Gaia
GAIA.ASU.SP.ESM.00007
Issue 2.00
Page 14 of 79
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GAIA.ASU.SP.ESM.00007 (Avionics SCOE Req Iss 2).doc
3.5 Timing, Synchronisation and Acquisition Requirements
3.5.1 Time Synchronisation
The overall timing requirements for Gaia EGSE are described in Section 5 of the Gaia EGSE ICD [AD01].
AVI-2937/CREATED/T,R
The Avionics SCOE Controller local time shall provide a UTC reference time source (T
REF
) to all other
EGSE requiring synchronisation to it.
AVI-3391/CREATED/T,R
The source of T
REF
shall be reference time with a granularity of better than 1us.
AVI-3390/CREATED/T
The Avionics SCOE shall provide IRIG-B time-coded signals to the 1553, SpaceWire and PacketWire
BUS interface cards for time-stamping of internal spy acquisitions.
AVI-2939/CREATED/T
All Avionics SCOE data acquisitions shall be time-stamped with T
REF
.
AVI-2948/CREATED/T,A
All data acquisition time-stamps of the Avionics SCOE shall be accurate to within 1us of T
REF
, this
including internal spy of the 1553 and SpaceWire cards.
AVI-3113/CREATED/T
The Avionics SCOE shall provide the Standard Network Time Protocol server function on the EGSE
local LAN for time synchronisation of all Gaia EGSE connected to it.
3.5.2 Synchronisation
AVI-1653/GSE-SYS-396/I,R
The Avionics SCOE instrumentation platform shall be synchronized to an internal clock, with a
stability better than 0.01 ppm (1.0+E10
-8
)
AVI-1656/CREATED/T
The Avionics SCOE shall provide synchronisation to the Real Time Simulator, Dynamic FPA
Simulator and Star Tracker SCOE's across the Real Time Network (RTN) - see Section 3.8.
AVI-1657/CREATED/T
The synchronisation shall be in the form of RTN global interrupts synchronized to the Major Frame
and Minor Frame control cycles of the Gaia Central Software (CSW).
AVI-2835/CREATED/T
Synchronisation to the CSW control cycle shall be achieved by detection of the Major Frame (1Hz)
and Minor Frame (8Hz) synchronisation mode code transmissions at sub-addresses TBC and TBC
respectively of the CDMU-SVM 1553 BUS.
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