Earth Observation (EO) satellites currently account for just over a third of all the operational satellites orbiting the Earth. As we described two weeks ago, according to the Union of Concerned Scientists database there were 1 738 operational satellites at the end of August 2017, and 620 of these have a main purpose of either EO or Earth Science.
This represents a massive 66% increase in the number of EO satellites from our 2016 update, and the percentage of overall active satellites is also up from one quarter. These figures demonstrate, once again, that EO is a growing industry.
What do Earth observation satellites do?
Looking more closely at what EO satellites actually do demonstrates that despite increases in satellite numbers in almost all categories, itâ€™s clearly growth in optical imaging which is the behind this significant increase. The purposes of active EO satellites in 2017 are:
- Optical Imaging: 327 satellites representing a 98% increase on last year
- Radar imaging: 45 satellites, a 32% increase on last year
- Infrared imaging: 7 satellites, no change to last year
- Meteorology: 64 satellites, a 73% increase on last year
- Earth Science: 60 satellites, a 13% increase on last year
- Electronic intelligence: 50 satellites, a 6% increase on last year
- 14 satellites with other purposes, a 133% increase on last year
- 51 satellites simply list EO as their purpose, a 100% increase on last year
Who controls Earth observation satellites?
Despite the huge increase in EO satellites, the number of countries who control them has not seen the same growth. This year there are 39 different countries listed with EO satellites, an increase of only 15% on last year. In addition, there are satellites run by multinational agencies such as the European Space Agency (ESA).
The USA leads the way controlling over half the EO satellites, although this is largely due to Planet who account for 30% on their own! Following USA is China with 14.4%, and then come India, Japan and Russia who each have over 3%.
The USA is followed by China with about 20%, and Japan and Russia come next with around 5% each. The UK is only listed as controller on 4 satellites all related to the DMC constellation, although we are also involved in the ESA satellites.
Size of Earth observation satellites
Itâ€™s interesting to look out the size breakdown of these satellites which shows the development of the small satellite. For this breakdown, weâ€™ve classed satellites into four groups:
- Large satellites with a launch mass of over 500kg
- Small satellites with a launch mass between 100 and 500 kg.
- Microsats with a launch mass between 10 and 100 kg.
- Nanosats/Cubesats with a launch mass below 10 kg.
For the current active EO satellites there are:
- 904 large satellites equating to 52.01%
- 178 small satellites equating to 10.24%
- 145 microsats equating to 8.34%
- 409 Nanosats/Cubesats equating to 23.53%
- The remaining 102 satellites do not have a launch mass specified.
Who uses the Earth observation satellites?
There has also been significant movement in the breakdown of EO satellites users since 2016. The influence of small commercial satellites undertaking optical imaging is again apparent. In 2017 the main users for EO were:
- Commercial users with 44.68% of satellites (up from 21% in 2016)
- Government users with 30.81% (down from 44% in 2016)
- Military users with 19.45% (down from 30% in 2016)
- Civil users with 5.16% (approximately the same as in 2016)
It should be noted that some of these satellites have multiple users.
Orbits of Earth observation satellites
In terms of altitude, unsurprisingly the vast majority, 92.25%, of EO satellites are in low earth orbits, 6.45% are in geostationary orbits and 1.3% are in an elliptical orbits.
There is a much greater variation in type of orbits:
- 415 in a sun-synchronous orbit
- 234 in a non-polar inclined orbit
- 17 in a polar orbit
- 8 in an equatorial orbit
- 5 in an elliptical orbit
- 5 in a Molniya orbit (highly eccentric elliptical orbits of approximately 12 hours)
- 45 satellites do not have a type of orbit listed
Few interesting facts about active Earth observation satellites
- Oldest active EO satellite is the Brazilian SCD-1 Meteorology/Earth Science satellite.
- Valentineâ€™s Day (14th February) 2017 saw Planet launch its Flock 3P meaning that 88 active EO satellites were launched on that day.
- Most popular launch site is Satish Dhawan Space Centre operated by Indian Space Research Organisation (ISRO) who have put 169 into space.
- ISROâ€™s Polar Satellite Launch Vehicle is also the most popular launch vehicle with 114 satellites.
- The EO satellite furthest away from the Earth is the USAâ€™s Electronic Intelligence satellite Trumpet 3 which has an apogee of 38 740 km.
Itâ€™s not clear whether the rapid growth in the number of EO satellites will continue into 2018. Planet, one of the key drivers, announced earlier this month that they had successfully completed their objective to image the globeâ€™s entire landmass every day – which is a massive achievement!
Thatâ€™s not say that Planet wonâ€™t push on further with new ideas and technologies, and other companies may move into that space too. China launched a number of EO satellites last weekend and there are already a number of interesting satellites planned for launch between now and the middle of 2018 including, Cartosat-2ER, NovaSAR-S, GOES-S and Sentinel-3B to name a few. .
One thing is for certain, there is a lot collected EO data out there, and it is increasing by the day!