Deployable Mesh Reflector Antenna for Global Navigation Satellite System Radio Occultation within 1U CubeSat Form Factor
Deployable Mesh Reflector Antenna for Global Navigation Satellite System Radio Occultation within 1U CubeSat Form Factor
Introduction
Over the past few decades, global warming has led to abnormal climate phenomena. Its frequency and intensity have increased for natural disasters such as heavy snowfall, floods, and droughts, negatively affecting human life [1]. Consequently, monitoring the Earth's atmosphere has become essential for minimizing damage to life and property.
Global Navigation Satellite System Radio Occultation (GNSS-RO) is an atmospheric observation technique utilizing satellites that measure GNSS radio signals refracted as they pass through the atmosphere [2]. Since the magnitude of refraction depends on temperature and water vapor concentration, atmospheric profiles can be derived.
Various satellites have been launched to support GNSS-RO missions [3], such as GRACE [4], CHAMP [5], FORMOSAT-3 / COSMIC [6], MetOp [7], and FengYun satellites [8]. While these missions commonly employ satellites heavier than 50 kg, CubeSats are a promising platform for GNSS-RO, offering advantages such as lower cost, smaller payloads [9], and improved coverage, [10].
CubeSat’s small size and reduced cost allow satellite constellations, providing comprehensive global coverage and frequent data updates for atmospheric monitoring [11]. Furthermore, their modular design supports rapid customization, meeting specific mission requirements [12]. The PSSCT-2 nanosatellite is an example of applying a CubeSat to a GNSS-RO mission [13]. Small satellites of commercial companies, such as Spire [14] and PlanetiQ [15], are also launched. They demonstrate the capability to deliver reliable atmospheric data with reduced resources.
Antenna gain is a critical factor in GNSS-RO. High antenna gain is needed for the reliable detection of weak signals that pass through atmospheric layers [16]. Conventional large GNSS-RO satellites employ choke ring antennas or patch antennas, which have a high gain of around 10 dB [17]. However, achieving high gain becomes challenging at the CubeSat scale due to the limited volume, which leads to degraded retrieval quality [18]. Although various techniques have been proposed, such as those utilizing metamaterials [19], opportunities for advancement persist.
The dual patch antenna of PSSCT-2 nanosatellite, whose overall dimensions are 76 mm × 76 mm × 10 mm, exhibits a gain of 6.2 dBic at L1 (1.57 GHz) frequency. Spire’s three-patch antenna for polarimetric radio occultation (PRO) has a peak gain of 9.75 dB, but its structure is incompatible with a modular 1U (10 cm × 10 cm × 10 cm) payload envelope. This situation motivated our exploration of a deployable antenna concept which can achieve high gain over 10 dBi while stowing compactly into a 1U module.
The paradigm for space missions has shifted from large satellites toward small, cost-effective CubeSat platforms. This trend enables new mission architectures, including large constellations for global coverage, but introduces the significant challenge of achieving high antenna gain within severely limited volume constraints.
To overcome this limitation, deployable antennas that can be stowed compactly for launch have become a primary area of research. One major approach is the deployable reflector antennas to create a large effective aperture. The studies focus on various foldable structures using metal mesh, such as tension truss antenna [20], fold rib antenna [21], wrapped rib antenna [22] the reflectors and are primarily optimized for high-frequency bands.
Other strategies explore self-deploying radiating structures, including lightweight and reliable helical antennas [23], and fully 3D-printed, self-deployable Yagi–Uda phased arrays that achieve significant gain and beam steering without needing any actuators [24]. Furthermore, studies have also focused on developing reconfigurable origami-inspired antenna which can switch between omnidirectional and high-gain modes [25], a compact S-band antenna system that utilizes the satellite structure itself via characteristic modes theory [26].
This review indicates that the advancement of deployable apertures is the dominant strategy for meeting the increasing demand for high gain in future CubeSat missions. While deployable helical antennas and novel approaches show promise, deployable reflector antennas are a well-established and straightforward way to create large effective apertures for missions demanding high performance.
The mesh antenna is a widely utilized type in space applications due to its lightweight and high storage ratio which is usually defined as the ratio of the reflector’s deployed diameter to its stowed diameter [27]. There are diverse types of mesh antennas: Tension truss antenna [28]; Fold rib antenna [29]; Wrapped rib antenna [30].
The tension truss antennas are constructed using numerous cables. The parabolic surface is formed by applying constant tension to the cable network. The structure has a high storage ratio and high surface accuracy, and research is currently being conducted to further improve the accuracy [31]. However, the cable network is significantly complex, which increases the risk of the cables becoming tangled.
The fold rib antenna features a simple, umbrella-shaped deployable mechanism, but has the disadvantage of a low storage ratio in height due to structural limitations. There are research papers to address this problem by using multiple rotating joints on each rib [32]. However, the crease lines may potentially compromise the integrity of the mesh. Additionally, foldable mesh reflector antennas utilizing elastic shape memory alloy (SMA) has been explored, which yields a lightweight and self-recoverable mechanism without permanent deformation [33]. However, this approach has a relatively low storage ratio despite its advantages.
The wrapped rib antenna has flexible ribs that can be rolled into a spiral shape around a hub to be stowed. The elastic potential energy of deformed ribs ensures a simple deployment mechanism. The wrapped rib antenna has a high storage ratio in both diameter and height, which can be suitable for CubeSat applications. As shown in Fig. 1(a), the ribs are vertically connected based on the top of the hub to ensure that the ribs wrap around the hub, reducing interference between the ribs. However, while rib’s flexibility offers advantages for efficient stowage, its high rigidity is also essential to maintain the deployed shape.
