Space-qualified, compact and lightweight pulsed DPSS UV laser for the MOMA instrument of the ExoMars mission

Abstract

A space-qualified pulsed UV laser has been developed as an irradiation source for the Mars Organic Molecule Analyser (MOMA) instrument aboard the “Rosalind Franklin” rover of the ExoMars mission (ESA/Roscosmos). MOMA will search for signatures of extinct and/or extant life on Mars. Its advanced analytical capabilities arise from the combination of a pyrolysis gas chromatograph and an ion trap-based mass spectrometer. With the addition of a compact UV laser system enabling laser desorption/ionization mass spectrometry, MOMA can detect a wide variety of both volatile and non-volatile, organic and inorganic molecules within Martian soil samples of interest. The design of the MOMA Laser Head is based on a longitudinally diode-pumped, passively Q-switched Nd:Cr:YAG oscillator generating millijoule pulses with nanosecond pulse durations at a wavelength of 1064 nm. A subsequent two-stage frequency quadrupling converts the fundamental infrared emission of the oscillator into the deep UV at 266 nm. The Laser Head emits UV pulses with a duration of about 1.5 ns and an energy tunable between 12.5 and 125 µJ for optimum adaptation to varying ionization thresholds of different molecular species. The complex but highly compact opto-mechanical design, enclosed in a hermetically sealed housing, is realized within an envelope of 200 × 56 × 45 mm3 with a total mass of less than 220 g. In this paper, we present a comprehensive summary of our development efforts towards the delivery of the LH Flight Model, which has been integrated to the MOMA instrument and finally incorporated into the ExoMars rover.