MOONDATA UPDATE-2008 AND RELATED COMMENTS

View as PDF MoonData_2008.pdf

ByDerwin King,W5LUU

 

 

The earth-moon distance and the cosmic (sky noise) temperatures in the direction of the moon are predictable, cyclical variables that set the basic quality of earth-moon-earth (EME) communications for frequencies below 1.0 GHz. Best conditions occur when the: 1) earth-moon distance (Range Factor) is at the absolute minimum and 2) Sky Temperature toward the moon, as seen from earth, is the coldest along the moon path. While the Range Factor is independent of frequency, Sky Temperature decreases with frequency, up to ~1 GHz and then levels out. TheEME signal-to-noise ratio, in dB, is usually degraded from the ideal by a factor (DGRD, see below), which varies with time over hourly, daily, weekly, monthly and yearly periods. The DGRD, in dB, for 144 and 432 MHz, and other pertinent EME data, are listed in W5LUU WEEKEND MOON DATA for each Sunday at 0000 UT to provide a guide for the basic EME weekend conditions. Random variables such as ionospheric disturbances, local noise, and polarization mismatch will increase the "apparent" DGRD.

EME conditions will generally improve in 2008 with all moon perigees at north declinations, but on many weekends the moon is at Right Ascensions where Sky Noise is 1 to 4 dB above minimum and five Good weekends are negated by new moon. Many weekdays will be Good or better. Over the next 1-2 years as perigees occur near the best cold sky region, conditions will improve. During the traditional ARRL EME Contest period there are no ideal, high declination weekends for VHF due to the high sky temperatures. Dates will have to be a compromise. For 1296 up, several high declination dates are near perigee and near ideal.

Definitions:

DEC. (deg): Moon declination in degrees north and south ( - ) of the equator. This is cyclical with an average period of 27.212221 days. The maximum declination during a monthly cycle, plus and minus, ranges from 18.15 up to 28.72 degrees with a period (maximum to minimum and back to maximum) in about 19 years. Last maximum was on 09/15/2006.

RA (hrs): Right Ascension, in hours, gives the East-West position of the moon against the sky background. Average period of RA cycle is 27.321662 days but it can vary by a day or so due to effects of the sun on the earth and moon motion.

144 MHz Temp (K): The 144 MHz cosmic (sky) noise in direction of moon expressed as absolute temperature.

Range Factor (dBr): The additional EME path loss, in dB, due to earth-moon separation distance being greater than absolute minimum (348,030 km surface-to-surface). Varies from a low of (0 to 0 .7 db) at perigee up to 2.33 + 0.1 dB at apogee.

DGRD, (dB): The degradation in EME signal-to-noise, in dB, due to: (1) the excess sky noise temperature, in dB, at the

stated position of the moon compared to the lowest cold sky temperature and the system noise temperature (all at the

frequency of interest); plus (2) the earth–moon range factor, dBr, for the listed time and date. The tabulated DGRD is

referenced to the lowest possible sky noise temperature along the moon path, for a system noise temperature of 80 K at 144

and 60 K at 432, an antenna beam width of ~150 and to the absolute minimum earth-moon (surface-to-surface) distance.

The dBr affects DGRD equally at all frequencies, but sky noise decreases rapidly as frequency increases. During a monthly lunar cycle DGRD can vary by 13 dB on 144 and 8 dB on 432. DGRD varies less with small antennas than with large.

Moon Phase: Shows new moon (NM) and full moon (FM) along with the number of days (d) or hours (h) before (–) or after (+) these events. At NM sun noise is a problem while at FM the EME conditions (at night) are usually more stable.

Conditions: Summary of EME conditions as controlled by DGRD at 144 MHz and NM. Conditions may be worse, due to ionospheric disturbance, local noise and polarity, but not better than indicated. In general, 144 MHzDGRD <1.0 dB is consideredExcellent, 1.0 to 1.5 is Very Good, 1.5 to 2.5 is Good, 2.5 to 4.0 is Moderate, 4.0 to 5.5 is Poor, and over 5.5 is Very Poor. Within a day of New Moon (NM), high sun noise can make conditions Very Poor regardless of the DGRD.

 

W5LUU WEEKEND MOONDATA – 2008

For Sundays at 0000 UT

Date 2008

Dec.deg.

RA hrs.

