Small step for China’s manned lunar mission: measuring the distance
China adds Lunar Laser Ranging to its capabilities as it revs up its space program with a view to a manned mission in 2020
The first thing to do before embarking on any journey is to plan the route and judge the distance.
Measuring the distance between moon and Earth is precisely what China has just done as it steps up a space program that includes plans to send ‘taikonauts’ to the moon.
According to calculations, China’s space travelers will have to traverse more than 385,000 kilometers before they can set foot on planet Earth’s only natural satellite.
Measuring the exact distance to the moon is known as Lunar Laser Ranging (LLR) in aerospace.
Xinhua reports that an applied astronomy group at the Yunnan Observatories in Kunming conducted China’s first LLR exercise with the aid of a 1.2-meter telescope. They were able to measure the distance between the lunar retro-reflector planted by the United States’ manned mission, Apollo 15, in 1971 – which emits laser pulses – and their own ground station. Between 9:25pm and 10:31pm. Beijing Time, on January 22, the distance was found to be within a range of 385,823.433 and 387,119.600 kilometers.
LLR measures the distance between the Earth and the moon by calculating the time a laser pulse takes to travel from a ground station to a retro-reflector on the moon and back again.
China’s own LLR project started from scratch and still lags behind that of the United States, which has revived its own lunar mission: it eventually hopes to use the moon as a staging post for exploration of Mars.
LLR data is vital to advanced research in astro-geodynamics, Earth-moon system dynamics and lunar physics. Before China joined the elite club, only the United States, France and Italy had successfully harnessed the technology.
China is on schedule to launch the Chang’e-4 lunar probe later this year. Intended to be mankind’s first ever soft landing on the far side of the moon, the probe will carry out in-situ and roving detection, and Earth-moon communication.
China’s own domestically engineered and made retro-reflector will also be placed on the moon.
China expects to stage its manned lunar project in around 2020, according to the Chinese cosmochemist and geochemist Ouyang Ziyuan, who has overseen all the country’s unmanned launches to date.
Plans also include two unmanned launches by the powerful Long March-5 cargo rocket.