Specifications

Gaia
GAIA.ASU.SP.ESM.00007
Issue 2.00
Page 34 of 79
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GAIA.ASU.SP.ESM.00007 (Avionics SCOE Req Iss 2).doc
3.6.5 Combined CPS Interfaces
The Gaia Combined CPS subsystem is controlled and monitored by the Spacecraft Electrical Interface Unit
(EIU) and comprises:
18 x Latch Valves (LV) operating in (9+9) cold redundancy: (8+8) for the Thruster lines, (1+1) for the Tanks
18 x Latch Valves status micro-switches operating in (10+10) cold redundancy
16 x Flow Control Valves operating in (8+8) cold redundancy to control 2 banks of (8+8) 10N Thrusters
4 x Pressure Transducers for Tank Pressure monitoring
AVI-311/GSE-SYS-405/T
The Avionics SCOE shall provide interfaces to the EIU to simulate the presence of the Combined
CPS subsystem.
AVI-295/EIU-701,EIU-702/T
The CPS Interfaces shall comprise the following functions.
LV Command Pulse Acquisition (18 LV, 1 x OPEN and 1 x CLOSED commands per Latch Valve)
LV Status Simulation (1 micro-switch simulation per Latch Valve)
FCV Command Pulse Acquisition (16 FCV)
4 x Pressure Transducer Simulations
3.6.5.1 CPS LV Command Pulse Acquisition
AVI-327/EIU-706/T
The LV Command Pulse Acquisition interface shall be provided by fixed loads (36x) simulating the
OPEN and CLOSE coils for each of 18 LV.
AVI-328/EIU-706/T
LV Command Acquisition interface shall conform to the following specifications: [AD06] Table 3.5-35
(Latch Valve Interface Specification - Receiver Circuit Specification).
AVI-382/GSE-SYS-405/T
LV Command Pulse Acquisition shall provide Latch Valve state (OPEN/CLOSE) and measurement of
the Command pulse width, as detailed below:
Pulse WIDTH resolution
100.0 µs - for nominal 50-100ms pulse
Latch Valve STATE OPEN = acquisition of a 'valid' pulse on the corresponding LV
OPEN coil
CLOSED = acquisition of a 'valid' pulse on the corresponding
LV CLOSE coil
A 'valid' pulse shall be as defined in [AD06] Table 3.5-35.
Table 3.6-2: CPS - LV Command Pulse Measurement Specification
AVI-1886/CREATED/T
Measurement of LV Command pulses shall be triggered asynchronously by detection of an incoming
pulse with the following specifications:
• Pulse Width > 1ms
• Pulse Amplitude > 10.0V
AVI-389/CREATED/T
LV STATE (OPEN/CLOSE) shall be made available to the RTS.
AVI-2768/EIU-3393, GSE-SYS-761/T
It shall be possible to acquire the LV pulses simultaneously on all channels.