Is It Time For Global Space Traffic Control?


Is It Time For Global Space Traffic Control?

As the space environment surrounding Earth becomes increasingly congested, the issue of managing space traffic safely, effectively and fairly needs to be addressed. Until recently, “Space Traffic Management” has been guided by a voluntary set of space operating procedure; this is the first step towards developing “Space Traffic Control”, which is the point at which lawyers become involved, and space regulations become both international and mandatory.

A recent report in the Daily Telegraph (paywall) suggests that the legal regime may soon be with us:

“Elon Musk and Jeff Bezos in star wars over plans for mega satellite constellations.” 

While it is encouraging that the mainstream media are taking an interest in the subject, let’s take a somewhat closer look at some of the issues raised in the Telegraph article:-

The two moguls’ rival satellite companies, SpaceX and Kuiper, have asked US regulators to decide their claims to the same orbital territory.

It’s probably worth noting here that the law as it stands doesn’t allow any organisation, commercial or governmental, to “stake a claim” to “orbital territory”. The international treaties signed back in the 1960s and 1970s establish the space domain as a “commons” and although there is an international frequency registration process, coordinated via the ITU, to avoid interference between satellites in the RF domain, this does not confer “rights” to certain orbits. It would also be somewhat presumptive of US regulators to make any specific determination in this case, since there are plenty of other space-faring nations around the globe who might feel somewhat aggrieved if their own plans to exploit certain orbits were pre-empted by a decision in the US.

 SpaceX, Mr Musk’s company, already has more than a thousand of its Starlink “microsatellites” in orbit out of a planned 12,000, and now wants to lower the orbit of around 2,800 of them in order to improve broadband speeds and lower the danger of future space debris.

It is true that lower orbits improve link budgets, and so enable improved broadband data rates. It is also true that lower orbits decay more quickly, and so reduce the debris risk. But this is emphatically not really why they’re arguing. As you might expect, in a disagreement between two of the world’s richest men, it’s all about money.

The key word missing from the Telegraph article is “latency” – the time it takes to deliver information. Financial traders will pay huge sums of money to receive data fractions of a second earlier than their rivals, and since satellite communications operate at the true speed of light, whereas fibre-optic cables achieve only about two thirds of that figure, if a satellite constellation is low enough it can “beat the cables”, despite the fact that the path length through the satellites is longer. For mega-constellations, therefore, the lower the orbit, the lower the latency, and the larger the profits – time really is money in this arena.

This is why Space X took the most unusual step of revising their orbit strategy for Starlink, since their original orbit altitude at 1200 km was too high to make an impression on the financial markets. It’s also why Amazon’s Kuiper is keen to keep them out of the lowest orbital filings. As the Telegraph article notes, they are both “satellite networks, which will beam down internet signal to some of the planet’s most remote areas.” But that isn’t where they’ll make their money. People in the planet’s most remote areas simply don’t have the spending power of Wall Street and the City of London.

Amazon’s Kuiper constellation will consist of “3,236 satellites” according to the Telegraph, which is clearly a very large number, but still quite small compared to Starlink. Both mega-constellations make Iridium’s existing global constellation (notionally consisting of 66 active satellites) look quite puny.

Why do these new networks require quite so many satellites? The answer lies in the desire to increase data rates – rather than delivering coverage to their entire footprints, these constellations focus on a comparatively small region close to their nadir position, thereby limiting the potential number of subscribers in the footprint who wish to stream videos of cats doing silly things.

And do these large numbers of low orbit satellites matter? Well, as discussed in a previous blog item, The impact of satellite operations on astronomy | GNOSIS Network they have the potential to complicate life significantly for the astronomical community. Arguably, if they are at lower altitudes, they will spend less time in twilight conditions; but they’ll be closer to the Earth, and hence appear brighter too…… More calculations are needed to establish which of these factors is most important.

Amazon and SpaceX’s dispute focuses on their differing orbital “shells”, meaning layers of space at different distances from the Earth’s surface where large numbers of satellites can orbit without crossing over.

While it is true that confining constellations to particular orbital shells below 600 km altitude would reduce the probability of inter-constellation collisions, it fails to address the potential issue of intra-constellation collisions between members of the same constellation. As this representative illustration of the Starlink constellation shows, there are many, many nodes where orbital planes intersect, and where two satellites could collide if they lose the ability to manoeuvre.

Relatively tightly defined “orbital shells”, of the sort that Space-X and Amazon are purportedly arguing about, actually increase the local density of satellite hardware and make such collisions more likely. Permitting constellations to use mildly elliptical orbits would spread the hardware over a larger volume of space, reducing both the chances of collisions, and, (in an ideal world), the insurance premiums of the operators. And at these very low altitudes, if a collision does occur, at least the debris would not take too long to re-enter the Earth’s atmosphere.


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