2005. Hayabusa surveyed the asteroid surface from a distance of about 20 km. Afterwards this spacecraft moved closer to the asteroid surface and further approached it for a series of soft landings and for the purposes of collection of samples. The capsule re-entered to the Earth’s atmosphere on June 13, 2010. By October 7, 2010, it was announced by JAXA that approximately 100 particles with a size smaller than 0.001 mm were collected by the sample canister, and some of them could even be cosmic materials.[133] Presently, scientists are researching on them and have also come out with some of initial findings.