We are well on our way to finalizing the “Command, Control and Telemetry” Data Link for our Google Lunar Lander system. We are approaching the < 100 Kelvin Radio Temperature we want in our 10 gram Command Receiver (20 grams with heavier, prototype circuit boards). The allows reliable, moderate data rate control with 5 nanovolts (0.005 microvolts) of received (50 Ohm) RF. Using a fairly simple “2 meter” antenna on the lander, 2 Watts ERBP (Effective Radiated Beam Power) is needed at the control transmitter on the Earth, and a small fraction of that will suffice with a good transmitting antenna.

The power from the Moon is a more serious limitation. With a more complex, but similar mass 70 cm transmitting antenna, 2 watts would serve for telemetry from the Moon with a simple receiving antenna on Earth. Clustering several good “70 cm” Yagi Ham antennas, the telemetry transmitter power can be pushed below 100 milliwatts, again at modest data rate. (The HDTV transmission will, as noted earlier, take more power, probably use 2.4 GHZ, and require an impressive Earth Station to get reasonable transmission time. But those components are also available.) More details later...