Optimizing the fine lock performance of the Hubble Space Telescope fine guidance sensors

This paper summarizes the on-orbit performance to date of the three Hubble Space Telescope Fine Guidance Sensors (FGS's) in Fine Lock mode, with respect to acquisition success rate, ability to maintain lock, and star brightness range. The process of optimizing Fine Lock performance, including the reasoning underlying the adjustment of uplink parameters, and the effects of optimization are described. The Fine Lock optimization process has combined theoretical and experimental approaches. Computer models of the FGS have improved understanding of the effects of uplink parameters and fine error averaging on the ability of the FGS to acquire stars and maintain lock. Empirical data have determined the variation of the interferometric error characteristics (so-called 's-curves') between FGS's and over each FGS field of view, identified binary stars, and quantified the systematic error in Coarse Track (the mode preceding Fine Lock). On the basis of these empirical data, the values of the uplink parameters can be selected more precisely. Since launch, optimization efforts have improved FGS Fine Lock performance, particularly acquisition, which now enjoys a nearly 100 percent success rate. More recent work has been directed towards improving FGS tolerance of two conditions that exceed its original design requirements. First, large amplitude spacecraft jitter is induced by solar panel vibrations following day/night transitions. This jitter is generally much greater than the FGS's were designed to track, and while the tracking ability of the FGS's has been shown to exceed design requirements, losses of Fine Lock after day/night transitions are frequent. Computer simulations have demonstrated a potential improvement in Fine Lock tracking of vehicle jitter near terminator crossings. Second, telescope spherical aberration degrades the interferometric error signal in Fine Lock, but use of the FGS two-thirds aperture stop restores the transfer function with a corresponding loss of throughput. This loss requires the minimum brightness of acquired stars to be about one magnitude brighter than originally planned

Program Notes: The Newsletter of Literary Managers and Dramaturgs of America, volume 2, number 2

Contents include: a report of the LMDA Columbia Conference, Performaturgy, an announcement of the 1987 LMDA Conference, books by members, excerpts of Dr. Howard Stein\u27s keynote at the LMDA Symposium, a response to Terrance McNally\u27s article, Samurai dramaturgy, an open letter to Terrence McNally, an excerpted letter to the American Laboratory Theatre from Francis Fergusson, and life after literary management. Issue editors: Richard E. Kramer, Laurence Maslon, and Jeffrey Lawson.https://soundideas.pugetsound.edu/lmdareview/1003/thumbnail.jp

Potential Impacts of Energy Price Changes on Consumer Food Costs

This paper documents actual energy inputs for selected agricultural products for all activities from production to home consumption. It then estimates the potential food cost impacts of several alternative energy pricing schemes. The findings of this analysis indicate that modest energy price changes are unlikely to have significant impacts on food costs, contrary to some beliefs