# An Overview of CubeSat Missions and Applications
## 3 CubeSats as Earth Observation and Earth Science Platforms
### The Role of CubeSats in Earth Science Missions  
Apart from traditional Earth observation applications such as terrain imaging and atmospheric condition monitoring, CubeSats can also serve as platforms that enable researchers to conduct advanced Earth-related scientific measurements and experiments. In that regard, a standout example is the QB50 project which was coordinated by the von Karman Institute for Fluid Dynamics. QB50 culminated in the creation of an international network of fifty 2U and 3U CubeSats for the study via in situ measurements, of the, until then, least explored layer of the Earth's atmosphere, the middle and lower thermosphere. For this mission, some of the program's satellites utilized equipment such as Ion and Neutral Mass Spectrometers (INMS) that could read the composition of the thermosphere by detecting and measuring heavy particles such as O, O\({}_{2}\), NO and N\({}_{2}\). Moreover, for the study of the electron temperature in the thermosphere, multi-Needle Langmuir Probes (mNLP), which are able to probe the electron density were used in some of the CubeSats. Finally, the rest of the QB50 CubeSats measured atomic and molecular partial pressures through the use of Flux Probe EXperiment (FIPEX) which comprises separate solid electrolyte sensors [113; 114; 115]. Another example of an Earth science CubeSat mission is the Polar Radiant Energy in the Far-Infrared Experiment (PREFIRE), comprising two 6U CubeSats in near-polar orbits that were developed jointly by NASA and the University of Wisconsin-Madison. The two PREFIRE CubeSats are equipped with a Thermal Infrared Spectrometer (TIRS), which is used to measure the amount of energy that is emitted by the Arctic and Antarctic regions of the planet towards space in the form of FIR radiation. One of the primary goals of the PREFIRE mission is to determine the amount of thermal energy that is radiated by the snow and ice covering the Earth's polar regions in the FIR spectrum and how this emitted energy fluctuates around the year. Furthermore, the CubeSats are also tasked with studying the polar greenhouse effect by measuring the amount of FIR thermal energy that is trapped by the cloud cover and atmospheric water vapor content of the polar regions. This data can then be used to create improved climate and ice-cover-evolution models for the two polar regions of the planet [116; 117]. A notable upcoming Earth science CubeSat mission is the PREcursory electric fiEd observation CubeSat DEmonstrator (PRELUDE), a mission involving the launch of a 6U CubeSat which is developed jointly by Nihon University, Shizuoka Prefectural University, and the University of Shizuoka under the mission of detecting local ionospheric fluctuations that indicate the upcoming occurrence of an earthquake, and in this way, aid in the prediction of upcoming earthquakes some hours in advance, offering short-term prediction and disaster mitigation capabilities. To perform its mission, the satellite will be equipped with two hybrid Very Low Frequency (VLF) sensory probes used for electric field and plasma field measurements, each in the free point of a 1.5 m extendable boom and a GNSS receiver which is going to be utilized for the monitoring of the ionosphere's electron density [118; 119]. PRELUDE is not the first CubeSat mission in this field, with past examples of CubeSat platforms which were also tasked with the mission of demonstrating the concept of earthquake prediction through the detection of disturbances in the ionosphere including QuakeSat-1 [120; 121] and APSS-1 [122]. An example of a notable recently launched Earth science CubeSat mission is Electrojet Zeeman Imaging Explorer (EZIE). EZIE comprises three 6U CubeSats that were developed by the Applied Physics Laboratory (APL) of the Johns Hopkins University. The primary mission of these three satellites will be to study the formation and behavior of auroral electrojets, testing how the proposed scientific models correspond to reality and thus provide a better insight into the physics of the Earth's magnetosphere.