## 2 Specification of Camera Module and Radiation Resistant Material  
During the final docking phase, the operation takes place at a distance range between at least 1 and 10 m and a FOV of \(\pm 30^{\circ}\) is required [3], which is used as the base for defining the major optical performance of the camera. The image sensor is the ON Semiconductor(r) Aptina(tm) MT9P031 CIS, and its major parameters are listed in Table 1[10]. A fixed focus lens, which does not contain moving parts, and is thus less sensitive to launching in an on-orbit environment, is preferable for the docking camera. With the fixed focus and small-aperture, a pan-focus lens is capable of giving deep depth of field (DOF) by setting the object distance at a hyperfocal distance [11]. The aperture can then be calculated with this object distance or hyperfocal distance. The procedure for evaluating hyperfocal distance/object distance and f-number are listed in Equations (1)-(6) [11]. \[H=\frac{f^{2}}{FN\cdot C}+f\, \tag{1}\]  
\[N_{L}=\frac{S\cdot(H-f)}{H+S-(2f)}\, \tag{2}\]  
\[F_{L}=\frac{S\cdot(H-f)}{H-S}\ ; \tag{3}\]  
\[N_{L}=H/2\, \tag{4}\] \begin{table}
\begin{tabular}{c c} \hline
**Parameters** & **Value** \\ \hline Optical Format & 1/2.5 inch (4:3) \\ Active Pixels & \(2592\mathrm{H}\times 1944\mathrm{V}\) (640 \(\times 480\), with binning) * \\ Pixel Size & \(2.2\ \mathrm{\SIUnitSymbolMicro m}\times 2.2\ \mathrm{\SIUnitSymbolMicro m}\) \\ Active Imager Size & \(5.70\ \mathrm{mm}(\mathrm{H})\times 4.28\ \mathrm{mm}(\mathrm{V})\), \(7.13\ \mathrm{mm}\) diagonal \\ Chief [PERSON] (CRA) & \(\leq 7^{\circ}\ \mathrm{Max}\). \\ Operating Temperature & \(-30^{\circ}\ \mathrm{C}\) to \(+70^{\circ}\ \mathrm{C}\) \\ \hline \end{tabular}  
* Pixel binning for sub-pixel resolution [3; 5].  
\end{table} 
Table 1: Major parameters of ON Semiconductor® Aptina(tm) MT9P031 CIS. \[F_{L}\rightarrow\infty\ (\text{infinity});\] \[\text{if}\ \ 1/F_{L}\approx 0\ \ \text{for}\ F_{L}>20\ \text{m}\] \[S=\frac{f\text{:}(f+FN\text{-}C)}{FN\text{-}C}\ \,\] (5) or \[FN=\frac{f^{2}}{C\text{:}(S-f)}\ \, \tag{6}\]  
where  
\(H\): Hyperfocal distance (mm);  
\(f\): Effective focal length (EFL);  
\(FN\): f-number;  
\(C\): Circle of confusion (CoC);  
\(N_{L}\): Near focus limit (mm);  
\(S\): Object distance (mm);  
\(F_{L}\): Far focus limit (mm);  
in the hyperfocal condition:  
The operation range condition required FOV around \(\pm 30^{\circ}\)[3]. In addition, the image height should be larger than the active imager size in diagonal (7.13 mm). Assume the image height given is 3% larger than the active imager size, i.e., estimated image height \(h_{i}\approx 7.4\) mm. The estimated EFL obtained is:  
\[\text{EFL}=h_{i}/2\cdot tan(FOV)\,;\ f\approx\ 6.4\ (\text{mm}),\]  
In the CoC estimation, common practice was a realistic blur spot diameter of 0.2 mm (5 lp/mm) at a distance of 25 cm in print diagonal (218.44 mm) for print CoC of 5 (inch) \(\times\) 7 (inch). Given the MT9P031 CIS active imager size in sensor diagonal was 7.13 mm. The estimated MT9P031 CIS's CoC obtained:  
\[\text{CoC}=1/[(5\ \text{lp/mm})\times(\text{print diagonal/sensor diagonal})];\ \text{C}\approx 0.0057\ (\text{mm}),\]  
The following assumption was made:  
\[\text{S}=\text{H}\approx 900\ \text{mm}\ \text{for a reasonable hyperfocal distance in Equation (5) or Equation (6),}\]  
thus  
\(FN\approx 8\) has been obtained from Equation (6) for targeting specification of system f-number,  
Based on the evaluation described above, the optical specification of the camera module is summarized in Table 2.  
The camera will be operated in a harsh radiation environment, which will include solar radiation, galactic cosmic rays, heavy ions, electrons and protons, therefore, they must be tolerant toward these radiation effects. Figure 1 shows a collection of radiation resistant optical glass materials for the design of compact radiation resistant lenses, as shown in the glass codes and glass types that are shown side by side in the glass chart to serve as a reference in the design process [12; 13].