MPB has developed a 10W Polarization Maintaining Optical Fiber amplifier (1550 nm) for space applications. The prototype is based on three stages of optical amplification with photodiodes at each stage, monitoring the output power. It includes the control electronics and software with feedback loops to dynamically control and monitor the amplifier. The design had to overcome many challenges to comply with the mechanical, thermal, radiation, and vacuum requirements for the LEO satellite space environment, while at the same time meeting the price targets for LEO constellations by maximizing the use of commercial off the shelf (COTS) components. The following were the main challenges: a) to effectively dissipate the heat generated (75-90 W); b) to select radiationtolerant electronics to drive the needed electrical current; c) to source and effectively implement components, such as the combiners and isolators, in the high power optical path compatible with vacuum at 10W output. The major challenge with regard to heat management was to find an optimal method to dissipate the heat from the third stage (high power) Erbium Ytterbium Doped Fiber. Commonly, this fiber is spooled on an Aluminium spool. The difference in the Constant Temperature Extension (CTE) between the fiber (low) and Aluminium (high) leads to a detachment of the fiber at low temperature with a high risk of breaking the fiber when passing from OFF to ON. At high temperatures, the Aluminium extends much more than the fiber, leading to an over tension on the fiber with a high risk of mechanical breakage. Different designs of the spool, supports inside the box, selection of materials, and process implementations were tried. An innovative, proprietary method was developed to satisfy this requirement. The unit successfully passed performance testing between -20°C and +40°C in vacuum with 10W output, with a wall plug efficiency of 11%. The lower temperature limitation was due to the specification of the high-power laser diodes. The higher temperature was limited by the local heating and risk of mechanical breaking of the third-stage COTS combiner and isolator. Vibration and mechanical shock are not foreseen to be an issue. The simulation demonstrated the prototype is complying with these requirements. Moreover, MPB has built similar instruments at lower power levels that have successfully passed these qualification tests. The components used were available as COTS products, including the radiation-tolerant electronics. All the components were qualified individually for > 30 krad, in vacuum, and for the temperature range -35°C to +65°C except for the highpower laser diodes which were limited to -25°C. MPBC is continuing the qualification, implementing minor design changes, in order to satisfy the complete temperature range (-35°C to +65°C).
It is surprising to see the wide range and versatile potential of applications of the VO2, due to its transition from a semiconductor phase at low temperature, to a metallic state at high temperature. Although this transition’s atomic mechanism is not yet well understood, the tuneability is very reproducible experimentally and can be monitored by various triggering schemes, not only by heating/cooling but also by applying a voltage, pressure, or high power single fast photonic pulse. Many of the recent applications use not only the low-temperature phase and the high-temperature phase, but also the transition slope to monitor a specific parameter. The paper starts with a summary of the VO2 thin film deposition methods and a table presenting its recent proposed applications, some of which our team had worked on. Then the development characterization and application of the VO2 as a smart thermal radiator is provided along with the recent progress. The experimental results of the emissivity were measured at low temperature and high temperature, as well as during the transition in vacuum based on the thermal power balance. These measurements were compared with those deduced from an average of Infrared Reflectance (2–30 µm) weighed with the blackbody reflection spectrum. The roadmap is to try alternatives of the multilayers in order to increase the emissivity tuneability, increase the device dimensions, have an easier application on space surfaces, while lowering cost.
