I'm sure most of you already know about LRO and LCROSS and the scientific value they have for our understanding of the Moon. We are all very excited about the results and hope they will be available in time for planing the Google Lunar X PRIZE mission. In the mean time, there are other very interesting engineering opportunities that we should not let pass by: With LRO in orbit, we have a unique radio signal source in orbit around the Moon that we can use to test our communication link models and equipment! The LRO ops team uses big dishes for receiving data from LRO. They need them because they are downloading data from LRO at up to 229 Msps in the K_a-band and 5 Msps in the S-band. Now, the question is, if we are not concerned about decoding the data at those high rates but just detecting the presence of the signal in a very narrow bandwidth (say few hundred Hz), could we do that using a much smaller setup? Therefore, we have decided to carry out a quick experiment and try to receive the LRO (and maybe LCROSS) signals in the S-band. We will be using mostly what we already have in the lab, including a 60cm dish and the open source USRP+GNU Radio software receiver that was presented some time ago. Why would this be interesting? Well, if we can detect a decent signal in a 500 Hz bandwidth, that would technically correspond to receiving data from the Moon @ 500 bits per second! Part 2 of the experiment would then be to scale up the receiver by using a larger dish (in our case 8 meter diameter) and see how much bandwidth we can receive. We should be able to go up to 50 kHz or more and this is where we are getting close to something useful for a small scale GLXP mission: The bitrate of a 320x240 video using state of the art video codecs is not much higher than 50 kbps! (In case you are wondering why we don't just use the 8 meter dish right away, the answer is that it takes more work to make it work in the space research downlink segment of the S-band than it does with a small portable dish.) A preliminary analysis shows that we should be able to detect the signal using a 60cm dish and a good RF front-end: The complete link budget sheet using the AMSAT / IARU link model can be downloaded here. It should be noted that the information about the LRO and LCROSS transmitters and antennas is very uncertain. If somebody has more accurate info we would really appreciate it! The critical parameter in a receiver is the figure of merit (G/T) which expresses the gain of the receiver versus the system noise temperature. Obviously, it is not enough to increase the gain as much as possible but we also need to reduce the system noise temperature, otherwise the signal would disappear in the noise – amplifiers also amplify the noise, not just the signal! Our assessment for our setup is a system noise temperature between 60 and 80 K, which is excellent. Here is a personal video blog from @csete posted a week ago giving a quick overview of the setup. A more thorough walkthrough of the system will be posted soon. A note from @csete: I said twice in the video that the tuners convert the high frequency to baseband. This is not quite true. The tuners convert the high frequency to intermediate frequency (IF-band), which is around ~5 MHz. Conversion to baseband happens in the FPGA using DDC and CIC filters.