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When the 'expert testimony' comes from space

Jonathan Amos | 18:27 UK time, Wednesday, 6 October 2010

It may have been the 53rd anniversary of Sputnik this week but satellites are still a relatively new phenomenon.

They're not quite all pervasive - although it's fast heading in that direction. As I posted recently, the average number of spacecraft launched per year this decade is expected to exceed 120, up significantly on the 77 per year during the 2000s.

More and more, what these "birds" do and see is going to impact our daily lives.

This was very evident from the fascinating workshop [100KB PDF] I attended this week organised by the London Institute of Space Policy and Law.

Increasingly, Earth observation (EO) data acquired by satellites is being introduced as evidence in courts and tribunals.

What sort of information is admissible? What weight should such evidence carry? Should it be treated any differently from the electronic evidence of a scientific nature presented by other expert witnesses? And do lawyers understand enough about what satellites are capable of doing to begin to examine the evidence properly?

Clearly, some American defence lawyers have cottoned on, and, wary of its power, have challenged this "newfangled" information on the basis of the Fourth Amendment to the US Constitution, which prohibits search without warrant.

It's something we're all going to have to get used to, however.

Radar image of oil spill

The elongated dark feature in this radar image is typical of an oil discharge from a ship

In Europe, we should see the first of a new fleet of remote-sensing satellites called the Sentinels launch in 2012/2013. Initiated by the EU and Esa, these spacecraft will be dedicated to environment and security monitoring.

They will have many tasks but a key one will be to help enforce EU and member state legislation.

Two good current examples give a glimpse of where this trend is going.

One concerns the Common Agricultural Policy and the direct payments made to Europe's agricultural businesses.

Farmers will receive some 43bn euros this year to look after the continent's land. A small portion of this cash is directed at supporting particular crops but the vast majority of it goes into ensuring farmers manage the countryside properly - to maintain soil quality and natural habitats, and meet certain animal welfare standards, etc.

To check they haven't put a golf course on a piece of land they took money to maintain as pasture, satellites are tasked with taking pictures of the farmland. Something like 430,000 farms across 24 EU member states will be monitored in this fashion this year.

The number is actually quite a small fraction of the total number of farms but because farmers have no idea when a satellite might pass overhead, there is very little non-compliance, the European Commission reports.

Nonetheless, lawyers will go after fraudsters with the satellite imagery in hand.

Sentinel-1

Europe will soon launch its Sentinels

Likewise, radar spacecraft are used by the European Maritime Safety Agency (EMSA) to monitor for any illegal discharges of waste oil by ships.

The presence of oil in the water works to flatten the sea-surface somewhat and if wind conditions are just right, radar can sense this damping effect.

The discharge will appear as a long dark band in a radar image. A ship "caught in the act" will appear as a bright spot at the head of the trail.

Aircraft are scrambled to check out a possible infringement; and since the CleanSeaNet system was set up in 2007, about a quarter of the 2,000 potential spills investigated up to 2009 were confirmed as transgressions. Subsequent prosecutions would have been taken up in member state jurisdictions.

To be honest, most of this is fairly straightforward, and the satellite evidence in these instances tends to be secondary or complementary anyway to other material presented in cases.

Where the arguments are likely to get more intense is in those cases that rely on information from very complex or novel observation approaches.

For example, litigators dealing in subsidence claims will resort to Persistent Scatterer Interferometry, a smart but tricky radar technique capable of sensing millimetric changes in the elevation of the land or cityscape over several years.

It's powerful stuff, but you can see how an opposing lawyer might want to cast doubt on the calibration of the satellite instrument, query the atmospheric conditions that can introduce noise into the radar signal, and even question the modelling that underpins the processing of the raw data squirted out the back of that instrument. And who wrote the software and how many errors does it contain?

As Dr Kevin Madders, an expert in space policy and law, explained to me, using satellite data in a legal context requires very exacting standards:

"This is all about a technology which is still new and we're still getting to grips with it in an environment where it really matters because you're affecting peoples' rights and duties, both before courts which are very obvious but also before administrative tribunals which have these days an enormous role to play in society. When that happens, the kind of scientific-research, public-service uses we've traditionally employed the satellite data for recede to a different level. The level we're talking about here is one of the most testing in terms of what you mean by 'fact', because you have to prove that under standards where it's not just something which will go into a science journal or textbook, however important that might seem. This is where you can change someone's position in relation to the state or another person."

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