HSTAR 11893: COS Suspend
Status Meeting
June 23, 2009
June 23, 2009
P. 1
HSTAR 11893: COS Suspend
Status Meeting
Observables
•
16:21:28
COS Suspended on OSM2 out of tolerance
– Event Status Buffer Messages:
173/16:21:28.479 COS 932
OSM2 Home Move Out of Tolerance
173/16:21:28.979 COS 934
OSM Mech Initialization Not Successful
173/16:21:29.479 COS 996
Slow Suspend Initiated
173/16:21:30.479 COS 995
Slow Suspend Complete
June 23, 2009
P. 2
HSTAR 11893: COS Suspend
Status Meeting
Analysis
•
Review of flight (FT & first recovery from safe) and ground test data
indicates a consistent off-set of ~1 step in same direction when initializing to
‘FSW Home’ position.
− Always within 1-step tolerance
LOM2POSF
LOM2ST P
$++,-$./0$$1.2
!"#$%"&'
2$.3.
72
8959
!"#(#)*)
$2-,
$++,-$.40..1.2
$++,-$.40./12/
2$.3.
52161
72
72
8959
,525
$2
25.8
$++5-./30.5143
$++5-.4$0.+14+
$++5-.6/0.31.5
2$.3/
52163
2$.34
72
71
94
,525
8959
8960
$2-,
$$-.
$$-,
(&7089:8;<8=
2$.3+
53
8958
Date
#8;>0%?@?A8<8@B
nominal step size of 100 arcsec.
16-bit coarse resolver monitors; 5 resolve counts = 1 motor step
8-bit fine resolver; ~21.4 resolver cnts = 1 motor step
June 23, 2009
LOM2POSC = OSM2 Coarse Resolver Position
LOM2POSF = OSM2 Fine Resolver Position
LOM2STP = OSM2 Motor Step
LOMFMTRT = OSM2 Motor Temp
P. 3
HSTAR 11893: COS Suspend
Status Meeting
Recommendation
• FSW Patch to re-center OSM2 ‘FSW Home’ Position
• Pros
•
•
•
•
•
Data indicates update to FSW fine resolver fiducial warranted
Preserves FUV SMS activities
Preserves FSW sensitivity to changes in initialization (maintains +/- 1step tolerance)
Maintains protection for OSM1 init protection
Reinstates 1 step tolerance
• Cons
• Due to uniqueness of flight mech, difficult to perform a bench test
• If observed error is worse, FUV timeline is affected
• Following successful initialization, command to ‘Science Home’ position
prior to FUV ramp
June 23, 2009
P. 4
HSTAR 11893: COS Suspend
Status Meeting
Other Options Considered
• Patch action response from suspend to ESB (932) only for initial recovery
• Monitor resolver response
• Patch the response back to suspend
Pros
• Preserves FUV SMS activities
Cons
• If Mech Fails to initialize, ESB (910) will be received anytime OSM2 is commanded
to an absolute position
• Removes protection for OSM1 initialization failure (Mech out-of-tolerance)
• Other protection in-place against bound mechanism
- Mech time-out, Over-heat Protection
• Rationale for Acceptance
•
•
•
June 23, 2009
OSM2 was successfully rotated 216 deg
Comparison of motor temp with equivalent move during SMOV & was in-family
The coarse resolver roll-over was within 4 resolver counts (4/5 motor step) of FSW fiducial
P. 5
HSTAR 11893: COS Suspend
Status Meeting
Other Options Considered
• Modify OSM2 ‘FSW Home’ position tolerance from +/-1 step to +/- 2
steps
• Superseded by recommended option (re-center OSM2 ‘FSW Home’ Position)
• Modify Boot Op3 Transition to avoid initialization of OSM2
• Only recommended if true OSM2 failure identified
June 23, 2009
P. 6