Astronomy 392E
ASTRONOMICAL INSTRUMENTATION

D. Jaffe and J. Lacy
Spring 1998, TTh 9:30

This course will teach the fundamentals of the design and construction of modern astronomical instruments. We will cover key aspects of some of the most important topics in the field: optics and optical design, mechanical design and machining, electronics design and fabrication, real-time computer control, project planning, and performance analysis. The course will be hands-on using both hardware and simulation/CAD software. Students will work together in groups to carry out the topical segments and in teams to build a computer-controlled optical instrument. Physics and engineering students with graduate standing are welcome. Enrollment will be limited to 20. For further information, contact Professor Jaffe (471-3425, dtj@astro.as.utexas.edu) or Professor Lacy (471-1469, lacy@astro.as.utexas.edu).

Target Population:

This course will be for graduate students in astronomy and related areas. We are very interested in having physics and engineering students take the course. Students in these areas will have the opportunity to learn about the problems of astrophysics and have a new venue in which to explore their talents and abilities. These students are important to us for the different attitudes and skills they will bring to the work.

Organization:

Students will be divided into "project teams." Each of the 4-5 students also belongs to a "segment group" consisting of one student from each project team. Over the course of the semester, the project team will work together on the design, construction, and testing of a small but sophisticated astronomical instrument. The segment groups will work together to master the different skill areas which will enable the teams to carry out the project. Since each project team will have members in four different segment groups, after only a few weeks, each team will collectively have completed the material for the course and have the expertise necessary to do the project.

Practical Segments:

We have divided the course material into four segments. Each segment will include a reading assignment, problems or exercises, a self-test, and a workshop or laboratory exercise. The segments will normally take around three weeks, but this will be flexible. Students will do the reading and the self-test individually. The segment group will work together on the problems and the lab exercise. The group can come together with an instructor for tutorial or mini-lecture on difficult aspects of the topic, as needed. The segments will be strongly (but not exclusively) focused on knowledge and skills needed to carry out the instrumentation project. We will always provide information about where to learn more in each area.

Project Planning: At the beginning of the course, we will have several lectures and exercises on this subject. Topics will include the elements of group organization, scheduling, record keeping, reviews, procurement, and budgeting.

  1. Mechanical Design and Machining: The reading assignments and the exercises will deal with basic mechanical design. We will discuss materials, production techniques, tolerances, and strength and flexure analysis. We will explain the basic techniques involved in making mechanical drawings and give the students the opportunity to teach each other the use of a CAD program for producing the drawings (AutoCad LT). There will be a basic course in machine-shop techniques. It will emphasize work with the milling machine. The segment will consist of 6-10 hours of instruction plus additional work time. This segment will be taught by a McDonald Observatory instrument-maker machinist.

  2. Optical Design and Optics: This segment will teach the basics of optics needed to design a grating spectrometer. The materials will deal with optical systems employing lenses and mirrors. Also covered will be the grating equations and some descriptive material on interference filters. The segment will include a pencil and paper analysis of a simple system and a more elaborate analysis using simulation/CAD software (Zemax). Experimental work will involve the use of lenses, mirrors, and gratings. It will include exercises in alignment of optics and an empirical look at aberrations.

  3. Electronics: This segment will include the basics of circuit design, various optional reading, paper problems, and breadboard labs. We will construct some circuits and make use of CAD/simulation software (CircuitMaker).

  4. Computer Interface: This segment will involve interfacing the computer to the real world (i.e., the instrument). There will be reading about how digital-to-analog and analog-to-digital converters work, as well as some generic reading about bus architecture. There will be practical exercises in interfacing to A/D, D/A boards, stepper motors, and other devices. Instrument control will be done using LabView and/or C++.

The Project:

The project the teams will carry out this spring is the construction of an optical grating spectrograph. It will be a scanning monochromator with the grating operated under computer control and a single solid-state detector.

All project groups will build the same kind of instrument during the semester. The teams will start out by reading an outline of a scientific problem and doing a set of paper exercises to clarify the relative merits of various technical options for a solution. They will then come up with a preliminary design which they will present at a Preliminary Design Review to the instructors and a selection of McDonald technical staff. The team will then construct, debug, and evaluate their instrument. They will present a report and make a demonstration of its function.