I will attempt a reply to both of these responses. On Fri, Sep 25, 2009 at 9:27 PM, Tony Langdon <vk3...@gmail.com> wrote: > At 09:34 AM 9/26/2009, James Craig wrote: >>Good point. Not everybody is interested in monitoring the one way >>downlinks on the majority of these more recent birds. Why is it that >>there is no problem getting large numbers of these types of satellites >>into orbit, yet good old fashioned two way linear and FM transponder >>birds are relatively far and few between?
The reason cubesats are being built is because they are seen as an excellent platform for educating space science students at the undergraduate level. The amount of money being spent per launch is pretty doable for many institutions or local granting agencies. These agencies and universities are likely simply not interested in providing you or me with a platform for two-way terrestrial communication if it is going to slow down their project or lower its probability of success. The cubesat design is quite constrained moreover, typically 10cm^3 and under one kg, even the milk-carton sized 3U format is pretty small for the power needs of a linear or FM transponder of the sort we are typically using. We owe a debt of gratitude to Delfi, which showed that a linear can be put up as a secondary mission, and to William for his 10cm^2 transponder implementation. Those are very recent developments, and I'd agree that we should jump on them as golden opportunities, noting however, that the result will still be very low altitude orbits and therefore small footprints. Similarly, SDX technology might be able to miniaturize the transponder further and reduce its power needs (while making one circuit a do-everything transponder!), so we're lucky that we're testing that technology in the near future. Please note that there is no contention for resources here: the opportunities the universities made use of are not available to us. If we want this phenomenon to work to the advantage of those of us who enjoy two-way voice communications, we need to either launch a cubesat ourselves or offer the university projects a reason that adding this capability will *improve* the time-to-launch or probability of success. This might be in the form of a free, tested, reliable communications board that happens to have two-way voice capability integrated into it. It also could be in the form of increased amateur enthusiasm for the transponder-bearing cubesat and the resulting increase in telemetry collection, a bargain which we proved to be good for in Delfi C3. > I for one was never a SWL, so I tend not to follow the one way > satellites, unless there's a compelling reason (e.g. for test > signals, or telemetry decoding - had fun decoding telemetry on AO-40 > when it was first launched). Nor was I, yet I very much enjoy listening to telemetry from cubesats, along with other activities in this corner of the hobby. I can offer you this reason: when I listen to telemetry, I'm listening to something which is in space and in orbit around the earth, one of the most exotic locales from which you could receive a message. If I talk to you on AO-51, I'm talking to you on earth by means of a space-borne vehicle. It turns out that what's fun about that for me is not necessarily your voice, but the vehicle. Telemetry tells me about those vehicles: how fast they are moving, how they are tumbling and the contents of the telemetry stream: how much power they're collecting and using. Moreover, with some of the cubesats, the decoding of this is very easy if one knows CW. Two more points in my brief "apologia pro cubesatibus" 1. So-called 'telemetry only' birds are not necessarily that. We had the opportunity to control COMPASS during its crisis last year. The low cost of the mission meant that any one of us was solicited to enter the appropriate codes. I'll never be a control station for a major bird, but I thrilled to do this for COMPASS. 2. Given that you admit above that telemetry collection is necessary for the maintenance of communication satellites, shouldn't you be glad that this steady stream of cubesats has allowed some enthusiasts to continue to hone their skills in this field? Finally, a truism that probably bears repeating, though not addressing the two comments quoted above: if we call cubesats 'not amateur radio', then we should tar OSCAR 1 with that same brush. 73, Bruce VE9QRP _______________________________________________ Sent via amsat...@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
