Aerospace and Electronic Systems - October 2018 - 2

In This Issue - Technically

DOI. No.

ANALYSIS AND DESIGN OF A STACKED POWER SUBSYSTEM ON A PICO-SATELLITE
The electrical power subsystem (EPS) for a pico-satellite is a combination of hardware and software that supplies energy demands
during a satellite's lifetime. This article aims to present several EPS classifications, promote a general discussion about EPSs and
to propose a new architecture for the EPS based on the distributed energy system (DPS), using the stacked DC-DC converters concept. The presented topology ensures that power peak tracking (PPT) is performed concomitantly with the bus voltage regulation.
Thus, the energy assigned for the DC bus is processed only once from the photovoltaic arrangement (PV). In addition, due to the
parallel connection of the input, this architecture allows energy redirection to the battery, reducing charge time and ensuring that
the battery is fully charged during satellite eclipse intervals. This article will describe the design of a new EPS architecture for a
CubeSat that uses the distributed system and stacked architecture and present the experimental results.

PERFORMANCE ANALYSIS OF GNSS UNITS IN MANNED HELICOPTER OPERATIONS
Obtaining accurate Global Navigation Satellite System (GNSS) positions for mapping events and features is a major problem in
aerial surveillance in Hawaii's forested watersheds due to exceptionally difficult terrain. Our study analyzed the performance of
survey-grade (Trimble® R10), mapping-grade (Trimble® Geo 7 and Trimble® Juno 5) and consumer-grade (ASUS® Nexus 7,
Motorola® Droid Turbo, and Garmin® Foretrex 401) GNSS receivers, recording inside the fuselage of a Hughes 500D helicopter while conducting low-altitude surveillance flights in the mountainous terrain of the East Maui Watershed (Hawaii, US). The
survey-grade GNSS performed poorly with frequent interruptions of the carrier phase signal particularly in low-altitude flight lines
where skyline visibility was reduced by steep topographical obstructions. Moreover, the main rotor of the aircraft compromised
signal lock. Overall, differential post-processing offers the most accurate positional data, while the consumer-grade GNSS was
well regarded for its cost-effectiveness and simplicity.

A SURVEY ON SECURING UAS CYBER PHYSICAL SYSTEMS
The fields of internet enabled devices (i.e., cyber devices) and embedded computer systems have converged, creating what are
known as cyber physical systems (CPS) that control some physical processes and are often connected to the outside world, possibly through a direct connection to the internet. Although these systems are often categorized as safety-critical, meaning a transient
or permanent failure may have catastrophic effects, their connection to the outside world makes them susceptible to cyber-attacks.
Thus, it is becoming increasingly important to secure these systems, many of which are part of critical infrastructures such as
the power grid, nuclear power plants, manufacturing systems, unmanned autonomous systems, and health care technologies. The
Flight Control System (FCS) of an Unmanned Aerial System (UAS) is a quintessential example of a safety critical CPS. In this article, we investigate and classify the methods and avenues that can be used to launch cyber-attacks against FCS and UAS systems
as well as what types of systems or techniques can be used to monitor, detect, and/or counter these attacks.

BEAM SHAPING OF X-BAND STEPPED CHOKE RING ANTENNA FOR LEO SATELLITE APPLICATIONS
Low Earth orbit (LEO) satellites operating below 1,400 km are currently in use for various applications, ranging from remote sensing
and weather forecast to voice and data communications and scientific research. Because of their shorter distance to Earth, simpler,
smaller, and therefore lower-gain antennas with wider angular coverage can be mounted on a LEO satellite to establish the communication link. The wide angular coverage of the satellites and their varying distances from Earth, make the effect of the satellite and
the antennas on the radiation beam more significant. The choke ring antenna is one of the best options among many types of antennas
being used for LEO satellites operating in microwave frequencies. This article reports on the design, optimization, fabrication, and
testing of a four-ring stepped choke ring antenna with a descending profile. The antenna was mounted on a satellite mock-up and the
effects of the satellite body and solar panels on the radiation pattern were fully investigated through simulation and measurement.

PERFORMANCE COMPARISON OF PARTICLE SWARM OPTIMIZATION AND CUCKOO SEARCH FOR ON-LINE ROUTE PLANNING
Besides military applications, unmanned aerial vehicles are being used in multiple civil applications. Soon, hundreds or even thousands of unmanned aerial vehicles will share the airspace with civil and commercial aviation. This creates the need for researching
and developing new intelligent systems capable of reducing the implied risks. These intelligent systems optimize and update their
flight trajectories to avoid collisions with buildings, mountains or other airships. This work proposes an on-line route planning
method for autonomous navigation of airships through unknown environments. The on-line route planning method is easy to
implement and it can be updated to different optimization algorithms based on populations. Two online planners are developed and
evaluated through simulation in this work: one uses Particle Swarm Optimization and the other uses Cuckoo Search. Both planners
are evaluated in terms of route length and execution time and then are compared to a graph based classic method. All experiments
were performed using a real geographic database from a region in the Colombian Andes and results are communicated in this article.

IEEE A&E SYSTEMS MAGAZINE

OCTOBER 2018

Aerospace and Electronic Systems - October 2018

Table of Contents for the Digital Edition of Aerospace and Electronic Systems - October 2018