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.
Control system designs for the shuttle infrared telescope facility
The Shuttle Infrared Telescope Facility (SIRTF) image motion compensation system is described in detail and performance is analyzed with respect to system noise inputs, environmental disturbances, and error sources such as bending and feedforward scale factor. It is concluded that the SIRTF accuracy and stability requirements can be met with this design.
History, criminology and the ‘use’ of the past
This article considers why, despite an apparent congruence of subject matter and methodologies, the disciplines of sociological criminology and criminal justice history are not more closely aligned. It contends that intellectual traffic between the two fields is not usually limited by institutional barriers, nor is it a legacy of the disciplinary antipathy which existed between history and sociology in Britain during the mid-twentieth century. Rather, it is due to the different ‘purposes’ with which sociological criminologists and criminal justice historians imbue their work and to the differing disciplinary perceptions of the relationship between the past, present and future which result from this. These different ‘purposes’ are traced via a consideration of the paths of development of the two disciplines from the 1940s. The article concludes by proposing an arena for future collaboration between criminal justice historians and sociological criminologists.