Transcript Document

EARLY SKYWAVE EXAMPLES
FROM U.S. COAST GUARD
PRIMARY CONTROL MONITOR SET DATA
KIRK MONTGOMERY, U.S. COAST GUARD NAVIGATION CENTER
BOB WENZEL, BOOZ, ALLEN, HAMILTON
ILA 32
NOVEMBER 2003
1
Previous Work …..
THE CLEAREST EXAMPLES OF A PROBLEM HAVE COME FROM
THE VERY NORTHERN LATITUDES
• Ad Hoc examinations done by the U.S. Coast Guard, but little
documentation in the literature
• A series of papers done on the early 1990’s regarding Alaska
stations, most notably the Port Clarence signal:
 ILA 22’s “Port Clarence Skywave Interference Study” by Ben
Peterson et al (Oct. 1993)
 ILA 23’s Analysis of High Latitude Loran-C Abnormalities in
Alaska by David Watkins’ (Nov. 1994)
 ILA 23’s Effects of Geomagnetic Activity on Skywave
Interference by Al Arsenault (Nov. 1994)
2
Previous Work …..
OF THE RECEIVER PERFORMANCE STANDARDS AT THE TIME
OF THESE STUDIES, ONLY ONE INDICATED EARLY SKYWAVE
PROBLEMS WERE PARTICULARLY SEVERE
Source
Mode
Min. SW Delay (usec)
SW/GW Ratio
RTCA/FAA
Aviation
35
+ 6 db
37.5
+ 10db
42.5
+ 15 db
45
+ 20 db
55
+ 25 db
37.5
+ 12 db
60
+26 db
32.5
+12 db
45
+26 db
RTCM/USCG
Transport Canada
Maritime
Maritime
The USCG Monitor receiver of the time could meet all the above, 3
though the 32.5 usec/+12 db requirement is very challenging.
The path from Port Clarence to Fairbanks is predominantly east-west in
central Alaska
72
+ Prudoe Bay
70
Latitude-deg
68
66
Port Clarence
+
Fairbanks
64
* Tok
62
+ Anchorage
60
-165
-160
-155
Longitude-deg
-150
-145
-140
4
Previous Work …..
THE “ALASKA PAPERS OF THE 1990’S” SHOWED THE
RECEIVERS OF THE TIME HAD PROBLEMS
• For the Port Clarence signal at Fairbanks, Ben estimated he was
seeing skywave delays as short as about 28 usec **
• In a particular case featuring a +6 db skywave at a delay of just
under 30 usec*** the Austron 5000 ECD had moved about - 3.4
usec from the nominal, a JET receiver was showing a change of
about – 3.2 usec
• Dave Watkins wasn’t equipped to measure the skywave, but he
showed Austron 5000 ECD variations in the Tok signal, as
monitored at Kodiak, of about 5 usec
BY THE END OF THE YEAR 2000, THE COAST GUARD HAD
REPLACED THE AUSTRON 5000 RECEIVERS WITH THE LOCUS
LRSIIID RECEIVERS WHICH SHOW ABOUT THE SAME – OR
5
SLIGHTLY BETTER PERFORMANCE
Recent Observations …..
LET’S FOLCUS ONLY ON JANUARY 2002. FIRST, LET’S LOOK
AT THE “BLINK RECORD”
7960-Z Blink Times
January 2002
1
0
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29
31
By themselves, these 6 incidents are significant because they average about 3hours in duration.
18 hours of blink over a 31-day period yields only a 97.6% availability for this
baseline, that month.
6
Pause …..
WENZEL STATEMENT: I STARTED THIS EFFORT
UNCONVINCED CROSS-RATE SKYWAVES EFFECTS HAD BEEN
ELIMINATED IN PAST STUDIES
• Dave Watkins, for example, was more interested in correlating
abnormalities with solar activity – for control purposes
• There were some coincidences, but there were nearly as many
questions
• Even Ben’s instrumentation suffered from a few problems that can
now be greatly reduced:
- Port Clarence was broadcasting with an AN/FPN-42 transmitter
which has “a complicated signal” after the peak
- “Due to several pulse building evolutions at Port Clarence and
other factors, we no longer consider our groundwave template
accurate.”
