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In order to be in a high state of readiness for any future volcanic eruptions, and also provide a platform capable of responding to a wider range of civil contingency events, the Met Office Civil Contingency Aircraft (MOCCA) has been commissioned.

The aircraft will be operated by the Met Office on behalf of the Civil Aviation Authority (CAA), and in a partnership between Cranfield Aerospace and DO Systems.

What is the Met Office Civil Contingency Aircraft?

The aircraft is a flexible twin engine pressurised Cessna 421 which operates with either one or two pilots and one scientist. It has been specifically chosen because it operates with piston engines at cooler temperatures. This means it is able to fly into higher concentrations of volcanic ash.

How is it going to be used?

The aircraft will be used to monitor ash during any future volcanic ash incidents. It will also be scrambled to operate in a range of situations where expert sampling of air pollutants may be required, such as oil fires like the one at Buncefield, ensuring the safety of those in the air and on the ground.

What can it do?

The aircraft is designed to monitor and measure gases and aerosols in the atmosphere. These include pollutants like volcanic ash, dust and smoke.

What instruments are on board?

The aircraft is currently configured to measure gases and aerosols in the atmosphere.

• Satellite communication gives simultaneous data and voice link to Met Office HQ Hazard Centre.
• AIMMS-20 air data probe - wing tip mounted probe that provides measurement of temperature, humidity and pressure.
• Cloud Aerosol and Precipitation Spectrometer (CAPS) probe - wing tip mounted measurement of aerosol particle and cloud hydrometeor size distributions.
• Aerosol lidar - UV aerosol backscatter lidar that provides information on distribution of aerosols / clouds above and below the aircraft.
• Gaseous inlet - supplies externally sampled air through four outlets for gas sampling instruments (currently sampling SO₂).
• SO₂ analyser.
• Iso-kinetic aerosol inlet.
• Integrating nephelometer.

How will it measure volcanic ash and other particluates?

On a typical flight the aircraft would initially fly above or below an ash layer looking at the position of the ash layers with the lidar. The aircraft will then fly in to the ash layers and measure the size and number of ash particles using the laser scattering probe on the wing. This probe works by firing a laser beam that hits the ash particles which scatter the laser light in different directions. The amount of laser light scattered gives information on the size of the particles.

Gases can be measured in flight or captured in Tedlar bags for analysis on the ground.

What happens to the observations once they are made?

The aircraft will be fully integrated in to the Met Office Hazard Centre, where the observations will be received direct via satellite by the forecasting and incident response teams.

This enables the full forecasting capability of the Met Office to be used in directing the aircraft's flight and also enables the forecaster and incident response teams to make informed decisions about the potential impacts of the ash cloud.

The observations made by MOCCA will be used to give better validation of the world-leading dispersion models used by the Met Office, which help airlines to fly safely when a volcanic eruption occurs.