Estimating tropical rain attenuation on the Earth-satellite path using radar data

Radar-return echoes, known as ‘reflectivity’, are exploited in the course of estimating rain attenuation along a slant path. Relevant radar gates or ‘range bins’ are identified to correlate a specific satellite path. The reflectivity value of each range bin is converted to rainfall rate using established radar reflectivity values – rainfall rates, (Z–R relation). Specific attenuation is then derived for all associated range bins. The attenuation for each bin is the product of specific attenuation and its effective path length. The summation of attenuation endured by all range bins is inferred as the attenuation along the slant path. In this study, an X-band slant path rain attenuation was estimated using 2.85 GHz (S-band) Terminal Doppler Weather Radar (TDWR) data. A technique to estimate rain attenuation by exploitation of radar information is elaborated in this article. Comparisons between the radar-derived attenuation estimations and actual satellite signal measurements are also presented. The findings were verified by comparing the generated values to the directly measured rain attenuation from the Razak satellite (RazakSAT). Radar reflectivity data were obtained from Kuala Lumpur International Airport (KLIA) radar station operated by the Malaysian Meteorology Department (MMD). Preliminary findings using the most recent Z–R relation (i.e. the generated radar-derived rain attenuation estimations) appear to show lower values than the actual measurements

Free Space Attenuation Analysis for X -band and S-band Satellite Link using Meteorological Radar Data in the Tropics

Free space fading for satellite link propagation studies in the equatorial regions are indeed particularly scarce, complicated and expensive to venture upon. Most of satellite propagation studies done in temperate climate are not reasonable for countries in the equatorial region due to its huge climate differences. In equatorial regions, the future stratospheric and space-based telecommunications systems are expected to operate with high elevation angle slant paths and high frequency of operation from the Earth stations’ point of view. These systems will also be sharing frequency bands with other terrestrial and space services. From this standpoint, a precise modelling of the vertical variation of free space path loss parameters will be of great interest for improving the prediction of the clear sky margin along the slant path in the tropics. In this paper, the Free Space Path Loss (FSPL) propagation link for Xband and S-band RazakSAT satellite will be analysed using a Terminal Doppler Weather Radar (TDWR) data. Both links will be evaluated and the assessment of the link’s fade margin will be suggested. An accurate estimation of the satellite fade margin will evidently save power from the satellite perspective and better transmission can be estimated. The outcome of this research will be very useful for future implementation of satellite link fade margin improvement during non-rain weather, both during clear sky and cloudy weather in the tropical region. This research will facilitate the key decision makers and the satellite designers to progress business, availability, and throughput proficiently. Therefore, hopefully, the spending is well reasonable with a better return on investment (ROI) and attracts more investors in satellite industries

Propagation measurements during Daytime for RazakSAT S-band space to earth satellite signal transmission

Two novel quinazoline derivatives named as; 3-[(4-hydroxy-3-methoxy-benzylidene)-amino]-2-ptolyl-3H-quinazolin-4-one (5) and 2-p-Tolyl-3-[3,4,5-trimethoxy-benzylidene-amino]-3H-quinazolin-4- one (6) in addition to one acetamide derivative named as 2-(2-Hydroxycarbonylphenylamino)-N-(4- aminosulphonylphenyl) 11 were synthesized, and evaluated for their anti-ulcerogenic & AntiUlcerative colitis activities. All of the three compounds showed curative activity against acetic acid induced ulcer model at a dose of 50 mg/kg, they produced 65%, 85% & 57.74% curative ratio for compounds 5, 6 & 11 respectively. The effect of the tested compounds 5, 6 & 11 at dose 50 mg/kg were significantly (P < 0.01) more effective than dexamesathone (0.1 mg/kg) in reducing all parameters. Compounds showed curative activity of for peptic ulcer (induced by absolute alcohol (at a dose of 50 mg/kg, it produced Curative of control ulcer 56.00%, 61.70% & 87.1% for compounds 5, 6 & 11 respectively at dose 50 mg/kg, while the standard drug (Omeprazole 20 mg/kg) produced 33.3%. In both tests, the activity of our target compounds were higher than the standard drugs used for treatment of peptic ulcer and ulcerative colitis. No side effects were reported on liver and kidney functions upon prolonged oral administration of this compounds. (C) 2017 The Authors. Production and hosting by Elsevier B.V. on behalf of King Saud University

