From: <>
Date: Fri, 23 Jun 1995 22:25:04 -0400

Neil T. Clifford said:

>As Bill Bard has said NASA certainly don't
>seem to mind. I suspect that they would prefer the very final appraoch
>(last 10 metres) to be in sunlight possibly. One limiting factor (and
>more important I guess) may be the requirement for both vehicles to be
>able to be in contact with their respective control centres throughout.

While daylight is certainly preferable to night time for orbital rendezvous operations it is not a factor for the Mir missions. There is a much higher requirement for Mir to be in contact with one of its ground stations so ground controllers can monitor mir's systems and perform backup commands if necessary. All of the Mir tracking stations are now located in Russia (no more tracking ships around the world from the era of unlimited budgets!) and only a given set of orbits each day will go over those stations. So that's the constraint which determines the crew's schedule during critical activities, and indirectly the wake/sleep cycle for the U.S. astronauts on any mission which docks with Mir!

Russia does operate two relay satellites, similar to TDRS, but they're rarely used because Mir's attitude has to be changed from solar inertial (best power generation for the solar panels) to an attitude where its high gain antenna is pointed towards the Luch or Altair satellites.

The shuttle normally does not have any ground track constraints because of TDRS, but it's highly desirable for the actual docking to occur when the shuttle is in range of TDRS (e.g. outside of the ZOE). Currently NASA is examining using the out of view TDRS (TDRS-1 and soon TDRS-3) for some specialized communications during the shuttle-Mir missions to help sew up the ZOE.

Philip Chien, Earth News - space writer and consultant PCHIEN_at_IDS.NET

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 Roger, go at throttle up         Space the final frontier
Received on Fri Jun 23 1995 - 22:45:39 UTC

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