# A New Orbiting Deployable System for Small Satellite Observations for Ecology and Earth Observation
## 2 Small Satellites for VIS, TIR, and MW Remote Sensing
### DORA: Deployable Optics for Remote Sensing Applications  
The development of small satellites highlighted how EO through remote sensing relies on the compromise between the necessity of high spatial, spectral, and temporal resolutions, payload miniaturization, and the availability of resources from space agencies and companies for the space program. The data acquired in the spectral range from VIS to MW suffer particularly from the smaller size of the telescope or antenna. The limited size and weight resources, mandatory for small satellites, implies a small primary mirror, and/or a lower length of the telescope assembly, reducing its performance in terms of spatial resolution and SNR. Large satellites can indeed host sensors as large as 500-600 mm in diameter, whereas small satellites can accommodate sensors with diameters as large as 300-400 mm (cf. Table 2 and Table S1 in the Supplementary Material). The lower area of the collector represents the troublesome challenge for having data at a high resolution. Remote sensing payloads operating in the MW suffer as well because of the antenna's size and the platform's altitude (the higher the platform altitude, the larger the antenna needs to be to obtain a reasonable spatial resolution). The new design concept, based on a deployable approach (e.g., [24]), represents a viable architecture to accomplish scientific objectives and applications that are otherwise difficult to reach by small satellites. The deployable technology allows both minimization of the payload volume during the launch and the cruise to the final orbit, and good performances, similar to those of the instruments mounted in larger platforms, during the period of activity. Precision-deployable, stable, optical telescopes, which can fit inside small and low-cost launch vehicles, are prime examples of a technology that will yield breakthrough benefits for future scientific and commercially-oriented applications (e.g., [87]). Similarly, SAR technology synthesizes the flying altitude through a tailored signal processing, allowing to increase the spatial resolution using an antenna much smaller than the physical antenna used in an RAR system [70]. The Italian Ministry of Research funded the \"Deployable Optics for Remote sensing Applications\" (DORA) project in the framework of the Italian National Research Plan 2015-2020, which will be active until April 2022. DORA is a partnership between private companies (led by SITAEL, the largest Italian private company operating in the space sector), research institutes (INAF--Institute for Space Astrophysics and Planetology (Rome) and INAF--Astronomical Observatory of Padua), and academic centers (University of Naples \"Parthenope\" and Politecnico of Milan) (e.g., [87]). The objective of the project is to design, realize, and test a prototype of a deployable optical system for remote sensing applications in the VIS to TIR spectral range, and a planned application in the MW spectral range. A deployable telescope and a straylight shield will be interfaced to a focal plane instrument, which can include either a camera or a Fourier spectrometer. The telescope, kept in a closed configuration during the launch to minimize the volume, is then fully deployed by means of actuators in its operative configuration once in flight. A similar deployable system could be eventually modified for extending the antennas used for microwave instrumentations (e.g., [65; 88]). The DORA system has been realized as a prototype for the next generation of space instruments for EO. It has, therefore, been designed to satisfy the requirements of a selection of applications in the ecological and environmental fields, which would best take advantage of deployable instrumentations. These applications will be presented and discussed in the following Section 3, to highlight the efficiency of the deployable systems, and to discuss more generally the efficiency of small space platforms for remote sensing acquisitions.