Satellite constellations: the private sector conquers space

Satellite constellations: the private sector conquers space
Satellite constellations: the private sector conquers space

By Guy Perrin

Astronomer at the Paris Observatory, Guy Perrin notably contributed to the Gravity instrument of the Very Large Telescope and to the study of the supermassive black hole at the center of the Milky Way. A member of the Academy of Sciences, he is co-author of the report “Large satellite constellations: issues and impacts” (see “Find out more”).

“Constellation”: this word designates a set of stars, in the etymological sense of the term. Among the best known are the 12 constellations of the zodiac, which served as time markers in ancient times. The constellations visible from the Northern Hemisphere were named by astronomers of Mediterranean civilizations; those visible only from the Southern hemisphere were baptized later, notably by Abbot Lacaille in the 18th centurye century. “Constellation” designates by extension a group, in the same way as “Pleiad”, which comes from a group of stars in the constellation Taurus.

This is how “constellation” was naturally used to designate sets of satellites operating either jointly or on behalf of a single operator. These constellations are placed in position by launchers on trajectories ranging from low orbits, at a few hundred kilometers of altitude, to geostationary orbits offering the advantage of satellites fixed in relation to the ground and of much higher altitude, at 36,000 km. Others also occupy intermediate orbits of 1,000 km to 20,000 km, some distributing their satellites between low and medium altitudes.

The emergence of “New Space”

The first artificial satellite in history, Sputnik 1, was launched in 1957 by the USSR. The United States followed in 1958 with Explorer 1, then France with its first satellite, Asterix, in 1965. These precursors, essentially intended to demonstrate the space capacity of States, very early on presented scientific interest.

However, it did not take long for their commercial interest to be seen in telecommunications. In 1962, Telstar 1, launched from Cape Canaveral, financed by private funds 1, is the first telecommunications satellite put into orbit, a historic turning point (including the first live television broadcast in mondovision) and experimental building block of a very first constellation of commercial satellites, Intelsat. Developed from 1965, this is representative of the constellations from the 1960s to 2000, made up of a few dozen satellites. The annual rate of orbital launches from the mid-1970s to the early 2000s ranged from 75 to 100.

This rate increased sharply from the end of the 2010s, rising to 300 in 2019, exceeding 1,000 in 2020 and reaching 2,900 in 2023. 14,000 satellites were identified at the start of 2024, the majority having therefore been launched during of the very last years. And the increase in launcher capacity bodes well for an increase in rate.

The last ten years have seen the advent of a new era in the use of space, the New Space (new space age) which combines new players – particularly from the private sector, including Elon Musk’s emblematic SpaceX –, reduction in launch costs thanks to reusable vectors, and reduction in manufacturing costs for satellites using cheap components and/or small platforms launchable by rockets within the reach of start-ups (including the number has quintupled in ten years). This upheaval in the space sector offers the possibility of low-altitude constellations of several thousand to several tens of thousands of satellites benefiting from technological progress and research described in a report from the Academy of Sciences published on March 30, 2024.

The website of the Academy of Sciences: www.academie-sciences.fr

“Large satellite constellations: issues and impacts”, by François Baccelli, Sébastien Candel, Guy Perrin and Jean-Loup Puget, report from the Academy of Sciences, March 30, 2024. Online, as well as a summary, on its website .

The website of the Academy of Sciences: www.academie-sciences.fr

“Large satellite constellations: issues and impacts”, by François Baccelli, Sébastien Candel, Guy Perrin and Jean-Loup Puget, report from the Academy of Sciences, March 30, 2024. Online, as well as a summary, on its website .

The website of the Academy of Sciences: www.academie-sciences.fr

“Large satellite constellations: issues and impacts”, by François Baccelli, Sébastien Candel, Guy Perrin and Jean-Loup Puget, report from the Academy of Sciences, March 30, 2024. Online, as well as a summary, on its website .

Services provided by constellations

Space is the only way to take an external look at the Earth with a large number of applications, from environmental monitoring2 to disaster monitoring, weather forecasting and geolocation, including agricultural and military applications, for which a large number of constellations exist, but made up of a small number of satellites. Another major application, telecommunications, connects any point on the globe using so-called “satellite” telephones. Added to this are the constellations for broadcasting television programs received via satellite dishes.

