We present the activities of the research School of Astronomy and Astrophysics at the Australian National University to implement adaptive optics techniques for quantum communications through a free-space channel. We have developed a portable horizontal quantum key distribution system with adaptive optics and demonstrated improved secret key rates when using AO in a turbulent channel. We also report on development to equip the Mt Stromlo optical communications ground station with an adaptive optics system to enable quantum communication links between the ground and space.
The Compact Hybrid Optical Rf User Segment (CHORUS) project is a collaborative research partnership between SmartSat CRC, DST Group, EOS Space Systems, EM Solutions, Shoal Group, the Australian National University, University of South Australia, and Lyrebird Antenna Research. The project has developed a prototype terminal capable of simultaneous operation in both radiofrequency and optical frequency bands through communications systems integrated into the same tactical platform. A full-size engineering model was developed and tested at the DST Group laser range at Edinburgh South Australia. The terminal is a modified existing platform from EM Solutions currently employed widely in the international defence sector focusing on maritime applications. The modifications made within this project include the integration of a custom aluminium mirror in the centre of the RF antenna. The optical communication signal is received at prime focus and a novel method for separating the RF and optical signals was designed, tested, and integrated. We report on the terminal design specifications and verification through field testing including performance of the optical and RF systems, pointing accuracy, and future technology directions.
Continuous variable quantum key distribution (CVQKD) is the sharing of a secret key between parties using the continuous quadratures of light, the phase and amplitude quadratures, which can infer the presence of an eavesdropper using fundamental quantum mechanics. A significant performance inhibitor of free-space CVQKD is turbulence which gives rise to optical wavefront distortions consisting of random phase and amplitude fluctuations (scintillation). In this work, we experimentally study the negative effects of turbulence on coherent states in a free-space channel for CVQKD. We demonstrate during coherent state transmissions from a continuous-wave laser in a turbulent channel, the interferometric visibility between a local oscillator and signal fluctuates and decreases with higher degrees of scintillation. This leads to the breaking of the phase-lock between the local oscillator and quantum signal and a decrease in the secret key rate (SKR). By incorporating an adaptive optics system, the degraded optical wavefront from turbulence can be corrected using a closed-feedback loop. This leads to the stabilisation and reduction in the decrease of the interferometric visibility in a turbulent channel. The improvement provided by adaptive optics leads to the increased performance of CVQKD, resulting in positive SKRs, which would have otherwise been infeasible in a turbulent channel.
The Australian Nation University (ANU) Quantum Optical Ground Station (QOGS) has been constructed in Canberra, Australia. Instrumentation is under development to enable lunar communications with QOGS. A receiver system and beacon transmitter will be installed on the telescope that is compatible with the Optical to Orion (O2O) terminal that will be onboard the Artemis II mission. Communication with spacecraft beyond the Moon is also possible by moving the receiver hardware to a larger telescope. The ANU operates Siding Spring Observatory where a 3.9 m or 2.3 m telescope could be used for deep space communications.
KEYWORDS: Transmitters, Telescopes, Receivers, Optical communications, Signal detection, Design and modelling, Prototyping, Free space optics, Space operations, Mirrors
The Australian National University (ANU) Optical Communications Ground Station (OCGS) is currently under development at Mt. Stromlo Observatory in Canberra, Australia. The OCGS will be compatible with a range of wavelengths, coding schemes, and techniques to cover satellites in Low Earth Orbit to Lunar and deep-space, and provide a platform for quantum communication from satellites. We have conducted a feasibility study and preliminary design review for the development of an instrument to support the CCSDS high photon efficiency (HPE) standard so the OCGS can support future lunar missions featuring optical communication terminals. The development of lunar communication capabilities in Australia offers site diversity and increased visibility, allowing for improved optical link availability during missions. We present the preliminary design for the transmitter and receiver which will integrate on the 70 cm telescope in the OCGS. A lab prototype of the transmitter has been built to demonstrate the generation of a pulse position modulation (PPM) waveform which is compatible with the CCSDS high photon efficiency (HPE) standard. The transmitter is made up of four 15 cm apertures which is mounted by a piggyback to the telescope. Each can operate as an independent channel with fine steering control through a fast steering mirror. The apertures are separated by characteristic atmospheric turbulence length r0 to minimise fading at the spacecraft. The receiver is installed at the Nasmyth port of the 70 cm telescope. The receiver features a fast steering mirror to maximise coupling into a multimode fibre. The signal is split with a photonic lantern and sent to several superconducting nanowire single photon detectors (SNSPD).
Characterisation and mitigation of atmospheric turbulence is critical for free space optical communication that relies on adaptive optics such as high bit rate coherent modulation or quantum key distribution. Turbulence profiling, i.e. measuring turbulence at different altitudes, provides more detail than typical seeing monitors and supports sophisticated AO and the possibility to forecast conditions. We present the implementation of a Ring-Image Next Generation Scintillation Sensor (RINGSS) instrument that profiles turbulence with a novel approach of defocused ring images introduced by A. Tokovinin (2021)1 . RINGSS is exceptionally low-cost, small, and fully automated, requiring significantly simpler equipment than previous turbulence profilers. We have demonstrated preliminary results that demonstrate the capability of this instrument for measurements of seeing and a low resolution turbulence profile. Future work is outlined that includes cross-calibration with a Stereo-SCIDAR instrument recently commissioned on the ANU 2.3m telescope at Siding Spring Observatory and plans for deployment at prospective optical ground station sites for an Australia-New Zealand optical network.
