ACS Current Status
M.Sirianni
TIPS Feb 15, 2007
Agenda:
• ACS Side-2 failure
• SBC reactivation
• ACS programs conversion
Timeline:
January 27, 2007
12:29:12 – ACS began WFC observation, shutter was closed because of a
GSACQ failure
12:34:17 – Initial spike in HST structure current
12:34:21 – Begin a 7-second ramp-up of HST structure and load bus current
12:34:28 – ACS PDU-2 fuse blows, ACS telemetry goes to zeros
12:34:33 – ACS suspended because of invalid mode
12:34:37 – NCS pressure sensor detects a pressure burst, initiating HV
protection and NCS safing
12:34:38 – ACS safed because of invalid mode
12:34:42 – HST enters Inertial Hold
January 29 – ACS Hybrid LEI team given “go” to prepare for Side-1 switch pending
ARB recommendation and HST Project approval
January 31 – ACS Side-2 ARB Kickoff Meeting. Goal: “Assess the risks of
recovering SBC Operations on ACS Side-1”
February 5 – ARB Status Briefing #1 to HST Project
February 9 - ACS heater zone B switched to Side-1
February 13 – ARB Status Briefing #2 to HST Project
February 15 - Flight Readiness Review
• HST was recovered from Inertial Hold Safemode DOY 028
– Health and Safety SMS intercept at 028/07:00
– HGA communications restored at 028:07:55
• Safing System is in its Nominal Operational Configuration
– Neon Leak Safemode Test was re-enabled 028/17:45 UT
• Battery performance is nominal
– Battery temperatures are below 0degC since event and converged
– System SOC increased 3-5 A-H
• TPS reporting nominal pressures
• FHSTs and FGSs powered back on
– Temperature and performance are as usual
• NCC was returned to its operate configuration on DOY 030/01:09 UT
• NICMOS was recovered to SAA Operate on 032/15:48 UT
– Subsequent filter wheel checkout was nominal
– Resumed science observations - NGC 4639
• WFPC2 resumed nominal science operations
– Calibration image of Omega Cen, a globular cluster
What was observed:
• Structure current elevated in two events separated by ~3.5s
– First event persisted for ~1.5s and peaked at ~6A
– Second event persisted for ~7s, increased gradually, was very noisy,
peaked at ~18.6A, and ended abruptly
• Main Bus current elevated during both events
– First event approximately tracked structure current
– Increase during second event peaked at ~37A
• PDU-2 current elevated only during second event, increase peaked at
~13.6A
• ACS input current monitor saturated at 12A during peak of second
event and returned to zero when event ended
• ACS input voltage sagged by ~1.5V during peak of second event and
dropped to zero when next sampled after drop in currents
• NCS/ESM Total Pressure Sensor measured peak pressure of 1.0E-4
torr
– Pre-anomaly reading was 1.6E-7
• After the overcurrent event finished, the gas pressure decreased
exponentially
Possible origin of fault:
1. MEB1- LVPS2 (Side-2)
2. Auxiliary Power Box (APB)
3. Harnesses between LVPS2 and APB
Most likely cause of the fault:
Exploding/burning tantalium capacitor
The ARB is still investigating ways to rule out origin of the fault.
So far the primary goal of the ARB has been the assessment whether
SBC can be safely operated under side-1.