The New Space revolution opens the way to constellations no longer made up of a few dozen satellites, but of thousands, even tens of thousands. This density allows the emergence of applications with very low latency, which is a function of the travel time of radio waves between a transmitter and a receiver at the speed of light.3. The lower the altitude of the satellites, the shorter the latency time. From 500 milliseconds for geostationary satellites, it increases to 30 milliseconds for satellites in low orbit, with the key to almost instantaneous telecommunications and Internet performance comparable to that of fiber networks on the ground. As satellites in low orbit move very quickly, many more networked satellites are needed to ensure permanent contact with users.

These new constellations are therefore synonymous with mobile telephony and high-speed Internet everywhere on Earth, independently of local anchoring stations on the ground. They thus allow operators to free themselves from any local control over telecommunications. And they are very resilient, the destruction of one or a few satellites does not prevent the operation of the network, which can be reconfigured. Crucial properties also for military applications, and which apply to telecommunications constellations as well as imaging constellations. These very interesting prospects in many areas, commercial but also strategic, are also an issue of sovereignty, having such capabilities conferring independence and autonomy to States on a strategic level.

Towards overpopulation in orbit

But this is not without side effects, potentially very worrying at the current rate of launches, about which a report from the Government Accounting Office (GAO, audit body of the American Congress) and that of the Academy of Sciences warn. The first of these is the consequence of this growth on the environment. The hundred or more annual launches in the future will generate their share of pollutants. They also increase the number of debris in low orbit which are a danger for the satellites and the launchers themselves given the high relative speeds.4, several tens of kilometers per second. And for any human presence. As a result, satellites must correct their trajectories to avoid debris when it can be detected.

But, even more worrying, the density of satellites in low orbit is becoming such that the prospect of Kessler syndrome can no longer be ruled out. According to this, after a critical density, a collision between two satellites will trigger an uncontrollable chain reaction leading to the significant production of debris, then to the destruction of a large number of these satellites hit by this debris, and so on. . This will be accompanied by the impossibility, at least temporarily, of carrying out new launches without risks, including space missions for scientific purposes.

Faced with worrying prospects, a need for regulation

In the field of astronomy, the presence of a large number of satellites in low orbit generates pollution that is harmful to observations from the ground. Satellites reflect sunlight, becoming bright sources at sunset and dawn that degrade data from most modern observatories. 30% of those of the Vera C. Rubin Observatory, a wide-field telescope which will be put into service in 2025 in Chile, risk being partly lost if the number of satellites is tripled. It is also the end of sanctuaries which protect radio observatories from terrestrial telecommunications emissions, such as the Karoo deserts in South Africa and Murchison in Australia, where the giant Square Kilometer Array Observatory network, expected to be the most efficient ever designed for low frequency radio astronomy, is under construction: it will not be safe from those coming from space.

These worrying prospects led the International Astronomical Union (IAU) to create the Center for the Protection of the Skies (CPS) and to take action with space industries but also with the UN committee on the peaceful uses of space. outer space (Cupeea), which put the subject on its agenda for the next five years. This cooperation is starting to bear fruit: for example, the latest generations of satellites in SpaceX’s Starlink constellation – which targets 42,000 satellites – are much less bright.

Likewise, protocols are being studied between astronomers and operators to interrupt direct emissions above radio observatories, although the own emissions from electronic devices on board remain a nuisance. If some operators play the game of cooperation, vigilance is necessary, as demonstrated by the example of the BlueWalker III communications satellite prototype put into orbit in 2022: its 64 m2 antenna make it the sixth brightest Source in the sky!

It remains possible that not all major commercial constellations are financially viable and that current growth will eventually slow down, avoiding the outbreak of Kessler syndrome. However, the practice of “first come, first served” has its limits and international regulation based on standards established by all stakeholders – to which the Academy of Sciences, according to its missions, intends to contribute through its report – is more than ever necessary to guard against possible abuses in this booming field.

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