Mars Global Surveyor
Parameter Descriptions Page
Distance from Target Center - distance from s/c to target body center in km
Emission Angle - emission angle at center of image.
The emission angle provides the value of the angle between the surface normal
vector at the intercept point and a vector from the intercept point to the spacecraft. The emission angle varies from 0 degrees when the spacecraft is viewing the subspacecraft point (nadir viewing) to 90 degrees when the intercept is tangent to the surface of the target body. Thus, higher values of emission anlge indicate more oblique viewing of the target.
Gain - gain mode is the operating mode of the camera that defines the sensitivity of the instrument (see documentation).
Image Description - Mission-generated text description of the nominal intent of the observation.
Incidence Angle - incidence angle at center of image.
The incidence angle provides a measure of the lighting condition at the intercept point. Incidence angle is the angle between the local vertical a the intercept point (surface) and a vector from the intercept point to the sun.
The incidence angle varies from 0 degrees when the intercept point coincides withthe subsolar point to 90 degrees when the intercept point is at the terminator (i.e., in the shadowed or dark portion of the target body). Thus, higher values of incidence angles indicate the existence of a greater number of surface shadows.
Latitude - center areographic latitude
Longitude - center longitude
North Azimuth - The angle in degrees clockwise from the reference axis
of the image (a line from the center to the right edge of the image)
to the direction to the north pole of the target body. If the
ORIENTATION parameter is 'MIRRORED', the image should be flipped
prior to applying this angle."
Offset - offset mode is the operating mode of the camera which specifies the additive component of the signal (see documentation).
Orientation - Because of the MOC's line-scan nature, depending on the
orientation and sense of rotation of the spacecraft and the optical
inversion properties of the camera system involved, MOC images can
either be normal or flipped left-to-right (independent of whether the
image is north up or south up.) This flag will be 'MIRRORED' if the image
should be flipped left-to-right, and 'TRUE' if it is already in normal
form. For those images having a value of 'MIRRORED', the JPEG images have been flipped left to right."
Phase Angle - phase angle at center of image.
The phase angle provides a measure of the relationship between the instrument viewing position and incident illumination (such as solar light). Phase angle is measured at the target. It is the angle between a vector to the illumination source and a vector to the instrument. If not specified, the target is assumed to be at the center of the instrument field of view. If illumination is from behind the instrument, phase angle will be small.
Spacecraft Altitude - distance from s/c to closest point on surface in km