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TRMM_readme_Navigation.shtml
TRMM Navigation

Name 
Format 
Description 
Spacecraft Geocentric
Position [3] 
3 X 4byte float 
The position (m) of the spacecraft in Geocentric Inertial
Coordinates at the Scan midTime (i.e., time at the middle pixel/IFOV
of the active scan period). The order of components is: x, y, and z.
Geocentric Inertial Coordinates are also commonly known as Earth
Centered Inertial coordinates. These coordinates will be True of Date
(rather than Epoch 2000 which are also commonly used), as interpolated
from the data in the Flight Dynamics Facility ephemeris files generated
for TRMM. 
Spacecraft Geocentric
Velocity [3] 
3 X 4byte float 
The velocity (ms ^{1}) of the spacecraft in Geocentric
Inertial Coordinates at the Scan midTime. The order of components is:
x, y, and z. 
Spacecraft Geodetic
Latitude 
4byte float 
The geodetic latitude (decimal degrees) of the spacecraft at the
Scan midTime. 
Spacecraft Geodetic
Longitude 
4byte float 
The geodetic longitude (decimal degrees) of the spacecraft at the
Scan midTime. Range is 180 to 179.999999. 
Spacecraft Geodetic
Altitude 
4byte float 
The altitude (m) of the spacecraft above the Earth Ellipsoid at the
Scan midTime. 
Spacecraft
Attitude [3] 
3 X 4byte float 
The satellite attitude Euler angles at the Scan midTime. The order
of the components in the file is roll, pitch, and yaw. However, the
angles are computed using a 321 Euler rotation sequence representing
the rotation order yaw, pitch, and roll for the rotation from Orbital
Coordinates to the spacecraft body coordinates. Orbital Coordinates
represent an orthogonal triad in Geocentric Inertial Coordinates where
the Zaxis is toward the geocentric nadir, the Yaxis is perpendicular
to the spacecraft velocity opposite the orbit normal direction, and the
Xaxis is approximately in the velocity direction for a near circular
orbit.
Note this is geocentric, not geodetic, referenced, so that pitch and
roll will have twice orbital frequency components due to the onboard
control system following the oblate geodetic Earth horizon. Note also
that the yaw value will show an orbital frequency component relative to
the Earth fixed ground track due to the Earth rotation relative to
inertial coordinates. 
Sensor Orientation
Matrix [3 X 3] 
3 X 3 X 4byte float 
The rotation matrix from the instrument coordinate frame to
Geocentric Inertial Coordinates at the Scan midTime. 
Greenwich
Hour Angle 
4byte float 
The rotation angle (degrees) from Geocentric Inertial Coordinates
to Earth Fixed Coordinates. 

