EARLY SKYWAVE EXAMPLES FROM U.S. COAST GUARD PRIMARY CONTROL MONITOR SET DATA

1

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

2

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)

3

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

RTCM/USCG Maritime 37.5 + 12 db

60 +26 db

Transport Canada

Maritime 32.5 +12 db

45 +26 dbThe USCG Monitor receiver of the time could meet all the above, though the 32.5 usec/+12 db requirement is very challenging.

4-165 -160 -155 -150 -145 -140

60

62

64

66

68

70

72

Port Clarence

* Tok

+ Anchorage

+ Fairbanks

+ Prudoe Bay

Longitude-deg

Latit

ude-

deg

-165 -160 -155 -150 -145 -140

60

62

64

66

68

70

72

Port Clarence

* Tok

+ Anchorage

+ Fairbanks

+ Prudoe Bay

Longitude-deg

Latit

ude-

deg

The path from Port Clarence to Fairbanks is predominantly east-west in central Alaska

5

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 SLIGHTLY BETTER PERFORMANCE

6

Recent Observations …..

LET’S FOLCUS ONLY ON JANUARY 2002. FIRST, LET’S LOOK AT THE “BLINK RECORD”

7960-Z Blink Times January 2002

0

1

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 3-hours in duration.

18 hours of blink over a 31-day period yields only a 97.6% availability for this baseline, that month.

7

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.”

8

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

-3

-2

-1

0

1

2

3

4

16 18 20 22 24 26 28 30 32

Phase Error (nsec) vs (In-Phase) Skywave Delay 0 db Skywave/Groundwave

-400

-300

-200

-100

0

100

200

300

16 18 20 22 24 26 28 30 32

9


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

49922.5

49922.55

49922.6

49922.65

49922.7

49922.75

49922.8

49922.85

49922.9

49922.95

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 FairbanksCSECD = +0.8 Tol = +/- 1.5 January 2002

-1

-0.5

0

0.5

1

1.5

2

2.5

3

3.5

4

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

10


HERE’S A BLOW-UP OF THE 1 JANUARY INCIDENT 7960-Z (Port Clarence) ECD at Fairbanks

January 1, 2002

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

1.70 1.75 1.80 1.85 1.90 1.95 2.00 2.05 2.10 2.15 2.20

7960-Z (Tok-Port Clarence) TD at FairbanksJanuary 1, 2002

49922.65

49922.7

49922.75

49922.8

49922.85

49922.9

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 FairbanksJanuary 1, 2002

0

1

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) Signal Strength Estimate at FairbanksJanuary 1, 2002

63

64

65

66

67

68

1.70 1.75 1.80 1.85 1.90 1.95 2.00 2.05 2.10 2.15 2.20

11

7960-Z ECD at Fairbanks 10-11 January 2002

0

0.5

1

1.5

2

2.5

10.70 10.80 10.90 11.00 11.10 11.20 11.30 11.40


HERE’S SOME MORE ALASKA DATA – FROM 10-11 JANUARY 2002

7960-Z TD at Fairbanks With LPAs Removed 10-11 January 2002

49922.6

49922.65

49922.7

49922.75

49922.8

49922.85

49922.9

10.7 10.8 10.9 11 11.1 11.2 11.3 11.4

7960-Z LPA Record 10-11 January 2002

-0.2

-0.15

-0.1

-0.05

0

0.05

10.7 10.8 10.9 11 11.1 11.2 11.3 11.4

7960-Z TD at Fairbanks 10-11 January 2002

49922.6

49922.65

49922.7

49922.75

49922.8

49922.85

49922.9

10.70 10.80 10.90 11.00 11.10 11.20 11.30 11.40

12

7960-Z ECD at Fairbanks 17-18 January 2002

0

0.5

1

1.5

2

2.5

3

3.5

4

17.45 17.55 17.65 17.75 17.85 17.95 18.05


HERE’S A FINAL EXAMPLE OF ALASKA DATA – 17-18 JANUARY

7960-Z Blink Record 17-18 January 2002

0

1

17.45 17.55 17.65 17.75 17.85 17.95 18.05

7960-Z TD at Fairbanks With LPAs Removed17-18 January 2002

49922.55

49922.6

49922.65

49922.7

49922.75

49922.8

49922.85

17.45 17.55 17.65 17.75 17.85 17.95 18.05

13


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

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

1 2 3 4 5


-1.5

-1

-0.5

0

0.5

1

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.

14


HERE’S A CLOSER LOOK AT THE INCIDENT ON THE EVENING (GMT) OF THE 10TH 7960-Z ECD at Fairbanks 10-11 January 2002

0

0.5

1

1.5

2

2.5

10.65 10.75 10.85 10.95 11.05 11.15 11.25 11.35 11.45


-1.5

-1

-0.5

0

0.5

1

10.65 10.75 10.85 10.95 11.05 11.15 11.25 11.35 11.45

15


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

-2

-1

0

1

2

3

4

5

1 6 11 16 21 26 31

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.