Derivation of Z-γ (Reflectivity-specific attenuation) relation for satellite link in tropical region

The investigation of deriving the Z-γ (reflectivity-specific attenuation) relation is critical in the development of a novel rain attenuation prediction for a satellite link using radar information. Comparison between S-band radar derived reflectivity data and measured received power signals of X-band RazakSAT’s Malaysian remote satellite link is presented. RazakSAT’s satellite link received power during clear sky and rainy conditions are compared to extract the rain attenuation values. The specific attenuation of the link can be derived from the rain attenuation values. The S-band radar with horizontal polarization reflectivity information was used to compare the likely rain attenuation along the same RazakSAT satellite propagation paths. Both reflectivity information and specific attenuation data are tabulated during the RazakSAT operation in 2009 to derive the relationship. Later, the radar reflectivity values, Z are converted into specific attenuation, γ using the derived relationship of the Z-γ to calculate the rain attenuation and fade margin for a slant path link. The current rain attenuation prediction is using point rainfall but in this technique the reflectivity values is being explored. The relationship is derived using similar path length, elevation angle, time and date from the RazakSAT link and the radar information for both stratiform and convective events. Therefore, the relationship can be a good landmark for the future engineers and researchers to estimate the rain attenuation using radar information

Comparison of radar derived rain attenuation with the RazakSAT’s X-Band link signal measurement

Abstract—The preliminary analysis involving comparison between radar derived attenuation using an S-band meteorological radar and measured signal of RazakSAT’s X-band satellite link is presented. The radar data employed was attained from the Malaysian Meteorological Department’s (MMD) terminal Doppler weather radar installed strategically in the vicinity of Kuala Lumpur International Airport (KLIA). The X-band (8 GHz) satellite-Earth signals of Malaysian RazatSat’s collected at the National Space Agency (NSA) space center have been analyzed and studied. The vertical polarization S-band radar reflectivity information was used to calculate the likely rain attenuation along the RazakSAT satellite propagation paths. This was carried out by first converting the radar reflectivity values into rainfall rate using the established Z-R relations of Marshall-Palmer equation and, afterwards, by evaluating the slant path attenuation through the assimilation of the specific rain attenuation derived at the rainfall rate

Rain fade estimations for the X-Band satellite communication link in the tropics

The X-band satellite communication (satcom) has been conventionally set aside for military and government organizations. It is also commonly known as the military band. The attributes of an X-band satcom hardware are expected to be designed specifically for military operations and they are expected to differ very much to those of commercial frequencies. The satcom will be likely to be exclusively designed to support smaller, low powered, tactical terminals deployed across various theatres of operation. In addition, X-band link is also anticipated to offer a more substantial increased of system capacity due to its higher frequencies compared to the forerunner S-band and C-band. The X-band satcom technology is drawing growing interest from military users including of the Malaysian authorities. However, there are many aspects of X-band that are harder to realize than of those of at lower frequencies. X-band frequencies certainly have higher atmospheric propagation losses, higher RF losses, and certainly much severe signal degradation due to rain. It is would be in the best interest of the satellite designers and engineers alike to accurately appraise the challenges of an X-band satcom link especially in the case of tropical regions where heavy rains are copious whilst the required technological advancements are in pursuit

Propagation Measurements during Daytime for RazakSAT S-Band Space to Earth Satellite Signal Transmission

