The SETI League, Inc., a membership-supported, non-profit {501(c)(3)}, educational and scientific organization Searching for Extra-Terrestrial Intelligence

SETI League EME (Moonbounce) Station

Tracking the Moon

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Unsurprisingly, a primary task when transmitting a signal to the Moon is the ability to know where it is and hence point the antenna at it. To accomplish this, we use "Nova" software by Northern Lights Software Associates. Mike Owen (W9IP) of NLSA generously donated a copy of the software, which runs on a PC.

An interesting bit of complication: The beacon system is really a large rack of precision test equipment, almost all of which is controlled by the IEEE-488 protocol. The Nova software runs on a PC, which has less than the stellar reliability of a Hewlett-Packard Unix computer. Nova determines when the moon is visible, and points the antenna using a Yaesu G 5600B Az/El rotator. While there is little danger of the moon getting misplaced or the antenna jumping off the tower if the PC crashes, it was felt that the Unix machine should control the critical components, including the 3 KW power supply and amplifier. Nova makes available "DDE" specifications which allow a Microsoft Visual Basic application to read the position of the Moon and transmit it over the PC's RS-232 link to the Unix computer. The only element actually used by the beacon is "Moon UP/ Moon DOWN," although the azimuth and elevation info is also provided on the web so you can tell when the beacon is on the air.

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this page last updated 4 January 2003
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