Photocatalytic solar water splitting has the potential to become a low‐carbon source of hydrogen fuel over the coming decades if the issue of low visible light absorption can be addressed without sacrificing chemical stability. We report on an investigation into the potential of the Bi–W‐oxides, Bi2WO6 and Bi6WO12, as visible light photocatalysts. X‐ray diffraction and Raman spectroscopy have been used to assess the structure of the oxides, whilst UV–vis diffuse reflectance spectroscopy analysed with the Kubelka–Munk function has been used to identify their optical band gaps. It has been revealed that Bi6WO12 shows significantly higher optical absorption in the region above 440 nm than either Bi2O3 or WO3, raising the possibility of enhanced photocatalytic activity under solar illumination. Bi2WO6 has a marginally lower band gap at 2.59 eV than Bi2O3 or WO3 but the results reported herein raise doubts concerning its chemical stability under aqueous, illuminated conditions for protracted periods of time. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Optical communication is becoming more prevalent in orbit due to the need for increased data throughput. Nanosatellites, which are satellites that typically weigh less than 10 kg, are also becoming more common due to lower launch costs that enable the rapid testing of technology in a space environment. Nanosatellites are cheaper to launch than their larger counterparts and may be a viable option for communicating beyond Earth’s orbit, but have strict Size,Weight, and Power (SWaP) requirements. The Miniature Optical Communication Transceiver (MOCT) is a compact optical transceiver designed to provide modest data rates to SWaP constrained platforms, like nanosatellites. This paper will cover the optical amplifier characterization and simulated performance of the MOCT amplifier design that produces 1 kW peak power pulses and closes three optical links which include Low Earth Orbit (LEO) to Earth, LEO to LEO, and Moon to Earth. Additionally, a benchtop version of the amplifier design was constructed and was able to produce amplified pulses with 1.37 W peak power, including a 35.7% transmit optics loss, at a pump power of 500 mW. Finally, the modulator, seed laser, amplifier, receiver, and time-to-digital converter were all used together to measure the Bit Error Ratio (BER), which was 0.00257 for a received optical peak power of 176 nW.

In this paper, we present the design and performance of the upgraded University of Florida torsion pendulum facility for testing inertial sensor technology related to space-based gravitational wave observatories and geodesy missions. In particular, much work has been conducted on inertial sensor technology related to the Laser Interferometer Space Antenna (LISA) space gravitational wave observatory mission. A significant upgrade to the facility was the incorporation of a newly designed and fabricated LISA-like gravitational reference sensor (GRS) based on the LISA Pathfinder GRS. Its LISA-like geometry has allowed us to make noise measurements that are more representative of those in LISA and has allowed for the characterization of the mechanisms of noise induced on a LISA GRS and their underlying physics. Noise performance results and experiments exploring the effect of temperature gradients across the sensor will also be discussed. The LISA-like sensor also includes unique UV light injection geometries for UV LED based charge management. Pulsed and DC charge management experiments have been conducted using the University of Florida charge management group’s technology readiness level 4 charge management device. These experiments have allowed for the testing of charge management system hardware and techniques as well as characterizations of the dynamics of GRS test mass charging. The work presented here demonstrates the upgraded torsion pendulum’s ability to act as an effective testbed for GRS technology.

Laser crosslinks can provide high data rate communications and precision time transfer and ranging, using low size, weight, and power (SWaP) terminals to enable constellations of small satellites. The CubeSat Laser Infrared CrosslinK (CLICK) mission will demonstrate terminals capable of conducting fullduplex, high data rate crosslinks and enabling high precision ranging on 3U CubeSats in low Earth orbit (LEO). An initial risk reduction mission, CLICK-A, will demonstrate a downlink of at least 10 Mbps to a 28 cm aperture optical ground station. CLICK-B and CLICK-C will follow to demonstrate laser crosslinks with data rates of at least 20 Mbps over separation distances ranging from 25 km to 580 km. The CLICK-B/C mission will also demonstrate precision ranging better than 50 cm. Key to achieving these capabilities are the performances of the transmitter and fine pointing, acquisition, and tracking (PAT) system. We present results from recent testing and characterization of the transmitter and PAT subsystems. The testing of the transmitter includes confirming the output power and modulation of the seed laser and semiconductor optical amplifier (SOA) and characterizing the output pulse shape. For the PAT system, testing focuses on characterizing the noise of the quadrant photodiode used for the closed-loop, fine PAT sequence. This testing was conducted using a dedicated hardware-in-the-loop testbed with an optical test setup. CLICK-A is expected to launch no earlier than May 2022 for deployment from the International Space Station (ISS) in June 2022, while CLICK-B/C is anticipated to launch in late 2022.