Transcript Document 7607017

THE GOES N GENERATION
SATELLTES
April 27, 2004
Peter Woolner, Mitretek Systems
1
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
2
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
3
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
4
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
5
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
6
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
7
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
8
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
9
GOES N Link Budget
Parameter
Data Rate
Modulation Type
FEC Coding Type
FEC Coding Rate
Ground Uplink Transmitter
Uplink Frequency
Transmit EIRP
Antenna Pointing Loss
Earth - To - Space
Path Distance (for 5 deg elevation)
Free Space Loss
Atmospheric Attenuation
S/C Receive Performance
Polarization Loss
U/L Incident Power
Antenna Gain (from 5 deg elevation)
G/T (incl cable losses)
Boltzmann constant
Uplink Thermal C/No
S/C Transmit Performance
Downlink Frequency
Transmit EIRP (to 5 deg elevation)
Units
bps
Value
9600
BPSK
Conv+RS
0.437
MHz
dBmi
dB
2034.70
76.7
0.5
km
dB
dB
41127
190.9
0.4
dB
dBmi
dBi
dB/K
dBm/Hz/K
dB/Hz
0.2
-115.3
14.8
-14.2
-198.6
69.1
MHz
dBmi
1692.70
44.8
Space - To - Earth
Path Distance (for 5 deg elevation)
Free Space Loss
Atmospheric Attenuation
Ground Downlink Receiver
Downlink Incident Power
Pwr Flux Density Rqmt (EOC in 4 kHz)
Power Flux Density (EOC in 4 kHz)
E/S G/T
Polarization Loss
Boltzmann constant
Downlink Thermal C/No
Eb/No Overall Calculation
Overall Composite C/No
Data Rate in dB
Eb/No Calculated
Required Eb/No Adjustments
Required BER
Theoretical Eb/No with no coding
Theoretical coding gain
Theoretical Eb/No with FEC coding
Ground Segment Implementation Loss
Satellite Segment Degradations
Required Eb/No
Eb/No MARGIN
km
dB
dB
41127
189.3
0.4
dBmi
dBW/m2
dBW/m2
dB/K
dB
dBm/Hz/K
dB/Hz
-144.90
-154
-156.9
-0.3
0.2
-198.6
53.2
dB/Hz
dB-Hz
dB
53.1
39.8
13.3
dB
dB
dB
dB
dB
dB
dB
1E-06
10.6
8.0
2.6
2.0
1.0
5.6
7.7
10