Engineering topics
Publications and source records attributed to Thorpe, T. E..
The fixed and variable Martian features investigated by the TV experiment on Mariner 9 are described. Articles are presented concerning the dust storm of October to November over the Southern Hemisphere; global surface geodesy and cartography; geology; and the satellite astronomy.
The large volume of picture data produced by the Mariner 9 Television Experiment, in addition to providing a description of the planet Mars, emphasizes the need for in situ verification of camera performance. Such data provide the basis for initial quantitative image interpretation by confirmation of the relevance of preflight measurement. This information must be the result of planned calibration sequences rather than extraction from nominal mission photography. A lack of sufficient numbers of frames restricted Mariner camera verifications to only limited operational modes under optimal conditions and required significant extrapolation over the duration of the mission. The evidence does suggest that measurable photometric changes occurred, whereas agreement with preflight data is observed for other parameters.
Based on limited data, the Mariner 9 performance appears consistent throughout its mission. Several corrections have been provided by inflight verification sequences. A change in photometric response, which will impair precise photometric analysis, has been observed. Hence, only qualified photometric measurement appears feasible under limited conditions. Conversely, certain geometric and electronic parameters appear both measurable and congruent with preflight prediction. The role of inflight verification has been emphasized by these data to assess the in situ camera health and to promote efficient data analysis and interpretation.
Mariner 9 achieved successful photography of the stars, the purpose of the experiment being to measure camera parameters associated with point source photometry, and to examine the feasibility of using stars as invariant calibration sources and a reference for optical navigation. The Mariner 9 camera-B photography demonstrated photometric response consistency over a limited sample of data to better than 15%. Camera performance verified the ability to model vidicon response characteristics as well as demonstrated an imaging capability sufficient to permit the use of stars for photometric calibration.
Mariner near encounter pictures with maximum discriminability, applying algorithms for contrast and resolution enhancement and noise removal