Concept Design and Realization Branch—Part I: Guest Editors’ Introduction
The Concept Design and Realization Branch within APL’s Research and Exploratory Development Department provides an array of engineering, design, and fabrication capabilities that broadly support the Laboratory’s mission and sponsored work. It has been more than 20 years since these areas have been reviewed in this publication, and during that time, the Lab’s ability to develop and build complex systems has advanced significantly. Computing power has exponentially advanced the enabling modeling, analyses, machine programming, and novel manufacturing methods—many of which were unimaginable 20 years ago. Electronics, sensing, artificial intelligence, and other technologies have merged and are increasingly embedded to create powerful automated tools. Today, the branch continues to serve the Lab with hardware design, mechanical and electrical fabrication, systems integration, and breakthrough manufacturing science that will benefit the programs and missions of the future. This issue, the first of two, describes examples of the wide-ranging work of the branch, highlighting how it directly contributes to APL’s position as a unique resource to the nation.
Inside Back Cover: APL Discovery Program Infographic
This infographic offers highlights from APL’s Discovery Program.
Learning through Discovery
Building career foundations is one of the three core tenets of the Discovery Program at Johns Hopkins University Applied Physics Laboratory (APL). New college graduates selected for this cohort-based rotational program create these foundations through the program’s carefully constructed training and mentoring component, which was developed collaboratively by Discovery Program leadership and APL’s Talent Development Office. To ensure that training is immediately relevant and useful, training opportunities are sequenced strategically throughout the program and offered at just the right time in the staff members’ evolution. This article describes the approach to helping APL’s Discovery Program staff members build strong foundations that will serve them well throughout their careers.
Reflections from Discovery Program Host Group Supervisors
In this article, four supervisors reflect on how APL Discovery Program staff members have made a positive impact on their teams.
Reflections from Discovery Program Alumni
In this article, four recent APL Discovery Program alumni reflect on their experiences in the program.
Microwave Photonics—Design of a Fiber Optic Recirculating Loop
This article outlines recent Johns Hopkins University Applied Physics Laboratory (APL) work on a fiber optic recirculating loop (RCL) system and describes some of the important design decisions. Optical RCLs were originally designed as a means to study long-haul data transmission systems in a compact, less-expensive manner. For this project, however, the RCL is used to transmit repeated radio frequency (RF) signals within a larger optical system. At its core, an RCL consists of a length of fiber and an amplifier. An optical switch is used to let an encoded RF signal enter the loop, while an optical coupler is used to let the encoded RF signal exit the loop. We made multiple design decisions while making this system. Most important, chromatic dispersion of the optical fiber disrupts transmission of the recirculated RF signal. To account for this, we evaluated multiple optical fiber types, encoded the RF signal using a single-sideband technique, and incorporated a programmable optical filter with dispersion compensation capabilities. Moreover, polarization-dependent loss (PDL) and polarization-mode dispersion (PMD) within optical components are compounded as light recirculates. To accommodate for this, we incorporated a polarization scrambler in the design. In this article, we walk through the RCL design process and mention the contributions of each optical component to the final design.
Waves Satellite Constellation Design and Analysis
Satellites are excellent platforms for communications, sensing, imaging, and navigation, providing the “high ground” for large-area fields of view and low-loss free-space paths for inter-satellite links. As development and production costs decline, large constellations (upward of thousands of satellites) are planned for near-future launches by both private and public entities. Designing these constellations is challenging because of the large trade space that includes altitude, inclination, total number of satellites, distribution of satellites in planes, and phasing between satellite planes. In this article, we discuss a new constellation design (patent pending), which we call a Waves constellation, developed by the Johns Hopkins University Applied Physics Laboratory (APL) to provide optimal coverage in a given latitude band. Further, we discuss our work to speed up the analysis of satellite constellation coverage, which can be used with the Waves geometry or any arbitrary constellation geometry.
Preliminary System Identification of Dragonfly’s Octocopter
The Johns Hopkins University Applied Physics Laboratory (APL) is leading Dragonfly, a mission to study the prebiotic chemistry of Titan, one of Saturn’s moons. Given Titan’s diverse surface environments, mobility is crucial to the science mission, so controls engineers are faced with the challenge of designing an autonomous flight-control system for an aerial vehicle that will operate in uncertain environments. Part of the flight controller development approach involves testing with a half-scale test vehicle in an Earth environment; and one part of this process is system identification. Here, we detail the design and testing of the first round of system identification experiments with the test vehicle in which random-phase multisines were injected into the attitude commands during hover. Four experiments were performed using the half-scale test vehicle. Because of significant wind disturbances, the collected data had low coherence and were ultimately unsuitable for nonparametric frequency response estimation. System identification is an iterative process, and we present several planned ways to improve the coherence of the flight data.
Kalman Filters for Forecasting Open-Ocean White Shipping Location
Merchant vessels travel across the ocean daily to deliver goods and transport cargo or passengers. Understanding the forecasted locations of these vessels is important for many reasons, including collision avoidance. Currently, their captains rely on radar, a global positioning system (GPS) satellite fix, and the Automatic Identification System (AIS) to maintain timely awareness of their surroundings. This article describes a Johns Hopkins University Applied Physics Laboratory (APL) team’s research into using a Kalman filter to improve forecasts of vessels’ locations. When provided historical geospatial data that contain uncertainties, the Kalman filter algorithm provides a means to estimate future locations of moving objects. The APL team confirmed that when using GPS and AIS data, the Kalman filter forecasting tool can predict the future location of a vessel 90% of the time within 15 nautical miles for 12 h into the future.
A Streamlined Approach to Analyzing Next-Generation Electronic Warfare Capabilities
With a rich history dating back over a century, electronic warfare has become a powerful tool at the warfighter’s disposal. However, as technology continues to advance, so must the capabilities of electronic warfare systems and the tools used to evaluate them. A team at the Johns Hopkins University Applied Physics Laboratory (APL) leveraged a unique combination of technical and operational expertise to develop a streamlined analysis approach to minimize turnaround time for analysis. This article overviews this approach and highlights a robust digital signal processing tool providing quick and thorough analysis results for mission-critical and operationally relevant test data.