# CubeSat-Based Observations of Lunar Ice Water Using a 183 GHz Horn Antenna: Design and Optimization
## 1 Introduction  
The enhancement of high-resolution scientific spectroscopic THz remote sensing is extensively spreading throughout the universe due to the ESA (European Space Agency) cornerstone Herschel Space Observatory [1]. Recently, THz and submillimeter technology have been widely used in remote sensing imaging. They offer unique advantages in detecting various materials and identifying their properties [2, 3], elements detection, and outer space exploration. A high-gain antenna in the THz frequency range is important to enhance the link budget and THz signal observing capabilities [4]. THz circuits have the potential for space-based communication systems with high data transmission rates and metal packaging can help to dissipate heat and reduce parasitic capacitances/inductances [5], and mini-sized THz horn antenna has a simple structure and provides better directivity and radiation efficiency. Horn antennas have been extensively utilized in various applications due to their myriad of beneficial properties. These antennas are known for their broadband performance, making them suitable for a broad range of frequencies, which is particularly advantageous for systems that need to receive or transmit signals over a variety of frequency bands [6]. Further enhancing their efficiency, horn antennas exhibithigh directivity and gain. This characteristic allows them to focus radio waves effectively in a specific direction, thereby improving transmission and reception efficiency, especially over long distances [7]. The advantageous low Voltage Standing Wave Ratio (VSWR) of horn antennas ensures efficient power transfer and minimizes signal loss due to reflections at the antenna-feed line interface [8]. Their robustness and reliability further add to their appeal, making them less sensitive to weather conditions than some other types of antennas. This advantage, coupled with their simple construction, contributes to their durability and reliability [9]. Another significant advantage of horn antennas lies in their ease of fabrication and design. Their relatively simple structure makes them not only easy to design and manufacture but also allows for customization to meet specific requirements [10]. Moreover, horn antennas are less prone to interference from other sources due to their high directivity. This makes them especially suitable for environments with high levels of electromagnetic noise [11]. Horn antennas demonstrate excellent compatibility, are able to be readily used with other microwave components such as waveguides and coaxial lines [12]. These advantages make it a promising candidate for THz communication systems [13]. For many years, corrugated horn antennas have been examined as antenna feeds, and due to technological development, it has become possible to fabricate [14; 15]. Outer space missions require high-quality factor subsystems. Utilizing deployable antenna mechanisms escalates the risk of a satellite malfunctioning, subsequently, satellite engineers focus on non-deployable antennas such as horns, patches, etc. In the THz range, the wavelength is miniature; therefore, manufacturing a patch antenna via current technology is impossible; therefore, horn antennas are logical choices [16]. Meteorology microsatellites to monitor atmosphere climate changes usually use a horn antenna feeder Corrugated horn antennas offer several benefits for CubeSat remote sensing applications. They have a high directivity and gain, which makes them suitable for long-range communication and remote sensing. Corrugations in the horn structure improve the antenna's impedance matching and reduce standing waves, which leads to better performance at higher frequencies. The use of corrugated horns can reduce unwanted side lobes and cross-polarization, which can improve the antenna's performance in space-based remote sensing applications [17]. The corrugated horn antenna fulfills all of the required remote sensing specifications [18; 19; 20].