skCUBE very-low-frequency radio waves detector and whistlers

skCUBE is 1U cubesat designed and developed in Slovakia over a period of years from 2012–2015 with expected launch in to the low-Earth orbit in 2017. It carries an experimental very-low-frequency (VLF) radio waves detector, which will attempt to record whistlers — radio signals from dispersed radio frequency components of lightning's. A lot has been found about these radio waves caused by classical lightning in past already, but there is not much known about VLF radio from rarer terrestrial luminous events (TLE) like gigantic jets. Gigantic jet is a type of lightning directed upwards between storm clouds and lower ionosphere. We will attempt to use VLF data from this detector to learn more about these phenomena. However, in essence we want to study peculiarities in all detected VLF spectrums regardless of type of lightning together with properties of Earth's ionosphere. Due to design limitation of skCUBE, we placed the VLF detector inside the satellite. The VLF detector consists of air-core loop antenna, trans-impedance amplifier and microcontroller capable of signal processing directly on-board. It works in two modes, slow and fast. Slow mode will detect gradual changes in VLF radio on timescales comparable to the whole orbit of satellite (< 90 minutes), whereas the fast mode will be capable of fast sampling of short events like whistlers (< 0.1 seconds) based on excess in pre-determined power flux density threshold.