Adequate fade margins for all conditions are critical in ensuring reliable satellite operation. The required fade margin value for specific desired quality of service (QoS) can be established from the statistics of outage due to attenuation. In the case of clear sky attenuation, the value is much dependent on the atmospheric layer conditions and their compositions. For absolute Free Space, the signal loss is only dependent on distance and frequency. In this study, the effects of distance were analysed in the investigation of identifying the most appropriate clear sky attenuation values during daytime. The RazakSAT received signal levels were matched according to the distances between the satellite and the Ground station. Clear sky conditions were confirmed using S-band (Terminal Doppler Weather Radar) TDWR reflectivity information. With this value, the satellite operator can decide execution of power uplink and mitigation technique if necessary. The RazakSAT S-band (2.232 GHz) transmission signal data of were furnished by Malaysian National Space Agency (ANGKASA) and radar data were acquired from Malaysian Meteorology department (MMD). The findings offer awareness of required fade margin as distance varies during each flight path. The collected data will also be employed in the investigation of Free Space Path Loss (FSPL) formulation applicable for satellite link in tropical region

Rain induced attenuation studies using RazakSAT space-Earth links

Rain induced attenuation is the main reason for the decrease of Space-Earth communication links’ received signal strength. This is more perceptible in the tropical regions due to copious heavy rainfall throughout the years. RazakSAT is a Malaysian remote sensing satellite that utilizes two frequencies which are the X-band and S-band. The X-band frequency is conventionally set aside for military or government organizations. This frequency differs from the common commercial frequencies. The attributes of X-band satellite communication hardware are expected to be designed specifically for military operations. The appropriate margin should be incorporated to ensure reliable and continual communication. Rain induced attenuation data involving S-band and X-band measurements from Malaysia RazakSAT’s satellite have been analyzed. The rain attenuation at higher frequency X-band (8 GHz) was estimated from the values at 3 GHz (S-band) frequency by the use of frequency scaling equation from established models. The paper highlights the assessments of the two RazakSAT’s satellite-Earth transmission link’s fluctuations during precipitations. The main research objective is to derive the appropriate frequency scaling equation of S-band to X-band applicable in tropical environmen

Observed received signal level of RazakSAT S-band space to earth satellite transmission during nighttime

In order to guarantee effective satellite service, the link budget for all conditions is important. From the path loss and attenuation statistics, the appropriate fade margin value calculated from the link budget for the specific desired quality of service (QoS) can be determined from outage statistics. In the case of a clear sky, the value depends significantly on the distance and conditions of the atmospheric layers and their composition. The signal loss depends only on distance and frequency in the absolute Free Space case. The results of distance in the investigation of determining the most suitable clear sky attenuation values at night time were explored in this report. The received signal levels of the Malaysian Low Earth Orbit (LEO) RazakSAT satellite were recorded according to the distances between the satellite and the Earth station. Using the S-band (Terminal Doppler Weather Radar) TDWR, the clear sky state where no water precipitation was reported. With established attenuation values, the satellite operator may determine whether it is appropriate to operate the power uplink and mitigation technique. The Malaysian National Space Agency (ANGKASA) provided the RazakSAT S-band (2,232 GHz) transmission signal data and received radar data from the Malaysian Department of Meteorology (MMD). As the distance varies along each flight route, the results provide understanding of observed path loss

Fade margin estimations for military X-band satellite communication links in tropical region

Satellite communications (SatCom) can offer rapid establishment of voice and data connectivity. The unique potentials of satellite communications are well suited to fill certain breach of contacts during catastrophic incidents and also in isolated places critical for military operation. Military satellite communication is designed to comprise highly steadfast delivery of voice, data and video services between military headquarters and field units. The paper briefly outlines the importance of such facility. The paper highlights an important concern pertaining to the performance predictions of the military X-band satellite communication link especially when facing challenges due to severe rain attenuation in tropical countries. It is proposed that a prediction technique can be employed as well as data acquired from meteorological radars can be exploited to provide estimations of required fade margin for the satellite link