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At least 955 records · Page 53
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NASA NTRS2019

Effectiveness of Redundant Communications Systems in Maintaining Operational Control of Small Unmanned Aircraft

As a part of NASA’s Unmanned Aircraft System (UAS) Traffic Management (UTM) research, a test was performed to evaluate the effectiveness of the redundant Command and Control (C2) communications system for maintaining operational control of small UAS in the airspace over a rural area. In the test, operators set up a primary and a secondary UAS C2 communications system, sent a maneuver command to an Unmanned Aircraft (UA) with and without a functioning primary system, then verified the execution of the sent command to confirm the operator control. Operators reported that the tested redundancy configurations were effective in maintaining operational control in the test airspace over rural locations. Since the next phase of UTM research focuses on operations in an urban area where an increased level of Radio Frequency (RF) activities occur compared to a rural area, four recommendations are provided to sustain the effectiveness of redundancy in urban operations. First, the operator should not include C2 systems that use the industrial, scientific, and medical (ISM) radio bands in redundancy configurations. Second, the operator should verify the RF characteristics of the intended operation area and examine the area’s radio noise floor. Third, the operator should monitor the availability, quality, and reliability of communications services used by a redundant system. Fourth, the small UAS community should adopt a standard set of contingency steps to handle the loss of C2 communications so that such events are managed in a consistent manner across the airspace. The insights from the test will be used to accommodate the FAA’s UAS integration effort.

Jung, Jaewoo↗
NASA NTRS2019

Space Communications and Navigation (SCaN) Tool Capabilities Updates for Antenna Pattern and Jitter

The ability to accurately simulate the dynamic misalignment of pointing across a communications link is critical to determining the link performance between/across spacecraft and/or ground stations. The communication system antenna pattern and dynamic misalignment are key components to understanding the pointing loss induced on the communications link. Currently, projects performing these analyses use a variety of simulation tools and packages. NASA's Space Communications and Navigation (SCaN) office aims to provide a unified tool set for these functions. However, the analysis tool to calculate antenna patterns is currently static, two-dimensional, and approximated based on limited input. Steps were taken to change the inputs used by the tool to create a more accurate approximation of the antenna's far field pattern as well as create a three-dimensional pattern. An additional tool was also developed to calculate time-dynamic pointing loss from the antenna pattern generated or observed antenna pattern data given dynamic pointing errors.

SCaN↗
NASA NTRS2016

Interoperable End-To-End Space Communications Architectures Using CCSDS Building Blocks

End-to-end space communication architectures must connect system elements that may be in space, on the ground in mission operations centers, or are shared assets such as ground communications stations. End-to-end connectivity involves space communications over RF links, but also cross support services, terrestrial network circuits, and a variety of application layer protocols for commanding, telemetry, and mission operations. CCSDS has developed a large suite of interoperable, and cross-supportable, protocols for these purposes. Each of these defines a specific “layer” of functionality, such as: RF modulation, space link error coding, cross support frame delivery, or network layer routing. CCSDS has recently published a Space Communication Cross Support Architecture Requirements Document (SCCS-ARD) that describes how many of these standards fit together and how they are intended to be used. This paper provides an overview of this document, presented so as to explain the concepts so that others may use them. These concepts will be described from several key viewpoints.

Shames, Peter M.↗
NASA NTRS2019

Cognitive Communications for NASA Space Systems

The Cognitive Communications Project at the NASA Glenn Research Center develops applications of data-driven, non-deterministic methods to improve the autonomy of space communication. The project emphasizes development of decentralized space networks with artificial intelligence agents optimizing communication link throughput, data routing, and system-wide asset scheduling. This paper discusses the objectives, approaches, and opportunities of the research to address growing needs of the space communications community.

