Article
Multi-Satellite Relative Navigation Scheme for Microsatellites
Using Inter-Satellite Radio Frequency Measurements
Shiming Mo
1,2
, Xiaojun Jin
1,2,
* , Chen Lin
1,2
, Wei Zhang
1,2
, Zhaobin Xu
1,2
and Zhonghe Jin
1,2
Citation: Mo, S.; Jin, X.; Lin, C.;
Zhang, W.; Xu, Z.; Jin, Z.
Multi-Satellite Relative Navigation
Scheme for Microsatellites Using
Inter-Satellite Radio Frequency
Measurements. Sensors 2021, 21, 3725.
https://doi.org/10.3390/s21113725
Academic Editor: Jeremy Straub
Received: 26 April 2021
Accepted: 23 May 2021
Published: 27 May 2021
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4.0/).
1
School of Aeronautics and Astronautics, Zhejiang University, Hangzhou 310027, China;
moshierming@zju.edu.cn (S.M.); 21924029@zju.edu.cn (C.L.); zwzju@zju.edu.cn (W.Z.);
zjuxzb@zju.edu.cn (Z.X.); jinzh@zju.edu.cn (Z.J.)
2
Key Laboratory of Micro-Nano Satellite Research, Hangzhou 310027, China
* Correspondence: axemaster@zju.edu.cn; Tel.: +86-130-9371-9072
Abstract:
The inter-satellite relative navigation method—based on radio frequency (RF) range and
angle measurements—offers good autonomy and high precision, and has been successfully applied
to two-satellite formation missions. However, two main challenges occur when this method is
applied to multi-microsatellite formations: (i) the implementation difficulty of the inter-satellite RF
angle measurement increases significantly as the number of satellites increases; and (ii) there is no
high-precision, scalable RF measurement scheme or corresponding multi-satellite relative navigation
algorithm that supports multi-satellite formations. Thus, a novel multi-satellite relative navigation
scheme based on inter-satellite RF range and angle measurements is proposed. The measurement
layer requires only a small number of chief satellites, and a novel distributed multi-satellite range
measurement scheme is adopted to meet the scalability requirement. An inter-satellite relative
navigation algorithm for multi-satellite formations is also proposed. This algorithm achieves high-
precision relative navigation by fusing the algorithm and measurement layers. Simulation results
show that the proposed scheme requires only three chief satellites to perform inter-satellite angle
measurements. Moreover, with the typical inter-satellite measurement accuracy and an inter-satellite
distance of around 1 km, the proposed scheme achieves a multi-satellite relative navigation accuracy
of ~30 cm, which is about the same as the relative navigation accuracy of two-satellite formations.
Furthermore, decreasing the number of chief satellites only slightly degrades accuracy, thereby
significantly reducing the implementation difficulty of multi-satellite RF angle measurements.
Keywords:
multi-satellite relative navigation; radio frequency measurement; distributed multi-
satellite range measurement; inter-satellite angle measurement; extended Kalman filter
1. Introduction
Microsatellites are relatively low cost and have a short development cycle and excellent
flexibility. Thus, they are a perfect substitute for traditional large satellites in multi-satellite
missions such as satellite formations, especially for large-scale applications. Missions
that cannot be achieved using a single satellite can be accomplished with multi-satellite
formations through inter-satellite cooperation. Consequently, microsatellite formations are
widely employed in a number of space missions.
Inter-satellite relative measurement and navigation are the premise and basis for inter-
satellite cooperation in the formation. The traditional method based on ground telemetry,
tracking, and command (TT&C) network suffers from limited observation time, low preci-
sion, and poor real-time performance, and therefore cannot satisfy the relative navigation
application demands for general satellite formations. To meet the high-precision, real-time
operations and autonomy requirements of satellite formations, most measurement methods
for inter-satellite relative navigation use global navigation satellite systems (GNSS), radar,
inter-satellite radio frequency (RF), and optical measurements [
1
]. Overall, GNSS and RF
measurement methods provide the best performance (Table 1) and are widely used. The
Sensors 2021, 21, 3725. https://doi.org/10.3390/s21113725 https://www.mdpi.com/journal/sensors
