The high resolution optical spectrograph (HROS) for Gemini is currently within its conceptual design phase. The science requirements for this instrument demand spectral resolutions of 50,000 and 120,000 with entrance slits of 0.57 and 0.24 arcsec respectively. Amongst the current large telescope projects, HROS will be the only instrument of its class to be mounted at a Cassegrain station and this will pose considerable technical challenges which are described in this paper: HROS will be a spectrograph with unique characteristics, like prismatic cross-dispersion, immersed echelle grating and active compensation of flexure. HROS is expected to perform better than any other high resolution spectrograph with respect to throughput, resolution and simultaneous spectral coverage.
This paper describes a real time optimization method for optical systems. We examine the features of the global-opt optical ray tracing program, which has been developed to provide the optical engineer with interactive optimization capabilities. We illustrate the program's main features through the results of design study into an F/1.0 camera for use in a planned astronomical spectrograph. This instrument is the high resolution optical spectrograph (HROS), which is part of the international Gemini project to build twin 8 m aperture telescopes towards the end of the decade. The global-opt program allows the optical engineer to ray trace, in batch mode, up to 1 million optical systems over a period of several hours. Once complete, the engineer can explore the properties (i.e. aberrations) of these million systems in real time in order to locate the most suitable one for a particular task. This is achieved by transferring the multi- dimensional optimization problem into 3 spatial dimensions in which all the aberrations and variable parameters are represented in a 'landscape' visualization. The user is then able to interact with these moving visualizations in order to attempt system optimization. Animation of these visualizations helps the user identify any features present, which directly represent specific attributes of the design form under investigation. We have noted that these moving features resemble water waves, hence the interactive optimization process described here is made analogous to 'surfing.'
This paper describes the features of a new optimization method developed to facilitate the real time design of optical systems. Additionally we illustrate the method by describing its application to the design of an F/1.0 camera for use in a planned Astronomical spectrograph. This instrument is the High Resolution Optical Spectrograph, which is part of the international Gemini project to build twin 8 m aperture telescopes towards the end of the decade. The author describes the capabilities of the Global-Opt optical ray tracing program. This program allows the optical engineering to ray trace, in batch mode, up to 1 million optical systems. Once complete, the engineer can explore the results in real time in order to locate the merit function minima.
This paper presents the results of a camera feasibility study for the High Resolution Optical/UV Spectrograph. We develop the concept of a sub-aperture long focus camera for this instrument,. This paper additionally illustrates the advantages of a new interactive optimization technique as applied to this study.
We define the stability requirements for a high-resolution spectrograph, then show how these can be met at Cassegrain by modern materials, mechanism design, thermal control, and passive and active compensation for structural flexure. We consider the optimization of the information throughput of the spectrograph, in terms of slit-throughput, with the superb imaging performance of modern large telescopes and sites, new developments in image slicers, the prospects for adaptive-optics feeds for spectrographs, and the internal transmission of the optics. We consider in detail the requirements of, and solutions for, high resolution spectrographs for two large telescope projects - the 6.5 m MMT conversion and the two Gemini 8 m telescopes.