Chelmins, David↗
NASA NTRS2020

Free-Space Optical Communication for CubeSats in Low Lunar Orbit (LLO)

The NASA ARTEMIS Program will include LunaNet, a highly extensible, open architecture, lunar communications and navigation network. A constellation of CubeSats in Low Lunar Orbit (LLO), 100 km, could form an optical communications and navigation network as part of LunaNet, with terminals on the lunar surface, including mobile ones such as with astronauts and rovers. The proposed CubeSat nodes should provide data relay and navigational aid services. The proposed effort herein is to develop a fine pointing capability for laser beam pointing to augment body pointing by CubeSats. Body pointing was used by Aerospace Corporation for the CubeSats in LEO in NASA’s Optical Communications and Sensors Demonstration (OCSD) program [1]. Previously, this fine pointing capability was computer simulated for the OCSD program [2,3]. With fine pointing, the spot size on the Earth was reduced by a factor of eight with a reduction in laser output power by a factor of sixty-four, thereby mitigating the thermal load challenge on the CubeSats. The same reductions in spot size and laser output power can be achieved for CubeSats in LLO. A new method is described for optical data transmissions from satellites, which uses laser arrays for laser beam pointing. It combines a lens system and an array of vertical-cavity, surface-emitting lasers and photodetectors, an VCSEL/Photodetector Array, (both mature technologies), in a novel way. This system is applied to CubeSats in low lunar orbit, (LLO), which use body pointing. Also, It may be able to replace current architectures which use dynamical systems, (i.e., moving parts) to point the laser, and which may also use vibration isolation platforms. The computer simulations used the optics code, OpticStudio, from Zemax, LLC, which has the capabilities to model the laser source and diffraction effects from wave optics. These capabilities make it possible to model laser beam propagation over long space communication distances.

Goorjian, P. M.↗
NASA NTRS2020

SCAN Space Communications and Navigation: Planning Activities for NASAs Future SATCOM Direction

This presentation provides an overview of NASA's planning activities for future satellite communications support of NASA missions. The focus of this future direction is to leverage the commercial satellite communications infrastructure and develop a transition strategy for future missions to use commercial communications services. During this transition timeframe, the development of a wideband user terminal capable of roaming between NASA and commercial services is the objective of the Space Communications and Navigation program. This presentation discusses this path forward and the demonstrations planned in support of the wideband terminal development.

Nessel, James↗
NASA NTRS2020

Potential Applications of Active Antenna Technologies for Emerging NASA Space Communications Scenarios

Abstract—The National Aeronautics and Space Administration (NASA) is presently embarking on the implementation of far-reaching changes within the framework of both space and aeronautics communications architectures. For example, near earth relays are looking to transition from the traditional few large geostationary satellites to satellite constellations consisting of thousands of small low earth orbiting satellites while lunar space communications will require the need to relay data from many assets distributed on the lunar surface back to earth. Furthermore, within the aeronautics realm, satellite communications for beyond line of sight (BLOS) links are being investigated in tandem with the proliferation of unmanned aerial systems (UAS) within the urban air mobility (UAM) environment. In all of these scenarios, future communications architectures will demand the need to connect and quickly transition between many nodes for large data volume transport. As such, NASA Glenn Research Center (GRC) has been heavily investigating the development of low cost phased array technologies that can readily address these various scenario conditions. In particular, GRC is presently exploring 5G-based beamformer technologies to leverage commercial timescale and volume production cycles which have heretofore not existed within the frequency allocations utilized for NASA applications. In this paper, an overview of the potential future applications of phased arrays being envisioned by NASA are discussed, along with technology feasibility demonstrations being conducted by GRC implementing low cost, 5G based beamformer technologies.

Nessel, James A.↗
NASA NTRSDate not supplied

A Novel RF Architecture for Simultaneous Communication, Navigation, and Remote Sensing with Software-Defined Radio

