Fall 2009 Issue

Moondata Update 2010
and Related Comments

One of the most important factors in EME communications is knowing when it is best to communicate via moonbounce.
W5LUU presents a summary and table of the best and
worst conditions for EME in 2010.

By Derwin King, W5LUU

The best EME conditions occur when: (1) the Earth-Moon distance is at the absolute minimum and (2) the Moon is in the coldest sky region along the Moon path. The effect of distance is independent of frequency, but sky temperature decreases with frequency, up to ~1 GHz and then levels out. The EME signal-to-noise ratio, in dB, is degraded, from the minimum, by a factor (DGRD, see below) which varies over hourly, daily, weekly, monthly, and yearly time periods. As a guide for the basic weekend EME conditions for 2010 the W5LUU Weekend Moondata 2010 lists the DGRD, in dB, for 144 and 432 MHz, and other pertinent EME information for each Sunday at 0000 UT. Factors such as local noise, antenna beam width, side lobes, polarization, etc., can also affect the signal-to-noise ratio of moonbounce signals. Low sunspot activity in 2010 will minimize disruptive ionosphere disturbances. Good conditions will prevail.

For frequencies below 1296 MHz, 2010 will be the best EME year until 2019 or later. Some good and excellent days will occur on weekends, but more during the week. Days listed below have a 144 MHz DGRD that is a minimum at d, day and h, hour and may last for plus or minus several hours.

January: 02d/2310h (0.18 dB) and 30d/1051h (0.02 dB); February: 26d/2215h (0.60 dB); March: 19d/1930h, (0.41dB); April: 22d/1430h, (0.65 dB); May: 19d/1930h (0.68 dB); June: 16d/0233h, (0.5 dB); July: 13d/1034h, (0.25 dB); August: 09d/2056h, (0.13 dB); September: 06d/0730h, (0.23 dB); October: 04d/1822h, (0.66 dB) and 31d/0003h, (0.75 dB); November: 27d/0534h, (0.81dB); December: 24d/1150h, (0.63 dB).


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) of about 19 years. The 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 the 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.

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