TIPS/JIM
October 18, 2007
Agenda:
INS Division News (Kriss)
COS Update: The NUV Gratings (Keyes)
Updates on the ACS Repair (Sirianni)
Pyraf/Pipeline Removal of SAA Persistence from NICMOS Data (Barker)
Next TIPS/JIM: November 15, 2007
1
Instruments Division News
10/18/2007
•
•
•
•
•
•
•
Congratulations to Massimo Robberto, the co-PI of SPACE, the Spectroscopic Allsky Cosmic Explorer. SPACE was selected for further study in 2008 (along with
DUNE) as part of ESA’s Cosmic Visions proposal opportunity for studying dark
energy. Other participating staff members include Stefano Casertano, John
MacKenty, Marc Postman, Neill Reid, Massimo Stiavelli, Rick White, and Steve
Beckwith.
Recent press releases by INS staff:
o Nor Pirzkal used Spitzer observations of the Hubble UDF to identify the
smallest known galaxies at high redshift.
o Have a look at Alessandra Aloisi’s stunning image of the nearby starforming galaxy I Zw 18. She identifies a large population of old stars in
what was previously thought to be a young galaxy, and Cepheid variables
nail down the distance.
Welcome to our newest staff members:
o Michael Wolfe, Data Analyst Group
o Pey-Lian Lim, Data Analyst Group
o Alex Viana, Data Analyst Group
o Jay Anderson, Webb Instruments Team
o Chris Long, Instrument Engineer, Telescopes Group
Tracy Beck will join INS on the WIT team on October 29. Tracy is an expert on
Integral Field spectrographs. She has been the projects scientist for the Near-Infrared
Integral Field Spectrograph (NIFS) at Gemini on Mauna Kea. Tracy studies T Tauri
stars and their disks and jets.
To accommodate the new staff we are adding, minor construction is underway, and
office moves are in progress:
o Dixie Shipley and Debbie Brenner have just moved to N408. They’re still
not completely settled in, so please see Robin Auer in N311 with any
urgent administrative matters today.
o Michael Wolfe and Alex Viani will move up to N410B next week.
o Additional moves over the next month or two will consolidate all of the
DAs on the 3rd and 4th floors.
HST news:
o WFC3 Thermal Vacuum 2 is complete! It is believed that the decreasing
IR throughput problems can be traced to the CASTLE ground system, and
the IR thermal control circuits are now functioning much better. Analysis
is still in progress. T/V 3 will start in February.
o There were successful SM4 sims for WFC3 and COS installation last
week at GSFC.
o The HST teams successfully presented their Activity Descriptions and
SMOV plans at a review at GSFC last Friday.
o The STUC is meeting here in the board room today and tomorrow.
JWST news:
•
•
•
o The conference on “JWST and Concurrent Facilities” in Tucson was a big
success.
o Some JWST ground-system development work has been delayed until just
before launch. This is leading to efforts to prioritize which instrument
modes will be fully supported at launch, and it is slowing down the ramp
up in staffing.
o The JWST SWG is meeting here next Tuesday and Wednesday.
Migration of teams to the central storage system continues. The ACS and NICMOS
teams have completed their moves. COS+STIS are moving soon.
We have received over 20 applications for Visiting Scientist positions and term hires.
The SRC is reviewing them to prepare a short list.
Kevin Lindsay has provided the following update from the INS Diversity, Culture
and Respect Working Group:
o We’ve had a change in venue and date for the next INS pizza lunch. Due
to conflicting needs for the boardroom and other facilities, I’ve moved the
data for this month to Friday, October 26th, in the Cafeteria Conference
Room. Cost will still be $5 per person.
o The WG has made five recommendations based on the initial set of roundtable discussions:
 Broaden the mentoring program to include Data Analysts.
 Have ISRs findable and searchable via ADS.
 Provide interim appraisal feedback at least 6 months before the end
of the year.
 Establish a committee to evaluate DA promotions.
 Rotate responsibility for planning social events among different
sub-groups in INS.
