Weathering heights

By investigating the upper reaches of our planet's atmosphere we can learn much about the earth's climate and our impact on it.

The problem is that the equipment for monitoring this extreme environment — from balloons, to satellites, to specialised research aircraft — is often expensive, sometimes unreliable, and simply unable to carry out the sort of continuous analysis that's required for truly accurate climate models.

The answer, according to a group of European scientists and engineers, is to tap into a resource that has been staring us in the face — or, to be more accurate, flying above our heads — for the past 50 years.

The team, an alliance of academics and engineers from industry giants Airbus, Lufthansa and BA is investigating the possibility of using existing commercial aircraft to create a global sensing network that will probe the troposphere and stratosphere with unprecedented regularity.

Dubbed IAGOS (Integration of routine Aircraft measurements into a Global Observing System) the EU-funded project is the continuation of an earlier initiative named MOZAIC, (Measurement of Ozone and Water vapour by Airbus In-service aircraft) which equipped a small fleet of passenger aircraft with a package of ozone, water vapour, carbon monoxide and nitrogen oxide sensors.

The project's leader, Dr Andreas Volz-Thomas of Germany's Juelich research centre, explained that the aim of IAGOS is to expand on this with a slimmed down, more advanced sensor package that will be deployed on a larger number of aircraft.

The initial plan is to install the payload on a fleet of 10 to 20 Airbus A340s for which the group has a so-called Supplemental Type Certificate (STC) authorising it to make particular modifications. Volz-Thomas said he hopes soon to gain a similar certificate for A330s which are typically flown on shorter routes and can therefore provide a more detailed vertical profile of the atmosphere.

Weighing around 220lbs (100kg), compared to the 180kg of the MOZAIC payload, the sensor package will be installed in the avionic compartment beneath the cockpit. A340s are particularly well-suited to the project as this compartment contains a handy bit of free space which is designed to accommodate a rarely used optional refrigeration system.

As for the nature of the payload, as well as the ozone, CO and NOx instruments from MOZAIC, IAGOS will contain a number of new instruments.

One of these, a cloud particle sensor, is currently under development by a Manchester University team.

The device weighs around 2kg and consists of a tiny laser, which will fire a beam through a small window in the avionic compartment, and a small telescope for retrieving the backscattered light. Volz-Thomas said the data acquired by this system could lead to big improvements in climate models. 'You need to know the particle distribution to do the radiative transport model to feed into climate models and to understand cloud formation,' he said.

The Manchester team is also working alongside scientists at the German Aerospace Centre (DLR) on the development of optical particle counters that, mounted inside the aircraft, will be able to measure the full range of particles in the air.