Envisat - the detail's in the data…
Envisat N° 4 In a cool, air conditioned room on the ground floor of a modern building on the outskirts of Rome, a young scientist is carefully handling a "pizza". But this "pizza" is certainly not for eating. It's the term coined by researchers at ESRIN, the European Space Agency's centre in Italy for the large rectangular cassettes on which information from space is soon to be stored.
Containing 1.7 km of tape, these "pizzas" will hold the huge amounts of data that will shortly stream down from Envisat, the environmental monitoring satellite from the European Space Agency, slated for launch at the end of February 2002. Perhaps the most complicated satellite the Agency has ever launched, Envisat will look down on the Earth with an unparalleled array of complex instruments. But it's not just the complexity of the instruments that's exciting scientists all over Europe. Many say it's more the quantity and quality of the data that will flow from Envisat that's the real cause of scientific interest.
For scientists involved in climate research, the belief is that the data in the "pizzas" will resolve some of the outstanding issues in global climate change. If this happens, say the scientists; they have no doubt that Envisat will also directly impact the actions of politicians at both national and European level.
Mark Doherty, head of the exploitation division at ESA/ESRIN is highly confident about the impact of Envisat. "Robust reliable global environmental information is going to be an economic, political and eventually a security must within the next 5 to 15 years. It's going to be red hot. And Europe must have the capability to get this information." He believes that Envisat can deliver this valuable resource not just for scientists and politicians but for citizens as well. So what convinces hard headed scientists like Mark Doherty that a lone satellite can so change the world we live in? It's the simple faith that good science can lead to political decisiveness and informed public opinion. And this belief is based on the bedrock of good data.
Most scientists, whatever their field, will concede that although they seek truth, they do not know it or even generate it. The only thing that science really has is observable evidence. As Francis Bacon said almost 400 hundred years ago: "For man is but the servant or interpreter of nature, what he does and what he knows is only what he has observed of nature's order, in fact or in thought".
But while evidence or data gives science the strength of its conclusions, the nature of data can also weaken science and cast doubt on its ability to characterise reality. Nowhere is this more evident than in relation to climate change.
Let's look at some of the outstanding areas of contention. Despite general scientific agreement on the role of carbon dioxide in causing global warming we are still uncertain about how much there is and how much is absorbed by the seas and forests.
Prof. Hartmut Grassl is a former director of the World Climate Research programme (WCRP). He says that our lack of scientific understanding about the release and retention of carbon dioxide feeds into a much broader political argument. According to Prof. Grassl, Envisat will provide an independent and unbiased resolution to this problem.
"There is a sensor on Envisat which will give us the CO2 content of the atmosphere - it's an instrument called SCIAMACHY. This will be a major breakthrough of our understanding of the carbon cycle. With this data we could derive the sources and sinks of carbon. If you have the full content of carbon in the atmosphere for a certain place and you measure it every few days, you can run a model and ask it how strong was the net source or sink of carbon over Germany or Britain or the Atlantic. By combining your model with information from Envisat, you would be able to say if the German forest is really a sink of carbon in the summer - this is a good example of the use of science data for a political decision."
This could have a major impact on current political negotiations. Arguments over the levels of carbon sequestration are dominating the negotiations between the parties implementing the Kyoto Protocol. According to Jos Delbeke, one of the leading negotiators for the European Union and director of the European Commission's climate change department, the promise of the Envisat data could really help the politicians.
"Satellite data in general are pretty weak except for carbon dioxide emissions. Non CO2 gases and carbon sequestration are the areas in which we have major uncertainties and indeed even methodological problems - But if we can get a regional and global picture on sequestration from the SCIAMACHY instrument that would be a major advantage. There are lots of questions on which we have not got good information and not even a good methodological basis, and this Envisat methodology could be useful for that."
As well as breaking new ground with instruments that are state of the art, Envisat will also impact because these instruments will work together in unprecedented ways. And for scientists the ability to have different data from different instruments, all working together is very exciting. According to Dr. Bryan Lawrence, head of the British Atmospheric Data Centre at the Rutherford Appleton Laboratories, this will be a key advantage of the data from Envisat.