7
Pause …..
BEN RECENTLY RAN LRSIIID RECEIVER SIMULATOR TESTS. THEY
SHOWED THE FOLLOWING RESULTS FROM A 0 DB (IN-PHASE) SKYWAVE
ECD Error (nsec) vs (In-Phase) Skywave Delay 0 db Skywave/Groundwave
4
3
2
1
0
16
18
20
22
24
26
28
30
32
-1
-2
-3
Phase Error (nsec) vs (In-Phase) Skywave Delay 0 db Skywave/Groundwave
300
200
100
0
16
18
20
22
24
26
28
30
32
-100
-200
-300
8
-400
Recent Observations …..
STICKING WITH JANUARY 2002, HERE ARE THE ECD AND TD PLOTS
7960-Z (Tok-Port Clarence) TD at Fairbanks
CSTD = 49,922.69 Tol = +/- 0.10 usec
January 2002
49922.95
49922.9
49922.85
49922.8
49922.75
49922.7
49922.65
49922.6
49922.55
49922.5
1.0
3.0
5.0
7.0
9.0
11.0
13.0
15.0
17.0
19.0
21.0
23.0
25.0
27.0
29.0
31.0
7960-Z (Port Clarence) ECD at Fairbanks
CSECD = +0.8 Tol = +/- 1.5
January 2002
4
3.5
3
2.5
2
1.5
1
0.5
0
-0.5
9
-1
1.0
3.0
5.0
7.0
9.0
11.0
13.0
15.0
17.0
19.0
21.0
23.0
25.0
27.0
29.0
31.0
Recent Observations …..
HERE’S A BLOW-UP OF THE 1 JANUARY INCIDENT
7960-Z (Tok-Port Clarence) TD at Fairbanks
January 1, 2002
7960-Z (Port Clarence) ECD at Fairbanks
January 1, 2002
49922.9
1
0.8
49922.85
0.6
0.4
49922.8
0.2
49922.75
0
-0.2
49922.7
-0.4
-0.6
1.70
1.75
1.80
1.85
1.90
1.95
2.00
2.05
2.10
2.15
2.20
49922.65
1.70
1.75
1.80
1.85
1.90
1.95
2.00
2.05
2.10
2.15
2.20
7960-Z (Port Clarence) Blink Time at Fairbanks
January 1, 2002
7960-Z (Port Clarence) Signal Strength Estimate at Fairbanks
January 1, 2002
68
1
67
66
65
64
63
1.70
1.75
1.80
1.85
1.90
1.95
2.00
2.05
2.10
2.15
2.20
0
1.70
10
1.75
1.80
1.85
1.90
1.95
2.00
2.05
2.10
2.15
2.20
Recent Observations …..
HERE’S SOME MORE ALASKA DATA – FROM 10-11 JANUARY 2002
7960-Z ECD at Fairbanks 10-11 January 2002
0.05
7960-Z LPA Record 10-11 January 2002
2.5
0
2
-0.05
1.5
-0.1
1
-0.15
0.5
0
10.70
10.80
10.90
11.00
11.10
11.20
11.30
11.40
-0.2
10.7
10.8
10.9
11
11.1
11.2
11.3
11.4
7960-Z TD at Fairbanks 10-11 January 2002
7960-Z TD at Fairbanks With LPAs Removed 10-11 January 2002
49922.9
49922.9
49922.85
49922.85
49922.8
49922.8
49922.75
49922.75
49922.7
49922.7
49922.65
49922.65
49922.6
10.7
49922.6
10.70
10.8
10.9
11
11.1
11.2
11.3
11.4
10.80
10.90
11.00
11.10
11.20
11
11.30
11.40
Recent Observations …..
