This paper presents a reliable and low cost greenhouse gas measurement system. The system mainly consists of an unmanned aerial vehicle (UAV), a set of calibrated sensors, a wireless system and a microcontroller. The system can measure the concentration of greenhouse gases namely carbon dioxide (CO2), methane (CH4) and ozone (O3) at different altitudes. It can also measure temperature, humidity and atmospheric pressure. The system is able to send data to a remote monitoring station. The UAV is equipped with image processing based navigation and landing system so that it can land autonomously on a designated place. To ensure safe landing the system uses a specially designed parachute. This paper also presents some data generated by the system.