TIPS/JIM
October 18, 2007
Agenda:
INS Division News (Kriss)
COS Update: The NUV Gratings (Keyes)
Updates on the ACS Repair (Sirianni)
Pyraf/Pipeline Removal of SAA Persistence from NICMOS Data (Barker)
Next TIPS/JIM: November 15, 2007
1
SPACE
TELESCOPE
SCIENCE
INSTITUTE
Operated for NASA by AURA
TIPS / COS Update
The NUV Gratings
18 October 2007
Last COS TIPS presentation: 21 December 2006
NUV grating characteristics
 COS NUV grating blanks coated with Au and Cr
 Original COS NUV gratings (G185M, G225M, G285M, and
G230L) also were MgF2 coated over Al to protect reflective
surface
 Routine design process shifts Wood’s anomaly out of spectral
region of interest to shorter wavelengths
– Anomalous distribution of energy in diffracted light; highly polarization
dependent; sensitive to groove spacing and depth comparable to
wavelength diffracted
– this is a resonance effect – it will not show up in bulk reflectivities, such
as from flat-mirror witness samples, but as a complicated wavelength and
polarization-dependent grating efficiency modulation.
Keyes – 18 October 2007
Slide 2 of 19
NUV Gratings
 For COS NUV gratings the addition of the last layer of coating
(MgF2) apparently shifts Wood’s anomaly directly into
bandpass of interest decreasing throughput substantially
– Solution 1: use MgF2-coated “longer-wavelength” grating in shorter
wavelength region where throughput is nominal
> Consequence: resolution degraded as Δλ does not change
> Shifting G225M for use in G185M region works well, G285M to G225M does
not
– Solution 2: do not apply MgF2 coating to Al surface; anomaly stays at
design location
> This is employed for G225M and G285M gratings
> Consequence: Al oxidizes within days of deposition; forms thin coating;
literature indicates oxide layer reaches maximum depth of ~5 nm.
Keyes – 18 October 2007
Slide 3 of 19
Variances in measured COS sensitivities
in vacuum 2006/2003
Bare Al
Bare Al
Keyes – 18 January 2007
Slide 4 of 19
Grating Efficiency Issues:
 2003 T/V data compared to 2006 T/V data
- this data shows significant variations in efficiency between 2003 and
2006, including indications that some channels at some wavelengths
improved in efficiency by as much as 40% and others diminished by ~25%
- the majority, but not all, of these discrepancies can be explained by the
polarization sensitivity of COS, and the difference in polarization
generated by the 2003 Calibration delivery system and the 2006 calibration
delivery system
- this polarization sensitivity has been demonstrated on the flight spares,
and in the flight optics
COS polarization data
Polarization and COS
1.800
1.700
Vertical/Horizontal
1.600
1.500
1.400
1.300
1.200
1.100
1.000
0.900
0.800
0.700
1200
1700
2200
2700
Wavelength (Anstroms)
Scrambled, CDS+RAS/Cal
Unscrambled, CDS Only
3200
Grating Efficiency Monitoring
 Grating efficiency monitoring tests of the NUV gratings
(no monitoring is done of the FUV gratings)
–
a sequence of exposures are performed on the NUV gratings at
various wavelength settings using the internal lamps, and the count
rates are recorded – ratios of count rates in different channels at the
same wavelength (when possible) are also calculated – this process
should remove the possible effects of lamp variability
 These tests indicate that the lamp is slowly losing
brightness (not unexpected and at an acceptable rate) – and
that G225M and G285M are experiencing steady and
continuing degradation
COS Spectral Layout
Internal Wavecals and Science Spectra
PtNe
NUV
Wavecal
MAMA C B A
External
Science
C
B A
– Obtain (continuous or flashed) internal PtNe spectra at
–
same time as science exposure
Track internal PtNe lines and apply shifts to science
spectrum (all events time-tagged) in COS data
pipeline
Keyes – 18 October 2007
Slide 9 of 14
G185M / G225M
G225M / G285M
Left: G185M / G230L Both MgF2
Right: G225M / G230L
G285M / G230L
Keyes – 18 October 2007
Slide 10 of 19
COS NUV Performance
Changes
TV06/TV03 Performance ratios with coupon
ratios (dashed)
1.1
1.05
TA1 Raw Ratio
1
G225 Ratio
G285 Ratio
0.95
G185 Ratio
0.9
G230 Ratio
'COS Aft' Al/MgF2
0.85
CW-9 Al/MgF2
CW-14 Al/MgF2
0.8
225F1 Bare Al
0.75
285D1 Bare Al
225F2 Bare Al
0.7
170
190
210
230
250
270
290
310
Wavelength
Compare G285M and G225M to G230L, TA1, and
to witness coupons (dashed)
NUV Performance Summary
 The degradation of the G225M and G285M gratings are
real – at the rate of 1.4%/year and 4.4%/year respectively.
