Skip to 0 minutes and 8 seconds My name’s Debbie Clifford, and I’m an Environmental Data Consultant at the Institute for Environmental Analytics. Satellites are a really important data source for environmental data analytics because they monitor the environment over years and continuously, and they give us a global picture, which we can’t really get from any other kind of data source. So the first Earth Observation satellites were launched in the 1960s. This was the Nimbus programme from NASA. Nimbus is Latin for cloud, and they were trying to measure some of these things that seem invisible in the atmosphere, like atmospheric temperature or the amount of water vapour. And these new global measurements really revolutionised weather forecasting and gave us much more accurate forecasts.
Skip to 0 minutes and 53 seconds We’ve continued to make observations of all sorts of parts of our environment ever since– the atmosphere, the oceans, the land surface, and the cryosphere. Different satellites will take pictures of the planet in different ways. You can have Earth Observation from what’s called a geostationary satellite, and that’s looking at the same point on the planet all the time. So you get very high resolution measurements in time, but not such high resolution in space because the satellite has to be a long way away to stay in that orbit. To get very high resolution measurements in space, very detailed, the satellite will be orbiting in a polar orbit. So it will cross the poles every day.
Skip to 1 minute and 34 seconds And that really depends on the design of the satellite and the different quantity that it’s trying to measure on the ground. As an example, the largest Earth Observation satellite ever launched was the European Space Agency’s Envisat platform. And this satellite was the size of a double decker bus, and it had nine separate instruments on it recording all sorts of measurements from rainfall to sea surface temperature to atmospheric composition. In the end, it delivered data for about 10 years, which was twice as long it was originally planned to be operational for. And all that data added up to about a petabyte. The new satellites from the European Space Agency is the Sentinel series.
Skip to 2 minutes and 16 seconds The Sentinel 2 satellites will produce around 800 terabytes of data every year. So where Envisat produced a petabyte by over 10 years, with our newest satellites, we’re getting almost that amount every single year. So we can use Earth Observation in all sorts of parts of the electromagnetic spectrum, not just the visible that we see with our eyes. So we can use, for instance, a comparison between the red part of the spectrum and the near infrared to tell us about how efficiently plants are photosynthesising. So this tells you about the health of your crops or your vegetation.
Skip to 2 minutes and 54 seconds We can also use infrared to understand the temperature of the land surface or the sea surface, which is really important for weather forecasting and climate modelling, but also for understanding more human things like the urban heat island and how that might change over time as we all live more in cities.
Observing the Earth from space
Watch Dr Debbie Clifford, Environmental Data Consultant at the IEA, explain why satellites are such an important source of data.
With satellites we can, in principle, monitor the whole planet all the time. About half of the operational satellites currently in orbit are for communications (eg for satellite TV, broadband) and there are around 100 navigation satellites, including those providing the GPS signal for your car or phone. There are also more than 350 satellites currently providing observations of our planet for mapping and cartography, or for feeding information into weather forecasting systems. These monitor various environmental conditions such as the health of crops and the amount of sea ice.
Google Earth (and the satellite imagery in Google maps) is a great introduction to the fascinating and beautiful information we can obtain from satellites, such as the varied features, colours and shapes of the land surface. As scientists we can do much more quantitative and detailed analysis of these images, for example, measuring the temperature and composition of different layers of the atmosphere.
The term Earth Observation (EO) can refer to any measurements collected about the Earth, but it’s most commonly used to refer to large-scale environmental measurements made with satellites. Satellites give us a global view of the planet, and are usually taking measurements continuously over many years. Although a measurement on the ground may be more accurate, from space we can do the large-scale, continuous monitoring which provides useful data for many applications.
Case Study: a visualisation of methane measured by satellite
This is an additional video, hosted on YouTube.
This visualisation shows data from GOSAT, the world’s first satellite dedicated to greenhouse gas monitoring. The video displays the location of methane gas concentrations detected by GOSAT since its launch in 2009 to the end of 2017. A benefit of Earth observation satellites is to gather data over previously unmeasured areas.
The video has been created for a general audience, so visual appeal and being self-contained by having explanatory text are both of value. The video was storyboarded to provide background information on methane as a greenhouse gas, as well as focusing on the importance of three different geographical areas and relevant research. The time steps in the video are variable; play speed is lower when emphasising an area and period of interest. Variable speed allows viewers to focus on the highlights whilst showing all of the data, more than 3000 days, in 2½ minutes. For the technical parts of the video visualisation, one important choice was the colour scheme. The colour scheme chosen is perceptually linear, meaning that the colour lightness values are seen to increase or decrease linearly over the measurement range. Linear colour scales are used to make it easy to interpret the data ordering, in this case, low values in the darker blue, through pinks to the higher values in the lighter yellow, without undue emphasis on any particular value.
The visualisation was created by Dr Guy Griffiths of the IEA. The underlying data was provided by Dr Robert Parker from the National Centre for Earth Observation at the University of Leicester, as part of the ESA Climate Change Initiative and Copernicus Climate Change Service projects, which we will hear more of in the open satellite data section next week.
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