Current Situation
28V
Spacecraft
Input
Power
(PDU)
28V
Spacecraft
Input
Power
(PDU)
ACS
Hold Power 1
Powered
Units
Unpowered
Units
Previously
Failed Unit
Hold
Circuits
Side-1
Hold
Circuits
Side-2
Zone A1
Zone A2
Zone B1
Zone B2
Heater Power 1
TEC Power 1
Hold Power 2
Heater Power 2
TEC Power 2
TEC
CEB Power 1
Anneal Power 1
CEB Power 2
Anneal Htrs
Side-1
CEB
Anneal Htrs
Side-2
Anneal Power
SBC
Operate Power 1
Mechanism
Power 1
MEB
Side-1
Mechanisms
Side-1
MEB
Side-2
Mechanisms
Side-2
Calibration
Power 1
Operate Power 2
Mechanism
Power 2
Calibration
Power 2
Calibration Lamp Controller
Side-1 powered on for SBC Operation
28V
Spacecraft
Input
Power
(PDU)
28V
Spacecraft
Input
Power
(PDU)
ACS
Hold Power 1
Powered
Units
Unpowered
Units
Previously
Failed Unit
Hold
Circuits
Side-1
Hold
Circuits
Side-2
Zone A1
Zone A2
Zone B1
Zone B2
Heater Power 1
TEC Power 1
Hold Power 2
Heater Power 2
TEC Power 2
TEC
CEB Power 1
Anneal Power 1
CEB Power 2
Anneal Htrs
Side-1
CEB
Anneal Htrs
Side-2
Anneal Power
SBC
Operate Power 1
Mechanism
Power 1
MEB
Side-1
Mechanisms
Side-1
MEB
Side-2
Mechanisms
Side-2
Calibration
Power 1
Operate Power 2
Mechanism
Power 2
Calibration
Power 2
Calibration Lamp Controller
ACS Side-1 Checkout Programs
– Filter Wheel Check (#11094, 2 internal orbits, P.I. = C. Cox)
• Commands the SBC filter wheel to each of its positions (in both
directions)
• Verifies proper motion of wheel through encoder readout
• Test has been used previously (e.g., Side-2 switch)
– SBC MAMA Recovery (#11048, 4 internal orbits, P.I. = C. Cox)
• Initial MAMA turn-on and recovery from anomalous shutdown
– SBC was off when ACS was safed, so this is a conservative procedure
• Brings the MAMA back to operating condition while watching for
possible problems
– Signal processing check
– Intermediate high voltage ramp-up
– Full high voltage ramp-up
• Fold analysis provides detailed performance information
– Measures charge cloud size on anode and gain
• Darks and flats obtained during test
• Test has been used previously (e.g., Side-2 switch)
– Three Stage Contamination Check/Monitor
• Modification of Internal Flatfield Program (#11052, P.I. = R.
Bohlin)
– D2 flat for all 6 filters (6 orbits)
– Subset of filters (2 orbits) each week to monitor until external
(NGC6681) observation is obtained (maximum of three weeks)
• Modification of SBC Flux Calibration Program (#11056, P.I. =
J. Walsh)
– Single orbit ASAP on white dwarf standard WD1657+343
(visible now)
» F122M, F165LP, PR110L PR130L
– Second orbit one week later
• UV Contamination Monitor (#11050, P.I. = R. Gilliland)
–
–
–
–
–
Observation of NGC6681 (1 external orbit)
NGC6681 becomes visible ~ February 28
Comparison against historical data
Exposures in all 6 filters and 2 darks (in occultation period)
Repeat up to 4 times
Conversion of ACS programs
SPD and HST MO have asked INS to review existing cycle15 ACS
proposals to identify candidates for a conversion to WFPC2 or NICMOS
~ 120 programs are receiving a double technical review by INS.
An internal Feasibility Review panel will asses science and time with
guidance from the technical reviews.
Most of the PIs will be notified in early March. (PI can/will appeal
Review of phase-1s is coordinated by L.Smith.
Phase-2s will be processed following the usual procedures
(with limited reviews).
Backup Slides
WFPC2: Omega Cen - f814W (after anomaly event)
APB
Debris possible
in LVPS2 and
APB Side 2
Physical
Isolation
Hold Power
presently active
LVPS 2
LVPS 1
Fuse
OK
SBC
Fuse
Open
CEBs
Physical
Isolation
Only new powered
state in vicinity of
anomaly suspects
is MEB1 CS/SES
sections; Physical
Isolation is provided
MEB 1
MEB 2
STIS MEB
ACS, Side-2 with panels removed
APB is mounted to truss; here shown unsecured and resting in cavity
WFC Dark Current
WFC Hot Pixels
The new the temperature setpoint
brought dark Current and hot pixels
back to the level after only 18 months
on orbit.