Preliminary Results from Skylab Experiment T002, Manual Navigation

Abstract

The Skylab Experiment T002 Manual Space Navigation Sightings was successfully completed on Skylab missions II and III. Performing the experiment inflight were Major Jack R. Lousma, pilot SL-II, and Lt Colonel William Poage, pilot SL-III. The purpose of T002 was to investigate the feasibility of a manual navigation system for use in back-up navigation applications and to investigate the capability of man to make the necessary celestial observations in terms of accuracy and precision under the conditions of long term space flight. The experiment, co-sponsored by NASA Ames Research Center and the United States Air Force, involves the use of a handheld space stadimeter for measuring altitude as a function of earth horizon curvature and a handheld space sextant for measuring space observable angles such as star to earth horizon and star to moon. This study provides an analysis of the Air Force functional objectives—the sextant starhorizon measurements and stadimeter altitude measurements. Included are the preliminary accuracy and precision data, horizon characteristics, and instrument performance. During Skylab II, 378 sextant sightings and 88 stadimeter sightings were made. These data resulted in definitive horizon altitude determinations as well as an evaluation of the ranging performance of the space stadimeter. Star to earth horizon sextant sightings yielded mean observable horizons heights at 9.63 km for the apparent earth 33.34 km for the dark to light transition layer at the base of the airglow horizon, and 95.13 km for the top of the air-glow horizon. Standard deviation for these horizons ranged from approximately 8.5 to 2.2 km during the sighting periods. The mean spacecraft height error for stadimeter sightings was 6.77 nm with standard deviations in the range of 2.28 to 6.45 nm.