Re: Shuttle orientation

From: Gerhard HOLTKAMP (
Date: Tue Dec 12 2006 - 08:30:06 EST

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    Dale Ireland asked about the Shuttle orientation when Roll, Pitch and Yaw are 
    given. As nobody has replied yet here is what I learned many years ago while 
    working on a Spacelab mission.
    The Shuttle Body-Axis coordinate system is defined as +X (roll axis) toward 
    the nose; +Y (pitch axis) toward the right; +Z (yaw axis) toward the bottom 
    of the Orbiter all taken from the center of mass. To specify the Shuttle 
    attitude Roll, Pitch and Yaw are given in that sequence (for historical 
    reasons) although the actually performed sequence to get from a reference 
    system toward the specified attitude would be first Pitch, then Yaw and then 
    Two reference-axis systems are in use: LVLH and M50. In LVLH (Local Vertical 
    Local Horizontal) the +Z axis is parallel to the radius vector and points 
    from the Shuttle's center of mass toward the center of the Earth. The +Y axis 
    is pointed in the direction of the negative angular momentum vector. If that 
    sounds complicated what it actually means is that in a circular orbit (which 
    the Shuttle approximates most of the time) the +X direction would point into 
    the direction of flight and +Y toward the right. So 0 Pitch, Yaw, Roll in 
    that system would be like an airplane flying. Pitch 180, Yaw and Roll 0 would 
    be Payload Bay Down, Tail Forward and Pitch 90, Yaw 0 and Roll 90 would be 
    Nose Up Left Wing Forward etc.
    The M50 system refers to inertial attitudes. It is the equatorial system but 
    referred to the epoch Mean of 1950 rather than the more modern J2000.0 which 
    is normally used in astronomy these days. If no particular reference system 
    is specified for the Shuttle attitude they probably mean LVLH as a default.
    An attitude deadband is specified for the various phases of the mission. 0.5 
    degrees in each axis would be typical if no special pointing requirements are 
    present. So the numbers Roll 0.3, Pitch 179.5 and Yaw 0.5 would be quite 
    normal on a real time display for the Shuttle attitude which was probably be 
    defined as Pitch 180, Roll, Yaw 0.
    Gerhard HOLTKAMP
    Darmstadt, Germany
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