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Size: 3187
Comment:
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Size: 3211
Comment:
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| {{attachment:ArndtSlideV4.png}} | {{attachment:ArndtSlideV4.png||height=300}} |
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| {{attachment:SSPSmag.png}} | {{attachment:SSPSmag.png||height=300}} |
SSPS Interference with Airport Radar
ARSR-4: Air Route Surveillance Phased array Radar
ASR-11: Airport Surveillance Radar, Terminal Area
( AN/GPN-30 )
PSR Probability of Detection: The PSR shall be capable of detecting a 1.0 m2 Radar Cross Section (RCS), Swerling 1 target to a range of 55 nmi in the clear and at the nose of the beam with a single scan Pd of 0.8 and a Probability of False Alann (PFA) of 10-6 •
Operational Subclutter Visibility: Operational SCV shall be 42 dB minimum at all ranges for nonfluctuating targets.
|
ARSR-4 |
ASR-11 |
|
Band |
L Band |
S Band |
|
Peak Power |
60 kW |
25 kW |
|
Average Power |
|
2.1 kW |
|
Wavelength cm |
21.4-24.7 |
10.3-11.1 |
|
Frequency GHz |
1.21-1.39 |
2.7-2.9 |
|
Max interference |
? |
-117 |
dBm/MHz!! assumed EIRP |
LNA bandwidth |
? |
? |
|
IF bandwidth |
? |
1 MHz |
Table D2 pg 107 13-490 |
Polarization |
Linear |
Linear |
|
|
Circular |
Circular |
|
Beam width |
1.41° |
1.41° |
|
Beam Elevation |
2.2° |
4.8° |
|
Antenna Gain |
|
34dB |
|
Antenna Size |
9 x 7 m |
5 x 3 m |
|
Pulse width |
|
1μs |
|
|
|
80μs |
|
Coverage nm |
250 nm |
60 nm |
|
Coverage km |
463 km |
111 km |
|
Scan period |
12 sec |
12 sec |
|
Weather map |
36 sec |
|
|
# deployed |
43 |
213 |
== =Guessing about radar ===
If the antenna gain is 34dB, and the peak pulse power is 25 kW, that suggests that the EIRP is 63 MW. A 1 m2 target at a range of 111 km gets 400 microwatts of illumination. If that radiates back with a 1 steradian spread, it delivers 83 pW to the antenna, -70 dBm ?
Sidelobe graph, Cleaned up from Arndt 1978
Note - This is the theoretical, average power without atmospheric scattering (rain, dust, etc.). Assume 1mW/m2, depositing 15 mW of carrier on a 5x3 m antenna
This is the noise from a magnetron. Not sure how to interpret it - if we assume a 1 MHz bandwidth and extrapolate to -70 dBc/Hz at 2.7 GHz, how much noise power is that assuming a 15 mW carrier?
Of course, the radar is typically not pointed within one or two degrees of an SSPS, but the dish does rotate, and scan vertically, so it will see any SSPS that appears near the horizon. If there are 100 in orbit, we can expect to see a few, and at low elevation there will be significant atmospheric scattering.