Citation: Teague, S.; Chahl, J.
Imagery Synthesis for Drone
Celestial Navigation Simulation.
Drones 2022, 6, 207. https://doi.org/
10.3390/drones6080207
Academic Editors: Andrzej
Łukaszewicz, Wojciech Giernacki,
Zbigniew Kulesza, Jaroslaw Pytka
and Andriy Holovatyy
Received: 19 July 2022
Accepted: 11 August 2022
Published: 15 August 2022
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Article
Imagery Synthesis for Drone Celestial Navigation Simulation
Samuel Teague
1,
* and Javaan Chahl
1,2
1
School of Engineering, University of South Australia, Mawson Lakes, SA 5095, Australia
2
Defence Science and Technology Group, Joint and Operations Analysis Division,
Melbourne, VIC 3207, Australia
* Correspondence: samuel.teague@mymail.unisa.edu.au
Abstract:
Simulation plays a critical role in the development of UAV navigation systems. In the
context of celestial navigation, the ability to simulate celestial imagery is particularly important, due
to the logistical and legal constraints of conducting UAV flight trials after dusk. We present a method
for simulating night-sky star field imagery captured from a rigidly mounted ‘strapdown’ UAV camera
system, with reference to a single static reference image captured on the ground. Using fast attitude
updates and spherical linear interpolation, images are superimposed to produce a finite-exposure
image that accurately captures motion blur due to aircraft actuation and aerodynamic turbulence. The
simulation images are validated against a real data set, showing similarity in both star trail path and
magnitude. The outcomes of this work provide a simulation test environment for the development of
celestial navigation algorithms.
Keywords: celestial; stellar; simulation; strapdown; imagery
1. Introduction
Celestial navigation in uncrewed aerial vehicles (UAV) has been a topic of interest for
over half a century (see, for example, [
1
]). The significance of this mode of navigation has
been overshadowed, however, by the ubiquity of global navigation satellite systems and
the integration of compact micro-electromechanical attitude sensors into aviation platforms.
Nonetheless, celestial navigation has unique advantages due to its independence from
critical infrastructure and robustness to external interference. We see recent works, such
as [
2
,
3
] integrating celestial imaging into their navigation solutions. Modern UAVs must
typically conform to size, weight and power constraints and, to this end, benefit from a
strapdown celestial implementation, as opposed to an actively stabilized alternative. In
a strapdown configuration, the imaging sensor has no control authority over the vehicle,
and therefore requires a larger field of view, and longer exposure intervals, to track stars
during motion. We propose here a method for simulating the imagery captured from such
a strapdown celestial system.
Celestial imagery is commonly used in spacecraft to obtain a highly accurate atti-
tude reference. This technique is less commonly used, however, in low altitude aircraft
navigation. Aircraft are subjected to many sources of noise that spacecraft are not, such
as light pollution, cloud cover, atmospheric diffraction, aerodynamic turbulence, engine
vibration and control/actuation, which all impact the signal strength of a celestial image
obtained from an aircraft. These effects are exacerbated by the need for long-exposure
imagery when operating at low-altitude (less than 500 m). The standard approach to this
problem is to use a stabilized viewing platform with a telescopic lens [
1
], which limits the
aforementioned attenuation. Such an approach is costly and adds significant weight to
an airframe. The design of this simulation has arisen from the desire for a low cost, low
weight, “strapdown” [4] celestial navigation solution.
As with all avionic navigation solutions, simulation plays an important role in the
system design and precedes the implementation. The intent of this work is to provide
Drones 2022, 6, 207. https://doi.org/10.3390/drones6080207 https://www.mdpi.com/journal/drones
