Displaced solar sail orbits : dynamics and applications

We consider displaced periodic orbits at linear order in the circular restricted Earth-Moon system, where the third massless body is a solar sail. These highly non-Keplerian orbits are achieved using an extremely small sail acceleration. Prior results have been developed by using an optimal choice of the sail pitch angle, which maximises the out-of-plane displacement. In this paper we will use solar sail propulsion to provide station-keeping at periodic orbits around the libration points using small variations in the sail's orientation. By introducing a first-order approximation, periodic orbits are derived analytically at linear order. These approximate analytical solutions are utilized in a numerical search to determine displaced periodic orbits in the full nonlinear model. Applications include continuous line-of-sight communications with the lunar poles

Resiliency by Retrograded Communication - the Revival of Shortwave as a Military Communication Channel

In the last three decades, the great powers have become increasingly dependent on satellite communication (SATCOM), very high frequency (VHF), and ultrahigh frequency providing high bandwidth line-of-sight communications. These military communication channels lack resilience because an electronic warfare (EW) campaign can affect both VHF and SATCOM simultaneously. The 1940s preferred spectrum, high frequency, with its different propagation patterns, offers an opportunity for military communication resiliency in the 21st century. The concept of retrograding could give an operational advantage and create the ability to sustain communication in EW saturated environment

Communications for UAS Integration in the NAS Phase 2 - Satellite Communications and Terrestrial Extension

In order to provide for the safe integration of unmanned aircraft systems (UAS) into the National Airspace System, the command and control communications link connecting the ground-based pilot with the unmanned aircraft must be highly reliable and robust, with national and international standards to enable interoperability and certification. Both line-of-sight (LOS) links using terrestrial-based communications and beyond-line-of-sight (BLOS) links using satellite communications, supported by national and international standards, are required for integrated UAS operations. The National Aeronautics and Space Administration (NASA) has undertaken an extensive technology development and test program in order to provide the required technical data needed to enable C2 standards development. NASAs UAS Integration in the National Airspace System (NAS), or UAS in the NAS Project, included as a major element the Command and Control Communications (C2) Subproject, based at NASAs Glenn Research Center. The successful first phase of the C2 Subproject, completed during 2012-2016, focused primarily on line-of-sight communications. Accomplishments included air-ground channel propagation characterization and modeling; CNPC prototype radio development; CNPC radio flight testing; satellite communications spectrum study and interference analysis; and development of C2 LOS communications standards development. The second phase of the C2 Subproject will focus primarily on beyond-line-of-sight communications, although a follow-on activity for terrestrial LOS communications, known as Terrestrial Extension, is also included. In addition to the terrestrial element, Phase 2 also includes technology development and testing activities for Ka-Band BLOS C2 Satellite Communications; Ku-Band BLOS C2 Satellite Communications; Ku-Band Interference and Propagation; and C-Band Satellite Communications. This paper will provide brief overviews of the C2 Subproject and its Phase I accomplishments, followed by a description of the plans for the C2 Subproject Phase 2

Conflict on the mesa: Assessing defensibility of plaza-oriented villages in the Salinas Pueblo Province, New Mexico

Previous archaeological investigations of plaza-oriented villages in the Salinas Pueblo Province investigated the reasons people may have aggregated in these larger towns. The threat of warfare and the need for defense is one possible explanation for the construction of plaza-oriented villages, whose layout is seemingly intended to limit access. This thesis further assesses the defensibility of these sites using Geographic Information Systems (GIS). The use of a GIS approach offers an opportunity to evaluate the potential for line-of-sight communications and inter-visibility between the plaza pueblo villages on Chupadera Mesa, factors which influenced their ability to signal allies and anticipate attack. GIS also offers an opportunity to determine the relative defensibility of the region’s landforms, providing insight into the pueblo inhabitants’ site selection process

Tunable graphene-based metasurfaces for multi-wideband 6G communications

The next generation of wireless communications within the framework of 6G will be operational at the low THz frequency band. Although THz systems will dramatically enhance several performance indicators such as the data rate, spectral efficiency, and latency, exploiting such technology is challenging. Electromagnetic waves confront severe propagation losses including atmospheric attenuation and diffraction. Thus, such communications are limited to line-of-sight scenarios. In 5G networks, Reconfigurable Intelligent Surfaces (RISs) are intro-duced to solve this issue by redirecting the incident wave toward the receiver and implement virtual-line-of-sight communications. In this paper, we aim to employ this paradigm for 6G networks and design a graphene-based RIS optimized to perform at multiple low atmospheric attenuation channels. We investigate the performance of this multi-wideband design through numerical and analytical analysis.Peer ReviewedPostprint (author's final draft