As an example, he points to the ongoing problems with Ozone. Despite successes in recent years in removing chloroflourocarbons or CFCs from the environment, Dr. Lawrence says there are still huge gaps in our understanding of the Ozone layer. "People keep saying that Ozone is a solved problem, we have these international agreements and it's all over now, we just have to wait for this stuff to get out of the atmosphere. It's just not that simple. We don't know about the chemicals that have replaced CFCs. Are they really that safe? Everyone thought that CFCs were safe, for 60 - 80 years they were the safest things going, you could drink the things, and they were that safe! Except nobody knew about his or her impact on Ozone. With some of the replacements we already know we don't understand the chemistry as well as we should. Envisat will give us instruments that will measure the chemistry with unprecedented resolution and it's the synergy of having those measurements that will be significant. Again it's the synergy of the data that will make it special."
These are just some of the controversial scientific questions that Envisat will attempt to answer. But what makes Envisat's answers different from any one of a dozen other space based platforms? It's the data. The quantity, quality, and evaluation of which break new ground for an earth observing satellite.
Envisat has ten instruments that will churn out a huge range of data. Every day enough data to fill the hard disks of hundreds of PCs will be beamed down to earth, collected via listening stations and assembled at ESA/ESRIN in Rome. According to Olivier Arino, who heads the project section developing application products for institutional users at ESRIN, Envisat is unique in data terms.
"It is the only one that will be providing, operationally in near real time, the bunch of data required by institutions to monitor the Kyoto protocol implementation and other environmental treaties". But size isn't everything. According to Mark Doherty, sometimes small amounts of data can give you vital information. "The altimeter on Envisat for instance can measure changes in sea surface level in centimetres, so if you want to monitor where sea levels are rising, this is essential. This instrument produces small amounts of data but the value of the information far outweighs the amount of data. The data amounts are interesting but its much more interesting to know the insights and the global vision that you get from them."
Data in whatever quantities can be very useful for scientists but only if it is reliable. There have been controversies in the past where information from satellites has not matched up to observations taken from the Earth. So how will ESA ensure that Envisat's data is trustworthy? "As a matter of credibility we are co-ordinating with a world wide organisation, the Committee on Earth Observation Satellites", says Yves-Louis Desnos, who manages the scientific projects of Envisat at ESA/ESRIN. "We ensure current data sets between the different earth observation missions, from NASA and ESA and others. We have financed a ship campaign in Miami, where we put on the same ship all the instruments used to calibrate and validate the measurements of the ocean temperature. With this information we can ensure that the measurements made by Envisat or by American satellites have the same traceability and are calibrated with each other. This allows us to be able to monitor ocean temperature variation over ten years with an accuracy of 0.3 degrees. Then we can monitor trends in the global climate with confidence."
Many other scientists across Europe are involved in this calibration and validation process. Dr Ian Robinson from the School of Ocean and Earth Science at Southampton Oceanographic Centre explained how he will ensure the accuracy of the information coming from the MERIS instrument. This medium resolution imaging spectrometer takes images of the sea surface and clouds and is able to see the colour of the ocean over ten wavelengths, "it lets us see not just what our eyes would see but much, much more" says Dr. Robinson.
He is calibrating the measurements himself using information from other sources such as buoys and ships and will compare the initial data from Envisat to these.
Ian Robinson also says that this time, ESA have really got ahead of the game when it comes to processing the information. "ESA are geared up more than ever before to swing into action, the algorithms are ready and waiting to receive the data for things such as chlorophyll measurements which is really important because it tells us how much CO2 is in the sea. They've had plenty of trial runs with dummy data sets. We know that the systems are in place."
Bryan Lawrence stresses that "ESA has spent a lot of money on validation of Envisat data. There's a big programme with a much higher priority than before. Scientists will be able to have much more confidence in the data. ESA has got the planning right."
Speed and immediacy of information are also critical. Yves-Louis Desnos says that the near real time capability of Envisat will make a very big difference. "Before you had to image a site and wait 35 days before getting data. If you wanted readings from different instruments it would be even longer. Now with Envisat we can have simultaneous observation of say, sea surface temperature, with high accuracy, we can monitor the waves on the ocean and the forests over land - and all this at the same time!"
The prospect of all this data is proving a splendid appetiser for European scientists. So far over 700 have applied to work with the information that will flow from Envisat. But given that there is so much data, and so many hungry scientists wanting to get their hands on it, how will the information flow smoothly from space to the lab?
