wmartin@brl-tgr.ARPA (Will Martin ) (12/09/85)
Is the Space Shuttle large enough to "shadow" or interfere with the transmissions between the surface and a geosync satellite? What about the proposed Space Station? If so, won't it interfere on a regular basis? If the shuttle interferes, it would do so fairly rarely, and this would be tolerable. If the Space Station scrambles the transmissions that are picked up by some cable system earth station every ninety minutes, I would think that an interesting court case might result... Will Martin UUCP/USENET: seismo!brl-bmd!wmartin or ARPA/MILNET: wmartin@almsa-1.ARPA
rjnoe@riccb.UUCP (Roger J. Noe) (12/11/85)
If the station is not in an equatorial orbit, then any such "shadowing" will not occur anywhere near as frequently as every 90 minutes. -- Roger Noe ihnp4!riccb!rjnoe
bde@ihlpl.UUCP (Ewbank) (12/11/85)
I would think that a space station would also be in geosync orbit?
If a space station is NOT in geosync orbit, I think that a larger
problem would come when it entered Soviet airspace.
--
Bryan D. Ewbank
>> one line generic disclamer here <<
# AT&T Bell Labs IH 6M-523 # ...!ihnp4!ihlpl!bde #
# Naperville-Wheaton Rd. # #
# Naperville, Illinois 60566 # 5813 Oakwood, Apt. E #
# (312) 979 - 4296 # Lisle, Illinois 60532 #hogg@utcsri.UUCP (John Hogg) (12/12/85)
A poster has raised the possibility that space station owners may be liable for damages due to shadowing communications satellites in geosynchronous orbits. Another poster correctly pointed out that this will not happen every time around - not by a long shot, since a station would not be put into equatorial orbit. Now allow me to finish pointing out the obvious. An object in LEO moves on the order of 10**4 m/sec. Assume a one-KILOmetre diameter space station - that's a kilometre of material with shadowing properties. It will cause a 1/10 second glitch in your signal, assuming no beam-spreading and atmospheric diffraction effects allow the beam to "bend" back far enough to reach your receiver. A smaller station or one which is less than opaque to a radio signal will of course have a smaller effect. Now for the key question: do you call your lawyer when a 747 flies overhead? Do you KNOW? -- John Hogg Computer Systems Research Institute, UofT ...utzoo!utcsri!hogg Disclaimer: the above may or may not contain sarcasm, and doesn't contain smiley-faces. If you can't read, don't flame me.
henry@utzoo.UUCP (Henry Spencer) (12/13/85)
> Now for the key question: do you call your lawyer when a 747 flies > overhead? Do you KNOW? There is at least one case on record in which a small jet's crew were thoroughly alarmed for a moment because their radar altimeter suddenly showed a much lower altitude than the barometric altimeter. Then suddenly things were back to normal. Then they realized there was a 747 a few thousand feet underneath, slowly pulling ahead of them...
brent@poseidon.UUCP (Brent P. Callaghan) (12/16/85)
>> Now for the key question: do you call your lawyer when a 747 flies >> overhead? Do you KNOW? > >There is at least one case on record in which a small jet's crew were >thoroughly alarmed for a moment because their radar altimeter suddenly >showed a much lower altitude than the barometric altimeter. Then suddenly >things were back to normal. Then they realized there was a 747 a few >thousand feet underneath, slowly pulling ahead of them... I guess this is getting the discussion a bit off the point, but it reminded me of the testimony of an Air New Zealand DC10 captain at the inquiry into the Mount Erebus disaster in 1980: He was giving evidence regarding the accuracy of the "AINS" (Area Inertial Navigation System). Air New Zealand has a 5,000 mile route to Honolulu. At the same time, two DC10's would depart Auckland and Honolulu on reciprocal courses. Several hours out over the Pacific the aircraft would pass each other at different altitudes. The crew on the high aircraft could see the low aircraft pass on their radar altimeter ! -- Made in New Zealand --> Brent Callaghan AT&T Information Systems, Lincroft, NJ {ihnp4|mtuxo|pegasus}!poseidon!brent (201) 576-3475
dsi@unccvax.UUCP (Dataspan Inc) (12/18/85)
> >> Now for the key question: do you call your lawyer when a 747 flies > >> overhead? Do you KNOW? Is it necessary? Back in the dark ages (when satellite antennas cost $2000 and there was no such thing as a 120 degree LNA) we were installing a satellite system on Interstate-85 in Charlotte, NC. This earth station turns out to be right at the end of R/W 5-23 at Douglas Field. I don't know what the horizontal distance is exactly to the end of 23 but the aircraft on approach are sufficiently low enough to see small mechanical parts. They are the usual short-haul stuff (727/737/DC-9/BAC 1-11) flying over (directly) and cause no problems for TASO Grade 1 downlinking of television. However, you can see the effects of the radar altimeter for about 5 sec after flyby...at the output of the LNA. It was not visible at the first IF and has caused our client no problems. In the transmit case, I don't know if the high EIRP (typically 5000 w) would cause the aircraft any problems, or for that matter, the occupants inside. However, I believe (and am going to check the dreaded cookie company rules and regulations) that you would have no standing if you were stupid enough to put your earth station at the end of a runway, or, for that matter, between the outer marker and the runway and 10000 feet on either side. Outside the controlled area (I'm not a pilot, and know very little from doing numerous broadcast applications) the "footprint" of a 747 wouldn't affect anything... If you can afford an uplink, you can afford a consulting engineer whose job is to plan for contingencies like this. The Commission common carrier bureau is a whole 'nother world from Mass Media, and they can be picky to the point of trivia. Has a 747-flyby actually screwed up someone's uplink? David Anthony Chief Development Engineer DataSpan, Inc.
ems@amdahl.UUCP (ems) (12/21/85)
> If a space station is NOT in geosync orbit, I think that a larger > problem would come when it entered Soviet airspace. Uh, the biggest problem from a space station entering Soviet *AIR*space would be the fireball ... -- E. Michael Smith ...!{hplabs,ihnp4,amd,nsc}!amdahl!ems This is the obligatory disclaimer of everything.
al@ames.UUCP (Al Globus) (12/31/85)
> I would think that a space station would also be in geosync orbit? > > If a space station is NOT in geosync orbit, I think that a larger > problem would come when it entered Soviet airspace. > -- With Sputnik, the Soviet's established a tradition that spacecraft may overfly national territories. 'Airspace' therefor ends at some undefined altitude. National control, of course, is limited by physical ability. If you can't destroy it, you can't control it. Since the ability to destroy satellites was non-existant in the late 50s and is very limited now, territorial control does not extend to space craft. If ASAT's become common, this could easily change - a fact those who support ASAT's and like (politically) free access to space should consider. For example, when the equitorial countries tried to claim control over geosynchronous satellites they failed. If they had access to ASAT's capable of reaching communication satellites the results might well have been quite different.