# Laser Technology in Photonic Applications for Space
## 3 Lasers in Space
### Science
#### 3.1.2 Spectroscopy  
Spectroscopy is a very common analytic technique that can be used to probe the composition of an object. Thanks to the electromagnetic radiation emitted from a body, the resulting spectrum can be analyzed to infer the physical properties of that object, such as chemical composition, mass, and temperature. This emission signal can be amplified by exciting the target with the energy of a source. Both passive and active spectroscopy are useful in a wide range of scientific and industrial applications, but also in space applications where they have allowed, for instance, to confirm the expansion of the universe [62]. Many different types of excitation sources can be used for active spectroscopy, such as light bulbs, flash lamps, ion, electron, or X-ray beams, although a number of spectrometers rely directly on Solar light, such as the devices used in the Chandrayaan missions. Spectroscopy is also commonly used to study astronomical bodies and samples in laboratories. Here, we will concentrate on the space application of spectroscopy techniques that rely on lasers, such as Raman Spectroscopy and Laser Induced Breakdown Spectroscopy (LIBS).  
In 2011, NASA sent the Curiosity Rover to Mars, which contained the ChemCam instrument that could analyze targeted samples composition up to 7 m away. The ChemCam LIBS instrument, one of the firsts of its kind launched in space, used a 1067 nm laser pulses of \(\geq\)10 MW/mm\({}^{2}\) generated by an Nd:KGW crystal to create laser-induced breakdown, to later analyze the generated plasma thanks to the also incorporated spectrometer device [63]. The future NASA 2020 mission to Mars intends to use improved devices, allowing moreover to search and analyze organic compounds. To do so, the SuperCam instrument, apart from being able to perform LIBS analysis, counts also with Raman spectroscopy capabilities. To allow for both analyses, the laser device is designed with an Nd:YAG crystal instead of an Nd:KGW as its predecessor was [64]. The mission intends also to perform proximity Raman spectroscopy using a 248.6 nm beam emitted from a Neon-Copper Transverse Excited Hollow Cathode laser. The latter device will be installed in the robotic arm instrument called Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals (SHERLOC) [65; 66; 67]. Similarly, the 2020 ESA mission will carry the Rosalind Franklin rover, which includes the Mars Organic Molecule Analyser (MOMA) and the Raman Laser Spectrometer (RLS) instruments [68]. Both instruments, independently designed and manufactured, are based on different laser approaches. The MOMA uses a 266 nm laser with a tunable beam between 35 and 250 MW/cm\({}^{2}\) generated from a frequency quadrupled beam from an Nd:Cr:YAG crystal [69; 70], while the RLS instrument incorporates a DPSSL designed with an Nd:YAG crystal emitting an output beam frequency doubled to 532 nm [71]. The rover internal laboratories and lasers will analyze samples that will have been previously extracted from the Martian underground thanks to a mechanical drill incorporated on the rover.  
Similar laser spectrometer devices will also be deployed in-situ, as, for example, on the Pragyan rover on the Chandrayaan-2 mission to the Moon. The mission is planned to be launched in September 2019 and will carry a LIBS device with an Yb:Er:Phosphate glass laser operating at a wavelength of 1534 nm, with pulse energies between 2 and 3 mJ and a pulse duration of 7 ns [72]. Other techniques, such as tuneable laser spectroscopy (TLS), have been used at the ISS and also incorporated in Mars missions for atmospheric composition analysis [73].  
With the astonishing results obtained by the Curiosity mission and the great possibility of being able to analyze the composition of planets and space bodies in-situ, the interest of developing new laser spectrometer devices for future missions has arisen, such as the Standoff ultracompact micro-Raman sensor developed by [PERSON] et al. (2018), for future planetary surface explorations.