We report on the design and development of a quantum backend for an optical ground station for space-based quantum communication and science experiments. The quantum backend will enable the Optical Communication Telescope Laboratory (OCTL) to establish links with quantum satellites in the future. We aim to test this quantum enabled ground station with upcoming satellite Quantum Key Distribution (QKD) missions. We present measurements of the ground station properties that are relevant for future quantum links. Specifically, we discuss the polarization disturbance imposed by the optical communication telescope and present mitigation strategies in the form of polarization control systems. In addition to the optical design, we also present an end-to-end QKD model that is used to guide the development.
KEYWORDS: Space operations, Telescopes, Signal processing, Receivers, Transmitters, Laser safety, Interfaces, Sensors, Deep space optical communications, Actuators
The National Aeronautics and Space Administration’s (NASA) Deep Space Optical Communications (DSOC) payload, launched with the Psyche spacecraft on October 13, 2023, is facilitating an ongoing Technology Demonstration (TD) of Free-Space Optical Communications (FSOC), from beyond the earth-moon system. The DSOC Flight Laser Transceiver (FLT), can acquire a 1064 nm uplink laser from earth, and return a 1550 nm, Serially Concatenated Pulse Position Modulated (SCPPM) signal, to earth. The FLT uses a 22 cm diameter unobscured optical transceiver assembly, coupled to a 4 W average power laser transmitter, supplemented with actuators, sensors, electronics and software. A 5-7 kW average power, multi-beam 1064 nm uplink laser assembly integrated to the Optical Communications Telescope Laboratory (OCTL) near Wrightwood, CA serves as the Ground Laser Transmitter (GLT). The DSOC Ground Laser Receiver (GLR) at the Palomar Observatory, Hale telescope (operated by Caltech Optical Observatories), consists of a Superconducting Nanowire Single Photon Detector (SNSPD) array, connected to a ground signal processing assembly. Signal photon arrivals are detected and processed to extract information codewords at the GLR. A Mission Operations System (MOS) co-located with the Psyche Project Mission Operations Center, at the Jet Propulsion Laboratory (JPL), coordinates DSOC technology demonstration activities. This paper presents a system overview, mission description and operations architecture for the TD. Early results that include downlink at maximum downlink data-rate of 267 Mb/s from 0.37 Astronomical Units (AU) or 55 million kilometers are presented.
The PAlomar Radial Velocity Instrument (PARVI) is a diffraction-limited, high-resolution spectrograph connected by single-mode fiber to the 200 inch Hale telescope at Palomar Observatory. Here, we present on-sky results for HD 189733 obtained during PARVI’s commissioning phase. We first describe the implementation of our spectral extraction and radial velocity (RV) generation codes. Through RV monitoring, we detect the Rossiter–Mclaughlin signal of the transiting planet HD 189733 b. We further detect the presence of water and carbon monoxide in the atmosphere of HD 189733 b via transmission spectroscopy. This work demonstrates PARVI’s high-resolution spectral capabilities at H band and current intra-night Doppler stability of ∼4 to 10 m s − 1 on an early K dwarf. Finally, we discuss the limitations to this work and ongoing efforts to characterize and improve the Doppler performance of PARVI to the design goal of ∼1 m s − 1 for late-type stars.
The Terabyte Infrared Delivery (TBIRD) technology demonstration commenced operations in June 2022 following the spacecraft launch in late May 2022. The Jet Propulsion Laboratory (JPL), Optical Communications Telescope Laboratory (OCTL), 1-meter diameter telescope was instrumented to serve as the ground station for TBIRD. The instrumentation was a combination of lasers and modem electronics supplied by the Massachusetts Institute of Technology Lincoln Laboratory (MITLL) along with optics, sensors, and an existing adaptive optics (AO) system. The AO was embedded in an existing Optical Ground Station (OGS-1) setup supporting NASA’s Laser Communications Relay Demonstration (LCRD). The transmitting and receiving optics for TBIRD were “threaded” around the OGS-1 optics without breaking configuration, and facilitated easy switching between LCRD and TBIRD operations with a few motorized actuators. In this paper we describe (i) the design and deployment of the ground station; (ii) the concept of operations and (iii) demonstration results.
KEYWORDS: Sensors, Signal to noise ratio, Stars, Cameras, Cadmium sulfide, Spectrographs, Single mode fibers, Adaptive optics, Signal detection, Telescopes
A wave of precision radial velocity (RV) instruments will open the door to exploring the populations of companions of low-mass stars. The Palomar Radial Velocity Instrument (PARVI) will be optimized to detect RV signals of cool K and M stars with an instrument precision floor of 30 cm / s. PARVI will operate in the λ = 1.2- to 1.8-μm-wavelength range with a spectral resolution of λ / Δλ ∼ 100,000. It will operate on the Palomar 5.1-m Hale telescope and use Palomar’s PALM-3000 adaptive optics system, single-mode fibers, and an H-band laser frequency comb to probe and characterize the population of planets around cool, red stars. We describe the performance of the PARVI guide camera: a C-RED 2 from First Light Advanced Imagery. The C-RED 2 will be used in a tip-tilt loop, which requires fast readout at low noise levels to eliminate any residual guide errors and ensure the target starlight stays centered on the fiber. At −40 ° C and a frame rate of 400 frames per second in nondestructive read mode, the C-RED 2 has a combined dark and background current of 493 e − / s. Using up-the-ramp sampling, we are able to reduce the read noise to 21.2 e − . With the C-RED 2, PARVI will be able to guide using targets as faint as 14.6 H magnitude.
The electric field conjugation (EFC) algorithm has shown promise for removing scattered starlight from high-contrast imaging measurements, both in numerical simulations and laboratory experiments. To prepare for the deployment of EFC using ground-based telescopes, we investigate the response of EFC to unaccounted for deviations from an ideal optical model. We explore the linear nature of the algorithm by assessing its response to a range of inaccuracies in the optical model generally present in real systems. We find that the algorithm is particularly sensitive to unresponsive deformable mirror (DM) actuators, misalignment of the Lyot stop, and misalignment of the focal plane mask. Vibrations and DM registration appear to be less of a concern compared to values expected at the telescope. We quantify how accurately one must model these core coronagraph components to ensure successful EFC corrections. We conclude that while the condition of the DM can limit contrast, EFC may still be used to improve the sensitivity of high-contrast imaging observations. Our results have informed the development of a full EFC implementation using the Project 1640 coronagraph at Palomar observatory. While focused on a specific instrument, our results are applicable to the many coronagraphs that may be interested in employing EFC.
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