The capacity of Ariane 5

How many satellites can Ariane 5 hold? Violaine Paturel

In its current “heavy” version known as Ariane 5 ECA, this European launch vehicle is optimised for carrying two satellites to geostationary transfer orbit (meaning that from this orbit, they will reach their geostationary position, which is the most frequently used for telecommunications satellites). Its payload capacity is 9.6 tonnes spread between the two satellites. Sometimes, depending on the flights, small ancillary satellites weighing a few dozen kilos can be transported in addition to the two main ones. In low Earth orbit, and more specifically at similar altitudes to the International Space Station (about 400 km), Ariane 5’s payload capacity increases to 20 tonnes; thus it is able to launch the ATV, the automatic European cargo ship. Obviously, it is possible to envisage other configurations in which multiple, lighter satellites could be placed in orbit at the same time, but as mentioned above, the launcher was predominantly designed for the geostationary orbit market, a market dominated by Arianespace, the company that commercialises Ariane 5.

How many satellites?

What is the number of satellites on earth orbit? Quentin Claveau

Since the first satellite, Sputnik in 1957, it is estimated that there have been more than 4,700 launches. However, not all the satellites launched are active, and some have even come back to Earth and been burnt up in the upper layers of the atmosphere. Today, there are still 800 active satellites. To that needs to be added the “waste” that has resulted from this launch activity. And there the figures speak for themselves: currently orbiting our planet are15,000 objects measuring more than 10 cm wide, 300,000 measuring between 1 and 10 cm and at least 30 million measuring between 1 mm and 1 cm. The problem is that this debris generates other smaller pieces of debris through collisions. This is why the space agencies, and for example the CNES in France (the figures in this article were taken from their data), are monitoring the sky in order to prevent any risk of a major impact with active satellites or manned spaceships. The space industry currently has three main lines of thought regarding this problem. Firstly, the development of launch vehicles that limit debris ejected into orbit during the launches (great progress has already been made). Secondly, the management of satellites according to a responsible policy that therefore includes the planning of their re-entry and destruction in the upper layers of the atmosphere at the end of their operational life to eliminate a potential source of the debris. Thirdly, and in the longer term, the drawing up of strategies for “cleaning” Earth orbit without which it will become more and more difficult to avoid collisions.

CNES article on the subject

Origin of the Moon

How was the Moon formed? Anthony Gibert

Several hypotheses have been envisaged by astronomers: formation at the same time as the Earth, captured asteroid, etc. Today, the most accepted scenario is based on a giant impact. At the very beginning of the constitution of the solar system (a little more than 4 billion years ago), an object the size of Mars is said to have crashed into the Earth. This massive shock would have ejected vast quantities of matter from our planet which would have combined to form the Moon. According to the different versions, the impactor would have been pulverised by the collision and the debris (at least part of it) would then have taken part in the constitution of our natural satellite.