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Microcap & Penny Stocks : Globalstar Telecommunications Limited GSAT -- Ignore unavailable to you. Want to Upgrade?

To: Maurice Winn who wrote (3958)	4/18/1999 6:40:00 PM
From: RMiethe	Read Replies (1) \| Respond to of 29987

Maurice-- You seem to misrepresent Reynen Readware's understanding of battery and or power function in a satellite. Not that it matters personally to me, but he is not here to reply. See my post of his Skybridge paper (Reply# 5434). Let me quote the sentence "In our four prior papers (one on narrowband) we had detailed our expectations for satcom telephony through CDMA satellite power conserving accomplishments for the Globalstar constellation. Path diversity and CDMA (which gives the LEO a 4-fold compression to make the Globalstar capacity the most economic and cost flexible) we saw as its lead over other proposed mobile systems". "CDMA satellite power conserving accomplishments". Seems to me that phrase has in mind exactly what your post states was an issue Reynen Readware thought should be left to satellite companies willy-nilly. The statement, in a Skybridge paper no less, shows that the reference in your post is incorrect. In the end it does not matter so much as Readware is not here to reply to what has been said in your post. But his paper, that I posted, is here to reply. While I appreciate your various explanations on the satellite industry, I am not clear on why you would seek to single him out, especially since what you ascribe to him, as the Skybridge paper indicates, is wrong. Everyone is entitled to views without malice being cast upon them-- and even more so if the malice is incorrectly placed.

To: Maurice Winn who wrote (3958)	4/18/1999 7:32:00 PM
From: CommSatMan	Read Replies (1) \| Respond to of 29987

Your insight never ceases to amaze me Maurice. A quick tutorial on orbital dynamics should help explain. Without getting into the math, satellites are launched into planes. Think of wrapping a string around a balloon. If you space each string some specific distance from the other, pretty soon you have several strings around the balloon. Now each separate string is a plane. Several satellites are launched into each plane. The earth rotates under the satellites. The important point is that it takes a lot of energy to move from one plane to another and typically satellites don't carry the fuel that allow them to change their orbital plane. Moving in plane takes much less fuel. Most of the fuel on board LEO satellites is used in changing the orbital altitude. The reason it does not take much fuel to maintain orbit is because these satellites are 3-axis stabilized. Torques in the orbit slot are normally controlled by gyros or more generally (because of lifetime & reliability) momentum wheels. Reaction wheels respond to disturbances on the satellite. For example, when a pointing error creates a signal which speeds up the wheel. The torque of the wheel corrects the vehicle. Secular disturbances, such as drag, cause the wheel to drift toward saturation. This is when an external torque, usually a thruster is applied. This is typically done automatically on the satellite. As a result, when in stable orbit, you don't use much fuel. What this means is that you have a satellite failure in plane x and your spare satellite is in plane y, then you have a problem. You will not have enough fuel to fill the hole with your spare because of the plane change. However, if your spare is in the same plane, then you are OK. A few comments about colliding satellites and orbital debris. If two satellites collide, think of it as an explosion where lots of shrapnel is generated. Now, all your other satellites in that plane have to fly through that debris. The probability that you could wipe out an entire plane of satellites is pretty high. That is the risk you take, if you don't control the satellites. Also, to simply the algorithms (and therefore software), you want handoff to be deterministic. The system needs to know which satellites are available and when. Probably the most important reason that you want to know where the satellite is located is so that you can provide better service. I am sure that there are billing areas and in order to ensure that the customer is billed properly for any particular area, you need to know his location. He either has to calculate it in the handset or the satellite has to figure out where he is. I think that pricing minutes according to load is a good idea, but if you look at the demographics of earth, you find most people are clustered in areas and not uniformly distributed. This will contribute to the battery loading issue I discussed and there is no easy answer. I've been a satellite engineer for over 20 years and whenever somebody says "trust me" I begin to worry. I am sure that the engineers at Loral and Motorola are learning a lot, because frankly, no one has ever flown systems with exactly these type characteristics and these type projected loads. I expect both are good and both will learn from their mistakes. From what I know about Iridium, technology is not the problem, marketing is. There is an old saying, but very true. "You have to know what business you are in." I am not sure that Iridium has figured that out yet. At least, from what I have read, their marketing seems to be disjointed and inconsistent. It is still too early to tell on G*, because they have not gone in to service. CSM PS. The amount of time a satellite can stay in orbit without any adjustments is dependent on its altitude and is a non-linear function (close to logrithmic). For example, a satellite at 400 Km at solar max has a lifetime of a couple of months, at 600 Km about 2 years, at 800Km about 60 years and 1000 Km over 600 years.

To: Maurice Winn who wrote (3958)	4/18/1999 11:26:00 PM
From: Mr. Adrenaline	Read Replies (1) \| Respond to of 29987

Opps, I spoke to soon! Hi Maurice! I prepared this for you, before I logged in: Well, if it is higgledepiggledy orbits you want, that is certainty doable. Although, probably not to the extent you are referring to. Loose orbit keeping requirements to save fuel is already part of the bag of tricks that all satellite operators use, as I alluded to in an earlier post. As it would apply to G* , the bent pipe architecture allows the satellite to just about anywhere. As long as you knew where that was, because your ground station has to know where to point its antenna. But, there really does need to be some discipline to get your assets in the optimum location, but also collision avoidance. As far as I am aware, no two man-made objects have ever gone bump in orbit, but you certainly don't want them to start, either. Teledesic is the example I love to pick on here. I'm not sure how to describe this to lay folk, but here goes. If you were an observer in space, looking "down" at the North Pole, you'd "see" all the Globalstar satellites make their most northern approaches, and the apex would trace a circle at 52 degrees north latitude. Iridium's orbit would trace a circle at 86 degrees. But the folks at Teledesic chose a perfectly polar orbit, that means the circle collapses to a point. And guess what?! All of those 288 satellite's orbits intersect! A gazillion people have pointed this out to the folks in Redmond, Washington, but there ain't hearing it. I suspect that once a "new" design surfaces out of the Teledesic-Celestri merger, you'll see something that isn't exactly polar anymore -- Motorola, in my opinion, will give the design some creditability. But the theory goes that once you have two satellites in similar orbits collide, their debris starts a chain reaction and any other satellites in similar orbits are doomed. Lot's of simulations have been run of this can of scenario. This isn't my field of expertise, but lots of folks have studied. This type of problem has a lot more creditability than, say, Leonids, in my opinion. One more thing. If I read correctly, I read in a recent post, perhaps yours, that satellites will eventually fall back to Earth. Not true. Only really low LEOs will. Once you get above the atmosphere (yes, there is atmosphere in near Earth orbits - its just is really thin, to say the least) there isn't any mechanism to degrade the orbit. In fact, energy, from the Sun, is being pumped into the orbit. So, shuttles and Space Stations will come back down, but Iridium, Globalstar, and GEOS are up there to stay. (I'm not sure where the transition is - what altitude something becomes permanently "up there" Mybe someone who has more LEO experience can chime in. But, I suppose Iridium may be under that altitude. Not sure.) Reagards, Mr. A ********* But while I'm at it, I'll say what others probably already said. Attitude control fuel is trivial. Orbit keeping is not, but it is "small" amounts compared to raising an orbit, or deorbiting. Although I think CommSatMan strecthed it a bit. Deorbiting does take fuel, but nowhere near 50 years worth. More like 1. But the point is still correct. Orbit keeping doesn't require near as much fuel as does changing an orbit.