To date no process has been identified that can explain the
observed behavior
 Over the past 3 years measurements of the flight spare
gratings have shown very similar degradation rates (1%
and 4.5%)
 Measurements of the witness sample mirror coupons have
shown no degradation over the past 5 years
Summary of observations



Little loss of efficiency in FUV channels
Anomalous efficiency loss in G225M and G285M
(high density, bare aluminum) – External and internal
calibration data give similar results
GSFC analysis shows gratings and coupons are very
clean
Possible explanations for loss of
efficiency considered to date
 Is efficiency loss due to simple hydrocarbon contamination?
– This is not consistent with FUV, coupon or TA1 data – we would
expect more loss in the FUV channels and in short wavelength
coupon data than we see
– wash/analysis of witness samples inside instrument revealed no
significant contamination
 Is loss due to migration of Au substrate into Al?
– No gold was observed in GSFC analysis, not consistent with
Al/MgF2 optic stability, and we would expect to see a similar
reflectivity loss in the bare aluminum witness coupon data
Possible explanations for loss of
efficiency considered to date (cont)
 Is the ‘loss’ due to change in test setups – change in polarization of
calibration signal?
– Polarization testing of COS indicates that this cannot explain all of
the loss in apparent efficiency
– NUV efficiency monitoring indicates continuing, steady
degradation
 Could in-air NUV testing be polymerizing hydrocarbons onto mirrors
and gratings, with stronger effect on high line density optics than on
low density or purely reflective optics?
– GSFC testing rules this out
Possible explanations for loss of
efficiency considered to date (cont)
 Could pin-holes be forming in Al coating or could mixing
of Au through Cr layer into Al be degrading reflectivity?
– pin-holing and layer mixing cannot be ruled out on flight gratings without
examination of flight units ; however no indications of either in detailed
special tests of spare gratings at GSFC
 JY modeling of gratings with a thick (9nm) Al2O3 layer is
consistent with our observed performance.
– This thickness is twice what is suggested likely by literature
– Continuing effort at GSFC to determine actual thickness of oxide
layer – possible update at Oct COS MSR next week
Current Status Summary – Oct 2007
 Degradation is real for G225M and G285M; no effect seen
for MgF2 coated NUV or FUV optics
 COS gratings show definite polarization sensitivity which
will be evaluated on orbit; most polarized astronomical
sources <5% polarized
 Current degradation rate projects to COS ≥ 4x STIS
efficiencies per exposure at launch (for likely COS target
flux-levels)
 Contamination has been ruled out
 Observational uncertainty and systematics have been ruled
out
Current Status Summary – Oct 2007
(cont)
 JY modeling with a thick (9nm) Al2O3 layer is consistent
with the observed G225M/G285M performance; literature
suggests that this is thicker than we should expect to see by
~2x; effort continues at GSFC to determine oxide layer
thickness
 Will it continue on orbit? – unknown at present
 Spare gratings have been fabricated and coated; are in
testing at GSFC at present
 No grating swap is likely at this point
Keyes – 18 October 2007
Slide 18 of 19
Background Information
Keyes – 18 October 2007
Slide 19 of 19
G285M flight and spare grating
performance changes
Estimated G285M-D (flight) vs G258M-E (spare)
0.7
Absolute Efficiency (Unpolarized)
G285M-E2/1/02 (G285M spare) Bare Al
0.6
G285M-E2/9/07 (G285M spare) Bare Al
0.5
G285M-D 1/16/02 (G285M Flight) Bare Al
G285M-D 12/06 est. (G285M flight) Bare Al
0.4
0.3
G285M-D 2006 modeled by
multiplying 2002 grating only values by
the 2003-2006 change in COS
G285M efficiency, and removoing
estimated TA1 contribution.
