robert@uop.UUCP (Robert McCaul--The Equalizer) (07/16/87)
with all the talk over "spy" sattelites, in addition to the wave of home satellite dishes, has anyone spent the time to downlink anything other than the usual?? (why watch HBO when you can watch the SPOT satellites, weather, or the kremlin?) just curious
henry@utzoo.UUCP (Henry Spencer) (07/20/87)
> with all the talk over "spy" sattelites, in addition to the wave > of home satellite dishes, has anyone spent the time to downlink > anything other than the usual?? (why watch HBO when you can watch > the SPOT satellites, weather, or the kremlin?) Not that easy, alas. Different and often unpublicized frequencies, unorthodox modulation schemes (it ain't yer normal video signal), probably encryption for the spysats, possibly tight-beam transmission with small footprints for the military stuff, and finally the general problem that most of the satellites in question are in low orbit, meaning that they aren't in line of sight when they're viewing the Kremlin! It is possible -- I've seen weather-satellite images, in particular, from amateur equipment -- but not simple. -- Support sustained spaceflight: fight | Henry Spencer @ U of Toronto Zoology the soi-disant "Planetary Society"! | {allegra,ihnp4,decvax,utai}!utzoo!henry
wtm@neoucom.UUCP (Bill Mayhew) (07/23/87)
I used to work on satellite transponder equipment. Probably all spy satellite stuff is encrypted to the point where is not worth the effort it takes to get the stuff back. If memory seves me right, the military uses ~14 GHz downlinks (get a copy of MSN magazine for details). Some are as high as 25 GHz (ugh!!). Russian spy satellies are designed for a duty cycle of ~6 months. They send film canisters back for reentry! No problems with radio security there. There are some Soviet spy satellites that do use video, though so I've heard. The Russian TV satellites are in two formats. One is called Gorizont (their word for horizontal) and is in synchronous orbit over Europe; this isn't viewable from the US. They have satellites called Molnyia (thier word for lightning) taht are in eliptical orbit. These can be seen from the US. Since they aren't geosync, an azimth/elevation dish is required to stay on track. I think they are visible for 6 Hours. There are 4 Molnyia, so as one is just setting on the horizon, another one is rising. Another option is Intelsat. These use circular polarization that is not common on many consumer dishes. Intelsat uses a so-called hemispherical footprint to cover nearly 1/2 the globe. Thus, thus received power is quite weak. You'd need a 5 to 8 meter dish to get an acceptible picture back. The best for unusual TV is to catch ocassional feeds that are routed through the US domestic satellite net as they make a multi-hop trip from Europe to Austrailia. Sometimes, Westar IV, transponder 14 has Russian TV (it carried Gorbachev's arms speech yesterday). Satcom F1 also carries BBC feeds on the upper transponders (sometimes #18). Satcom F4, transponder #2 is shared with RAI TV from Itay with Bravo Entertainment channel and other services. The RAI is intended for US consumption, and thus arrives already converted to NTSC; watch for this around 1600 hours, eastern time. US standard monitors often have enough lattitude in their sync controls to be able to lock onto the scan frequencies used in European TV. A multistandard monitor is is reuqired if you want to watch in color, though. A book, "The Hidden Signals on Satellite TV", is useful for information about how to retrieve FSK weather pictures, SCPC audio, Teletext, etc. Bill (wtm@neoucom.UUCP)
bill@ut-ngp.UUCP (Bill Jefferys) (07/25/87)
In article <633@neoucom.UUCP} wtm@neoucom.UUCP (Bill Mayhew) writes: }The Russian TV satellites are in two formats. One is called }Gorizont (their word for horizontal) and is in synchronous orbit }over Europe; this isn't viewable from the US. They have satellites }called Molnyia (thier word for lightning) taht are in eliptical }orbit. These can be seen from the US. Since they aren't geosync, }an azimth/elevation dish is required to stay on track. I think }they are visible for 6 Hours. There are 4 Molnyia, so as one is }just setting on the horizon, another one is rising. Actually, " gorizont " means " horizon ", presumably because, being in synchronous orbit over Europe it is above their horizon at all times. The word for " horizontal " is " gorizontal' ". A small point, perhaps, but "horizontal" would make no sense.