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The plane tangent to celestial sphere for extrasolar objects; On the plane of reference, a zero-point must be defined from which the angles of longitude are measured. This is usually defined as the point on the celestial sphere where the plane crosses the prime hour circle (the hour circle occupied by the First Point of Aries), also known as ...
Here, n = n x, n y, n z is a vector pointing towards the ascending node. The reference plane is assumed to be the xy-plane, and the origin of longitude is taken to be the positive x-axis. k is the unit vector (0, 0, 1), which is the normal vector to the xy reference plane. For non-inclined orbits (with inclination equal to zero), ☊ is undefined.
It is expressed as the angle between a reference plane and the orbital plane or axis of direction of the orbiting object. For a satellite orbiting the Earth directly above the Equator , the plane of the satellite's orbit is the same as the Earth's equatorial plane, and the satellite's orbital inclination is 0°.
Note: This page uses common physics notation for spherical coordinates, in which is the angle between the z axis and the radius vector connecting the origin to the point in question, while is the angle between the projection of the radius vector onto the x-y plane and the x axis. Several other definitions are in use, and so care must be taken ...
The attitude of a lattice plane is the orientation of the line normal to the plane, [12] and is described by the plane's Miller indices. In three-space a family of planes (a series of parallel planes) can be denoted by its Miller indices ( hkl ), [ 13 ] [ 14 ] so the family of planes has an attitude common to all its constituent planes.
The perifocal coordinate system (with unit vectors p, q, w), against the reference coordinate system (with unit vectors I, J, K) The perifocal coordinate (PQW) system is a frame of reference for an orbit. The frame is centered at the focus of the orbit, i.e. the celestial body about which the orbit is centered.
The axes of the original frame are denoted as x, y, z and the axes of the rotated frame as X, Y, Z.The geometrical definition (sometimes referred to as static) begins by defining the line of nodes (N) as the intersection of the planes xy and XY (it can also be defined as the common perpendicular to the axes z and Z and then written as the vector product N = z × Z).
The user may choose to replace the inclination angle by its complement, the elevation angle (or altitude angle), measured upward between the reference plane and the radial line—i.e., from the reference plane upward (towards to the positive z-axis) to the radial line. The depression angle is the negative of the elevation angle.