No abstract

Rainfall is observed as a main contributing factor in the degradation of electromagnetic signal for frequency above 10GHz through absorption and scattering, resulting a weak or fading signal. Broadcasting satellite service operates in Ku band (12GHz to 18GHz) is widely used has caused congestion, therefore Ka band is exploited to meet the customer demand. However, the rain attenuation effects on Ka band are higher than Ku band. In this study, the rain attenuation effects of Ka band downlink signal of the Measat-5 satellite are analysed to assess the rain fade properties using TRMM 3B42 data for eleven (11) years from January 2009 until December 2019 for fourteen study areas. All data are processed to obtain 1-minute integration data using Segal Model and the prediction of rain attenuation are implemented using ITU-R P.618-13 model. This study summarizes, there are three, (3) main factors that influence the impact of rain attenuation, namely the value of specific attenuation, receiver station altitude and elevation angle of the satellite signal receiver antenna. The signal availability impact on rain attenuation shows, eight (8) study areas could receive 99.90% of service readiness, while the rest at 99.00% to comply with the ITU unavailability requirements. Overall, the value of rain attenuation on the West Coast of Peninsular Malaysia is smaller than the East Coast of Peninsular Malaysia and the value of rain attenuation in the East Coast of Peninsular Malaysia is closer to the value of rain attenuation in Sabah and Sarawak.

Malaysia is located in an equatorial region with high and stable temperatures, high humidity, and rainy throughout of the year. The rains are caused by the monsoon regime and influenced by local topography. However, Malaysia is near the Equator and surrounded by the sea, there is no real dry season. The weather in Malaysia is mainly affected by two monsoon regimes which is the Southwest Monsoon (MBD) from May to September, while the Northeast Monsoon (MTL) from November to March for every year. The sea in Malaysia are causing the effects of sea breeze and land breeze that have a huge impact on wind patterns. The abundant rainfall in Malaysia which is suitable in this study is to analyze the 3B42 rainfall data from Tropical Rainfall Measuring Mission (TRMM) and 14 study areas including of 8 areas from Peninsular of Malaysia (SM) and 6 areas from East of Malaysia (MT) for the period of 11 years of data from 2009 to 2019. This paper is to study the intensity of diurnal rainfall according the temporal and spatial data using Segal models which is conversion the 1-minute rainfall interval in Malaysia. The Segal model is the best model for conversion of rainfall data for Malaysia. This paper also analyses the rainfall data in Malaysia. The conversion of 1-minute rainfall interval data can give the statistical stability of rainfall distribution that influenced by the diversity of landforms, the movement of monsoon winds, and the latitude of surface areas. The result of this study show that Kuching, Sarawak received 1-minute rainfall data at 175.25mm/hour with the highest annual rainfall of 4641.34mm in the entire study area within Malaysia. The lowest 1-minute rainfall data for SM is Cameron Highlands, Pahang which came up to 103.09mm/hour while the highest 1-minute rainfall data is Kota Bahru, Kelantan at 171.13mm/hour. Kota Bahru study area also received the average of highest annual rainfall data for SM which is at 3013.33mm. Cameron Highlands is located near Titiwangsa Range, where the backbone of SM is located, and the area is protected by strong MTL winds. The results found that the lowest average daily, monthly, and annual rainfall is Mersing, Johor at 1992.98mm for the entire study area. The pattern of rainfall distribution as overall show the east coast area of SM and the entire state of Sarawak received heavy rainfall affected by MTL winds and have the same average diurnal rainfall pattern which has two maximum rainfall points per day. The amount of rainfall distributions is different from one area to another and changes from time to time. The El Nino and La Nina phenomenon known as the El Nino Southern Oscillation (ENSO) is also affecting the rainfall distribution in Malaysia because of the sea surface temperature that keeps changing in the equatorial Pacific Ocean. Almost the entire study area were affected by the ENSO phenomenon in 2015 and 2016. This rainfall distribution study in Malaysia is very useful and helps government and private sectors to make prepararations for the seasonal rainfall, flood, and drought.

Reverberation Acoustic Test Facility (RATF) is a one of the mechanical satellite testing facility in the Assembly, Integration and Test Centre at National Space Agency (ANGKASA). This is the reverberation type of chamber with external volume at 999.5m3, has the capability to regenerate high intensity acoustic noise ambiance that will be experienced during the launching stage. This paper will describe on reverberation chamber characteristics, the noise generating system and capabilities, and the chamber configuration for high intensity acoustic testing in empty chamber condition. This paper recommends the measurement setting for three variant spectrum levels in generating high-intensity acoustic noise from 130dB to 155dB with center frequencies from range 31.5Hz to 1250Hz.

Assembly, Integration and Test Centre at National Space Agency (ANGKASA) consist of Reverberation Acoustic Test Facility (RATF). The test facility are used to generate very high sound pressure levels for satellite testing, space vehicle components including flight hardware. This reverberant type of chamber is capable to simulate acoustic field of rocket launch. This paper is discussed on the requisite of high-intensity acoustic testing. The characteristic of chamber and the noise generating capabilities for high-intensity acoustic testing are described. The maximum requirement of chamber at 155dB spectrum profiling result is discussed in this paper.