The Video data from remote sensing satellite is transmitted serially frame after frame. To mark the beginning of video data a known unique code is embedded at the beginning of the video data frame. This is known as Fr...
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ISBN:
(纸本)9781467326193
The Video data from remote sensing satellite is transmitted serially frame after frame. To mark the beginning of video data a known unique code is embedded at the beginning of the video data frame. This is known as Frame Synchronizer code. Pseudo-Noise sequences are chosen as frame synchronizer codes as they are easy to generate, detect and have auto correlation property. Generally, for all Indian Remote sensing satellite series 127 bits Pseudo-Noise sequence is chosen as frame synchronizer code. On-board the satellite, the video data buffering is in serial fashion and for appropriate processing it is required to be formatted in data packets. Hence, data formatting is done onboard the satellite and then the Pulse Coded Modulated data is transmitted to ground station. The previous Indian Remote Sensing satellites series has data rate of 105 Mbps. The Present data rate of Radar imaging satellite-1 (RISAT-1) is 640 MBps. In order to accommodate such high data rates in the limited bandwidths, the video data is transmitted in Right hand Circular Polarization (RHCP) and Left Hand Circular Polarization (LHCP). The QPSK modulation is used for video data transmission. Hence at such high data rates an advanced high speed frame synchronizer is required to cater to such high data rates. The advanced parallel processing technique of frame synchronism, detection and monitoring is unique as it doubles the operating frequency of the Frame synchronizer. Also with the same hardware, the frequency response of the hardware circuit can be doubled. If the maximum operating frequency is `f' Hz then using Advanced Parallel Frame synchronizer technique, the operating frequency response is doubled to `2f' Hz using the same hardware chip. In this paper Advanced frame synchronizer circuit is been implemented and is put to use to archive video data from Indian Radar Imaging satellite-1.
The Indian Remote Sensing (IRS) ground station operates in both X-Band and S-Band frequencies. The video data is transmitted from the IRS series satellite in X-Band. Also, the telemetry, tracking, telecomm and, acquis...
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The Indian Remote Sensing (IRS) ground station operates in both X-Band and S-Band frequencies. The video data is transmitted from the IRS series satellite in X-Band. Also, the telemetry, tracking, telecomm and, acquisition and housekeeping data of satellite is transmitted in S-band. The position of IRS satellite was derived by Interferometry and ranging techniques. These techniques gave the position of satellite at a specified given time and also the positional values derived were less accurate. Hence, there was a need of data which could give more positional accuracy. These accurate values were included in the SPS data, which are currently transmitted in S-band from the IRS series satellites with Global Positioning System (GPS) receivers on board. From this SPS data, satellite imagery products, standard products etc, can be generated more accurately for various applications such as agriculture, forestry, etc. The SPS data is transmitted only for 2minutes approximately during the real-time pass of the satellite. In the absence of this data, it is necessary for the S-band SPS chain to be validated for any kind of malfunctioning of the S-band receive chain systems and subsystems, just before the actual pass of the IRS satellite. The Sband receive chain consists of Phase Demodulator, BPSK demodulator, etc. During the real-time pass of the satellite, it is necessary that the SPS chain should function appropriately for acquiring the SPS data transmitted from the satellite. Hence, to assess the required performance of receive chain in the absence of satellite signal; a specially designed simulator is essential. The proposed simulator is designed and developed specifically to match the onboard signal spectrum of all IRS Series of satellites. This paper discusses about the design and implementation of different SPS data formats (Multi-mission) Simulator for checking the SPS data chain. This system is found to be validating and evaluating the entire SPS data receive chain.
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