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Ref : CM-DFH4-2014-1
BEAZLEY Issue : 1

DFH 4 Series Spacecraft Date : 28 Sept 2014
Page 20 of 38

CHINASAT 9 Observation Comment /Assessment Cri

 Page 70. It seems That tha OBC and ADCE are  See comment on the left
in cold redundancy. This is a concern in case of
failure on the nominal path, The redundant
configuation will not know the context of
switch ON. What about the patches loaded ?
Implication of the FDIR.

AOCS  Page 70, The PVS in triple redundancy is in See comment on the left.
Subsystem cold redundancy. What will be the implication
in case of failure of the primary PVC ? all the
AOCS will be unpowered, how the FDIR is
managing this event ?
 Page 76.Operations mode and algorithm.  Explain the difference with The ECM mode and the FDIR.
 Is there an EDAC protection to correct soft  See comment on the left.
errors and prevent SEU effects?
OBDH  Page 82, It will be good to have on block  See comment on the left.
Subsystem diagram, all redundancies (cold, hot) and the
power distribution.
 Page 85-90. If we trust all the good wording on  To substantiate the heritage, it will be interesting to get
these pages, one can conclude that the solar feedback for the in-orbit satellites (operational performances
array is in good shape. versus predictions)..

 It will be good to know which cell type they  See comment on the left.
are using, thickness of the cover glass
minimum distance between cells and max  Can they confirm that the qual of this SA has been obtained
Solar Array voltage between adjacent cells. How the inner with the same cell on the program referenced in their
panel is populated. document fleet 2 and 9. DFH 4 makes use of triple junction
cells !
 The BPBTA is not described.  See comment on the left.

 Deployment mechanism not described.  See comment on the left.

 Which units need to be modified to  Is there a need to review unit categorization?
accommodate a 100 Volt bus?

 Just a comment.
EPS liIon and NiH2 for chinasat 9 ?
Subsystem  What is the fusing strategy ? where the fuses  See comment on the left.
are located (hopfully not inside each unit).
 Are the units and spaccraft subject to ESD  See comment on the left.
testing.
 Is the EPS and entire spacecraft tested for 
TDMA mode if applicable.
 C band. There is only two command receivers.  .Minimum redundancy.
On other programs (and the industry standard)
is a minimum of 3 command receivers..
During launch the telemetry is send only by the
Tx, there is no usage of the TWTA, same for
TC & R the GEO. May be is it due to the fact that the
Subsystem payload is only Ku. There 4 SSPAs to
compensate, nevertheless the TLM Tx
redundancy is minimum, (2 for 1 redundancy)
 Page 100 the telemetry bit rate is only 2000 
bps, (4096 bps on other spacecrafts), therefore
the spacecraft observability will be reduced
Deployment  Solar array deployment and strategy for Just a comment.
Mechanisms deployment not addressed.

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