Optical wireless based on high brightness visible LEDs

This paper is on a novel use of lighting or signaling devices constructed by light-emitting diodes (LEDs). The idea is on their concurrent use for simultaneous signaling and communications. The visible light from LEDs can be modulated and encoded with audio or data signal. Hence, an LED indicator lamp or traffic light can become an information broadcasting device. Such a system made up of high brightness visible LEDs can provide the function of open space, wireless broadcasting of audio or data signal. An implemented system with experimental results is shown. A portable receiver is designed to demodulate the optically transmitted information. The distance for audio transmission of an LED traffic light can reach over 20m. The optical link employs intensity modulation with direct detection. The system is limited to line-of-sight communications. However, this concurrent use of LEDs will open up many new applications.published_or_final_versio

Phased Approach to the Space Operations Center

The Space Operations Center and the Space Manufacturing and Processes Systems have major characteristics of compatibility and can be mutually influential in formulating the next major space initiative. The Phase Program Plan of the SOC provides for increasing capabilities and can be integrated with a Space Manufacturing System\u27s concept in which both the development and operational phases can be implemented. The requirements for the Space Manufacturing System appear to be suitable for SOC on-board development and then operationally as a tender of a free-flying satellite in a station-keeping orbit. The free-flying satellite can be placed in an orbit which hovers about the SOC and never exceeds line of sight communications limits. The services and reboost requirements can likewise be accommodated. The concepts of phased programs, development and operations, station-keeping orbit envelopes, propulsive Harbor Tugs and aspects of servicing will be an issue and presented

MQ-25A Manned/Unmanned Teaming

NPS NRP Project PosterManned aircraft coordinate with tankers locally through voice, hand signals and lighting. MQ-25A coordination is through a remote operator, typically through beyond line of sight communications. Degradation or loss of that communications link would inhibit refueling capability. Human machine teaming may be a key enabler for increased reliability and resilience in the unmanned tanking mission. Further, advanced human machine teaming capability may enable force multiplier missions, increasing war fighting capabilities of the carrier air wing. Co-Active Design and interdependence analysis are two proven methods for identifying human machine teaming requirements that enable resilience, reliability, and identify potential pitfalls. This year's research effort focuses on enhancing mission capabilities by exploring two key areas: enhanced ISR capabilities, and operations in non-permissive communications and position, navigation, and timing environments.ASN(RDA) - Research, Development, and AcquisitionThis research is supported by funding from the Naval Postgraduate School, Naval Research Program (PE 0605853N/2098). https://nps.edu/nrpChief of Naval Operations (CNO)Approved for public release. Distribution is unlimited.

MQ-25A Manned/Unmanned Teaming

NPS NRP Executive SummaryManned aircraft coordinate with tankers locally through voice, hand signals and lighting. MQ-25A coordination is through a remote operator, typically through beyond line of sight communications. Degradation or loss of that communications link would inhibit refueling capability. Human machine teaming may be a key enabler for increased reliability and resilience in the unmanned tanking mission. Further, advanced human machine teaming capability may enable force multiplier missions, increasing war fighting capabilities of the carrier air wing. Co-Active Design and interdependence analysis are two proven methods for identifying human machine teaming requirements that enable resilience, reliability, and identify potential pitfalls. This year's research effort focuses on enhancing mission capabilities by exploring two key areas: enhanced ISR capabilities, and operations in non-permissive communications and position, navigation, and timing environments.ASN(RDA) - Research, Development, and AcquisitionThis research is supported by funding from the Naval Postgraduate School, Naval Research Program (PE 0605853N/2098). https://nps.edu/nrpChief of Naval Operations (CNO)Approved for public release. Distribution is unlimited.

Low-Cost Portable Laser Communication Device

The portable laser communication device (PLCD), is a low cost system used to set up networks in data isolated regions via an optical line-of-sight communications protocol. In this manner the PLCD transmits at 9600 baud using UART protocol over the visible light band at 635nm. The device is intended to operate in indoor conditions and be semi-permanent until redeployed. The PLCD is built as a transmitter, receiver pair and when installed, utilizes tracking to find each other and automatically set up communication within a window of 30° laterally and 10° vertically. Each side of the system is less than 15 lb and portable with a volume of 1 cubic foot to allow for minimum bulk when transporting the device and installing it. The PLCD pair will communicate over lengths around 50 meters. The system latency does not exceed 30 ms and the system can interface with external USB devices. The PLCD does not exceed 6W in power consumption