The rapid growth of SmallSat and CubeSat missions at NASA has necessitated a re-evaluation of communication and remote-sensing architectures. Novel designs for CubeSat-sized single-board computers can now include larger Field-Programmable Gate Arrays (FPGAs) and faster System-on-Chip (SoCs) devices. These components substantially improve onboard processing capabilities so that varying subsystems no longer require an independent processor. By replacing individual Radio Frequency (RF) systems with a single software-defined radio (SDR) and processor, mission designers have greater control over reliability, performance, and efficiency. The presented architecture combines individual processing systems into a single design and establishes a modular SDR architecture capable of both remote-sensing and communication applications. This new approach based on a multi-input multi-output (MIMO) SDR features a scalable architecture optimized for Size, Weight, Power, and Cost (SWaP-C), with sufficient noise performance and phase-coherence to enable both remote-sensing and navigation applications, while providing a communication solution for simultaneous S-band and X-band transmission. This SDR design is developed around the NASA CubeSat Card Standard (CS2) that provides the required modularity through simplified backplane and interchangeable options for multiple radiation-hardened/tolerant processors. This architecture provides missions with a single platform for high-rate communication and a future platform to develop cognitive radio systems.

Advanced Avionics, Hybrid Processing, Data Process↗
NASA NTRS2017

Using Optical Communications Links for Deep-Space Navigation

Abstract—Optical communications systems that are being developed for deep-space missions could also be used to perform deep-space navigation. A two-way optical communications system could be modified to support ranging, and the laser signal emitted by a spacecraft could be tracked against background stars to perform plane-of-sky observables. We have been analyzing a number of deep-space navigation scenarios to understand the advantages and disadvantages of using optical communication systems for navigation. Our objectives were to evaluate the performance achievable with optical systems, and to study under what circumstances these systems could be sufficient to navigate the mission, reducing the requirements for radio systems to perhaps just to be a backup for emergency communications.

Karimi, Reza R.↗
NASA NTRS2018

Deep Space Optical Communications

The future demand for enhanced telecommunication capacity required to support human and robotic exploration from deep-space has motivated the advancement of free-space laser communication technologies for the past few decades. Steady advances in these technologies, validated through space-to-ground demonstrations, have resulted in incremental advances with the deep-space optical communications (DSOC) technology demonstration being one of the next milestones on NASA’s roadmap. NASA’s Psyche Mission to launch early next decade plans to host a DSOC flight laser transceiver for link demonstrations extending from 0.1 to farther than 2 astronomical units (AU). The capabilities validated though this demonstration, we expect, could spur the use of optical communications infrastructure around Mars in the next few decades. In this paper we summarize ongoing activities underway at the Jet Propulsion Laboratory in preparation for the DSOC technology demonstration and go on to present discussions on the drivers for developing a robust deep space laser communications operational capability.

Hoppe, Daniel↗
NASA NTRS2018

Deep Space Optical Communications (DSOC)

NASA’s future deep space science and exploration missions will require enhanced communications and navigation services. Laser communications offers expanded bandwidth and the potential for satisfying this need, with comparable mass and power as state of the art telecommunication systems. Consequently, NASA is planning a Deep Space Optical Communications (DSOC) technology demonstration, to retire the risk for future enhanced optical communication services. NASA’s upcoming Psyche Mission scheduled to launch in August of 2022 plans to host a DSOC flight laser transceiver (FLT) for demonstrating optical links from deep-space to earth. Existing ground assets retrofitted with laser transmitters and photon-counting receivers will be used for the technology demonstration. Advancing optical technology from near-Earth ranges to deep space (> 0.01 astronomical units or AU) involves orders of magnitude increased link difficulty (defined as data-rate squared distance). The plan to bridge the difficulty gap implements new technologies developed over the past two decades. These technologies emphasize high photon efficiency (HPE) with the use of high-peak-to-average power laser transmitters in space, and single photon counting sensitivity detectors, that together support signaling schemes for achieving approximately 23 information bits per detected photon. Implementing HPE schemes relies on accurate and stable pointing of narrow laser beams from space platforms using active control. Key developments needed for future technology infusion, following a successful DSOC technology demonstration, include, cost-effective ground infrastructure, long term reliability of space lasers and detection systems, and solutions for high precision laser ranging. The current status of the DSOC Project and plans for future development will be discussed in this paper.

