NASA’s Origins, Spectral Interpretation, Resource Identification, Security – Regolith Explorer (OSIRIS-REx), launched in September 2016 is on a mission to gather samples from the surface of asteroid Bennu and return them to Earth (see my previous reports here and here). It’s a huge undertaking, one which will take the vehicle on a journey of some 7.2 billion kilometres (4.5 billion miles).
Part of this journey involved OSIRIS-REx looping past the Earth in September 2017, in a gravity assist manoeuvre design to increase its velocity by some 13,400 km/h (8,400 mph) to almost 44,000 km/h (27,500 mph), and swing it on to an intercept with the asteroid, which it will reach in October 2018. During this Earth flyby, scientists carried out an extensive science campaign, allowing them to check and calibrate the probe’s suite of science instruments.
A part of this campaign involved testing the probe’s camera system, using it to take pictures of the Earth and Moon during September and early October. Several of these images, captured on October 2nd, 2017, were used by NASA used to create a to-scale composite image of the Earth-Moon system, which was released into the public domain on January 3rd, 2018 (seen above).
At time the images were taken, the spacecraft was approximately 5 million km (3 million mi) from Earth – or about 13 times the distance between the Earth and Moon. It was created by combining pictures captured using blue, green and red filters, allowing it to present a true colour view of the Earth and Moon as they reflect sunlight. Looking at it, one cannot help by be reminded of just how small and fragile our place in the universe really is.
China’s Space Ambitions
In reporting on China’s space programme, I’ve frequently noted the growing ambitious nature of their endeavours. A mark of this is that in 2017, China mounted more than 20 successful launches – including some for foreign nations such as Venezuela, as a part of China’s desire to expand their commercial launch operations – matching Russia’s launch efforts, and sitting not that far behind the USA.
At the start of January 2018, the China Aerospace Science and Technology Corporation (CASC) upped the ante, indicating that in 2018, they plan to carry out 35 launches through the year. At the same time, CASC’s sister organisation, China Aerospace Science Industry Corporation (CASIC) indicated it would be carrying out at least 5 launches during the year – four of them in the span of a week – while the Chinese private sector corporation, Landspace Technology, indicated it would commence launch operations during the year. Like America’s SpaceX, Landspace plan to become a major force in commercial sector launch operations, initially with satellite payloads, but ramping to flying people into space in around 2025.
One of the more notable missions China plans to launch in 2018 is the Chang’e 4 mission to the Moon’s far side. This is a two-phase mission, commencing in June 2018 with the launch of a communications relay satellite to the Earth-Moon Lagrange point. It will be followed in December by a lander / rover combination which will land on the lunar far side to commence science studies. It will mark the first attempt to carry out long-term studies on the side of the Moon permanently facing away from Earth – not to mention the first far side lunar landing.
The CE-4 Relay satellite is required in order for communications to take place between Earth and the Chang’e 4 lander and rover.
As the Moon is tidally locked with Earth, and always keep the same side pointed towards us, there is no way to have direct communications with any vehicle on the lunar far side. This is overcome by placing a satellite in the Earth-Moon L2 position, where it can maintain a steady position relative to the Earth and the Moon’s far side, enabling communications between the two, and keeping scientists and engineers on Earth in contact with the lander and rover.
The lander / rover combination will explore part of the 180 km (112.5 mi) diameter Von Kármán crater, believed to be the oldest impact crater on the Moon. It lies within the South Pole-Aitken Basin, a vast basin in the southern hemisphere of the far side which extends from the South Pole to Aitken crater.
The crater is of general interest because it contains about 10% by weight iron oxide (FeO) and 4-5 parts per million of thorium, which can be used as a replacement for uranium in nuclear reactors. In addition, the South Pole-Aitken Basin – one of the largest impact basins in the solar system (about 2,500 km / 1,600 mi across and some 13 km / 8.1 mi deep) – also contains vast amounts of water ice. These deposits are believed to be the result of impacts by meteors and asteroids over the aeons, which deposited ice within the basin, which lies in almost permanent shadow.
The water deposits will be part of Chang’e 4’s studies – China has already announced its intent to establish a human mission on the lunar surface, and relatively easy access to water ice could be a critical part of sustaining a human presence there. To carry out their studies, both the rover and the lander will carry a range of science instruments and experiments, including systems supplied by Sweden, Germany, the Netherlands and Saudi Arabia.
In addition, the lander will include a container with potato and rockcress seeds, together with silkworm eggs to see if plants and insects can survive in the lunar environment. It is hoped that if the eggs hatch, the larvae would produce carbon dioxide, while the germinated plants would release oxygen through photosynthesis, allowing both to establish a simple life-sustaining synergy within the container. If successful, it might allow larger biotic systems to be developed and used to augment the life support systems in a lunar base while providing additional foodstuffs.
2018 should also mark the return to flight of the Long March 5, China’s most powerful launch vehicle. This entered service in November 2016, but flights were suspended in 2017 following the failure of the vehicle’s second launch in July of that year. Long March 5 is critical to China’s ambitions, as it will be the launch platform for the Chang’e 5 (2019) and Chang’e 6 (2020) lunar sample return missions, the modules to be used in a planned space station, due to start in 2019 with the launch of Tianhe unit, and boost the Mars Global Remote Sensing Orbiter and Small Rover mission to the red planet in 2020.
The 2018 return-to-flight of the Long March 5 will likely involve placing a Dongfanghong-5 (“The East is Red”) communications satellite, which will be placed in low Earth orbit.