144 MHz Temp.K

Range Factor

dB

DGRD, dB

  1.            432

MHz                 MHz

Moon Phase

CONDITIONS

Jan 06

- 27.7

17.0

905

2.14

8.2

3.8

NM – 2.5d

Very Poor

13

- 2.9

23.1

244

1.15

2.3

1.5

Good

20

28.0

5.7

512

0.53

4.3

1.8

FM – 2.7d

Poor

27

- 2.9

12.0

259

1.77

3.2

2.1

Moderate

Feb. 03

- 28.0

17.6

2227

2.04

11.8

5.6

 

Very Poor

10

0.9

23.7

247

0.90

2.1

1.3

NM + 2.9d

Good

17

27.6

6.4

407

0.81

4.0

1.8

 

Moderate

24

- 1.5

12.4

306

1.84

3.8

2.4

FM + 2.9d

Moderate

Mar 02

- 27.7

18.2

2732

2.01

12.6

6.5

 

Very Poor

09

5.3

0.3

262

0.61

2.0

1.0

NM + 1.3d

Good but NM on 03/08

16

26.0

7.1

344

0.97

3.3

1.6

 

Moderate

23

- 10.2

12.9

313

1.99

4.0

2.5

FM + 2.6d

Moderate

30

- 26.8

18.8

1351

2.02

9.7

5.3

 

Very Poor

Apr06

9.2

0.8

277

0.38

2.0

0.8

NM - 3.9h

Good but NM

13

23.4

7.9

229

1.00

2.0

1.2

Good

20

- 13.9

13.5

321

2.14

4.3

2.6

FM - 9.9h

Poor

27

- 25.1

19.4

654

2.05

6.8

3.7

 

Very Poor

May04

12.8

1.3

290

0.29

2.1

0.8

NM - 1.5d

Good

11

20.1

8.6

186

0.92

1.3

1.0

 

VERY GOOD

18

- 17.5

14.0

350

2.25

4.7

2.8

FM – 2.1d

Poor

25

- 22.6

20.0

380

2.04

4.8

2.8

 

Poor

Jun.01

16.3

1.8

313

0.34

2.4

0.8

NM – 2.8d

Good

08

16.7

9.2

172

0.83

0.9

0.8

 

EXCELLENT

15

- 20.7

14.6

392

2.29

5.1

3.0

FM - 3.7d

Poor

22

- 19.5

20.7

337

1.95

4.3

2.5

 

Poor

29

19.7

2.4

351

0.48

2.9

1.1

 

Moderate

July06

13.3

9.7

185

0.81

1.1

0.8

NM + 2.9d

VERY GOOD

13

- 23.3

15.2

433

2.28

5.5

3.1

 

Poor

20

- 16.0

21.3

341

1.78

4.1

2.3

FM + 1.7d

Poor

27

22.9

3.1

364

0.62

3.2

1.3

Moderate

Aug 03

9.8

10.2

193

0.89

1.3

1.0

NM + 1.4d

V. G. but NM 08/02

10

- 25.3

15.8

493

2.25

5.9

3.2

 

Very Poor

17

- 12.3

21.9

299

1.56

3.4

2.0

FM + 2.7h

Moderate

24

25.4

3.9

363

0.69

3.2

1.3

 

Moderate

31

6.1

10.7

204

1.09

1.7

1.2

NM + 4.0h

Good but NM

Sept 07

- 26.6

16.4

657

2.24

7.0

3.5

Poor

14

8.6

22.3

252

1.34

2.6

1.7

FM - 1.4d

Moderate

21

26.9

4.7

430

0.64

3.8

1.5

 

Moderate

28

2.0

11.3

222

1.35

2.2

1.5

NM - 1.3d

Good but NM 09/29

Oct. 05

- 27.2

17.0

867

2.26

8.1

3.9

Very Poor

12

- 4.9

22.9

244

1.19

2.4

1.9

FM - 2.8d

Good

19

27.3

5.5

514

0.47

4.3

1.7

 

Poor

26

- 2.6

11.8

251

1.59

2.9

1.9

NM – 2.9d

Moderate

Nov02

- 27.2

17.6

2175

2.31

11.9

5.8

 

Very Poor

09

- 1.2

23.3

244

1.18

2.4

1.5

 

Good

16

26.7

6.1

468

0.25

3.7

1.4

FM + 2.7d

Moderate

23

- 7.2

12.4

303

1.75

3.7

2.3

 

Moderate

30

-26.6

18.2

2659

2.35

12.0

6.8

NM + 2.3d

Very Poor

Dec 07

2.9

23.8

249

1.26

2.5

1.6

 

Good

14

25.5

6.8

385

0.08

2.9

0.9

FM + 1.3d

Moderate

21

- 11.4

13.0

313

1.79

3.8

2.3

 

Moderate

28

- 25.3

18.9

1152

2.33

9.3

5.3

NM + 0.5d

Very Poor and NM

 
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