An important aspect of coherent optical satellite communication technology is the power consumption of the employed laser systems. Therefore, an enhanced wall-plug efficiency of the optical amplifiers is required. We present the prototype design (technology readiness level 4, TRL) and optical characterization of a 10-channel amplifier system for the use in WDM optical communication infrastructures operating at 1 μm wavelength. Combining the experience of in-house manufactured fiber components and laser systems, an all-fiber amplifier solution was designed to realize an overall wall-plug efficiency of around 30%. All ten input channels were simultaneously amplified up to a combined power of 100W.
When setting up a lunar station, technologies for the use of locally available materials are crucial. Such technologies drastically reduce the need for transportation from Earth. We aim to provide proof of a key technology, namely Mobile Selective Laser Melting (M-SLM) for terrain modelling i.e. for building large structures such as launch/landing pads, but also building infrastructures like shelters protecting astronauts or equipment against radiation and micrometeorites on the Moon. The M-SLM technology has the advantage that only electrical energy and a moving system are required. For M-SLM, a mobile high power laser beam is directed on lunar regolith leading to its melting. Subsequently, the melt cools down and solid structures are generated. The MOONRISE instrument should serve in a short-term mission as a proof-of-principle experiment for the M-SLM technology on the lunar surface. In a first step, an Engineering Model (EM) of our MOONRISE instrument with a volume of 10 cm x 10 cm x 15 cm and a mass of about 2.7 kg has been built and thoroughly tested on ground. It could be accommodated on a rover or a robotic arm to move the laser spot in order to create 1D, 2D and even 3D regolith structures on the Moon. Recently, three new projects have been initiated in order to (1) develop the MOONRISE payload towards a Flight Model (FM) with accommodation on a commercial lunar lander, in order to (2) apply 2D laser beam deflection techniques for process scaling on a potential follow-on payload and in order to (3) investigate the detailed process of regolith laser melting under lunar gravity conditions in the Einstein-Elevator.
In-Situ Resource Utilization (ISRU) technologies pave the way for a sustainable colony on the Moon. Above all, the construction of structures using only the available resources is an important factor in reducing costs and logistical effort. The MOONRISE project aims to melt lunar regolith using lasers on mobile platforms for the Additive Manufacturing of structures. This process is called Mobile Selective Laser Melting (M-SLM) and has the advantage that only electrical energy and a moving system are required. In order to validate the laser melting of lunar regolith simulants on ground, a vacuum chamber was designed to host powder material at pressures of around 10-2 mbar. Laser exposure and high speed monitoring were performed through a window. Prior to finalizing the payload design, the type of laser source, appropriate spot size, power, and duration of exposure were determined by means of experimentation. For reasons of cost-efficiency, the payload development approach is to profit as much as possible from components commercial off-the-shelf (COTS), i.e. commercially available components, which have no formal space qualification. These components, e.g. built for automotive application, often withstand harsh environments or even have space heritage without the costly and long-lasting process of formal space qualification. For MOONRISE, COTS parts – partly based on space heritage - have been screened in environmental tests and selected for the payload. A detailed preliminary design review of the MOONRISE payload was conducted in 2019. The payload mainly consists of a printed circuit board (PCB) for system communication, a fiber coupled diode laser, an electrical diode driver, a beam focusing optics, and an LED illumination. For baseline operation, a laser power of typically 70W will be applied for 6s to the lunar surface at a distance of about 25cm. The LED illumination is supporting visualization of the molten regolith by external cameras. The MOONRISE payload can be accommodated to a rover or a robotic arm to ensure mobility for the melting experiments. Following that, an Engineering Model (EM) has been assembled and tested for functionality. The dimension of the payload is 1.5U CubeSat and it has a mass of about 2.5kg with further reduction potential towards flight model (FM) development. In the following steps, environmental tests, such as vibration and thermal-vacuum cycling, will be carried out with the EM. As laser melting of regolith under vacuum conditions produced dense material, tests were continued under low gravity conditions in the large-scale research device Einstein-Elevator at the Hannover Institute of Technology (HITec) of the Leibniz University Hannover (Germany), which is a further development of a classical drop tower with which experiments are carried out under conditions of microgravity [3]. It allows experiments under zero gravity conditions for about four seconds. The flight can be repeated up to 300 times per day. The Einstein-Elevator also enables adjustment of the gravity level from 0 to 5g, a feature that was used to carry out melting experiments with the EM under lunar gravitation conditions.
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.
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.
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.
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.
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 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.
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 mm3 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.
A laser-desorption mass spectrometer will be part of the ESA-led ExoMars mission with the objective of identifying organic molecules on planet Mars. A UV laser source emitting nanosecond pulses with pulse energy of about 250 μJ at a wavelength of 266 nm is required for the ionization of nonvolatile soil constituents. A passively q-switched, diode-pumped Nd∶YAG laser oscillator with external frequency quadrupling has been developed. The basic optical concept and a previously developed flight-near prototype are redesigned for the engineering qualification model of the laser, mainly due to requirements updated during the development process and necessary system adaptations. Performance issues like pulse energy stability, pulse energy adjustment, and burst mode operation are presented in this paper.
A near-flight prototype of a pulsed UV laser has been developed for the Mars Organic Molecule Analyzer (MOMA) of the ExoMars mission. The laser head is based on a Nd:YAG oscillator with subsequent frequency quadrupling and emits nanosecond pulses with an energy of > 300 μJ at a wavelength of 266 nm. The design is compact and lightweight. Tests in relevant environment regarding temperature, vibration, and radiation have been performed.
A prototype of a compact light-weight passively Q-switched diode pumped Nd:YLF solid-state laser system for harsh environments has been developed. It emits 2ns pulses at a wavelength of 1053nm with a repetition rate of up to 50Hz and an energy of 1.5mJ. The beam propagation factor M2-has a value of 1.2. The total mass of the prototype electronics, consisting of an electronic board including pump diodes and thermal control to be accommodated with other electronics in a shared electronics box, and the complete solid-state laser head is 189g with further potential for mass reduction with respect to a flight model development. Applications of this laser system are amongst others laser-induced breakdown spectroscopy (LIBS) for planetary surface exploration or short range altimetry.
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