Status of the ACS Repair
M. Sirianni
TIPS May 22, 2008
Anomalies chart
MAIN GOAL OF ACS-R
ACS-R is designed to restore full, non-redundant operation
to ACS by
1) Replacing the original WFC CEB boards with the CEB-R
2) Replacing the original LVPS with the LVPS-R
Power from the LVPS-R will allow operation of WFC on
ACS by using the new CEB-R, and the HRC will be
restored by powering the original HRC CEB through the
WFC (backpowering).
The repair is designed so that failure of HRC backpowering
does not pose risk to the success of the WFC repair.
Where is what…
ACS-R concept
FLIGHT CEB-R and LVPS-R
FLIGHT LVPS-R
Flight CEB-R
SM4 Activities
• During SM4, ACS-R will be broken into two parts, in
order to fit within the available (EVA) time.
• The major events associated with ACS-R, in their proper
sequence, include:
–
–
–
–
–
–
–
ACS Preparation
Install Guide Studs
Remove the EMI Grid
Remove WFC Access Cover Plate and CEB Top Plate
Remove 4 WFC CEB electronics boards
Install WFC CEB Replacement module (CEB-R)
Install Power Supply Module (LVPS-R) to ACS handrail
• Mate Power Intercept Element (PIE) connector to LVPS-R
• Mate Power Output Element (POE) connector to CEB-R
– ACS worksite cleanup
the Screen Grid Cutter (SGC) will be used
to remove the EMI grid over the WFC CEB
After removal, the cover and top plates will be
accessible to the astronauts for removal.
This will require the use of a
Fastener Capture Plate (FCP) which allows
removal and containment of screws from ACS
Four Card Extraction Tools (CETs) will
facilitate removal of the old CEB cards.
The CEB-R is inserted into the WFC CEB, and the Hard Dock
Clamps lock the module in place. The four connector drive screws are then
used to connect the four CEB-R boards to the WFC.
Contingency tool drill
• ACS WFC-CEB in an awkward position. If the original
plan does not work and the Tool developed for STIS is
CREW FAM
Functional, Environmental,
and Systems I&T
ACS-R SMOV optimization plan
• The CEB-R must communicate with the existing ACS
MEB.
• The CEB-R controls and reads out the ACS WFC CCDs.
This aspect is the most problematic, and has driven
many of the design features for on-orbit flexibility.
• it is very hard to ensure that the ground devices and
configurations are the same as those on orbit for all
critical parameters
• the CEB-R has been made to be as flexible as
reasonably possible to allow for on-orbit adjustments to
optimize its operation with the flight CCDs
What can be optimized
•
•
•
•
•
CCD bias voltages (provide power to various elements inside
the CCD, including the output stage )
CCD clock rail voltages ( control the analog charge shifting
function within the CCD)
CCD readout timing pattern (control the waveforms and
phasing of the clocks to shift the charges to the CCD output
amplifiers, control the CCD output amplifiers, and control the
video processing circuitry to interpret the CCD output amplifier
output voltages)
The Science Data Control Register in the FPGA can
be set to control the detailed timing of the science data
transmission from the CEB-R to the MEB.
The SIDECAR ASIC that generates these signals is
fully programmable and the Flight Assembly Code
(FAC) can be modify on orbit.
O-scope Mode
• This kind of optimization is usually done
on the lab with an oscilloscope…
• The flexibility of the ASIC allow to bring the
oscilloscope on orbit..
O-scope mode
• Runs a 4-output full field
readout
– 4-quadrants (channels) of 2100
columns by 2200 rows
– Includes over-scan
• Place 40 windows with respect
to a quadrant
C
D
A
B
12-pixels / window
• Windows comprise of 12consequtive pixels
40 windows / frame
88 samples / pixel
• Each pixel is sampled 88 times
– Video channel is sampled at a rate
of 4MHz
B
O-scope campaign
• During the first 3 weeks of SMOV we will run the O-scope campaign
for WFC
• Normal frames (bias, EPER, darks) will be paired with O-scope
frames for diagnostic purposes.
• We will have several iterations.
• During each iteration a single parameter will be investigated.
• Before each iteration there will be a real time commanding uplink of
a new configuration. The new configuration will use the best setting
for the parameter studied during the previous iteration.
• ACS-R and STScI are working very closely for the definition of this
mode and for the SMOV optimization program. During those 3
weeks there will be a lot of synergy between the teams to reach the
best configuration and start science and calibration with the best
“defaults”.
Noise decision Matrix
Recommended
action
<4.5
4.5-5.5
Test
performance
Test
performance
<4.5
4.5-5.5
NONE
NONE
Remove 3rd week of
OM campaign
Move SMOV
programs earlier
Do not test 1/2 speed
mode
remove 3rd week of
OM campaign
Move SMOV
programs earlier
Remove 3rd week
of OM campaign
Move SMOV
programs earlier
Final Read Noise (e-) & Impact
5.5-7.5
7.5-10
LOW
MODERATE
10-15
>15*
SEVERE
SEVERE
Do not test 1/2 speed Do not test 1/2
mode
speed mode
Starting Read Noise (e-)
5.5-7.5
Run Full OM
campaign
Do not test 1/2 speed
mode
Do not test 1/2
speed mode
Test 1/2 speed mode
during cycle 17
Offer 1/2 speed mode
in cycle 18
Test 1/2 speed ASAP
Test 1/2 speed mode
but maintain normal
during cycle 17
speed as default
7.5-10
Run Full OM
campaign
Do not test 1/2 speed
mode
Do not test 1/2
speed mode
Delay execution of
RN limited programsOffer 1/2 speed mode Offer shared risk or
conversion to WFC3
in cycle 18
Offer 1/2 speed
mode in cycle 18
test 1/2 speed mode
during cycle 17
> 10
Run Full OM
campaign
Do not test 1/2 speed
mode
Do not test 1/2
speed mode
Activate 1/2 speed
Test 1/2 speed ASAP Test 1/2 speed ASAP mode as default
but maintain normal but maintain normal Interrupt WFC SMOV
speed as default
speed as default and rework ~ all
proposals
Triage WFC
programs Delay execution of
Delay execution of conversion to 1/2
RN limited programs- RN limited programs- speed or WFC3
Offer shared risk or Offer shared risk or Modify Cycle 17
Offer 1/2 speed mode conversion to WFC3 conversion to WFC3 calibration plan to
support 1/2 speed
in cycle 18
mode
Offer 1/2 speed
mode in cycle 18
Offer 1/2 speed
mode in cycle 18
* if the noise is still >
15 e- with the 1/2
speed mode then
decomission WFC
WEB SITE
Summary
• The concept of the ACS-R was defined
only 14 months ago
• We are now testing flight units.
• Noise levels on the ground are very
promising
• For the first time a laboratory tool will be
“installed” with the instrument to allow onsite optimization.
• Stay tuned…