Maurice, a message regarding batteries from Readware on AOL.
Those who don't follow the Loral board, Readware is a very knowlegeable expert in satellite communications. He is a consultant in the satellite industry and contributes to the Motley Fool board on AOL, He knows his stuff.
Subject: Re: Batteries and LEOs
Date: Thu, Oct 9, 1997 21:25 EDT
From: Readware
Message-id:
You are right about battery life. It has to be kept at 65% capacity on a LEO. There will be times, then, when a LEO will not be providing telephony access to an area. Since a LEO will not always be in the sunlight, its solar panels will not always be charging the battery. Economies of traffic require that high teledensity areas (= high population) be assured access first, so a LEO may be turned off when in orbit over a thinly populated area, denying
it telephony coverage in favor of a high density area.
Obviously the outage time will be minimized and curved as telephony traffic is tracked over a period of time. I know of no first generation constellation that can guarantee 24 hour uninterrupted telephony. The matter could be resolved in a second generation system with more LEOs, or improved solar panel conservation capabilities. Again, you must remember in the first generation (either Iridum or Globalstar) that a constellation has LEOs in a plane,
with different planes situating LEOs over different areas, so that as one LEO moves away from a low density area, another LEO with battery power capacity (that the exiting LEO in the higher or lower plane no longer had) will move in to take its place. That also will minimize the effect of favoring a high teledensity area for a low teledensity area. The issue you address is not something new, and has been worked on for quite some time. Economies of
traffic, where the money is to be made, is what governs satellite systems, and will be no different in this case. As solar panel capacities or in-orbit battery conservation efficiencies occur, this problem will be increasingly minimized. I do know in repeated and repeated simulated tests Globalstar has tried to anticipate every battery downtime situation imaginable to minimize service interruption as much as possible. |