A critical aspect according to Bryan Lawrence is the application of Internet technologies for distribution. He believes that the Grid will make a big impact on the flow of data. The Grid is a more complicated form of the Internet that uses the processing power of all the computers connected to a network to vastly increase the abilities of any one machine. "What's happening is that the research community is starting to use tools developed by computer scientists and network communities to make things happen in ways that are cheap and fast, instead of having to build a multi-billion Euro infrastructure to move the information around. It's simply the bandwith - with the Internet now and the Grid in the future, and the fact that it's prevalent and pervasive."
Jean Paul Malingreau is an adviser in the Joint Research Centre of the European Commission. This is a separate directorate that provides the scientific advice and technical know how to support EU policies. He agrees that the present flow of data from present space missions into the hands of politicians is very slow. "It is slow, for various reasons, the issues are rather complex, and scientists have to convey the complexity of the issues and often there is uncertainty over the causes particularly in relation to climate change. What is clear is that there is more in the research output than reaches politicians and the public - In terms of satellite data collection there is a lot of it that is not used to optimum level."
He says that politicians now have far more awareness of the need for good data particularly in the years ahead when negotiations over the environment will intensify and accurate ways of checking up on agreements are desperately needed. "It's certainly true we would like to see more of the research being used and the politicians would like to have more of the research on standby, if you like, in the course of negotiations or in the course of making decisions."
Members of the European Commission according to Malingreau will warmly welcome Envisat. "Envisat is a formidable machine, it's of a highly complex nature, with ten instruments on board and will provide a broad variety of data and information on a variety of parameters which are important for the evaluation of global change. I think it will have significant impact on the research and on the progress on understanding the phenomena of global change. When that is done it must still be conveyed to politicians, but its part of a chain of information. And good input equals a good result." Scientists say that Envisat offers a unique new development that will make a greater impact on the political process. It is user driven. Bryan Lawrence says that Envisat will be "more responsive to end user demands". Oliver Arino from ESA/ESRIN says that he and his colleagues are now talking to EU politicians and planners, particularly the Environment Directorate of the European Commission. "We are trying to find out at EU level what their needs are."
He quotes the example of the EU wide directive on the use and conservation of water. "Envisat can give a regional picture across the EU. They can get information from national governments but they need an instrument that can allow them to make comparisons across the whole of the EU. Data from Envisat is the only way to provide it".
And it is not just at the European level that Envisat is set to make an impact. At national level Envisat data will be used to ensure that countries are keeping their commitments under the Kyoto Protocol. And the word has spread down from governments to political and civil institutions. Olivier Arino quotes the example of the Italian civil protection authorities. "They came and saw us in ESRIN, and asked us to demonstrate the ability of Envisat to map burnt forests, something that's a legal requirement in Italy. These people are ready with finance to access this information when we can deliver it".
The launch of Envisat is coming at a good time when both politicians and scientists are aware of the capabilities of the satellite and both are hungry for its information for different purposes. But according to Jos Delbeke, of the EU's Climate Change department, scientists must overcome one big hurdle if they want their data to really impact the political process.
"Science has an open recognition of the uncertainties in the system. We have to have the courage to sum up from time to time and to build on a majority view of scientists to communicate to the politicians where we stand. If we are going to wait for a final answer from science, for a 100 percent consensus, I think we are waiting for Godot. If everything is uncertain then politicians won't be able to sort out issues on which we can already act. So increased levels of confidence by scientists in their data would help the political process enormously."
According to Bryan Lawrence this is a core strength of the Envisat data. "People will only need to know what they want, not how to get it. All they need to do is ask the right questions, they won't need to know how to get to the information to answer them - I may never be able to give a politician a black or white answer, but thanks to the complexity and speed of the data from Envisat, I'll certainly have far more confidence in my response."
Another key point for the acceptance of Envisat data on a political level is that it must make "a real difference to real people" according to Ian Robinson. "Its payback time. Scientists have been funded for many years to develop an understanding of the oceans, now that we can measure surface temperature, and the colour, etc. it's time for society to benefit. ENVISAT will also be useful when it comes to things like algal blooms and detecting waves and monitoring pollution and oil spills. In these real time scenarios ENVISAT will make a real difference to people."
And even if science and politics cannot solve all the problems of the environment, Ian Robinson says there is one overwhelming reason why data from Envisat will have a global impact. "It's all about the continuity of data. We owe it to the world to go on collecting the statistics. In many ways we've only just begun and we need to go on to the next generation. We may hand our children an environmental mess but at least we can have accurate data with which to develop solutions. It's our moral duty to collect this data and hand it on".
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