The first example was airborne. The second example was in Earth orbit. Now we go to Mars! During the latter years of the twentieth century and the beginning of the next, NASA will send a small vehicle to Mars. It will roam the surface to some extent and carry out scientific investigations to determine such things as the past or present presence of water and the composition of various minerals. This chapter presents some thoughts on possible designs for imaging spectrometers that can perform these interesting tasks economically and efficiently. Some of the thoughts arose during a study I made with the Infrared Solutions Company and the Jet Propulsion Lab. I am indebted to Paul Kruse of Infrared Solutions and Marc Foote of JPL for comments, contributions, and criticisms.
This study is a useful example of the development of criteria, requirements, and designs from a set of desires rather than a set of rigorous specifications. It is a classic case of âI wantâ and âI can.â It is iteration to infinity with slow convergence. It is highly realistic of many design problems in the field!
16.1 Requirements Definitions
A constant trade-off exists between what is wanted and what can be done. People want more, and technology responds. Technology advances, and people want more. In the computer field, new memory was very desirable, and it became available. Then, the different applications used more memory, and more memory was required.
One version of the requirements is to carry out spectroscopy with resolution of about 1 wavenumber with a spatial resolution of about 1 Î¼m through the visible and infrared spectral ranges over a wide field of view. This sort of requirement arises from the ever-present curiosity of scientists to know more and better. And given a little more information, even more is desired. We can close down on this some, however, because it is clear that this dream is unattainable within the limitations of space, power, and weight of a vehicle that will make the trip. These are approximately 1 W, 1 kg, and a data rate of 10 kHz. This latter is the data rate the antenna to Earth can support.
So, can something useful be obtained with more modest spatial and spectral resolution and smaller spectral and spatial extents?
Online access to SPIE eBooks is limited to subscribing institutions.