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.

The western-equatorial meteor radar was installed at Kototabang on equatorial (0.20° LS 100,32°BT) and has been operational since 2002. It is used for observing meteor as they enter the Earth's atmosphere to provide the wind data profile in both zonal and meridional direction besides meteor echo rate data which have only one wide beam signal transmission vertically. MWR system hardware comprises two main components: The antenna system and feeders, and the radar system itself. The antenna system is typically composed of two-element Yagis for transmission and five 2-element Yagis for reception. The instrument cabinet contains all of the remaining elements of the MWR radar system i.e. the RF components and the data acquisition which equipped with a GPS-locked real time clock for accurate acquisition time stamps. Those mentioned above will be described in this paper about the radar system, along with the details of the experiment and analysis techniques. Also an initial results are presented, indicating the radar produces count rates around thousands meteors per day.

Thirty infrasound sensors have been operated over Japan since 2015. We developed the irregular array data processing in order to detect and estimate the parameters of the arrival source waves by using infrasound data related to the sequence of the volcanic eruption at Mt. Shinmoedake in March 2018. We found that the apparent velocity at the ground was equal to the acoustic velocity at particular reflection levels. The results were confirmed through a comparison of the findings of the apparent velocity with a wave propagation simulation on the basis of the azimuth, infrasound time arrivals, and the state of the atmospheric background using global atmospheric models. In addition, simple ideas for estimating horizontal wind speeds at certain atmospheric altitudes based on infrasound observation data and their validation and comparison were presented. The calculated upper wind speed and wind observed by radiosonde measurements were found to have a qualitative agreement. Propagation modeling for these events estimated celerities in the propagation direction to the sensors that were consistent with the tropospheric and stratospheric ducting. This study could inspire writers, in particular, and readers, in general, to take advantage of the benefits of infrasound wave remote-sensing for the study of the Earth’s atmospheric dynamics.

We investigated meteor height and number of meteor echoes over a 13‐year observation period, with the data recorded by the meteor wind radar systems in Kototabang (0.20°S, 100.32°E) and Biak (1.17°S, 136.10°E), Indonesia. We aimed to investigate the changes in meteor peak height according to solar activity, represented by the solar radio index F10.7, and the number of solar sunspots, R, compared with the empirical results of the Mass Spectrometer Incoherent Scatter Extending (MSISE) and Committee on Space Research International Reference Atmosphere models. We found that (i) the daily meteor count rates at both sites in the period from 2003 to 2016 could be used to determine the dynamics in the upper atmosphere, where peak conditions occurred in the middle of the year; (ii) through a statistical approach using the normal distribution function, the variation in meteor peak height showed a positive correlation with the trend in solar activity; and (iii) comparison between the two empirical models and our observations showed two points where annual air density seemed to have a clear relationship with peak meteor height. In addition, the annual neutral density pattern of the model was related to the daily meteor count every year, although it showed a pattern opposite to the solar activity trends.

"The importance of radio telescopes for astronomy, geodesy, and other disciplines has been demonstrated by the growing number of radio telescopes worldwide, including in South-East Asia. Timau National Observatory has also considered a radiotelescope development program, which is expected to contribute both on a national and global scale. The diameter for the single dish is planned to be around 20-meter with a frequency range of 1-50 GHz. This paper outlines potential research for the planned radio telescope as a single dish as well as a part of future interferometer/VLBI collaboration. We collected several studies conducted with single antenna with a diameter of around 20-meter as a comparison to study its potential use as a single dish. As it is also essential to consider using an interferometer network, we also examined its capability as a part of VLBI, including the UV coverage and object simulation. Finally, it can be concluded that many studies can be conducted using the 20-m radio telescope as a single dish. Its location slightly below the equator can also play an important role in completing the global VLBI network."

The formations type of solar radio bursts can be known base on the frequency range that is detected. The CALLISTO system works with a wide band of the frequency making it possible to detect several types of solar burst. Indonesia exactly at Sumedang, CALLISTO system detected the formation of solar radio bursts forms of type II for the first time on 5 November 2014. On the other side, CALLISTO spectrometer detects and traces the phenomenon of CME (Coronal Mass Ejections) which causes the solar radio burst type II occurrence. In this paper will be calculated frequency drift rate during the occurrence of solar radio bursts of type II phenomenon on 4th November 2015 at 03:30 UT. The results of these calculations will be discussed as a related study of drift rate during the phenomenon of burst type II radio bursts associated with CME. The obtained drift rate during the solar radio bursts events above 2.8 MHz / s with low drift rate so that the speed of the CME that occurred only about 790 km / s as shown from LASCO.