SPIRE Design Description - Research Services

Draft SPIRE Design Description Document
3. To provide adequate EM shielding and stray light shielding to the photometer and spectrometer such
that the detectors see no spurious sources of EM power.
The structure is comprised of three main components; the Spire Optical Bench (SOB), the photometer cover
and the spectrometer cover. The Spire Optical Bench is machined from a single block of Al-6061
approximately 675 mm long (aligned with the Spacecraft Z axis, See Figure 2-2) by 410mm high (aligned in
the X axis) and 50 mm thick. All the optical components of the spectrometer are located on the +Y side of
the SOB while all the components of the photometer are located on the –Y side. The mass of the SOB is
minimised by machining ribbed pockets (nominally 70 x 70 mm) on both sides. The nominal thickness of
the ribs is 2 mm and the centreline plane of the bench is 2 mm (TBC) as shown in Figure 4-40-A.
Optical Component
SPIRE OPtical Bench
8-32 UNC
Thru bored
Hollow dowel pin
8-32 UNC Helicoli Screw Insert
3
70 Nom.
A B
Figure 4-40 Details of (A) SOB lightweighting and optical component interfaces and (B) cover joint design.
The optical components are located on the bench by hollow dowel pins and 8-32 UNC screws provide
positive the mechanical attachment. The SOB is manufactured and toleranced in such a way so that the
position of the components located on the bench are in the correct position when the bench has undergone
the contraction during cooling from room temperature to the nominal operating temperature of 4K.
Figure 4-41 - FPU/HOB interface strut.
The ribbed design of the SOB gives it excellent bending stiffness but it will have a relatively low torsional
stiffness. The required torsional stiffness is achieved through the photometer and spectrometer covers. The
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