Abstract: The road from the drawing board to the launch pad is always challenging and contains lots of surprises. In traveling down it, the instrument designer learns many lessons, both from things that work well and from those that cause problems. The documentation of this experience is an important service to be performed for the benefit of those who will design our next generation of instruments. This paper is offered in that spirit. The soft x-ray telescope (SXT) is a component of the Japanese Solar-A satellite mission that was launched in August, 1991 for the study of solar flares. The SXT employs glancing incidence optics, a CCD detector, and a pair of filter wheels for wavelength selection. A temperature compensated metering structure keeps the telescope in focus over the range of temperatures expected in orbit. A coaxially mounted lens system operating in visible light provides images of sunspots and magnetic plages as well as aspect information to aid in aligning the soft x-ray images with those from the Solar-A hard x-ray telescope and from ground-based observatories. The instrument electronics are microprocessor based, and are embedded in a tightly integrated distributed system. The control software is divided between the instrument microprocessor and the spacecraft's control computer. The discussion concentrates on the optical, mechanical, and detector systems of the SXT design. !0
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