app.c Apollo Over the Moon: A View from Orbit

Appendix C

Basic Data Analysis 

Scheme for Preparation of Lunar Maps*

(1) Identification of star images on the stellar photographs, measurement of their image coordinates, and computation of the orientation of the camera in the right ascension and declination Earth-centered stellar coordinate system

(2) Computation of the orientation of the mapping camera in the stellar coordinate system by using the precalibrated relationship between the stellar and mapping cameras

(3) Transfer of the orientation of the mapping camera from the Earth-centered stellar coordinate system to the Moon-centered geographic system-this transformation involves the ephemeris and physical librations of the Moon

(4) Selection of lunar-surface points (approximately 30 per frame) on the mapping camera photographs and identification of them on all overlapping frames on which they appear

(5) Measurement of the coordinates of the selected points and correction of the points for film deformation, lens distortion, and displacement of the focal plane reseau

(6) Triangulation of groups of photographs-this computation includes the measured image coordinates, the attitudes obtained with the stellar camera, the laser altimeter data, a state vector obtained from the tracking data, and a gravity model a

(7) Assembly of the triangulated groups into a single adjusted network-the output of this computer program will be a geometrically homogeneous set of coordinate values for all selected points on the lunar surface, plus the position and orientation of each photograph in the same Moon-centered coordinate system a

(8) Preparation of small-scale maps from the mapping camera photographs

(9) Transformation of the panoramic photographs into equivalent vertical photographs for interpretation and mapping

(10) Preparation of large-scale maps from the panoramic photographs



*From Doyle (1972).


a The procedure in steps 6 and 7 was not actually followed because errors in the spacecraft tracking data proved to be much larger (up to 1.5 km) than those in the photogrammetric measurements (about 30 m).

In the control solution performed by the Defense Mapping Agency Aerospace Center, each orbital pass was triangulated separately using spacecraft tracking data as constraints. Pass 44 on Apollo 15 gave the best fit between photogrammetry and tracking data. It was adopted as the fundamental control, and all other passes were subsequently adjusted to ht.

In the control solution performed by the U.S. Geological Survey, the entire photogrammetric network was computed in a single simultaneous solution without tracking data constraints. This network was subsequently adjusted to the tracking data from pass 44 on Apollo 15.