KEYWORDS: Cameras, Space operations, Scintillation, Receivers, Laser communications, Laser communication terminals, Calibration, Short wave infrared radiation, Engineering, Control systems
The Deep Space Optical Communications (DSOC) project launched in October 2023 hosted by the Psyche spacecraft. The DSOC flight laser terminal will be periodically closing links starting a few weeks after launch and extending out to Mars ranges. The DSOC Engineering Model (EM) flight laser transceiver terminal was built to serve as a replica of the flight terminal in space to be integrated into an EM testbed at JPL. The EM testbed characterized the EM flight laser transceiver terminal under test conditions emulating deep space. These tests helped to understand acquisition, tracking, pointing and the bi-directional communications performance. The EM testbed includes a gravity offload structure and the Laser Test Evaluation Station (LTES) testbed that emulates the ground transmitter and receiver. The LTES testbed was developed at NASA/JPL to serve as a pseudo transmitter and receiver ground station for deep-space flight terminals. This paper will describe the EM testbed capabilities that provide calibrated uplink irradiances overfilling the 22 cm aperture, provides a zero-gravity environment, and characterizes the downlink beam. Atmospheric fading and additive background noise can be injected, while performing uplink/downlink communications characterization. The gravity offload is capable of injecting a disturbance spectrum with a hexapod system allowing for a range of spacecraft environments to be emulated. The LTES architecture can be expanded to allow for multiple flight terminals to be tested in parallel for future projects. Key DSOC validation and performance tests with the EM testbed are reported in this paper.
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.
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