SPIRE Design Description - Research Services

Draft SPIRE Design Description Document
Figure 4-51 - Routing of the 300-mK strap from the cooler tip to the spectrometer BDAs inside the 2-K detector box.
The strap crosses the SPIRE optical bench.
4.13 Harness
There are five sets of harnesses for the SPIRE instrument. They are briefly described below in Table 4-7.
Table 4-7 – SPIRE harnesses.
Name Prefix Connection One Connection Two Description
FPU Harnesses F JFP, JFS, RF Filters FPU subsystems Internal connection
within FPU RF shield
Cryo-harnesses C CVV Wall bulkhead JFP, JFS, FPU Relays FPU signals
connectors
within CVV
Interconnect Harness I DCU, FCU CVV Wall bulkhead Relays analogue signals
109
connectors
from CVV wall
Warm Interconnect W DPU DCU, FCU Digital and power
Harness
interfaces
Test T EGSE HSDPU, HSFCU Test harnesses only used
during testing of
integrated electrical
systems
The cryo-harnesses represents a critical part of the design. Previous experience in cryogenic harnesses for
space application has shown that they are a common failure point. For this reason, great care is to be taken in
the thermal/mechanical deign, connector selection, fabrication and routing design.
The harnesses from the detectors to the JFET boxes also represent a critical part of the design of the
instrument. As previously stated in §3.7.3, the detectors are very susceptible to signal disturbances caused by
microphonic vibrations of the harnesses To minimise this, these harnesses have the following provisions:
(i) they are mechanically clamped at intervals of approximately 10 mm to raise the first mode of
vibration of the harnesses as high as possible;