In the previous research, the composite materials are used, and the angle between the hub and the rib is adjusted to resolve the dilemma by reducing the stress of the rib’s root in the stowed state [34]. Also, a reinforcement structure is installed to apply tension in the direction opposite to the wrapping direction in the deployed state [35]. However, this structure still makes the ribs vulnerable to bending in the wrapping direction, and installing additional structures is difficult for CubeSat antenna systems due to the small volume.
Basically, the robustness in the wrapping direction can be addressed by a horizontal connection between the rib and the hub as shown in Fig 1(b). But this configuration presents a challenge in the stowage process. Thus, technological advancements that integrate the high storage ratio of the vertical configuration with the rigidity of the horizontal configuration are required.
The presented antenna is anticipated to be employed to acquire GPS signals modulated with Binary Phase Shift Keying, Rate 1 (BPSK-R(1)). Based on prior research, a received signal power of approximately –120 dBm for GPS L1 signals is indicated with a 4 dBi antenna [36]. The received signal power can be increased to -114 dBm by using antennas with the gain of 10 dBi, which enhancement facilitates reliable operation across most GNSS-RO scenarios.
For the deployable reflector antennas, it is essential to preserve the antenna’s shape in the deployed state to ensure geometrical stability. In other words, it requires high surface accuracy, which is an evaluation metric that quantifies the deviation of the reflector's shape from an ideal parabolic surface. A larger reflector is better for increasing gain, but storing the antenna in a compact volume while ensuring high surface accuracy presents a significant design challenge. Structures with high compressibility often require multiple deformable or foldable components, increasing the risk of distortion and compromising geometric stability after deployment. Therefore, this paper focuses on researching the deployable mesh reflector, as it represents a critical path toward enabling the next generation of CubeSat applications.
In this paper, a 1U-scale deployable mesh reflector for GNSS-RO CubeSat is presented. The proposed mechanism addresses competing demands by using cross-axis folding hinges applied to the central hub. In the stowed state, each rib’s bending axis is vertical to the top of the hub, which achieves efficient wrapping and high storage ratio. In the deployed state, the ribs pivot so that the top of the hub becomes parallel to each rib. This orthogonal shift allows a larger contact area with the mesh, mitigating distortion and preserving the antenna’s shape once deployed, thus enhancing its geometrical stability.
Experimental results show that the proposed system can deploy from a 1U volume into a 0.5 m-diameter reflector antenna, and the measured surface accuracy exhibits a root mean square (RMS) error of 5.41 mm even after the first deployment. Radiation pattern measurements confirm a peak directivity of 13.07 dBi for the proposed reflector antenna, which closely approaches 14.14 dBi of an ideal, non-deployable solid reflector. It also represents a 61% improvement in directivity compared to the commercial CubeSat patch antennas of Spire.
Section snippets
Specifications of antenna
The specifications to be achieved by the deployable reflector antenna are summarized in Table 1. An axisymmetric reflector configuration and a front-feed antenna were selected as the feed type for the prototype and the focal ratio of 0.4 is selected arbitrarily. The diameter of the reflector was determined considering the gain. The gain, G, of a parabolic reflector antenna is given by: where is the diameter of the reflector, is wavelength, and is the aperture efficiency
Mechanism of deployable mesh reflector antenna
The hub, ribs, and gores are the main components of the reflector. The hub contains the cross-axis folding hinge, which changes the angle of the rib. When the antenna is deployed, the top of the hub and the rib are connected in parallel. On the other hand, they are in vertical contact when the antenna is stowed. The rib serves as a frame, which is required to be flexible enough to be rolled up, yet rigid enough to maintain the form of the reflector after deployment. The rib has curvatures in
Reflector fabrication
The prototype of the mesh reflector is presented in Fig. 12. The hub component is manufactured using 3D printers. The hub and hub column are made of Aluminum, and the others are made of Onix filament. Ribs are first made by laser-cutting PET according to the design of the rib. Then, the cut PET is placed between 3D-printed jigs and thermoformed in an oven at 100°C for 30 minutes. The gore is cut to the shape of the defined dimensions. The reflective surface for the system-level deployment test,
Discussion
In this paper, a 1U-scale deployable mesh reflector antenna is presented to meet the increasing demand for GNSS-RO missions employing CubeSats. The cross-axis folding hinge is utilized for the hub design, which can change the angle of the rib. The reflective surface and the rib are connected in parallel in the deployed state, preventing the rib’s bending in the wrapping direction. But they are facing each other vertically in the stowed state, reducing the angle between the hub and ribs. Thus,
CRediT authorship contribution statement
Gagyeong Park: Writing – review & editing, Writing – original draft. Dong-Wook Yang: Methodology, Investigation. Min-Woo Oh: Methodology, Investigation. Jang-Soo Chae: Resources, Investigation. Hyosang Yoon: Conceptualization. Jae-Hung Han: Conceptualization. Dae-Young Lee: Writing – review & editing, Methodology, Conceptualization.
Declaration of competing interests
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
This work was supported by the National Research Foundation of Korea funded by the Ministry of Science and ICT under Grant 2022M1A3C2069728, Future Space Education Center.
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