16

7960Z TD/ECD 1 to 3 Apr 2001

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

50:

00:0

7

1:56

:27

3:52

:47

5:49

:07

7:45

:27

9:41

:47

11:3

8:07

13:3

4:27

15:3

0:47

17:2

7:07

19:2

3:27

21:1

9:47

23:1

6:07

1:12

:27

3:08

:47

5:05

:07

7:01

:27

8:57

:47

10:5

4:07

12:5

0:27

14:4

6:47

16:4

3:07

18:3

9:27

20:3

5:47

22:3

2:07

0:28

:27

2:24

:47

4:21

:07

6:17

:27

8:13

:47

10:1

0:07

12:0

6:27

14:0

2:47

15:5

9:07

17:5

5:27

19:5

1:47

21:4

8:07

23:4

4:27

Time

uS

ec

A1 ECD A1 TD A2 ECD A2 TD

011055Z to 011324Z X-Ray Event M5.5Occurred before the area came into view

011944Z to 011956ZX-Ray Event M4.0

291635Z Mar 01 to 010600Z Apr 01 >10Mev Proton Event

Geomagnetic Field: Major/Severe Levels 31 Mar - 010900Z Apr 01

prf1335.pdfprf1336.pdf

0600 - 0900ZK=6


021004Z to 021020Z X-Ray Event X1.4021058 to 021205Z X-Ray Event X1.1

022132Z to 022203ZX-Ray Event X20Crossing the West Limb

022340Z to 061340Z >10Mev Proton Event030120Z to 03 2025Z >100Mev Proton EventGeomagnetic Field intermittently disturbed

030325Z to 030455ZX-Ray Event X1.2

17

7960Z TD/ECD 4 to 6 Apr 2001

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

50:

00:0

7

1:56

:27

3:52

:47

5:49

:07

7:45

:27

9:41

:47

11:3

8:07

13:3

4:27

15:3

0:47

17:2

7:07

19:2

3:27

21:1

9:47

23:1

6:07

1:12

:27

3:08

:47

5:05

:07

7:01

:27

8:57

:47

10:5

4:07

12:5

0:27

14:4

6:47

16:4

3:07

18:3

9:27

20:3

5:47

22:3

2:07

0:28

:27

2:24

:47

4:21

:07

6:17

:27

8:13

:47

10:1

0:07

12:0

6:27

14:0

2:47

15:5

9:07

17:5

5:27

19:5

1:47

21:4

8:07

23:4

4:27

Time

uS

ec






Geomagnetic Activity: 4-5 Apr Minor prf1336.pdf

022340Z to 061340Z >10Mev Proton Event030120Z to 03 2025Z >100Mev Proton Event

18

7960-Z TD/ECD 7 to 9 Apr 2001

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

0:00

:07

1:56

:27

3:52

:47

5:49

:07

7:45

:27

9:41

:47

11:3

8:07

13:3

4:27

15:3

0:47

17:2

7:07

19:2

3:27

21:1

9:47

23:1

6:07

1:12

:27

3:08

:47

5:05

:07

7:01

:27

8:57

:47

10:5

4:07

12:5

0:27

14:4

6:47

16:4

3:07

18:3

9:27

20:3

5:47

22:3

2:07

0:28

:27

2:24

:47

4:21

:07

6:17

:27

8:13

:47

10:1

0:07

12:0

6:27

14:0

2:47

15:5

9:07

17:5

5:27

19:5

1:47

21:4

8:07

23:4

4:27

Time

Val

ues


Geomagnetic Activity: 7-8 Apr Major/Severe

Proton Events: None

0300Z to 0600 K=50600Z to 0900Z K=6 1500Z to 2100Z K=5

prf1336.pdfprf1337.pdf

1500Z to 1800Z K=5


19

7960-Z TD/ECD 10-12 Apr 2001

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

0:00

:07

1:56

:37

3:53

:07

5:49

:37

7:46

:07

9:42

:37

11:3

9:07

13:3

5:37

15:3

2:07

17:2

8:37

19:2

5:07

21:2

1:37

23:1

8:07

1:14

:37

3:11

:07

5:07

:37

7:04

:07

9:00

:37

10:5

7:07

12:5

3:37

14:5

0:07

16:4

6:37

18:4

3:07

20:3

9:37

22:3

6:07

0:32

:37

2:29

:07

4:25

:37

6:22

:07

8:18

:37

10:1

5:07

12:1

1:37

14:0

8:07

16:0

4:37

18:0

1:07

19:5

7:37

21:5

4:07

23:5

0:37

Time

uS

ec


0900Z to 1200Z K=51200Z to 1500Z K=61500Z to 1800Z K=81800Z to 2100Z K=72100Z to 2400Z K=8

0000Z to 0300Z K=6


1000850Z to 131055Z > 10MeV Proton Event

A PCA was associated with this event.

121305Z to 121950Z >100MeV Proton Event

Geomagnetic Levels: 11 Apr - Major Storm


20

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.

EARLY SKYWAVE EXAMPLES FROM U.S. COAST GUARD PRIMARY CONTROL MONITOR SET DATA

Documents

Transcript of EARLY SKYWAVE EXAMPLES FROM U.S. COAST GUARD PRIMARY CONTROL MONITOR SET DATA