In this paper, we introduce the performance test results of digital data processing system for KVN (Korean VLBI Network). The digital data processing system for KVN consists of DAS (Data Acquisition System) and high-speed recorder which called Mark5B system. DAS system performs the digitalization of analog radio signal through ADS-1000 gigabit sampler with 1 Gsps/2-bit and process the digital filtering of digital signal. Mark5B system records the output data of DFB (Digital Filter Bank) with about 1 Gbps. In this paper, we carried out the preliminary evaluation experiments of the KVN digital data processing system connected between DAS system and Mark5B with VSI (VLBI Standard Interface) interface which is designed for compatible in each VLBI system. We first performed all of the KVN digital data processing system connected by VSI interface in the world. In factory inspection phase, we found that the DAS system has a memory read/write error in DSM (Digital Spectrometer) by analyzing the recorded data in Mark5B system. We confirmed that the DSM memory error has been correctly solved by comparing DSM results with Mark5B results. The effectiveness of KVN digital data processing system has been verified through the preliminary experiments such as data transmission, recording with VSI interface connection and data analysis between DSM and Mark5B system. In future work, we will perform the real astronomical observation by using the KVN 21m radio telescopes so as to verify its stability and performance.

In this paper, we describe the radio astronomical data processing system implementation using Mark5B and its development. KASI(Korea Astronomy and Space Science Institute) is constructing the KVN (Korean VLBI Network) until the end of 2007, which is the first VLBI(Very Long Baseline Interferometery) facility in Korea and dedicated for the mm-wave VLBI observation. KVN will adopt the DAS (Data Acquisition System) consisting of digital filter with various function and 1Gsps high-speed sampler to digitize the radio astronomical data for analyzing on the digital filter system. And the analyzed data will be recorded to recorder up to 1Gbps data rates. To test this, we have implemented the system which is able to process 1Gbps data rates and carried out the data recording experiment.

In this paper, we propose a small-scale Gigabit VLBI observing system for the Korean VLBI Network (KVN) under construction. The system consists of high-speed sampler, IP-VLBI board, PC-VSI board, and software correlator. Radio signal received by receiver is sampled by high-speed sample. at 1 Gsps (Gigabit sample per second) rate with 2 bits quantization. The digitized signal is recorded in PC and the software correlator does the cross correlation. IP-VLBI board will be used for the geodesy VLBI observation, while PC-VSI board is for the astronomical VLBI observation. The PC-VSI board adopts the VSI-H (VLBI Standard Interface Hardware). The proposed system is based on commercial PCs and therefore can be built inexpensively.

In the past, radio astronomers have sought isolation from man-made signals by placing their telescopes in remote locations. These measures may no longer safeguard scientific observations, since NGSO satellite systems, particularly low-Earth orbit (LEO) systems, are usually designed to provide global or wide regional coverage. Further, radio astronomers have historically made their observations in the frequency bands allocated for their use by the member countries of the International Telecommunication Union (ITU). The science of radio astronomy could be adversely impacted by the deployment of large constellations of new non-geostationary orbiting (NGSO) satellites for telecommunications, navigation and Earth observation, and the proliferation of new, high-power broadcasting and telecommunication satellites in geostationary (GSO) orbits. Radio telescopes are extremely sensitive, and, in certain situations, signals from satellites can overwhelm the signals from astronomical sources. This paper describes the problem in detail and identifies ways to mitigate it without adversely affecting the continued vigorous growth of commercial space-based telecommunications.

In this paper, we introduce the development of the large storage system in order to record the observed space radio signal in the Korean VLBI Network(KVN) with high-speed. The KVN is the Very Long Baseline Interferometery(VLBI) to observe the birth of star, the structure of space by constructing radio telescope with diameter 21m at the Seoul, Ulsan, Jeju from 2001 to 2007 years. To do this, Korea Astronomy Observatory joined the international consortium for developing the high-speed large storage system(Mark 5), which is developed by MIT Haystack observatory. The Mark 5 system based on hard disk has to record up to 1 Gbps the observed space radio signal. The main features of Mark 5 system are as follows; First it is able to directly record the input data to the hard disk without PC1(Peripheral Component Interconnect) internal bus, and the second, it has two hard disk banks, which are able to hot-swap ATA/IDE type very cheap up to 1 Gbps recording and playback. The third is that it follows the international VLBI standard interface hardware(VSI-H). Therefore it can be connect directly the VSI-H type system at the input/output. Finally it also supports e- VLBI(Electronic-VLBI) through the standard Gigabits Ethernet connection.

Most radio astronomy issues at WRC-03 (World Radiocommunication Conference-03) revolved around satellite downlink allocations, particularly to NGSO (Non-Geostationary Satellite Orbit) satellite systems, in bands adjacent to or close to a radio astronomy frequency band. Out of a total of 50 agenda items, ten were of interest to radio astronomers. This paper provides some details about the important outcome of the radio astronomy related issues at the WRC-03.

WRC-03 was held between 9 June and 4 July 2003 in Geneva, Switzerland. Over 2,200 delegates from 138 ITU Member States attended the Conference. The delegates considered some 2,500 proposals, and over 900 numbered documents related to 50 agenda items. The final output of the Conference consists of 527 pages of new and revised text of the Radio Regulations. This paper provides some details about the outcome of the radio astronomy related issues at the WRC-03 Conference. It is divided into two part: a) Agenda item1.8.2 and b) Agenda item 1.32, related to radio astronomy. Relevant extracts from the Final Acts of WRC-03 are given in the Appendix. Agenda item 1.8.2 was one of the most controversial Agenda Items at WRC-03. Studies were carried out within ITU-R TG 1/7 for the last three years; the results of these studies are summarized in Recommendation ITU-R SM.1633. The Conference adopted a new footnote (5.347A), that calls for the application of Resolution 739 (WRC-03) in the 1452-1492 MHz, 1525-1559 MHz, 1613.8-1626.5 MHz, 2655-2670 MHz, 2670-2690 MHz and 21.4-22.0 GHz bands. Agenda item 1.32 is to consider technical and reglatory provisions concerning the band 37.5-43.5 GHz, in accordance with Resolutions 128 (Rev.WRC-2000) and 84 (WRC-2000). WRC-03 reviewed and adjusted the New footnotes 5.551H and 5.551I cover the protection of radio astronomy observations in the 42.5-43.5 GHz band from unwanted emissions by non-geostationary (5.551H) and geostationary (5.551I) FSS and BSS systems, respectively.