Earth Observation (EO) satellites account for just over one quarter of all the operational satellites currently orbiting the Earth. As noted last week there are 1 419 operational satellites, and 374 of these have a main purpose of either EO or Earth Science.
What do Earth observation satellites do?
According to the information within the Union of Concerned Scientists database, the main purpose of the current operational EO satellites are:
- Optical imaging for 165 satellites
- Radar imaging for 34 satellites
- Infrared imaging for 7 satellites
- Meteorology for 37 satellites
- Earth Science for 53 satellites
- Electronic Intelligence for 47 satellites
- 6 satellites with other purposes; and
- 25 satellites simply list EO as their purpose
Who Controls Earth observation satellites?
There are 34 countries listed as being the main controllers of EO satellites, although there are also a number of joint and multinational satellites â€“ such as those controlled by the European Space Agency (ESA). The USA is the leading country, singularly controlling one third of all EO satellites â€“ plus they are joint controllers in others. Of course, the data from some of these satellites are widely shared across the world, such as Landsat, MODIS and SMAP (Soil Moisture Active Passive) missions.
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.
Who uses the EO satellites?
Of the 374 operational EO satellites, the main users are:
- Government users with 164 satellites (44%)
- Military users with 112 satellites (30%)
- Commercial users with 80 satellites (21%)
- Civil users with 18 satellites (5%)
It should be noted that some of these satellites do have multiple users.
Height and Orbits of Earth observation satellites
In terms of operational EO satellite altitudes:
- 88% are in a Low Earth Orbit, which generally refers to altitudes of between 160 and 2 000 kilometres (99 and 1 200 miles)
- 10% are in a geostationary circular orbit at around 35 5000 kilometres (22 200 miles)
- The remaining 2% are described as having an elliptical orbit.
In terms of the types of orbits:
- 218 are in a sun-synchronous orbit
- 84 in non-polar inclined orbit
- 16 in a polar orbit
- 17 in other orbits including elliptical, equatorial and molniya orbit; and finally
- 39 do not have an orbit recorded.
Our first blog of 2016 noted that this was going to be an exciting year for EO, and it is proving to be the case. Weâ€™ve already seen the launches of Sentinel-1B, Sentinel-3A, Jason-3, GaoFen3 carrying a SAR instrument and further CubeSatâ€™s as part of Planetâ€™s Flock imaging constellation.
The rest of the year looks equally exciting with planned launches for Sentinel-2B, Japanâ€™s Himawari 9, Indiaâ€™s INsat-3DR, DigitalGlobeâ€™s Worldview 4 and NOAAâ€™s Geostationary Operational Environmental Satellite R-Series Program (GOES-R). We canâ€™t wait to see all of this data in action!