# Laser Technology in Photonic Applications for Space
## 4 Technical Specs and Requirements  
Despite the recent developments in small satellites and launching technologies, space missions remain expensive projects and, once the instruments are deployed in space, it is almost impossible to repair or maintain them. For that reason, the devices have to pass stringent qualification campaigns before launching them to space. Tests should prove that devices can withstand harsh environmental conditions without alteration of the optical performances [5]. Although the environmental requirements depend on the specific mission (launch methodology, low orbit, high orbit, inter-planetary, sun, or deep space [130]), ESA reports in [5] the common standard requirements for photonic devices:  
* reliable for several operational years (commonly 10-20 years),
* ionization resistance for doses of 100 Krad(Si) (LEO 50 to 10 Krad [131]), and proton radiation with a fluence as 5 \(\times\) 10\({}^{10}\) protons/cm\({}^{2}\)[132] without alteration of the optical performances,
* usual operation and non-operational temperatures between \(\leq\)\(-\)45 \({}^{\circ}\)C to \(\geq\)+85 \({}^{\circ}\)C; although those vary depending on the mission space target (Figure 4), or different objects with more or less proximity to the sun [132], tenths of cycles between minimum and maximum limits have to be performed on materials and devices for them to be qualified,
* harsh vibration (Table 1) and shock (usually 1500 g) resistance, conditions normally due to launch take off and possible planetary landing,
* vacuum compatibility (10\({}^{-9}\) torr),
* no contamination. Low out-gassing, in terms of total mass loss (TML) and collected volatile condensable materials (CVCM) <0.1%.  
Figure 4: Different environmental mission requirement depending on the selected space target. Image source [PERSON] et al. [133].  
Monitoring tests must be performed on individual components and final prototypes before, in some cases during, and after environmental tests in order to detect any deterioration of optical performances that might have occurred. Those tests, aimed at demonstrating that material batches and assembly processes ensure a high repeatably and reliability margin that allows operation in the required mission environments, are expensive and time-consuming. Therefore, most missions tend to use devices as similar as possible to devices that have already been tested, qualified, and, if possible, launched. For instance, the NASA LIDAR missions MOLA, GLAS, CALIOP, MLA, and LOLA all used similar DPSSL configurations, since it worked successfully in the first Martian mission in 1996 [52]. Nevertheless, new developments in the fields of photonic and laser devices provide novel instruments with better performance and new wavelengths that allow for new applications or improved results. The fact that they are not space qualified makes their use risky and they tend to be included only if they really are a game changer key element or are extremely compulsory for the mission purpose.  
A considerable amount of work is taking place regarding standardization of the qualification of photonic devices, such as that reported in the following articles: [52] or [132]. Moreover, NASA and the European Cooperation for Space Standardization are working on the development of standards [133; 134; 135; 136] for the manufacture and qualification of photonic and laser devices, helping to disseminate them to the key players and project partners with platforms, such as the one reported in [134].