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Feed assembly development for INCUS 1.6 m mesh reflector antenna

Published online by Cambridge University Press:  04 April 2025

Gaurangi Gupta*
Affiliation:
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
Alessio Mancini
Affiliation:
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
Paolo Focardi
Affiliation:
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
*
Corresponding author: Gaurangi Gupta; Email: gaurangi.gupta@jpl.nasa.gov
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Abstract

INCUS (INvestigation of Convective UpdraftS) is a NASA Earth Science mission scheduled to launch in 2026. The goal of the mission is to study in detail how water vapor and droplets move inside tropical storms and thunderstorms and understand their effects on weather and climate models. To carry out this study, the mission will use three almost identical SmallSats, each equipped with a Raincube-heritage Ka-band radar. The deployable mesh reflector antenna is a new 1.6 m design provided by Tendeg, which is fed using a seven-horn feed assembly to generate overlapping secondary beams. This paper discusses the approach used to design and fabricate the feed assembly and presents the measured and calculated RF performance parameters.

Information

Type
Research Paper
Creative Commons
Creative Common License - CCCreative Common License - BY
This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0), which permits unrestricted re-use, distribution and reproduction, provided the original article is properly cited.
Copyright
© Jet Propulsion Laboratory, California Institute of Technology, 2025. Published by Cambridge University Press in association with The European Microwave Association.
Figure 0

Figure 1. INCUS observatory configuration.

Figure 1

Figure 2. A pictorial representation of the INCUS constellation showing the three observatories and their radar swaths (INCUS1, INCUS2, and INCUS3). INCUS 2 also hosts a radiometer with a swath of 500km.

Figure 2

Figure 3. A close-up nadir view of the three smallsats showing the footprint of the seven partially overlapping reflector beams sweeping across a common ground track. Visualization created using satellite orbit analysis program (SOAP) developed by the aerospace corporation. (a) INCUS 1 view, (b) INCUS 2 view, (c) INCUS 3 view.

Figure 3

Figure 4. Mesh reflector antenna optical prescription.

Figure 4

Figure 5. Feed assembly model with seven ports and feeding network. (a) Single horn interior profile, (b) single horn fabricated prototype, (c) seven-horn cluster arrangement and feeding network.

Figure 5

Figure 6. Fabricated feed assembly prototypes. (a) Golden Devices prototype (hybrid additive manufacturing and casting aluminum), (b) Frontgrade Technologies prototype (standard machining aluminum and standard tooling for aluminum waveguide), (c) Custom Microwave Inc. Prototype (aluminum metal additive manufacturing for horns and standard tooling for copper waveguides).

Figure 6

Figure 7. Reflection and coupling coefficients for different prototypes. (a) Golden Devices SLA copper prototype, (b) Golden Devices aluminum cast prototype, (c) CMI doubly-curved rectangular-to-circular transition, (d) CMI linear rectangular-to-circular transition, (e) Frontgrade prototype, (f) simulation results from Ansys HFSS.

Figure 7

Figure 8. Waveguide insertion loss measurement set-up for Golden Devices prototype using shorting tool. Shorting tool is shown on right.

Figure 8

Table 1. Insertion loss (dB) at 35.755 GHz for different prototypes waveguides

Figure 9

Figure 9. Radiation pattern measurements test set up for feed assembly.

Figure 10

Figure 10. Directivity comparison for different prototypes at 35.755 GHz.

Figure 11

Figure 11. Measured and calculated normalized radiation patterns for Golden Devices prototypes port 1 and port 4 on 0°, 90° cuts for co-pol and cx-pol. C1 are measured results from a copper-plated polyimide assembly (black), A1 are measured results from a cast aluminum assembly (blue). Simulations are in red.

Figure 12

Figure 12. Measured and calculated normalized radiation patterns for CMI prototypes with doubly-curved rectangular-to-circular waveguide transition. Port 1 and port 4 on 0°, 90° cuts for co-pol and cx-pol. CMI1 are measured results for assembly (blue). Simulations are in red.

Figure 13

Figure 13. Modified antenna feed assembly.

Figure 14

Figure 14. Measured S-parameters for the modified feed assembly.

Figure 15

Figure 15. Measured and calculated normalized radiation patterns for modified feed assembly for port 1 and port 4 on 0, 45, and 90 cuts for co-pol and cx-pol.