90 likes | 97 Views
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.
E N D
Low - Rate Information Transmission (LRIT) Downlink and Reception Satellite Direct Readout Conference for the Americas Frank Eng, Computer Sciences Corp. December 10, 2002
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
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
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
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
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
Propagation Link Performance 1-meter dish Satellite Direct Readout Users Conference for the Americas
Receiver Link Performance 1-meter dish Satellite Direct Readout Users Conference for the Americas
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