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In this paper, a circularly polarized slot-patch antenna for nanosatellite is presented. The novel design of the circularly polarized wave conducted by two asymmetrical rectangular-truncation techniques implemented on a circularly-slotted-patch on the front side and a deformed-shifted-feedline on the back side of the substrate. The antenna is printed on substrates with the dielectric constant of 2.17 and thickness of 1.6 mm. The resonant frequency of the proposed antenna is set at 2.2 GHz with the minimum requirement of the axial ratio bandwidth (ARBW) of 300 MHz. The proposed antenna produces under 10 dB impedance bandwidth (IBW) 1.2765 GHz or equal to 58% (1.7235-3 GHz) with Left-Handed Circular Polarization (LHCP). The average antenna gain reaches 4.5 dBic at 2.2 GHz and the ARBW 327.5 MHz or about 14.88% (2.0275-2.355 GHz). This paper includes the description and presentation of the completed discussion.

Radio beacons enable measurements of ionospheric radio scintillations and total electron content (TEC). These beacons transmit unmodulated, phase-coherent waves in S-band frequencies. Many satellite applications require circularly polarized (CP) wideband antennas. Their compact size, lightweight, and simple fabrication method make CP antennas suitable for small satellite systems. The slot antenna has wideband impedance, but the 3 dB axial ratio bandwidth (ARBW) is narrower compared to the impedance bandwidth (IBW). In this paper, a circularly polarized circular-slotted antenna (CSA) is proposed to enhance the ARBW and the antenna gain. A pair of asymmetrical rectangular slots, a simple 50 Ω feedline and a parasitic patch were introduced to a CSA to enhance the 3 dB ARBW and the antenna gain. Rectangular slots were inserted on the diagonal axis of the CSA, the feedline was shifted to the left side of the x-axis, and a parasitic patch was attached to the circular slot. The lengths of the rectangular slots correspond to the resonant frequency, and the parasitic patch width corresponds to the higher frequency of the 3 dB ARBW. The asymmetrical rectangular slots, the shifted feedline, and the parasitic patch successfully improved the measured 3 dB ARBW of the antenna by 787.5 MHz or 35.79%. The measured gain of a CSA with left-hand circular polarization (LHCP) was also improved by shifting the feedline and the rectangular slot, achieving a peak gain of 5 dBic.

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We report on the measurements of radio frequency interference (RFI) at Mount Timau, Kupang, Indonesia, which is intended to host a future radio astronomy observatory. These measurements were taken twice in October 2020 and December 2020 to obtain the RFI environment, at frequencies between 70 and 7000 MHz. Due to the limitations of the measurement data, the results presented in this paper are based on peak detection rather than statistical analysis. Based on the measurement results, the frequency interval between 70–88 MHz and 120–150 MHz is relatively quiet, and the frequency range of 150–300 MHz is relatively clear. The frequency interval of 300 to 800 MHz is relatively quiet, except at the frequency of 600 MHz. The frequency range of 800–1400 MHz is also relatively quiet. The predominant terrestrial services in this band are at 840 MHz, with an amplitude around 32 dB, and 916 MHz, with an amplitude around 12 dB, and the global system for mobile (GSM) signals around 954 MHz have an amplitude around 20 dB above the noise floor. The frequency range of 1400–7000 MHz is also relatively quiet. In this band frequency, we can see RFI at 2145 and 2407 MHz, emitted by local Wi-Fi, and at 2683 MHz, with amplitudes of 18, 40 and 15 dB, respectively, from the noise level. We conclude that, for this period, the frequency band allocated for astronomy can possibly be used for radio telescope development.

There are many critical parameters in the design of a radio telescope, such as antenna gain and antenna resolution. In telecommunications, radar, and radio telescopes, an antenna is a very important component. There are many designs of the antenna, such as dipole array and parabolic antenna. Parabolic antennas also have many sub-reflector and antenna methods that control the radio wave, such as the Cassegrain type. A Cassegrain-type antenna is a parabolic antenna in which the feed antenna is mounted at or behind the surface of the main parabolic reflector dish. For the transmitter system, the beam of radio waves from the feed antenna illuminates the secondary reflector (sub-reflector), which reflects it back to the main reflector dish and then forward to space. The Cassegrain design is widely used in parabolic antennas, for large antennas in satellite ground stations, communication satellites, and radio telescopes. In this paper discusses the design of a Cassegrain-type antenna for radio telescope, basic calculation, diameter size of the main reflector of 20 meters, the diameter size of sub-reflector of 2.5 meters, and frequency of 22 GHz and 43 GHz.

Electromagnetic wave backscattering by corner reflectors in an anechoic chamber is studied using our developed computational tool. The tool applies the Finite-Difference Time-Domain (FDTD) method to simulate the propagation of the wave’s electric and magnetic fields. Experimental measurement in an anechoic chamber is also carried out as a comparison. The two results show agreement, including the finding that the backscatter intensity variation amongst the four circularly polarized modes is significantly smaller than the variation amongst the four linearly polarization modes.

National Institute of Aeronautics Space (LAPAN) develops satellites for many applications, such as for remote sensing, with camera and sensors for atmospheric parameter measurement. Distribution of electron density in altitude 60 to 1000 km, is very important for many applications, such as for radio communication and as early warning indicator. Many papers indicate the correlation of electron density variation to earthquake event and also mountain eruption. For covering wider area on ionosphere region of earth are needed a sensor based on satellite to collect the ionospheric data. Nanosatellite in constellation give more data in space and time. Although nanosatellite limited in of size and power, some nanosatellites already implemented and launched for scientific mission. In this research, we conduct a simulation and then fabrication steps, to validate the consistency of simulation one and the measurement. The antenna for beacon transmitter, and for telemetry has been fabricated and have a good result with antenna gain more than 4 dB. This paper discusses the design of ionospheric sensor that is proposed for ionospheric TEC measurement and its progress.