Biswas, Abhijit↗
NASA NTRS2018

THz Technology for Space Communications

As space instruments become ubiquitous along with advancing capabilities, one of the central challenge is to provide more efficient communication links, between the control center and the instrument or between a cluster of satellites or instruments. Similarly, high-data rate communications between a mother ship and a lander is highly desirable not only for navigation but for science data as well. THz communications systems present a number of advantages in implementing efficient data-links between various scenarios for space applications. This review article will discuss some of the recent advances in solid-state coherent sources that has now made it possible to design and implement THz communication systems specifically for space applications. An example architecture at 240 GHz has been suggested as it is now possible to achieve >100 mW of output power at 240 GHz. With highly sensitive and linear heterodyne mixers, such a system could potentially provide higher data rate capability than in use today.

Jornet, Josep M.↗
NASA NTRS2018

THz technology for space communications

As space instruments become ubiquitous along with advancing capabilities, one of the central challenge is to provide more efficient communication links, between the control center and the instrument or between a cluster of satellites or instruments. Similarly, high-data rate communications between a mother ship and a lander is highly desirable not only for navigation but for science data as well. THz communications systems present a number of advantages in implementing efficient data-links between various scenarios for space applications. This review article will discuss some of the recent advances in solid-state coherent sources that has now made it possible to design and implement THz communication systems specifically for space applications. An example architecture at 240 GHz has been suggested as it is now possible to achieve >100 mW of output power at 240 GHz. With highly sensitive and linear heterodyne mixers, such a system could potentially provide higher data rate capability than in use today.

Jornet, Josep M.↗
NASA NTRS2020

Simultaneous Optical Links with the Inter-Satellite Omnidirectional Optical Communicator

As the onboard data volume for smaller platforms such as CubeSats increases, Radio Frequency (RF) communications systems may be unable to adequately support the required downlink demand. Optical communications (lasercom) systems can relieve the data bottleneck as they can support higher data throughput than RF for comparable Size, Weight, and Power (SWaP). Lasercom crosslinks are of particular interest for spacecraft swarms and constellations because they enable additional mission robustness for distributed science observations and remote sensing applications. The Inter-Satellite Omnidirectional optical Communicator (ISOC) is capable of supporting simultaneous lasercom crosslinks between multiple spacecraft at separations of up to thousands of kilometers in orbit. The ISOC architecture features a truncated dodecahedron chassis containing an array of photodetectors and gimbal-less MEMS mirrors, enabling full-duplex communications. The main objectives of the ISOC terminal include: 1) full sky coverage, 2) Gbps data rates, and 3) the ability to maintain multiple simultaneous links. We show ISOC can support up to 12 simultaneous links with the current architecture at 1-Gbps at 200-km separation with 10-9 BER. Compared to current lasercom transceivers (i.e., point-to-point), ISOC offers increased throughput performance for similar SWaP. A detailed link budget for both scenarios is presented, and the limiting factors for maximum number of simultaneous links are discussed.

Cahoy, Kerri↗
NASA NTRSDate not supplied

Joint Spectrum Access and Power Control in Air-Air Communications - A Deep Reinforcement Learning Based Approach

This paper considers the dynamic spectrum access and power control problem in a single-hop point-to-point Air-Air Communication Network (AACN). Due to spectrum scarcity, we assume the number of Aircraft-to-Aircraft (A2A) communication links is greater than that of the available channels, such that some communication links need to share the same channel, causing co-channel interference. We formulate the joint channel selection and power control optimization problem to maximize the Weighted Sum Spectral Efficiency (WSSE). A distributed and dynamic deep Q learning-based algorithm is proposed to find the optimal solution. Specifically, we design two different policies that are trained by conducting a trial-and-error scheme. Each communication link can achieve the optimal policy by exploiting the local information from its neighbors, and this distributive approach make it scalable to large networks. Finally, our experimental results demonstrate the effectiveness of the proposed solution in various AACN scenarios.

