# A New Orbiting Deployable System for Small Satellite Observations for Ecology and Earth Observation
## 5 Radiometric Model as Tool for DORA Feasibility Study
We performed a feasibility study only of those applications that demanded a sensor in the VIS to IR spectral range. We carried out a radiometric analysis on the system, which allowed to quantify the radiation flux gathered by the optical system, at varying observing conditions and needed resolutions, and the signal-to-noise ratio (SNR). The SNR is then compared to the specific values given by each application to determine whether or not DORA can reach the requested requirements. In Table 4, the columns 2 to 5 and 7 summarize the requirements, from each of the applications listed in Section 3, to accomplish their specific goals. We also included for completeness the MW-related applications, listing all their requirements, and for a couple of them we assessed their feasibility. To evaluate the characteristics and performances of the optical instrument, a radiometric model has been developed. The core of such a model represents the response of the instrument, by correctly assessing the spectral response of all its constituting optical elements [305]. On the other hand, the final signal gathered by the detector also depends on the observed sources, which varied from one application to another, and the targets of which have been thus used to compute the output signal and related SNR. Due to the lack of a physical model of the instrument we are considering, in order to produce reliable and meaningful results, the spectral properties of the instrument were assumed based on previous similar projects or instruments in operation [305; 306]. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**ID** & **Scientific Area** & & **Goals** & **State-of-the-Art** & **What We Need** \\ \hline \multirow{6}{*}{_A6_} & \multirow{6}{*}{_Sea state from the vessel motions_ analysis_} & \(\bullet\) & Continuous monitoring of sea state conditions to improve the statistics of long-term wave data and optimize the route by balancing variations of the weather conditions and navigational constraints & SAR imaging (e.g., Sentinel-1, TerraSAR-X) to accurately estimate the wave parameters such as height, average length, and direction & Radar imaging GNSS and onboard instrumentation to determine the sea states from the ship movements Daily/hourly revisiting time \\  & & & & \\ \cline{1-1}  & & & & \\ \cline{1-1}  & & & & \\ \cline{1-1}  & & & & \\ \cline{1-1}  & & & & \\ \cline{1-1}  & & & & \\ \cline{1-1}  & & & & \\ \hline \multirow{6}{*}{_A7_} & \multirow{6}{*}{_EO for vessel detection_} & All-day and all-weather capabilities, large area coverage, dense revisit time, fine spatial resolution details are key assets to generate added-value products to be delivered to end-users (e.g., policymakers, local authorities) & SAR observation of vessels is a well-established and mature application & The possibility of having a constellation of platforms with a very short revisiting time (2–3 h) VHR images at lower costs \\ \cline{1-1}  & & & & \\ \cline{1-1}  & & & & \\ \cline{1-1}  & & & & \\ \hline \hline \end{tabular}
\end{table}