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 4th 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 Parameter GOES I/M GOES N/O/P

Transmit Frequency 1690.725 MHz 1692.7 MHz

Available 3 dB Bandwidth

1 MHz (share with WEFAX)

50 kHz

Minimum EIRP 51 dBmi 44.8 dBmi

Modulation Type DFSK BPSK

FEC Coding None Required

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 EB/NO

8

EMWIN TEST RESULTS (2)

• Minimum levels for acceptable performance, i.e., BER of 10-6 or better:– Theoretical EB/NO : 2.6 dB

– Measured EB/NO back-to-back: 6.0 dB*

– Measured EB/NO 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

Parameter Units ValueData Rate bps 9600Modulation Type BPSKFEC Coding Type Conv+RSFEC Coding Rate 0.437

Ground Uplink TransmitterUplink Frequency MHz 2034.70

Transmit EIRP dBmi 76.7Antenna Pointing Loss dB 0.5Earth - To - Space

Path Distance (for 5 deg elevation) km 41127Free Space Loss dB 190.9Atmospheric Attenuation dB 0.4S/C Receive PerformancePolarization Loss dB 0.2U/L Incident Power dBmi -115.3

Antenna Gain (from 5 deg elevation) dBi 14.8G/T (incl cable losses) dB/K -14.2Boltzmann constant dBm/Hz/K -198.6Uplink Thermal C/No dB/Hz 69.1S/C Transmit Performance

Downlink Frequency MHz 1692.70Transmit EIRP (to 5 deg elevation) dBmi 44.8

Space - To - EarthPath Distance (for 5 deg elevation) km 41127

Free Space Loss dB 189.3Atmospheric Attenuation dB 0.4Ground Downlink ReceiverDownlink Incident Power dBmi -144.90

Pwr Flux Density Rqmt (EOC in 4 kHz) dBW/m2 -154Power Flux Density (EOC in 4 kHz) dBW/m2 -156.9

E/S G/T dB/K -0.3Polarization Loss dB 0.2Boltzmann constant dBm/Hz/K -198.6Downlink Thermal C/No dB/Hz 53.2Eb/No Overall CalculationOverall Composite C/No dB/Hz 53.1Data Rate in dB dB-Hz 39.8Eb/No Calculated dB 13.3Required Eb/No Adjustments

Required BER 1E-06Theoretical Eb/No with no coding dB 10.6Theoretical coding gain dB 8.0Theoretical Eb/No with FEC coding dB 2.6Ground Segment Implementation Loss dB 2.0Satellite Segment Degradations dB 1.0Required Eb/No dB 5.6Eb/No MARGIN dB 7.7