This is our annual update on the satellites currently orbiting the Earth.
How many satellites are orbiting the Earth?
According to the Index of Objects Launched into Outer Space maintained by the United Nations Office for Outer Space Affairs (UNOOSA), there are 4 857 satellites currently orbiting the planet; an increase of 4.79% compared to last year.
So far in 2018, UNOOSA has recorded 204 objects launched into space. This is already more launches than was achieved in any entire year before 2013, and very close to the number of launches in 2013, 2014, 2105 and 2016. However, it did not beat last year as 2017 was a bit of a record breaker! There were 453 objects launched last year alone, which equates to over 5% of the objects ever launched into space!
A significant proportion of the 453 were cubesats for Earth Observation or communication purposes, and it is these smaller satellites that are driving the increase in objects being put into space. According to UNOOSA, in history 8 126 objects have been launched into space, and over 22% of these are within the last eight years alone. Both technology developments and improved interest in space, particularly from start-up companies, are behind the recent drive.
How many of these orbiting satellites are working?
The Union of Concerned Scientists (UCS) keeps a record of the operational satellites and their latest update records details to the end of April 2018. Using this database together with the UNOOSA Index shows that there are currently 1 980 active satellites in orbit. Whilst this is 13.92% increase over the number of active satellites last year, it still represents only 40% of the satellites orbiting the planet.
This means that there are 2 877 pieces of useless metal hurtling around the Earth at high speed! Interestingly this is actually 20 less than when we did the 2017 update, meaning a number of inactive satellites either deorbited and came back to Earth or burnt up in the atmosphere. Â This is not as rare as you might think, as one average about one satellite a week returns to Earth in one form or another.
According to the UCS database of the 453 objects launched in 2017 only 390 of them were still in space at the end of the April 2018. 14% had already returned to Earth, of course some may have been brought back due to to malfunctions, but a lot of the small satellites only have short lifespans and could have already completed their missions.
What are all these satellites doing?
Using the UCS update as at the end of April, the main purposes for the operational satellites are:
- Communications: 792 satellites, a 6.7% increase on last year.
- Earth observation: 661 satellites, a 10.9% increase on last year.
- Technology development/demonstration: 213 satellites, a 10.4% increase on last year.
- Navigation/Positioning: 121 satellites, a 12% increase on last year.
- Space science/observation: 76 satellites which is no real change from last year.
- Earth science: 23 satellites, which is no real change from last year.
Although, it should be noted that some of the satellites have multiple purposes. Weâ€™ll examine the Earth observation category in more detail in a future blog.
Who uses the satellites?
The four categories of users in the previous section shows that:
- 826 satellites are listed as having commercial uses
- 523 with government uses
- 399 with military user; and
- 138 with civil uses
It should be noted that 278 satellites (14.6%) are listed as having multiple uses.
Which countries have launched/operate satellites?
According to UNOOSA 81 countries have launched satellites, although this is slightly complicated by the fact that satellites are also launched by institutions and organisations such as the European Space Agency.
Looking at the UCS database, there are 65 countries listed as currently operating satellites, although there are 65 satellites simply listed as having multinational operators. There is an interesting infographic on the UCS site showing the change in countries operating satellites between 1966 and 2016.
In terms of countries with the most satellites the USA significantly leads the way with 859 satellites, China is second with 250, and Russia third with 146. These are then followed by Japan (72), India (55) and the UK (52).
What types of orbits are the satellites in?
For the current active satellites:
- 2.1% are in Elliptical orbits which vary between less than 1 000 km to above 40 000 km above the Earth.
- 29.1% are in Geostationary Earth Orbits (GEO) which is just under 36 000 km above the Earth.
- 5.9% are In Medium Earth Orbits which are anything between 8,000 km and 24,000 km above the Earth.
- 62.9% are in Low Earth Orbits (LEO) which varying between 250 km and 1 500 km above the Earth; and of these LEOâ€™s (although 12 â€“ 1.01% – have no track listed):
- 57.5% are in sun-synchronous orbits which means they pass the equator at the same time each day.
- 22.85% are in non-polar inclined orbits.
- 16.1% are in polar inclined orbits.
- 1.69% are in equatorial orbits
- 0.76% are in elliptical orbits.
- 0.08% (Actually, just 1 satellite) is in a cislunar orbit.
When you gaze up at the stars, there are thousands of active, and inactive, satellites also up there and their numbers are on the increase.