Conference 7.286::space

They still need to reenter on an orbit that takes them over the landing area.
In the old days they were more particular due to the uncontrollability once
reentry was begun. With the shuttle they can compensate for being one orbit 
off but they can't glide across the entire country once in the atmosphere.
They also try to make it so that the lighting conditions are certain ways to 
improve visibility. Rentry to Florida is the backup plan tomorrow if 
conditions are still not perfect at Edwards. This would be a different orbit 
than Edwards if needed. You still need to reenter "into the wind" so you want 
to be "close" to the landing area on your orbital path.

  I agree with .1 except that the shuttle needs to "land" into the wind, not
"reenter" into the wind (or as close as possible into the wind). Other than
that, I agree. 

  George 

    The reentry window is influenced by a number of factors:
    
    1) Cross range capacity of the orbiter (approximately 1200 miles, but
        this varies depending on wieght and cg placement.  The path does
        not have to be "over the landing area", but must take the orbiter
        within the cross range window (with a safety margin).
    
    2) Flight path.  Reentry to either Edwards or KSC can be made on either
        ascending or decending orbital nodes.  For example, approaches to
        KSC from high inclination orbits can take the flight path over 
        the central US down to Florida or up through Central America
        across the Gulf of Mexico.  The preferable path is over the US in
        order to maintain radar and HF radio contact (after blackout).
        Although the actual landing is made "into the wind" (or a
        reasonable cross wind), the terminal glide from aproximately 100K
        ft to the heading alignment circle (for final approach) is made
        based on energy management (not wind direction) and is calculated
        by radar data, flight data from the orbiters air probes, and TACAN
        navigational data.
        
    3) Atmospherics.  Once entering the atmosphere, the flight path can be
        affected by the jet stream and/or other high altitude weather.  In
        all cases, the flight path is selected so that the orbiter will not
        encounter moisture ladened clouds.  The tiles are most vunerable
        to damage during approach (far more so than ascent, where the tiles
        are subject to air pressure for a shorter period of time).
    
    4) Consumables.  Once the payload bay doors are closed, the orbiter has
        approximately a 2.5 hr window to operate in (without the radiators
        and primary cooling loop operating).  This provides only a 2 orbit
        capability which covers 2 attempts at the primary landing site and
        usually one at the secondary.  After a second "waive off"  the
        payload bay doors are usually opened and the flight extended
        another day.
    
      All in all, there is some flexibility in the reentry opportunities. 
    But if you compare it to the Mercury, Gemini, and earth orbital
    Apollos where in an emergency you could plunk down in just about any
    ocean or, for that matter, land mass, there are less landing
    opporunities.  (But in the shuttle, the view is much more spectacular!)

Sorry, should have been a smiley face around the "reenter" comment. I simply 
meant that the forward momentum of the ship will cause it to travel through 
the upper atmosphere generally along the orbital path. My "into the wind"
comment was referring to the relative wind due to reentry. They tend to refrain 
from making any Mach 20 turns so you want the landing site to be out in front
of you when reentering. Touchdown is into the wind as with a normal plane and 
this helps reduce the actual groundspeed at touchdown.