The flight model of the laser system for the Mars Organic Molecule Analyzer (MOMA) instrument within the ExoMars 2020 mission for Martian planetary surface exploration has been developed, assembled, tested, and finally integrated to the NASA Goddard Space Flight Center (GSFC) mass spectrometer. The nanosecond laser system consists of a longitudinally pumped, passively Q-switched Nd:YAG based laser oscillator with a two-stage frequency doubling to 266 nm. The laser design was implemented in robust and lightweight models of the laser head (LH) with the pump unit in a separate electronics box.<p> </p>In parallel to the laser head integration and testing, materials and optics qualification and acceptance tests have been performed, e.g. to determine the optical damage threshold or the susceptibility to laser induced contamination processes.<p> </p>Before delivery to the NASA GSFC for integration to the mass spectrometer (MS) flight model (FM), the laser system has been qualified in an environmental test campaign including vibration, shock and thermal-vacuum testing. After delivery to GSFC and integration to the FM MS, the system has been successfully re-tested on the instrument level.
A hermetically sealed laser head (LH) emitting laser pulses at a wavelength of 266 nm has been developed and tested for the Mars Organic Molecule Analyzer (MOMA) instrument of the ESA/Roscosmos ExoMars 2020 mission. MOMA comprises a gas chromatograph (GC) and a laser desorption mass spectrometer (LDMS). Its primary function is to search for traces of present or past signs of organic molecules in subsurface material probes. The LH is used as an excitation source for the LDMS part of MOMA. Its design fulfils stringent mass and volume requirements and is realized as a hermetically sealed system. It consists of a laser diode pumped Nd:YAG based laser oscillator, a frequency conversion stage for frequency quadrupling of the fundamental laser oscillator wavelength, a compact monitoring stage for internal laser pulse detection, a beam shaping telescope and an adjustable laser beam steering unit with the purpose of guiding the generated UV laser beam to its target position in front of the mass spectrometer (MS) ion inlet.<p> </p>The system has undergone extensive functional and environmental testing including vibration, shock and thermal vacuum chamber tests. After completion of the functional and environmental test campaign, the LH has been integrated on the MOMA mass spectrometer. Here we report on the mechanical design of this LH and its environmental testing. Furthermore, the LH was successfully tested both functionally and environmentally on LDMS level.
A space-qualified flight model of a pulsed ultraviolet (UV) laser has been developed for the Mars Organic Molecule Analyzer (MOMA) instrument of the ExoMars 2020 mission. The design is based on a passively Q-switched Nd:Cr:YAG laser oscillator with subsequent two-stage frequency quadrupling. It emits nanosecond pulses with an energy tuneable between 13 μJ and 130 μJ at a wavelength of 266 nm.<p> </p>Considering its small physical dimensions and weight, the interior of the laser head is rather complex. Besides the aforementioned infrared oscillator and frequency conversion stage it contains the pump optics, two wavelength division assemblies within main beam path, a complex monitoring stage including two photodiodes for pulse energy measurement, a beam shaping setup and a deflection unit for fine adjustment of the beam pointing towards the sample location within the instrument. Most of the laser head is enclosed in a hermetically sealed housing, while the deflection unit is sealed separately. Both volumes are filled with 1 bar of dry, filtered air.
For the ESA/Roscosmos ExoMars 2020 mission a pulsed UV laser source as part of the Mars Organic Molecule Analyzer (MOMA) instrument was developed, assembled and thoroughly tested concerning thermal, vibrational and shock loads. The characterization was performed before and after integration to a mass spectrometer, which serves as the detector for ionized fragments desorbed from the Martian soil samples due to UV irradiation. The opto-mechanical design of the flight model and the verification of its suitability for the mission requirements are presented here. A longitudinally pumped, passively Q-switched oscillator emits bursts of up to 50 pulses with an output energy of 1.1 mJ at 1064 nm and an intra-burst repetition rate of 100 Hz. Via a two-stage frequency quadrupling with a KTP and a BBO crystal this radiation is converted to 1.5 ns long pulses at 266 nm with an output energy of 130 μJ which can be decreased by temperature tuning of the nonlinear crystals to less than 10% of the nominal energy. The laser head also comprises beam shaping and steering optics to adjust the spot size and position on the sample and the capability to measure the UV energy and the pulse release time. The complex opto-mechanical design is realized within an envelope of less than 220×57×45 mm<sup>3</sup> and has a total mass of less than 220 g. To minimize negative effects of the harsh Martian environment on the coatings the laser head is enclosed in a hermetically sealed housing filled with dry synthetic air.