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Chapter 2 Boundary

Chapter 2 Boundary Conditions 2.1 Requirements A first requirement compilation for the MSTS was proposed from the MERTIS instru- ment team at the German Aerospace Center (DLR) in spring 2007. Table 2.1 lists the reviewed requirements annotated with priorities. Further boundary conditions which must be considered are summarized in the experiment interface documents [11] and [12]. The shutter blade must cover the slit periodically as expressed in figure 2.1. Hereby, the required velocities and accelerations of the blade can be estimated and used for the selection of an applicable shutter actuation principle presented in the following chapter. Lifetime and fail safe are quoted as most important requirements. When multiplying the lifetime of two years with one closing and one opening stoke in a period of 109 ms, a total number of cycles of 1.577 · 10 9 results [5]. A required security factor of 1.25 for moving mechanical components [11] increases the number of cycles to around two billion. If the MSTS will fail, the shutter blade shall never cover the infrared light beam to guarantee at least resticted operation of the instrument. Therefore, a fail safe mechanism shall be foreseen in the MSTS design. It must be mentioned, that several requirements and priorities had changed during the design phase. Some of them had to be discussed due to installation interferences with other MERTIS components. However, table 2.1 lists the requirements which were valid during the shutter actuation principle study. 6

Contrast ratio tbd tbd Reflector surface properties (e.g. max. radiation power, absorption) Switching mode tbd tbd 10 ms close open 2 – BOUNDARY CONDITIONS FigureT 2.1: = 109 Shutter ms, f = blade 9,2 Hz switching mode. T = 20 s, f = 0,05 Hz Table 2-1: STS and LTS requirements 2.2 Integration 99 ms 200 ms 19,8 s As indicated in figure 1.3, the MSTS shall be integrated between the MERTIS En- trance Optics (MEOP) and the MERTIS Spectrometer Optics (MSOP). The light beam escapes from the MEOP and then passes the MERTIS Radiometer Focal Plate and Slit (MRAD) before it will be blocked by the MSTS blade during its closed phase. The blade shall be placed with a distance of 0.5 mm to MRAD in direction of the beam propagation. C:\Dokumente und Einstellungen\Andreas Hurni\Desktop\MSTS\Papers & Presentations\MER-KTM-TN-005-Issue-1 Draft_c_Shutter_Study_05.09.2007.doc This document is proprietary. Any dispatch or disclosure of content is authorized only after written authorization by Kayser-Threde. Kayser-Threde GmbH, Wolfratshauser Str. 48, 81379 Munich, Germany, Tel.:+49 (0) 89 / 72495-0, E-Mail: info@kayser-threde.com, www.kayser-threde.com The MRAD consists of a tiny silicon plate without providing space for furter mounting screws. Therefore, the MSTS shall be mounted at the MSOP housing. Figure 2.2 shows a bird’s eye view of the MSTS integration space. When considering the slit dimensions (tab. 2.1), it is reasonable that the blade stroke shall be oriented across the slit width for fast operation. Enough space for mounting the MSTS on the MSOP housing is provided at the right side of the window (fig. 2.2). All boundary conditions had to be considered for the study and the ultimate selection of the shutter actuation principle. close open 7

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