IEEE - Aerospace and Electronic Systems - August 2022 - 3

In This Issue -Technically
MAXIMIZATION OF LEO NANOSATELLITE'S TRANSMISSION CAPACITY TO MULTIPLE GROUND
STATIONS: ORBIT SELECTION AND REQUIREMENTS ON ATTITUDE CONTROL
This article presents the study of an optimized orbital configuration for a three-axis stabilized 6U
LEO nanosatellite that accommodates a polarized calibrator designed to transmit a calibrated signal
to seven ground telescopes devoted to cosmic microwave background detection with an accepted
maximum absolute pointing error of 4 arcmin; visibility windows and revisit time are maximized by
orbit selection and active attitude control considering no possibility of orbital mobility. The solution
approach is divided into two parts: in the first part, a dedicated sensitivity study is conducted to find
the optimal orbital parameters that maximize the mean contact time between the spacecraft and the
list of ground telescopes; in the second part the identified promising orbital configurations are propagated
to evaluate the attitude change maneuvers needed during the passage above each telescope to
guarantee continuous signal transmission. The results of the sensitivity study report the maximum
values for the duration and frequency of the CubeSat-to-Ground station visibility periods. The
required performance in terms of pointing accuracy and repointing velocity is later used to propose
an attitude control loop for precision pointing and to define a commercial off the shelf Attitude
Determination and Control System architecture.
COOPERATIVE CONTROL OF UAVS OVER AN UNRELIABLE COMMUNICATION NETWORK
This article proposes a method for the cooperative control of two unmanned aerial vehicles (UAVs)
to guarantee collision avoidance. The UAVs are locally controlled and are able to change their trajectories
at any time. They are connected over an unreliable communication network that may induce
packet losses and transmission delays. The network has no coordinator and necessary information
for collision avoidance can solely be communicated. In order to reduce the communication effort,
information are only transmitted at discrete time instants when they are necessary. Depending on the
current situation, one UAV is responsible for avoiding the collision by adjusting its trajectory. To
this aim, a control unit is introduced for the UAVs that uses the idea of event-based control and combines
methods from communication technology and control theory. The control unit has to execute
four tasks: estimation of the current network properties, prediction of the movement of the neighboring
object, invocation of communication in an event-based fashion, and planning of the collision
avoiding trajectory. It is proved that the control aims are satisfied even in the presence of time delays
and packet losses induced by the communication network. A simulation study with two quadrotors
shows the suitability of the method.
INTEGRATING MULTIBAND ACTIVE AND PASSIVE RADAR FOR ENHANCED SITUATIONAL
AWARENESS
This article presents the data fusion results of integrating several multiband active and passive radar
sensors for enhanced situational awareness. The two sensor technologies come with partially complementary
properties, thus a suitable mix provides improved performance in a couple of situations
of operational interest. The presented results have been obtained during a trial measurement campaign
of the NATO Science and Technology Organization, which took place on 3-13 September
2019, in Poland. Held under the code name Active Passive Radar Trials-Ground-based, Airborne,
Sea-borne (APART-GAS), this trial campaign was attended by over 70 participants from 10 countries.
It covered many new predefined military scenarios tested in real time. This article's results verify
and validate the Deployable Multiband Passive Active Radars (DMPAR) concept developed
during previous work by various NATO research groups.
AUGUST 2022
IEEE A&E SYSTEMS MAGAZINE
3

IEEE - Aerospace and Electronic Systems - August 2022

Table of Contents for the Digital Edition of IEEE - Aerospace and Electronic Systems - August 2022