WB5RMG_20080113

APRS posit beacon relay in Low Earth Orbit !

We have gotten so accustomed to hearing of the numerous school contacts with the amateur radio station onboard the International Space Station, many have forgotten about the digital mode. The Expedition 16 crew currently has a busy construction schedule, and has not scheduled many school contacts. This actually was welcome news to some hams, as the ARISS station has been in "unattended digipeat" mode recently.

I have a page in here from 2005 describing how this works, but this is a good time for a quick review. This time I'm using AGWPE & UIView32 with the sound card in the PC instead of an external modem (TNC). These programs provide PTT signaling on the RTS pin of Com1. My longitude and latitude are provided in the beacon text, and the only real change to the program from terrestrial APRS operations, is to specify "ARISS" in the 'unproto' field. This sets the broadcast destination of the beacon packets to request that the ISS digipeater re-transmit your beacon. When a ground-based APRS-IS gateway station hears your beacon on the ISS downlink frequency of 145.825, it will forward that information off to the great global APRS-IS database, making it available to internet portals such as www.findu.com . Once word spread last fall that the ISS digi was back on, hams world-wide started sending their beacons. This is the most activity I've ever seen on the ISS/APRS frequency.

Of course, it helps to know when the station is coming by. I still use Instant Track.

This tells me when, what direction, and how much doppler shift to expect.
As it happens, I have only a simple vertical in the attic right now for 145.825, so there is no need to aim. I've been heard by ISS when it was as low as 6 degrees above the horizon (over Canada) using only ~15 watts output. Higher gain antenna might require less power, but then it would require some pointing/tracking. Some stations simply set their beacon for every 60 sec, and don't need a schedule, or pointing. Others interact, and acknowlege the other stations heard. I have even received QSL cards . . . This is really neat ..!.. Thanks NASA !!!

I guess one glorious result of this is seeing your name in lights, so to speak . . .
Here are snips from the FindU page showing who has been recenly heard, as well as the raw packets.

In addition to the maps (as the example above) you can see callsigns from all over the world, with their location. Using FindU further, and clicking on a callsign, you can get a more detailed and interactive map interface ...

This simple activity is a good jump point into the world of Amateur Satellites . Take this opportunity to check it out, while the ISS is still in 'digi-mode'. . .
Additional resources for these activities can be found easily : http://home.comcast.net/~k9jkm/ARISS_Packet_How_To/
http://www.amsat.org/amsat/archive/amsat-bb/48hour/threads.html

All these projects tie together, as my new omnidirectional satellite antennae are also useful for VHF/UHF weak-signal/ssb activities. The EggBeater II from K5OE presents circular polarization for satellites, but is effectively horizontally polarized at the horizon. Not too many choices available for horizontal-omni antennae.

This is the 70cm edition, the 2m version should be done this week. Thanks Jerry... 73