# An Overview of CubeSat Missions and Applications
## 9 Review Conclusions and Discussion
### CubeSats in Earth Observation and Earth Science Missions  
Since the advent of CubeSats, Earth observation and science has been one of the primary fields in which these platforms are employed in, with the number of satellites of this category eclipsing all the other ones. Over the years, a considerable number of missions has been undertaken with the goal of testing and demonstrating the operation of a variety of passive Earth observation instruments such as imagers, spectrometers which operate in the visual or IR bands, radiometers, as well as radar imaging instruments. Through these missions, the quality and effectiveness of such payloads have steadily improved, eventually leading to an array of mature, high-performance commercially available products such as cameras and spectrometers from a variety of different suppliers. The existence of such commercial products has contributed to the exponential rise of new Earth observation CubeSat missions, lowering the barrier of entry into the Earth observation sector and enabling institutions with otherwise limited monetary and technical resources to develop Earth observation missions of their own. Moreover, the low costs associated with the design, manufacturing, and launch of CubeSats have facilitated the creation of large constellations that are aimed at providing continuous data of the surface of the planet regarding applications such as terrain visual imaging and wildfire monitoring through the use of TIR instruments. Apart from optical instruments, microwave sensory instruments have also been utilized by CubeSats as a means of Earth observation. More specifically, due to their low power consumption, passive microwave instruments have been heavily utilized by Earth observation and imaging CubeSat platforms, with notable examples being scatterometers which are used for missions that involve altimetry and terrain mapping through the use of the GNSS-R technique. Furthermore, despite their small size and low electrical power generation capacity, some active radar sensors have also been successfully incorporated in CubeSat missions, with a notable example being JPL's RainCube mission which used a deployable Ka-band active mesh reflector antenna to observe precipitation processes. Moreover, as of 2025, there have been a variety of CubeSat platforms under development that aim to utilize active radar sensors in the form of SAR for Earth imaging missions from LEO altitudes. It should be noted that these SAR CubeSat concepts do not only encompass single-platforms demonstration missions but relatively large constellations as well, something that suggests a considerable degree of miniaturized SAR technology maturity. Furthermore, in a manner similar to their large counterparts, Earth observation CubeSats have also been widely employed in the field that is dedicated to atmospheric condition and weather monitoring with Spire Global's Lemur constellation being a well-known example, utilizing the GNSS-RO technique to access the conditions of the atmosphere and ionosphere. Another prominent example is NASA's TROPICS constellation that utilizes radiometry to perform remote measurements on the generation and evolution of tropical storms. Furthermore, new commuted cloud tomography technologies are going to be demonstrated in the immediate future by the CloudCT mission and if they prove feasible, these new atmospheric condition monitoring technologies will help in refining the accuracy of weather monitoring and forecasting. The success of CubeSats in this specialized subfield of Earth observation is reasonable as CubeSat platforms can form the cornerstone of medium and large atmospheric monitoring constellations that provide continuous, real-time atmospheric condition data flows over large areas and therefore significantly improve weather monitoring and prediction capabilities. Therefore, the number of atmospheric research CubeSats is most certainly expected to rise significantly over the next decade.