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SPIRE Design Description - Research Services

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Draft <strong>SPIRE</strong> <strong>Design</strong> <strong>Description</strong> Document<br />

Figure 4-51 - Routing of the 300-mK strap from the cooler tip to the spectrometer BDAs inside the 2-K detector box.<br />

The strap crosses the <strong>SPIRE</strong> optical bench.<br />

4.13 Harness<br />

There are five sets of harnesses for the <strong>SPIRE</strong> instrument. They are briefly described below in Table 4-7.<br />

Table 4-7 – <strong>SPIRE</strong> harnesses.<br />

Name Prefix Connection One Connection Two <strong>Description</strong><br />

FPU Harnesses F JFP, JFS, RF Filters FPU subsystems Internal connection<br />

within FPU RF shield<br />

Cryo-harnesses C CVV Wall bulkhead JFP, JFS, FPU Relays FPU signals<br />

connectors<br />

within CVV<br />

Interconnect Harness I DCU, FCU CVV Wall bulkhead Relays analogue signals<br />

109<br />

connectors<br />

from CVV wall<br />

Warm Interconnect W DPU DCU, FCU Digital and power<br />

Harness<br />

interfaces<br />

Test T EGSE HSDPU, HSFCU Test harnesses only used<br />

during testing of<br />

integrated electrical<br />

systems<br />

The cryo-harnesses represents a critical part of the design. Previous experience in cryogenic harnesses for<br />

space application has shown that they are a common failure point. For this reason, great care is to be taken in<br />

the thermal/mechanical deign, connector selection, fabrication and routing design.<br />

The harnesses from the detectors to the JFET boxes also represent a critical part of the design of the<br />

instrument. As previously stated in §3.7.3, the detectors are very susceptible to signal disturbances caused by<br />

microphonic vibrations of the harnesses To minimise this, these harnesses have the following provisions:<br />

(i) they are mechanically clamped at intervals of approximately 10 mm to raise the first mode of<br />

vibration of the harnesses as high as possible;

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