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 Deep Space Optical Communication (DSOC) project will conduct its technology demonstration concurrently with NASA’s Psyche mission, which hosts the DSOC flight transceiver (FLT) on its spacecraft and will operate it over an approximate range of 0.05 to 3.0 AU. The DSOC Ground Laser Transmitter (GLT), located at the Jet Propulsion Laboratory’s Optical Communication Telescope Laboratory (OCTL) near Wrightwood, CA, has been developed to provide a high-power optical uplink beacon that serves as a line-of-sight FLT downlink pointing reference and delivers low rate (1.8 kbps) uplink command data to the FLT. In this paper we present an overview of the completed GLT and its subsystems: (i) the multi-beam Uplink Laser Assembly (ULA) capable of transmitting up to 7 kW of average power, (ii) the Uplink Data Formatter that modulates the ULA, (iii) the GLT Optics Assembly that manages the ULA high power output beams and couples them to the OCTL telescope, (iv) the Uplink Laser Safety Assembly that automatically avoids hazardous laser irradiation by shuttering the laser output, and (v) the custom-developed Monitor and Control software used to test and operate the entire system. We discuss various implementation and operational challenges, and review results from key system performance verification and operational tests, indicating the readiness of the Ground Laser Transmitter station to fulfill the DSOC technology demonstration objectives.
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.
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