Abstract. Space Science Center of Indonesian Institute of Aeronautics and Space called LAPAN has installed several solar radio receivers named CALLISTO in various parts of Indonesia. The equipment has made some solar radio observational data which is indicate solar radio burst since its operation. All of the observational data stored in the file format of Flexible

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The Ionosphere layer can influence radio wave propagation from one place to another place with a very long distance on the Earth and between satellites to the receiver. Each ionosphere layer has different characteristics and the presence of the ionosphere changes daily according to solar activity. The D layer is the innermost ionosphere layer, starting about 60 - 95 km above the Earth’s surface. Observation of the D layer cannot be carried out by balloon, ionosonde, and satellite because it is too low so that continuous observation is very difficult. VLF/LF radio web can be traveled hundreds to thousands of kilometers from the transmitter with multiple reflections between the earth and the ionosphere that is known as the Earth-Ionosphere WaveGuide (EIWG). VLF/LF receiver is an instrument that can be used to observe changes in the low region ionosphere layer due to solar activities.

An ionospheric tomography reconstruction using Algebraic Reconstruction Technique (ART) method has been successfully carried out recently. Data utilized on this work was a campaign-based Gnu-Radio Beacon Receiver (GRBR) observation in West Java during 8-10 November 2016 and 25-29 September 2017 data. Grid resolution of the tomography previously had been increased in the in the latitudinal (0.5o horizontal direction) and altitude (~25 km in vertical direction) scales. Although the quality of the tomography has also met a compatibility level through the correlation analysis (e.g. 85% of correlation coefficient), the computation result should be improved in order to get the best value of bias frequency (i.e. < 1 MHz). Through this opportunity, the result of the tomography within the grid resolution of 0.5o and ~25 km for the latitude and altitude respectively is presented.