LOGO.049
Hubble Space Telescope Program
HST
MOSES
Goddard Space Flight Center
ROC Limit Violation
DOY 215 / 2009
and
Preliminary Impacts of the NCS
Operation and Post SM4 Load
Aug. 4, 2009
S. Krol
1
Hubble Space Telescope Program
HST
MOSES
Goddard Space Flight Center
ROC Violation Event
● On DOY 215 12:30 – 12:45, the Battery Rate Of Charge Limit was
violated for 544 seconds (counts) while the system was in full
charge
– Full Charge limit = 21.3A – 13.79A = 7.51A
– During a maneuver the ROC limit (ROCLIM) is reduced by
MANROD = 15A
• ROCLIM = 7.51A – 15A = -7.49A
– The minimum ROC was -80A
– A violation of ROCLIM for 800 sec (counts) results in soft safing with
loadshed.
● This ROC limit violation was due to a large vehicle maneuver and
SA slew which resulted in near zero SA output
● The duration of the violation was influenced by the duration of the
maneuver / SA slew and the increased electrical load with the NCS
operating
2
Hubble Space Telescope Program
HST
MOSES
Goddard Space Flight Center
ROC and Error Counters
Trickle Chg Elapse Timer
Battery ROC
ROC Limit
ROC Error Count = 544 sec
3
Hubble Space Telescope Program
HST
MOSES
Goddard Space Flight Center
Solar Array Output
Vehicle Maneuver / SA Slew
4
Hubble Space Telescope Program
HST
MOSES
Goddard Space Flight Center
MEGG Timeline
Time of ROC Limit Violation
5
Hubble Space Telescope Program
HST
MOSES
Goddard Space Flight Center
Frequency of ROC Error Count Events
● ROC Error counts have hit the 400-500 counts range several times
this year.
– 2009.051 06:37:53.581 427 counts
– 2009.053 11:20:17.585 339 counts
– 2009.156 06:13:53.777 195 counts
– 2009.204 14:33:53.868 535 counts
● What is different this year versus years in the past?
– From Jan 2006 until the implementation of FSW 3.2A in Jan 2009,
the ROC test was desensitized due to the use of the ACR for Taper
Charge
– 2005 highest was 444
– 2004 highest was 408
This information is courtesy of Brian Vreeland.
● Increased load of the new and recovered Science Instruments
combined with the NCS operation will increase the frequency and
durations that the ROC limit violations unless the limit is adjusted
6
Hubble Space Telescope Program
HST
MOSES
Recommended Actions
Goddard Space Flight Center
Near term action:
● Disable the ROC test until the limit change can be prepared and
uplinked
Long term action:
● Adjust the ROC delta for maneuvers (MANROD) to accommodate
the full load
– As this event and others have demonstrated, the SA output can
drop to zero and the batteries assume the full load
– Present Limit for Full Charge with Maneuver:
• ROCLIM = FULROC – ROCTHR - MANROD
• ROCLIM = 21.3A - 13.79A – 15A = -7.49A
– Proposed Change for Full charge with Maneuver:
• ROCLIM = 21.3A – 13.79A – 97.51 = -90A
– Predicted full-up electrical load with NCS operating =~90A
7
Hubble Space Telescope Program
HST
MOSES
Goddard Space Flight Center
Recommended Actions
Long term action (continued):
– ROC Limit for Full charge with Off Nominal Roll and Maneuver:
• Used when the “Type 28” command is issued
• ROCLIM = ONRROC – ROCTHR - MANROD
• ROCLIM = 14.3A – 13.79A – 97.51 = -97A vs -14.49A
– ROC Limit for Trickle charge with Maneuver:
• ROCLIM = TRKROC – ROCTHR - MANROD
• ROCLIM = -90A – 13.79A – 97.51 = -201.3A vs -118.79A
– ROC Limit for Eclipse with Maneuver:
• ROCLIM = ECPROC – ROCTHR - MANROD
• ROCLIM = -90A – 13.79A – 97.51 = -201.3A vs -118.79A
● No changes proposed to the ROC error counter (ROCERL) = 800 sec
8
LOGO.049
Hubble Space Telescope Program
HST
MOSES
Goddard Space Flight Center
Impacts of the NCS Operation
and Post SM4 Load
9
Hubble Space Telescope Program
HST
MOSES
Goddard Space Flight Center
Impacts of the NCS Operation and Post SM4 Load
● Predicted electrical load increases from the pre-SM4: 2125 watts to
2610 watts (SI powers have been updated but not fully verified)
– Present electrical load is ~ 2480 watts with NCS in surge and
NICMOS Safed
● Battery temperatures are above the redundant heater set-points
and hovering between -2 and +1 deg C since the NCS restart on
DOY 213 / 09
– Temperatures could further increase as the load increases and with
beta peaks
 PSMM energy balance analysis indicates that the power system
can presently support the full-up SI load, including NCS / NICMOS,
with SA incidence angles of 20.6 deg (planned 18.05 deg)
10
Hubble Space Telescope Program
HST
MOSES
Electrical Load Capability and Projected Full Load
Goddard Space Flight Center
PROJECTED HST LOAD CAPABILITY (Case 11)
SA INCIDENCE ANGLES 0, 5.8, 15, 20 and 25 DEG.
3500
2 Batts reach charge cut-off, 5 minutes of trickle charge
Orbit day durations were based on an approximation of the
Beta Angle and may not reflect the actual dates for the
peaks.
3400
3300
2-SIGMA PEAK
3200
3100
Bus Load (Watts)
3000
2900
2800
2700
2600
MEAN
2500
SM4
2-SIGMA PEAK
2400
MEAN
2300
2200
2100
2000
1900
2008
2-SIGMA PEAK
MEAN
NICMOS, ACS (Side 1 SBC),
WFPC2, NCS
(Case 11)
NICMOS = Norm Op
NCS = Norm Op (7100 RPS)
STIS = Norm Op (CCD On,
MAMAs On)
ACS = Norm Op, Side-1, 2-Ch
W FC3 = Norm Op Side2
COS = Norm Op (FUV, NUV)
2009
2010
NCS=Idle (6600 rps)
NICMOS=safed
Preliminary! New SI Loads Are Updated
but Not Fully Verified
2011
2012
2013
2014
YEAR
MB_Pwr_0deg
MB_Pwr_5.8deg (min slew cmd)
MB_Pwr_15deg
MB_Pwr_20deg
MB_Pwr_25deg
Pre-SM4 ACS 1-ch Mean
Pre-SM4 ACS 1-ch 2-Sigma Peak
Post-SM4 Mean
Post-SM4 2-Sigma Peak
Post-2010 Mean
Post-2010 2-Sigma Peak
11