The Mount Stromlo LGS facility includes two laser systems: a fiber-based sum-frequency laser designed and built by EOS Space Systems in Australia, and a Semiconductor Guidestar Laser designed and built by Aret´e Associates in the USA under contract with the Australian National University. The Beam Transfer Optics (BTO) enable either simultaneous or separate propagation of the two lasers to create a single LGS on the sky. This paper provides an overview of the Mount Stromlo LGS facility design, integration and testing of the two sodium guidestar lasers in the laboratory and on the EOS 1.8m telescope.
This paper presents a preliminary analysis of the first results we have obtained from the adaptive optics systems built for EOS 1.8 m telescope at Mount Stromlo. This presentation focuses on the single-camera stereo-SCIDAR for monitoring the atmospheric seeing. We briefly summarize the system, describe its on-sky performance during commissioning, compare results to numerical simulations and evaluate the remaining challenges going into the future.
Space debris in low Earth orbit (LEO) below 1500 km is becoming an increasing threat to spacecrafts. To manage the threat, we are developing systems to improve the ground-based tracking and imaging of space debris and satellites. We also intend to demonstrate that it is possible to launch a high-power laser that modifies the orbits of the debris. However, atmospheric turbulence makes it necessary to use adaptive optics with such systems. When engaging with objects in LEO, the objects are available only a limited amount of time. During the observation window, the object has to be acquired and performance of all adaptive optics feedback loops optimised. We have implemented a high-level adaptive optics supervision tool to automatise time-consuming tasks related to calibration and performance monitoring. This paper describes in detail the current features of our software.
We report on the design and initial laboratory testing of the Adaptive Optics Imaging (AOI) system. AOI has been developed by the Research School of Astronomy and Astrophysics (RSAA) at the Australian National University (ANU), in partnership with the Space Environment Research Centre (SERC), for imaging satellites and debris in low Earth orbit (LEO) and geostationary orbit (GEO). From AO corrected images we will resolve features greater than 50 cm allowing size, shape and orientation characterisation.
As space debris in lower Earth orbits are accumulating, techniques to lower the risk of space debris collisions must be developed. Within the context of the Space Environment Research Centre (SERC), the Australian National University (ANU) is developing an adaptive optics system for tracking and pushing space debris. The strategy is to pre-condition a laser launched from a 1.8 m telescope operated by Electro Optics Systems (EOS) on Mount Stromlo, Canberra and direct it at an object to perturb its orbit. Current progress towards implementing this experiment, which will ensure automated operation between the telescope and the adaptive optics system, will be presented.
We present the status of the site-characterisation campaign at Mount Stromlo Observatory. The main goal of the project is to aid the development and operation of new adaptive optics (AO) systems for space debris tracking and pushing as well as satellite imaging. The main method we use for the characterisation is based on the SCIntillation Detection And Ranging (SCIDAR) technique. We have designed a unique version of the SCIDAR instrument: a stereo-SCIDAR system that uses a roof prism to separate beams from a double-star system to obtain two isolated pupil images on a single detector. The instrument is installed on the 1.8 m telescope of Electro-Optic Systems (EOS), sharing facilities with the adaptive optics systems we are currently building. The SCIDAR instrument will be operated intermittently, weather and availability permitting, until sufficient amount of data has been collected to characterise the site. This paper reports the current status of the project: we have recently started the commissioning phase and obtained first measurements with the instrument.
GMTIFS requires a deformable mirror (DM) as part of its on-instrument wavefront sensor (OIWFS). The DM facilitates wavefront correction for the off-axis natural guide star, with the objective being to maximize the energy in the diffraction core and improve the signal-to-noise ratio of the guide star position measurement. It is essential that the OIWFS be positionally stable with respect to the science field. The use of J–K to observe the guide star, and thus the need to limit thermal background, essentially requires the DM in the OIWFS to be operated at or below −40°C. This is below the standard operating temperature range of currently available DMs. In cooperation with the manufacturers we are testing the performance of three DMs at temperatures from ambient to −45°C, or cooler. In the context of the OIWFS adequate stroke, open-loop positioning stability, hysteresis, interactuator surface figure and dynamic response are key performance criteria. A test system based around high spatial sampling of the DM aperture with a Shack-Hartmann wavefront sensor has been built. The opto-mechanical design permits a DM to be contained in a cryostat so that it may be cooled in isolation. We describe this test system and the test cases that are applied to the ALPAO DM-69, Boston MicroMachines 492DM and the IrisAO PTT111 deformable mirrors. Preliminary results at ambient temperatures are presented.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.