Active Image Stabilization for Shuttle-Based Payloads
This paper presents a pointing performance analysis of the Space Infrared Telescope Facility (SIRTF) as a generic example illustrating the fundamental dynamics and control problems related to optical instruments that are, or will be, flown mounted on the Space Shuttle. The disturbance level on the Shuttle, and slew requirements of the payload itself, along with the limitations of the present instrument pointing system (IPS) is found to seriously limit the pointing accuracy of optical payloads. The implementation of an active image stabilization (AIS) system, using an active secondary mirror, is shown to provide substantial improvement in performance. Two control strategies are presented, using IPS-mounted rate integrating gyros only, or in conjunction with a focal plane sensor feedback loop.
Orbital Operations with the Shuttle Infrared Telescope Facility (SIRTF)
The Shuttle Infrared Telescope Facility (SIRTF) is a cryogenically-cooled, 1-m-class telescope that will be operated from the Space Shuttle as an observatory for infrared astronomy. Over the 2- to 200-μm band, SIRTF will be 100 to 1000 times more sensitive than existing infrared facilities. This paper discusses the scientific constraints on and the requirements for pointing and controlling SIRTF as well as several aspects of SIRTF orbital operations. The basic pointing requirement is for an rms stability of 0.25 arcsec, which is necessary to realize the full angular resolution of the 5-μm diffraction-limited SIRTF. Achieving this stability requires the use of hardware and software integral to SIRTF working interactively with the gyrostabilized Shuttle pointing-mount. The higher sensitivity of SIRTF, together with orbital and time constraints, puts a premium on rapid target acquisition and on efficient operational and observational procedures. Several possible acquisition modes are discussed, and the importance of source acquisition by maximizing the output of an infrared detector is emphasized. The ability of the pointing-mount to slew the telescope over a range of angles is discussed, including its capability for executing raster scans over limited areas. Both minimum-time scans and constant-rate scans, which may take significantly longer in some cases, are discussed.
Mandating Identity: Citizenship, Kinship Laws and Plural Nationality in the European Union
For over a century it has been the case that a person exists, at least for legal purposes, only after she has been recognized by the state. As a unique element of this acknowledgement, nationality has also been an essential component of individual identity. Now, under pressure from a variety of directions, the nature of the link between state and individual is changing, with as yet unclear implications and long-term effects. In this original and insightful analysis, Eniko Horvath focuses on three processes of legal evolution in Europe that affect the meaning of membership and individual identity: the increasing salience of supranational culture and rights; kinship; legislation privileging non-nationals with linguistic, cultural, and ethnic ties to a given state; and the emergence of plural nationality as an acceptable (and even welcome) phenomenon.The author's treatment is notable for its informed appreciation of both the content of relevant European and national laws and the ways in which these laws are embedded in particular social and political frameworks. In addition to extending the legal theory on citizenship and nationality, the analysis draws on sociology, social psychology, and political theory to anchor its insights and recommendations. After two in-depth chapters introducing the complexities of the subject matter, three distinct but interwoven chapters show how each of the three processes has unfolded in a given context, offer detailed explanations and suggestions as to why each development has occurred in the manner that it has, and discuss the legal, political, and sociological issues raised by the particular development.A comprehensive reference section with extensive lists of laws, cases, and scholarship concludes the volume. It is likely that this book will come to be recognized as a foundational work in the legal analysis of the concept of cultural identity, and especially its role in setting norms of membership, as that way of seeing the world becomes ever more clearly defined in coming decades. It is sure to be not only studied and cited by academics and legal theorists, but of special value also to policymakers in the areas of nationality and citizenship.