Big Toe thanks for your take on the telecomm thread. I want to expand that somewhat to focus on commercial communication satellites in particular. Im not saying that milsatcom isnt important but 1) the general population doesnt use military sats, 2) military sats are more complex because of the mission requirements, and 3) we cant discuss their design on the web. I did a little digging from my classes to confirm what I had said in the previous post. Let me give my take on these satellites.

First, commsats are in geo orbits. For those of you who know what this means you can skip this paragraph. These sats move some 23,000 miles above the earth. They move according to the laws of physics, just as the moon has for billions of years. The geo orbits are circular, meaning their velocity is constant as opposed to elliptical orbits where the velocity changes depending on the position. I bring out this fact because of the solar panels to be discussed later. These sats picked this altitude because they must have the same view of the earth at all times. Its period is the same as the earth rotation, slightly less than 24 hours. (I bet you didnt know that did you?) If you look up, you see the same satellite in the same position no matter what hour, minute, second, or year it is on earth. This fact is important because the ground stations will not have the problem that Big Toe mentioned in the other thread. Ground stations can acquire the sat at any time needed.

Second, satellites have two basic subsystems: payload and spacecraft bus. As I mentioned in the earlier thread, the payload contains an antenna. The design of these payloads date back to 1945, very simple technology. (Opinion: my knowledge is a decade old, so things may have become more complex. But, the designers first rule is keep it simple. With increased complexity, risk increases. Space operations is too costly to increase the risk needlessly. Satellite owners do not need additional risk.) The antenna receives and transmits data, nothing more. The payload also amplifies the signal. (Opinion: I dont know about embedded chips in this type of payload but from what Ive read, embedded chips are not needed. This is a passive design. And why risk it?)

The spacecraft bus contains the attitude control, propulsion, power, and telemetry systems. Attitude control comes from either a momentum wheel or a satellite spin. The satellites that use the momentum wheel, generally use solar panels. The momentum wheel may have a circuit to ensure that it keeps spinning to maintain attitude. But the laws of motion in a space environment tend to keep the thing spinning. (I cant say if they have embedded chips that may fail). The solar panels have a drive mechanism which keep them oriented toward the sun. They perform one revolution during the satellite period at a constant velocity. (I cant talk about that mechanism but it shouldnt be any more complicated than the small hand on your clock). In the dual-spin system, solar cells are place all over the satellite, so they are oriented toward the sun at all times. These kinds of satellites look like spinning cylinders with antenna sticking out the top. I feel these are more complex because the antennae need to be separated from the spinning body. That mechanism may fail (cant say for sure). The power system on both kinds includes batteries for operations during an eclipse which occurs for 1.5 hours each day. Telemetry is needed for battery conditioning and other health maintenance. These routine functions could be performed in December 99 to ensure entering the new year will not cause any additional problems.

I tried to simplify the satellite design and functioning to help you understand. But, the facts mentioned do highlight major functions. True, the devil is in the details but how much detail do you really want? Now draw your own conclusions about whether or not telecomm satellites will fail. Comments Big Toe?

Will Huett, Hows that for original thought? And thanks for your assessment of my intelligence. I value your opinion, NOT. Jack, I apologize for the logic comment but you left yourself open and I jumped on it :) Andy, I can tell you for sure that Russia is already toast. Y2K wont make that much difference. Communism kept their economy a secret for decades. They were always on the edge of collapse. Dont know about France or Germany. Maria: My conclusion on my house: My *apparent* Y2K preparedness stems from my frugality, not fear of Y2K.

Troll Maria

-- Maria (anon@ymous.com), January 09, 1999

Answers

"My apparent y2k preparedness stems from my frugality, not fear of y2k"

My point was that no poster had the right to assume either that you aren't preparing or that you don't take y2k seriously on the basis of what evidence you had provided at that time, simply because you disagreed with their evaluation of how big the consequences of y2k will be. It has nothing to do with agreeing or disagreeing with you. About Germany-- its problem may be that it cannot support itself without trade. It lives off of the import or raw materials and export of specialized tools and parts. It also imports both electricity and oil on a large scale. So it is highly dependent on the shipping industry- even assuming it has no problems itself.

-- Maria (encelia@mailexcite.com), January 10, 1999.

Maria: Neat info. Thank you for the design details.

My daughter (13) has a girl scout project about space, and space-related careers coming due in the next two-three weeks. Can she (and a friend) contact you for info about what you did (unclassiified, of course), what you studied, where you went to school/industry/service, etc. What you liked, didn't like, would do differently, and other questions.

-- Robert A. Cook, P.E. (Kennesaw GA) (cook.r@csaatl.com), January 11, 1999.