axe de roulis

CONT: Le repère orbital local est défini en chaque point de l'orbite par les trois vecteurs unitaires. Ces vecteurs sont construits à partir du vecteur position et du vecteur vitesse du satellite : le vecteur L est colinéaire au vecteur position P (sur l'axe centre Terre, satellite). Il définit l'axe de lacet. Le vecteur T est perpendiculaire au plan de l'orbite (vecteur L, vecteur V). Il définit l'axe de tangage. Le vecteur R complète le trièdre. Il appartient au plan (vecteur L, vecteur V) et définit l'axe de roulis. Il ne coïncide pas exactement avec le vecteur vitesse à cause de l'excentricité de l'orbite.
OBS: axe de roulis : terme uniformisé par le Groupe de travail de la terminologie de la Station spatiale internationale (GTTSSI) et par le Groupe de travail de la terminologie de RADARSAT-2 (GTTR).

CONT: The local orbital reference system is defined at each point of the orbit by three unit vectors. These vectors are derived from the satellite position and velocity vectors: Vector L is colinear with position vector P (on the axis between the Earth's centre and the satellite). It defines the yaw axis. Vector T is perpendicular to the orbital plane (vector L, vector V). It defines the pitch axis. Vector R completes the set of orthogonal axes. It lies in the plane defined by Vectors L and V and defines the roll axis. It does not coincide exactly with the velocity vector due to the eccentricity of the orbit.
CONT: Spacecraft axes. The three orthogonal axes of rotation: roll, pitch and yaw. If the spacecraft has a recognisable longitudinal axis or a specified forward direction of flight, the axes are analogous to those of an aircraft, where the roll axis is the longitudinal axis; the pitch axis is in the plane of the wings; and the yaw axis is the ""vertical"" axis, orthogonal to both the roll and pitch axes. The axes are mutually perpendicular, with an ""origin"" at the vehicle's centre of mass. For a winged spacecraft such as a Space Shuttle, the similarity with an aircraft is obvious. For expendable launch vehicles the roll axis is the axis which is vertical at launch and the other axes are more-or-less arbitrarily assigned since the vehicle rotates about the roll axis in flight. ... The axes of a cylindrical spacecraft (e.g. Apollo, Suyuz, etc.) are similar to those of an ELV [Expendable Launch Vehicle] at launch, but one orbit assume the axis-definition of an aircraft (i.e. defined relative to the pilot's seat). The axes of a satellite mirror those of an aircraft ""flying along the orbital arc"": the roll axis is aligned with the direction of travel; the yaw axis passes through the sub-satellite point; and the pitch axis is orthogonal to the other two. For a satellite in an equatorial orbit, the pitch axis is aligned approximately with the Earth's spin axis. The pitch axis is also the spin axis for the spin-stabilised satellite.
OBS: In the compilation of engineering drawings the three orthogonal axes are often labelled in Cartesian fashion: x=roll, y=pitch, z=yaw. For the three-axis stabilised spacecraft, the x-axis and y-axis are otherwise known as the east-west and north-south axes, respectively; the z-axis passes through the sub-satellite point. This leads to the definition of the box-shaped satellite's faces as follows: the ""plus-x face"" faces east; the ""minus-x face"" faces west; +y faces south; -y faces north; +z is the Earth-pointing face; and -z is the ""anti-Earth face.""