Zhe Wang↗
NASA NTRSDate not supplied

Joint Spectrum Access and Power Control in Air-Air Communications - A Deep Reinforcement Learning Based Approach

This paper considers the dynamic spectrum access and power control problem in a single-hop point-to-point Air-Air Communication Network (AACN). Due to spectrum scarcity, we assume the number of Aircraft-to-Aircraft (A2A) communication links is greater than that of the available channels, such that some communication links need to share the same channel, causing co-channel interference. We formulate the joint channel selection and power control optimization problem to maximize the Weighted Sum Spectral Efficiency (WSSE). A distributed and dynamic deep Q learning-based algorithm is proposed to find the optimal solution. Specifically, we design two different policies that are trained by conducting a trial-and-error scheme. Each communication link can achieve the optimal policy by exploiting the local information from its neighbors, and this distributive approach make it scalable to large networks. Finally, our experimental results demonstrate the effectiveness of the proposed solution in various AACN scenarios.

Zhe Wang↗
NASA NTRS2020

Q4 – A CubeSat Mission to Demonstrate Omnidirectional Optical Communications

We are proposing a technology demonstration mission for JPL’s Inter-Satellite Optical Communicator (ISOC). The ISOC has the potential to enable up to 1 Gbps data rates over a distance up to 200 km in free space. Key features of the ISOC include full sky coverage and the ability to maintain multiple links simultaneously. The Q4 mission consists of (4) 6U CubeSats furnished with ISOCs to demonstrate high data rate communications among the spacecraft. More specifically, we seek to demonstrate the omnidirectionality of the ISOC by providing simultaneous optical links between one spacecraft and the other three. Q4 will be a demonstrator for small spacecraft swarm capabilities. Following a proposed deployment from the ISS, the CubeSats will utilize their onboard thrusters to enter their desired orbit. The orbit consists of one “leader” spacecraft in a circular orbit with a 400 km LEO altitude and three “follower” spacecraft in slightly elliptical orbits rotating azimuthally about the leader. The main mission will consist of three consecutive phases: First, the spacecraft will demonstrate pointing, acquisition, and tracking using newly developed protocols. Next, link establishment and different channel access methods (CDMA and TDMA) will be tested. Finally, Delay Tolerant Network protocols will be implemented to allow fast data sharing among the spacecraft. The distance between the communicating spacecraft will be increased as the mission progresses to characterize the link quality as a function of distance. All communications over the course of the mission will be recorded and analyzed on the ground using bit error rate as a metric for success. The current design for each the four Q4 CubeSats contains an XACT advanced ADCS system for precision beam pointing. Other components currently under consideration include MiPS cold gas thrusters for orbital maneuvering and gimbaled eHaWK 84W solar arrays. In this paper we present design considerations for the Q4 CubeSats, link budget calculations, results from preliminary mission analysis, and expected results.

Velazco, Jose E↗
NASA NTRS2021

Evaluation of asynchronous geiger-mode avalanche photodiode arrays for deep-space optical communications

The NASA Psyche mission is set to explore an asteroid located between Mars and Jupiter with a launch date in 2022. On-board the Psyche spacecraft is experimental demonstrator technology that will allow scientists to explore the capabilities of optical communications – a program called Deep Space Optical Communication (DSOC) led by Jet Propulsion Laboratory (JPL). DSOC seeks to improve communications performance by developing a space-based Flight Laser Transceiver (FLT) and a ground-based transceiver to enable photon-efficient communications with equipment in deep space. An integral part to this FLT system is a high-efficiency photon-counting camera (PCC) that is able to detect both the 1064nm uplink/beacon laser photons and 1550nm downlink laser photons with low background noise, and is capable of withstanding the rigors of space-travel. The paper details the characterization of several asynchronous Geiger-Mode Avalanche Photodiode (GmAPD) arrays developed by MIT Lincoln Laboratory for use in the PCC- specifically evaluating the temperature dependence of background noise, photon detection efficiency at 1064nm and 1550nm wavelengths, pixel lifetime testing, and angle of acceptance measurements. The results of this characterization are used to determine the nominal conditions for the device to operate in while in flight to maintain an efficient link with the ground-based transceiver.

Duerr, E.↗