1 THE GOES N GENERATION SATELLTES April 27, 2004 Peter Woolner, Mitretek Systems

2 WHY GOES N IS CHANGED The power flux density for EMWIN on GOES I/M does not comply with ITU requirements Sharing a transponder with WEFAX produces intermodulation products that do not comply with ITU requirements Therefore EMWIN on GOES N/O/P MUST have lower power and a new frequency

3 EMWIN N DESIGN Basic rules for EMWIN N –Use BPSK modulation (satellite standard) –Require contractor to provide maximum EIRP –Users must be able to keep existing antenna size Additional gain still needed to close link –Adding Forward Error Correction (FEC) coding is the only practical way to make the link work

4 STATUS OF GOES N/O/P All hardware has been designed and built GOES N is currently in Thermal/Vacuum testing (now in 4 th cold cycle) GOES O is ready for Thermal/Vacuum testing as soon as N is finished GOES N launch is scheduled for 12/1/04 GOES N check-out period is 6 months

5 EMWIN RF PARAMETERS Satellite ParameterGOES I/MGOES N/O/P Transmit Frequency MHz MHz Available 3 dB Bandwidth 1 MHz (share with WEFAX) 50 kHz Minimum EIRP51 dBmi44.8 dBmi Modulation TypeDFSKBPSK FEC CodingNoneRequired

6 SATELLITE CONCERNS The satellite transmitter is saturated The satellite receiver uses gain control The bandwidth is limited to 50 kHz Therefore the EMWIN signal WILL be distorted to some extent –Tests are needed to measure degradation –Actual transmit and receive systems must be used on satellite and ground

7 EMWIN TEST RESULTS (1) Results for 9.6 kbps, BPSK, Convolutional rate ½ + Reed-Solomon (255,223) FEC Real-time current EMWIN signal was transmitted through the GOES 9 satellite and received using the prototype system with no errors over about 15 minutes Measurements made of error rate versus E B /N O

8 EMWIN TEST RESULTS (2) Minimum levels for acceptable performance, i.e., BER of or better: –Theoretical E B /N O : 2.6 dB –Measured E B /N O back-to-back: 6.0 dB* –Measured E B /N O through GOES 9: 8.5 dB* Resulting minimum link margin: 4.8 dB * THESE PRELIMINARY VALUES ARE CONSIDERED UNCERTAIN BECAUSE ERRORS OCCURRED DURING THE TESTS THAT COULD NOT BE EXPLAINED

9 MORE TESTS NEEDED GOES 9 BER results were higher than expected and are possibly in error Plan EMWIN tests on GOES 11 in June when it is brought out of storage for housekeeping –Do not need to coordinate with GMS WEFAX so longer test periods will be possible –High elevation allows use of standard receiver

10 GOES N Link Budget