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LRIT Downlink and Reception Conference: Link Budget and System Performance Analysis

This conference explores the link budget and system performance analysis for LRIT downlink and reception, including spacecraft parameters, propagation parameters, receiver parameters, and system performance considerations.

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LRIT Downlink and Reception Conference: Link Budget and System Performance Analysis

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  1. Low - Rate Information Transmission (LRIT) Downlink and Reception Satellite Direct Readout Conference for the Americas Frank Eng, Computer Sciences Corp. December 10, 2002

  2. Introduction • This session and presentation will address • The space to ground link budget for broadcasting and receiving GOES LRIT signals. • Link budget calculations, based on spacecraft and ground system characteristics, and their relationship to LRIT user station design. • Description of the spacecraft parameters that impact the link budget. • Conclusions, with a description of the relevant receiver characteristics resulting from the link budget analysis. Satellite Direct Readout Users Conference for the Americas

  3. GOES LRIT System Parameters • Frequency: L-band • GOES spacecraft transponder power • GOES I-M : 12 Watts • GOES N-P: 7 Watts • Data Rate: 128 kbps • Forward Error Correction: • Reed Solomon, 1/2 rate Convolutional Satellite Direct Readout Users Conference for the Americas

  4. Propagation Parameters • Propagation Distance : 35,000 to 42,000 km • Atmospheric Absorption : 0.04 to 0.4 dB • Free Space Loss : 188 to 190 dB • Polarization Loss : 0.2 dB • Pointing Loss : 0.3 dB • Rain Attenuation : 0.01 to 0.1 dB Satellite Direct Readout Users Conference for the Americas

  5. Receiver Parameters • 1 Meter Antenna Gain : 22.5 dB • System Temperature : 190.50 Kelvin • G/T : -0.3 dB • Filter Insertion Loss : 1 dB • Turn around (uplink) loss : 0.17 dB • Modulation Loss : 2.30 dB • Coding Gain : 7 to 9.4 dB Satellite Direct Readout Users Conference for the Americas

  6. System Performance Considerations • Conservative assumptions: 3 dB link margin • Highly Reliable Link : BER objective of 10-8 • Scintillation Losses : 5 dB at specific times and places • Potential RFI from cellular systems • Relatively low cost: less then $5000 Satellite Direct Readout Users Conference for the Americas

  7. Propagation Link Performance 1-meter dish Satellite Direct Readout Users Conference for the Americas

  8. Receiver Link Performance 1-meter dish Satellite Direct Readout Users Conference for the Americas

  9. Link Summary • Performance objectives satisfied down to 150 elevation angle • Existing 1 meter WEFAX antenna is sufficient in most cases • Low cost objective should be readily achieved with availability of NOAA S/W • Preliminary link testing completed • Final link testing in early 2003 Satellite Direct Readout Users Conference for the Americas

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