HERE’S A FINAL EXAMPLE OF ALASKA DATA – 17-18 JANUARY
7960-Z ECD at Fairbanks 17-18 January 2002
4
3.5
3
2.5
2
49922.85
7960-Z TD at Fairbanks With LPAs Removed
17-18 January 2002
1.5
49922.8
1
0.5
0
17.45
49922.75
17.55
17.65
17.75
17.85
17.95
18.05
7960-Z Blink Record 17-18 January 2002
49922.7
49922.65
49922.6
1
49922.55
17.45
0
17.45
17.55
17.65
17.75
17.85
17.95
12
17.55
17.65
17.75
17.85
17.95
18.05
18.05
Recent Observations …..
WHAT ABOUT ELSEWHERE? THE MAGNETIC LATITUDE OF THE
NORTHEAST IS GREATER THAN THAT OF THE NORTHWEST, U.S.
9960-W ECD at Sandy Hook January 2002
9960-W ECD at Sandy Hook January 2002
1
1.2
1
0.5
0.8
0.6
0
0.4
0.2
-0.5
0
-0.2
-1
-0.4
-0.6
-1.5
1
2
3
4
5
10
11
12
13
14
• The markers occur during the first 5 “incidents noted in Alaska
• They show the times when the Port Clarence ECD variations were
notable.
• The Sandy Hook shows no perceptible phase variations.
However, there are notable ECD indications, though they don’t
perfectly align with the Alaska times.
13
Recent Observations …..
HERE’S A CLOSER LOOK AT THE INCIDENT ON THE EVENING
7960-Z ECD at Fairbanks 10-11 January 2002
(GMT) OF THE 10TH
2.5
2
1.5
1
0.5
0
10.65
10.75
10.85
10.95
11.05
11.15
11.25
11.35
11.45
9960-W ECD at Sandy Hook January 2002
1
0.5
0
-0.5
-1
-1.5
10.65
14
10.75
10.85
10.95
11.05
11.15
11.25
11.35
11.45
Recent Observations …..
A SEARCH OF THE SPACE ENVIRONMENTAL CENTER’S DATA FOR “VERY
ENERGETIC” SOLAR EVENTS DIRECTED OUR ATTENTION TO APRIL 2001
7960-Z ECD at Fairbanks April 2001
5
4
3
2
1
1
6
11
16
21
26
31
0
-1
-2
The ECD is out of Tolerance for much of the first 2-3rds of the month.
The following slides show more detail of this month.
15
7960Z TD/ECD 1 to 3 Apr 2001
5
prf1335.pdf
prf1336.pdf
4.5
022132Z to 022203Z
X-Ray Event X20
Crossing the West Limb
4
011055Z to 011324Z X-Ray Event M5.5
Occurred before the area came into view
021004Z to 021020Z X-Ray Event X1.4
021058 to 021205Z X-Ray Event X1.1
030325Z to 030455Z
X-Ray Event X1.2
3.5
020014Z to 020040Z
X-Ray Event M3.2
2.5
2
011944Z to 011956Z
X-Ray Event M4.0
0600 - 0900Z
K=6
1.5
1
Time
A1 ECD
A1 TD
A2 ECD
A2 TD
16
23:44:27
21:48:07
19:51:47
17:55:27
15:59:07
14:02:47
12:06:27
10:10:07
6:17:27
4:21:07
2:24:47
0:28:27
22:32:07
20:35:47
18:39:27
16:43:07
14:46:47
12:50:27
10:54:07
8:57:47
7:01:27
5:05:07
3:08:47
8:13:47
022340Z to 061340Z >10Mev Proton Event
030120Z to 03 2025Z >100Mev Proton Event
Geomagnetic Field intermittently disturbed
1:12:27
23:16:07
21:19:47
19:23:27
17:27:07
15:30:47
13:34:27
11:38:07
9:41:47
7:45:27
5:49:07
Geomagnetic Field: Major/Severe Levels 31 Mar - 010900Z Apr 01
3:52:47
0
291635Z Mar 01 to 010600Z Apr 01 >10Mev Proton Event
1:56:27
0.5
0:00:07
uSec
3
7960Z TD/ECD 4 to 6 Apr 2001
5
4.5
050200Z to 050311Z
X-Ray Event M3.1
4
050837Z to 050954Z
X-Ray Event M8.4