<p>Finding suitable quantities of key resources for life-support and refueling is vital to future sustained lunar manned bases and commercial activities. There are large uncertainties in the lunar near-surface distribution of water ice volatiles and relevant in-situ resources, such as ilmenite (FeTiO<sub>3</sub>). Moreover, planned future lunar orbiter missions have relatively limited spatial resolution, in the km range, for the volatile mappings relative to typical lander and rover range capabilities, especially for operations within the lunar Permanently Shadowed Regions (PSRs) that could shelter accumulated water ice deposits.</p><p>VMMO, for <strong>V</strong>olatile and <strong>M</strong>ineralogy <strong>M</strong>apping <strong>O</strong>rbiter, &#160;is a low-cost 20 kg 12U Cubesat that comprises the Lunar Volatile and Mineralogy Mapper (LVMM) multi-wavelength chemical lidar science payload, the Compact LunAr Ionizing Radiation Environment(CLAIRE) monitoring payload, a COTS electronics test bed, and the supporting 12U Cubesat bus with propulsion, direct to Earth S-band and 1560 nm optical communications, on board data processing and a suite of altitude and pointing sensors for semiautonomous vision-assisted navigation from lunar orbit.</p><p>VMMO will most likely be deployed from a commercial lunar transportation provider, such as Astrobotics, into a suitable near-polar injection orbit. The on-board propulsion will be used to achieve a stable lunar frozen orbit for the subsequent science operations with a perilune over the south pole under 100 km to assist the LVMM volatile and mineralogy mappings.</p><p>The compact LVMM is a multi-wavelength Chemical Lidar (<6.1 kg) which will use single-mode (SM) fiber lasers emitting simultaneously at 532 nm, 1064 nm and 1560 nm.&#160; This will permit stand-off mapping of the lunar water ice distribution using active laser illumination, with a focus on selected permanently-shadowed craters in the lunar south pole;Shackleton, Faustini and Cabeus. This combination of selected laser spectral channels can provide very sensitive discrimination of water/ice in various types of Mare and Highland regolith, based on breadboard validation. The use of the SM fiber lasers enables a small laser beam divergence to provide high spatial resolution in the 10 m range at the lunar surface. There is some relevant flight heritage as part of the Fiber Sensor Demonstrator (FSD) payload on ESA&#8217;s Proba-2 spacecraft that is still operational after more than 10 years in low earth orbit.</p><p>LVMM can also be used in a passive multispectral mode at 300 nm, 532 nm, 1064 nm and 1560 nm to map the lunar ilmenite in-situ resource distribution during the lunar day using the characteristic surface-reflected solar illumination. By combining the passive lunar day measurements with the active lunar night measurements, some new insights into the lunar diurnal water cycle should be possible.</p><p>This paper discusses the VMMO science requirements and the supporting 12U Cubesat platform and LVMM multiwavelength chemical lidar payload and some of the associated design trade-offs.</p>
MPB is developing space qualified 10 W End Of Life (EOL) optical amplifiers for longer range applications. Their design employs Polarization Maintaining (PM) Erbium and Erbium-Ytterbium Double Clad Fiber (EDF, EYDF) singlemode fibers. Absorption losses of the EDF and EYDF due to radiation in space are the major challenge to overcome. The gamma radiation tests show that the PM fibers have a greater sensitivity than standard fibers. However, in many applications, PM amplifiers show greater performances which is important for the power consumption.Furthermore, MPB's design minimizes Stimulated Brillouin Scattering in the fibers, a major obstacle to be overcome at this power level, even for on ground applications. Moreover, the compatibility with space environment (vacuum, temperature cycling, and radiation) of the high-power optical and electronic components (isolators, laser-diode pumps, current drivers) has to be demonstrated.The proposed optical designs compensate for radiation-induced losses, without resorting to the use of expensive radiation qualified fibers-a unique method of power recuperation through the photo-bleaching of the active fiber.
Satellite-to-satellite laser communication technology underpins high-speed l0-Gbps optical links for the new generation of satellite constellations that will serve as global telecommunications networks. LEO satellite-to-satellite links may extend over distances of >5000 km, necessitating an optical-power budget of ~70 dB to compensate for diffraction-limited opticalbeam divergence. This can be achieved by boosting the transmitted laser diode signal to around 1 W, and by amplifying the received signal by 40 dB. Such performances are attained by terrestrial fiber amplifiers, operating in the telecom 1550nm wavelength window, which are produced in volume of thousands and are (in relative terms) of low cost. Based on MPBC's large volume production experience of fiber amplifiers and its heritage of space system design and manufacturing, a new product line of Laser Communication Terminals (LCTs) for space is presented. It is designed to be lower cost, exploiting commercial off-the-shelf (COTS) components whenever possible. Most of these fiber-optic components are extensively employed in large terrestrial telecom equipment and are already qualified to telecommunications standards. However, additional tests are required to ensure reliable long-term operation in a space environment. We have subjected the components, both active and passive, to gamma-and proton-radiation tests including total ionization doses of up to 100 kRad, Temperature vacuum cycling over extended temperature range have been performed and are still ongoing. Finally, considering manufacturing costs, we are packaging both the transmission optical booster unit and receiver optical amplification unit in the same housing, in order to co-locate both the transmit and receive functions of the link. These units are compact and stackable and save on the enclosure weight.
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