Kessler effect and the failure of GPS and comm satellites

space debris by ESA

Kessler effect

Kessler effect – it’s a scenario in which the density of objects in orbit is high enough that collision between objects could cause a cascade in which each collision generates space debris that increases the likelihood of further collisions. It would cause catastrophic failure of GPS and communication systems. Some experts thing we are already at critical mass in low-Earth orbit.
In 2009, two communications satellites collided – the active commercial Iridium 33 and the derelict Russian military Kosmos-2251. The crash produced respectively 1,668 and 628 pieces of catalogued debris, of which 1,141 and 364 pieces of tracked debris remained in orbit as of January 2016 (only golf ball size and bigger objects are tracked). Fengyun-1C satellite was destroyed in a Chinese anti-satellite missile test in 2007 (As of April 2019, 3000 pieces are still a threat to ISS).
Less than 2 years ago, ESA’s observation satellite had to fire its thrusters, moving it off a potential collision course with a SpaceX satellite.
Avoidance process is largely manual and ad hoc, without proper cooperation between agencies.

“Today, this negotiation is done through exchanging emails – an archaic process that is no longer viable as increasing numbers of satellites in space mean more space traffic.”

Holger Krag, Head of Space Safety at ESA.

Growing numbers

Exponential growth of satellites in orbit

We have nearly 60,000 man-made objects in space.
Number of active satellites is growing rapidly. In 2020, there was an estimated total of 3,368 active satellites orbiting the Earth, an increase from 2,298 active satellites in 2019. shows lower number of operating satellites: 2,787 (as of 08/2020)
Most comprehensive database GCAT, published recently by Jonathan McDowell is a great resource.
UNOOSA recorded that 580 objects were launched into space during 2019, almost 30% more than in each of the previous two years. By the end of March 2020 there had already been 356 launches. The types of satellites already in orbit:

  • Communications: 1 211 satellites – increase of 55% since the start of 2019.
  • Earth observation: 884 satellites – increase of 24.5% since the start of 2019.
  • Technology development/demonstration: 312 satellites – increase of 40% since the start of 2019.
  • Navigation/Positioning: 148 satellites – increase of 8% since the start of 2019.
  • Space science/observation: 93 satellites– increase of 9% since the start of 2019.
  • Earth science: 18 satellites – a decrease of 28% since the start of 2019.

Space internet

Plans for beaming internet from space will grow the numbers of satellites dramatically.
SpaceX plan for Starlink constellation will consist of 42000 not so small satellites (v1.0 weights 260kg).
Amazon’s Kuiper constellation approved in July by FCC is made of 3,236 satellites (fortunately Amazon must submit plan for dealing with orbital debris, since the design of its satellites aren’t finalized yet). Another big contender for providing internet from space is OneWeb, which downsized it’s plans from 47,844 to 6,372 satellites in Jan 2021.
Apart from space junk issue, there is a light pollution problem. You can already see “Starlink train” on the sky. One of its satellites – DarkSat, had its albedo reduced using a special coating but the method was abandoned due to thermal issues and IR reflectivity. Anyway, it was still too bright for astronomers. As of 15 October 2020 over 200 Starlink satellites have a sunshade. Analysis found them to be marginally fainter than DarkSat.

Debris and defunct satellites

Data from ESA’s Space Debris Office (as of Feb 2020).

Number of satellites rocket launches have placed into Earth orbit: 9600
Number of these still in space:5500
Number of these still functioning:2300
Number of debris objects regularly tracked by Space Surveillance Networks and maintained in their catalogue:22 300
Estimated number of break-ups, explosions, collisions, or anomalous events resulting in fragmentation:More than 500
Total mass of all space objects in Earth orbit:More than 8800 tonnes.
Number of debris objects estimated by statistical models to be in orbit:
34 000 objects >10 cm
900 000 objects from greater than 1 cm to 10 cm
128 million objects from greater than 1 mm to 1 cm

There are no rules about satellite orbits or even right-of-way. If a collision occur, it’s not clear who would have to clean up the debris. The only law, from 1972 says: whoever launched the satellite has to clean up the mess on the Earth surface.
Most satellites today are private and most debris remains abandoned in orbit, because there are no regulations.

Here are two webapps to watch satellites in orbit:

Celestrak – with timelapse option,

Esri Satellite Map – with toggles to filter satellite sizes, countries, etc.


Fortunately there are some countermeasures in the works to this growing threat. UKSA has given over £1m to seven firms to advance tracking and analysis, which in future would feed automated traffic management systems.
NASA and ESA have dedicated websites. Hopefully, development of those systems and debris cleanup programs will be swift. International regulation is also sorely needed (as it is in aviation).
Astroscale is trying to make space debris collection a viable business (company has raised $140 mln to date). First debris removal practice mission is scheduled to launch on a Soyuz rocket in March 2021. Spacecraft with a mass of about 175 kg and a 17 kg client satellite will repeat dock and release procedure.

I’ll leave you with this animated short, which shows (in the second half) how badly it could all end:


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