Greenhouse gases, the Earth’s temperature, weather, oceans, land and all of humanities’ creations can be observed and measured from space. In fact, satellites have been observing the Earth for over 40 years. The earliest satellites carried hi-resolution cameras and returned their images in specially designed recovery capsules. These satellites were the secret military reconnaissance satellites that were the makings of many espionage movies in the 1970s.
The military have always had spy satellites capable of taking optical imagery of the earth and listening to radio broadcasts. The technology continues to get more sophisticated and now include satellites that can ‘see’ through cloud and smoke with radar. All these satellites have the capacity to beam their images back to earth.
This information can be used to exploit the Earth’s resources, or to conserve them, dependent upon the end objectives of who is analysing the data.
Then came civilian satellites, firstly the weather monitoring satellites like METEOSAT and NOAA (National Oceanic and Atmospoheric Administration), followed by LANDSAT (optical and infra-red, over a range of spectrums) and RADARSAT (radar, multiple beam modes). Some civilian satellites, such as ENVISAT (radar, infra-red, multiple instruments), paid for, owned and operated by the European Space Agency (ESA), are intended completely for civilian use, whereas others such as RADARSAT-1 and -2, although intended for principally civilian use, have been ‘appropriated’ by the military, often without the knowledge of the general public who originally provided the taxpayer funds to build them. Others, such as LANDSAT, clearly were dual use from the very beginning.
So what is this satellite imagery and how can we use the satellite information? Satellites either passively measure selected wavelengths of reflected radiation from the Earth’s surface features or they actively radiate areas of the planet with an electromagnetic pulse and capture the return signal. The observed data is digitised and sent back to Earth for processing. Once the raw image data is received, it can be post processed to provide useful information on many things, such as the following:
Land features: such as surface terrain topography for mapping and measuring geographical information, measuring population centres (from small villages to large cities), road and rail links, coastal and river erosion, volcano eruptions, fires (as shown in an image of California below), land subsidence and the movement of the earth’s continents.
Vegetation: forest size, density and health; land use (crops, urban sprawl), changes in flora and desertification, soil moisture.
Water features: river flows, lake sizes, snow and ice coverage, thickness of sea ice, monitoring ice-bergs (as a danger to shipping or indication of ice sheet break-up); ocean temperature, wave height, oil spillage and ocean ‘dead’ zones.
Atmosphere: global and local carbon dioxide (and other gases such as methane) measurements as shown in the image below, air temperatures, wind velocities, aerosols and atmospheric dust, ozone concentration, moisture content.
Weather: storm systems, cloud coverage, global (ocean and land) temperatures, wind velocities, tsunami warnings.
All of this information is put together by many organisations into geological (GIS), ocean (OIS) and weather information systems (WIS). This information is then used by analysts in universities, governments, businesses and other organisations, around the world, to better understand the processes that drive and influence how the Earth natural environment works, and how we as a species are impacting those natural processes.
This information can be used to exploit the Earth’s resources, or to conserve them, dependent upon the end objectives of who is analysing the data.
In many cases the first satellite observations did not correspond with measurements taken on the ground, in the ocean or by aircraft/scientific balloon measurements. This led to re-assessing both the terrestrial measurements and those taken from space. Now scientists and engineers understand the reasons for many of the informational differences.
Current and future space-based satellite measurements will now provide unprecedented opportunities to help us make the right choices to limit our impact on the planet’s resources, eco-system and hopefully help reduce global warming before it is too late.
One such dedicated environmental monitoring satellite is the Japanese Space Agency (JAXA) Greenhouse Gases Observing Satellite "GOSAT" which is designed to measure both carbon dioxide and methane gas.
Another new future 263MEuro (410MUS$) ESA satellite is called EarthCARE (Earth Clouds, Aerosols and Radiation Explorer). This is the sixth Earth Explorer mission in ESA’s Living Planet Program and is due for launch in 2013. It also carries a JAXA instrument and is designed to compliment GOSAT.
The EarthCARE satellite will study how aerosols, cloud formations, and the Sun’s radiation, interact and affect climate. This will provide important information to improve weather forecasting models, since aerosols influence cloud properties, clouds generate precipitation and convection drives stratospheric humidity that in turn affects the Earth’s ability to reflect or absorb the Sun’s radiation. These measurements are obtained with an Atmospheric Lidar (laser imaging radar), Broad-Band Radiometer, Multi-Spectral Imager and Cloud Profiling Radar.
The Earth Explorer series of spacecraft are designed to measure and monitor the atmosphere, biosphere, hydrosphere, cryosphere and the Earth's interior, to help us learn about the effects of human activity on Earth’s natural processes.
NASA was, and is, actively involved in climate monitoring satellites, along with NOAA and the US DOD (Department of Defence), working on the US$12billion NPOESS (National Polar-orbiting Operational Environmental Satellite System). An entire constellation is planned for future orbit. It should be a phenomenally powerful aid in monitoring Mother Earth that hopefully will not be taken over by the military or the political whims of government.
Many other space-faring nations also launch Earth observation satellites, such as Brazil and China who have worked on the optical, multi-spectral and infra-red imaging CBERS satellites. Some satellites, such as SSTL (Surrey Satellite) NigeriaSat-2 are much smaller and more economical than the satellites mentioned above, but nonetheless are powerful instruments in monitoring the planet.
Resources
ENVISAT performs radar and multi-spectral imaging of troposphere and stratosphere trace-gases, radiometer measurement of sea surface temperature, atmospheric water vapour and cloud water content, surface emissivity and soil moisture: visit http://envisat.esa.int for some really cool images of Mother Earth.
JAXA: See the latest status on the GOSAT satellite at http://www.jaxa.jp/projects/sat/gosat/index_e.html
NASA: NASA's Orbiting Carbon Observatory (OCO) will collect precise global measurements of carbon dioxide (CO2) in the Earth's atmosphere. Check out http://oco.jpl.nasa.gov. Also check out NPOESS at http://www.ipo.noaa.gov to see what 12 billion dollars will buy you.
NOAA provides weather and environmental monitoring services for the US and North America: http://www.noaa.gov/satellites.html
SPOT-Image: provides optical data from a mainly French satellite series and visit their dedicated climate change site at http://www.planet-action.org
Trevor Williams is a University of Victoria Mechanical Engineering PhD candidate specialising in renewable energy, power grid modelling and plug-in hybrid electric vehicles. He has a bachelors in Aeronautical Engineering, a Masters in Management Science and over 23 years international experience in the space industry, having worked on Earth observation and telecommunications satellites.
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