**4. Potential Instrument, Suitable Platforms, and Technological Limitations**

After the survey of the suitable EO technologies in terms of the spatial resolution, swath, mass and power consumption, in this section, the suitable small commercial platforms and technological limitations of the potential sensors are identified. Tables 6 and 7 show the potential technologies studied in this work, with the suitable platforms and limitations with respect to the needs detected in the horizon 2020–2030. Platforms are selected according to their capacity to support the instrument mass and power consumption (available commercial platforms surveyed, Tables A1–A3). Additionally, it takes in to account the platforms with minor categorization (e.g., nano-, micro-, or mini-platforms), that satisfy both requirements. Special attention has been paid to the possibility to use new techniques and smaller platforms, focusing on the quality of the measurements as compared to the ones generated by full-fledged payloads onboard large spacecrafts. Indeed, since a small platform also means less volume, mass, power and data rate for the payload, the measurements are usually of reduced quality. Depending on the mission (i.e., environmental data), this may be compensated by more frequent data acquisitions (exchange between measurement quality and revisit time), yet to be evaluated on a case-by-case basis. A brief the potential instruments, suitable platforms, and technological limitations are explained below:


(Table 7). Scatterometers are valuable sensors for wind measurements. However, the main limitations are the coarse accuracy and spatial resolution of the data. However, their wide swath and the possibility of scatterometer constellations open the door to improve the accuracy and spatial resolution, combining the data from multiple passes of different satellites.





**Table 6.** *Cont*.

and mass requirements:

 very lightgray:

nano-platform;

 light gray:

micro-platform;

gray:mini-platform.

#### *Remote Sens.* **2019**, *11*, 175


