The scientific objective of the SCRAP experiment is to verify theories on electron density fluctuations in dusty plasmas by measuring the scattering of radio waves, using an incoherent scatter radar, on mesospheric micro particles.
Some background. At altitudes of about 85 km the temperature is low enough that water molecules can form small ice particles. At high latitudes these layers of ice crystals can sometimes be observed during sun set and are called noctilucent clouds. It is a fantastic sight when you see the bright wavy structures when everything else is descending into the dark of the night.
Related to noctilucent clouds are strong radar echoes from similar altitudes. The radar echoes frequently observed in summer are thought to occur due to charged aerosol particles scattering the radar waves. The aerosol particles get charged by the surrounding ionized gas. Due to their relative large size compared to other constituencies they introduce new dynamics and effects in the physics taking place.
These radar echoes are observed more and more frequently and have been discussed with respect to the changing climate. However, the understanding of the radar echoes is not good enough to use the echoes for remote sensing of mesospheric properties. Here the SCRAP experiment is aiming to contribute. By releasing a cloud of known particles and measure the radar echo from this cloud we are hopefully able to refine models and verify existing theories on radar scattering from aerosols.
To release a cloud of microparticles is the technical objective of the SCRAP experiment. For the time being we are investigating three approaches which are small explosive charges, pressurized gas, and a type of spray. The decision for one of the approaches depends on the reliability and safety. We will keep you updated with regular posts on the test progress.
For the radar system to be used for the observations a limited number of choices is available. EISCAT is a international association which operates two radars in Tromsø. Their UHF (930 MHz) antenna can be pointed in any direction giving us the possibility to point it towards the rocket trajectory. It is planned to run a test radar campaign in March 2014 which will get the students familiar with the radar system. Also data of electron densities will be measured to be used in modelling of the charging of the microparticles.