051651Z to 051814Z
X-Ray Event M5.1
061910Z to 061931Z
X-Ray Event X5.6
3.5
2.5
2
1.5
1
0.5
Time
A1 ECD
A1 TD
A2 ECD
A2 TD
17
23:44:27
21:48:07
19:51:47
17:55:27
15:59:07
14:02:47
12:06:27
10:10:07
8:13:47
6:17:27
4:21:07
2:24:47
0:28:27
22:32:07
20:35:47
18:39:27
16:43:07
14:46:47
12:50:27
10:54:07
8:57:47
7:01:27
5:05:07
3:08:47
1:12:27
23:16:07
21:19:47
prf1336.pdf
19:23:27
17:27:07
15:30:47
13:34:27
11:38:07
9:41:47
7:45:27
5:49:07
3:52:47
0
1:56:27
022340Z to 061340Z >10Mev Proton Event
030120Z to 03 2025Z >100Mev Proton Event
Geomagnetic Activity: 4-5 Apr Minor
0:00:07
uSec
3
A1 ECD
A1 TD
A2 ECD
23:44:27
Geomagnetic Activity: 7-8 Apr Major/Severe
21:48:07
Proton Events: None
19:51:47
17:55:27
15:59:07
1500Z to 2100Z K=5
14:02:47
12:06:27
10:10:07
8:13:47
6:17:27
4:21:07
2:24:47
0:28:27
22:32:07
20:35:47
18:39:27
16:43:07
14:46:47
12:50:27
10:54:07
8:57:47
7:01:27
5:05:07
3:08:47
1:12:27
23:16:07
21:19:47
19:23:27
17:27:07
0300Z to 0600 K=5
0600Z to 0900Z K=6
15:30:47
13:34:27
11:38:07
9:41:47
7:45:27
5:49:07
3:52:47
0
1:56:27
3
0:00:07
Values
7960-Z TD/ECD 7 to 9 Apr 2001
5
4.5
4
3.5
091524Z to 091703Z
X-Ray Event M7.9
1500Z to 1800Z K=5
2.5
2
1.5
1
0.5
prf1336.pdf
prf1337.pdf
Time
A2 TD
18
7960-Z TD/ECD 10-12 Apr 2001
5
4.5
4
1000850Z to 131055Z > 10MeV Proton Event
A PCA was associated with this event.
121112Z to 1206Z
X-Ray Event X2.0
3.5
2.5
100459Z to 100810Z
X-Ray Event X2.3
2
0900Z to 1200Z K=5
1200Z to 1500Z K=6
1500Z to 1800Z K=8
1800Z to 2100Z K=7
2100Z to 2400Z K=8
1.5
1
0.5
121305Z to 121950Z >100MeV Proton Event
0000Z to 0300Z K=6
Time
A1 ECD
A1 TD
A2 ECD
A2 TD
19
23:50:37
21:54:07
19:57:37
18:01:07
16:04:37
14:08:07
12:11:37
10:15:07
8:18:37
6:22:07
4:25:37
2:29:07
0:32:37
22:36:07
20:39:37
18:43:07
16:46:37
14:50:07
12:53:37
10:57:07
9:00:37
7:04:07
5:07:37
3:11:07
1:14:37
23:18:07
21:21:37
19:25:07
17:28:37
15:32:07
13:35:37
11:39:07
9:42:37
7:46:07
5:49:37
3:53:07
1:56:37
0
Geomagnetic Levels: 11 Apr - Major Storm
0:00:07
uSec
3
CONCLUSIONS
• There is strong evidence of extreme early skywave interference along this long
path in Alaska
• These events are initiated by high energy solar activity. Unlike “classical”
skywave, the effects are visible during the day, and disappear at night.
• High performance receivers like the Austron 5000 and the Locus LRSIIID easily
meet RTCA and RTCM Mops
• However, under these Alaska anomalies which feature delays 10 usec or more
less than previously spec’d, even these “monitor grade” receivers show effects that must
be called “unusable”
• We’d need special monitor equipment to nail down the exact delay/amplitude of the
skywaves
• Similar ECD effects, somewhat attenuated, can be seen in very long baselines in the
NEUS chain. Phase changes were not discernible in the small number of NEUS records
examined.
20