Satellites & Orbit

Low Earth orbit stopped being empty about a decade ago. There are now tens of thousands of active satellites where there were hundreds, most of them in constellations flying as single systems, and the consequences reach both up and down. On the ground, connectivity has genuinely changed. In orbit, conjunction warnings are routine and the station has manoeuvred dozens of times. Astronomically, the constellations streak long-exposure images and transmit across bands radio telescopes were promised would stay quiet.

The physics underneath is unforgiving. A one-centimetre fragment at orbital velocity carries roughly the energy of a hand grenade, and there is no shielding against it that is light enough to fly. Altitude decides everything that follows: below about 600 kilometres the residual atmosphere drags a dead satellite down within a handful of years, which is why the busiest shell is also the self-cleaning one; above 800 it decays over centuries, and anything abandoned there is abandoned for longer than the industry has existed. Kessler's 1978 argument — that beyond a certain density, collisions generate debris faster than the atmosphere removes it — is not a hypothetical any more. It is a design constraint, and the deliberate anti-satellite tests of 2007 and 2021 each added thousands of trackable fragments to exactly the wrong altitudes.

What is genuinely new is that regulation has started to move. The old guidance was to clear an orbit within twenty-five years of end of life; the current US rule is five, and operators are increasingly designing for controlled reentry rather than hoping. The remaining hard problem is that orbit is a commons with no way to charge for it and no authority above the national licence. A constellation is approved by the country its operator is registered in, and the sky it crosses belongs to everybody else. Astronomy has no standing in that process at all, which is why the mitigations that exist — darkening coatings, orienting solar panels away on the way up — are voluntary, and mostly the result of astronomers asking politely.