0.2
0.1
0
250
260
270
280
290
Wavelength
300
310
320
The Degradation Projection Scenario
 Linear extrapolation of observed degradation to 9/11/2008
launch date at ~ 0.5% per month yields additional ~11% loss of
sensitivity before COS gets to orbit; compared to TV I values:
– G285M will have lost ~25% throughput waiting to fly
– G225M will have lost ~20% throughput waiting to fly
 In comparisons to follow, we have assumed 25% degradation
(i.e., launch throughput = 0.75 x TV I throughput)
Keyes – 18 October 2007
Slide 21 of 19
Observing Efficiency Comparison:
COS vs STIS – darks included
HST orbits required to reach S/N=10 at 2500 _ (R~20,000 (0.12 _ ) binning)
-13.0
-13.5
-14.0
log Flux (erg cm
-2
sec
-1
_ -1 )
STIS E230M + 0.2x0.2 aperture
3x7 binning
COS G225M; 3x7 binning
25% degradation;
worst-case dark
-14.5
-15.0
-15.5
COS G225M; 3x7 binning
no degradation;
ground dark
-16.0
COS G225M; 3x7 binning
no degradation;
worst-case dark
COS G225M; 3x7 binning
25% degradation;
ground
dark
Keyes
– 18 January
2007
-16.5
0
10
20
30
40
50
HST Orbits
60
70
80
Slide 22 of 19
90
100
Impacts: Ratios of exposure to achieve same S/N
with degraded sensitivity
Object
Flux
COS Exposure ratio
to reach S/N = 10
25%-degraded Sλ
vs no-loss COS Sλ
with COS ground dark
(with worst-case on-orbit dark)
COS/STIS Exposure ratio
to reach S/N = 10
25%-degraded COS Sλ
vs STIS Sλ
with COS ground dark
(with worst-case on-orbit dark)
1.e-13
1.33
(1.34)
0.43 (0.44)
1.e-14
1.35
(1.41)
0.29 (0.36)
1.e-15
1.45
(1.64)
0.09 (0.24)
5.e-16
1.50
(1.69)
0.07 (0.23)
2.e-16
1.62
(1.74)
[>40 orbits]
0.05 (0.22) [>40 orbits]
1.e-16
1.68
(1.76)
[>40 orbits]
0.04 (0.21) [>40 orbits]
Keyes – 18 October 2007
Slide 23 of 19
Impacts – Single COS grating setting used
 Single COS grating setting used:
– Bright limit (ignore background): simply increase science exposures to
compensate for sensitivity loss: 1.25-1.3x to achieve same S/N
> In bright limit: STIS/COS(no-loss) exposure ratio ~3x; so COS Sλ must
degrade to 0.33 TV I level for COS=STIS efficiency
– Faint “limit”:
> For a 40-orbit COS observation to achieve S/N=10 at 2500 Ǻ.:
• No-loss case with ground dark: Fλ=2.0 e-16
• No-loss case with worst-case dark: Fλ=4.0 e-16
• With 25% degradation and ground dark: Fλ=2.5 e-16 ; however, this
flux requires 26 orbits in no-loss case (1.5x longer with degradation)
• With 25% degradation and worst-case dark: Fλ=5.5 e-16 ; however, this
flux requires 24 orbits in no-loss case (1.7x longer with degradation)
– the limiting flux for a STIS 40-orbit observation is 1.2e-15
Keyes – 18 October 2007
Slide 24 of 19
Impacts: Summary and Questions
 For observing the fainter targets with degraded Sλ, two considerations
important:
– Brighter limiting flux for observation at a particular S/N
– Increase of exposure time to reach a target at a specific S/N
 For most STIS targets the modest difference in COS limiting flux due to
the degradation does not appear to be an important consideration
 Targets with the faintest fluxes attempted by STIS (~1.e-15) in 40 orbits
are important, but with 25% degradation and worst-case background would
require ~12-13 orbits for a single grating setting with COS (or ~7-8 orbits
if no degradation).
– Question: is 8 versus 12 orbits significant for science at this flux level?
> Depends on number of targets and/or COS grating settings required
> In most cases where multiple COS grating settings are needed; COS
probably would not be chosen as the SI of choice
 The difference in limiting flux between 25% degradation and no
degradation (for S/N=10 at 2500 Å and worst-case background) is 6. e-16
versus 4. e-16 (or for best-case dark, 2. e-16)
Keyes – 18 October 2007
Slide 25 of 19
TIPS/JIM
October 18, 2007
Agenda:
INS Division News (Kriss)
COS Update: The NUV Gratings (Keyes)
Updates on the ACS Repair (Sirianni)
Pyraf/Pipeline Removal of SAA Persistence from NICMOS Data (Barker)
Next TIPS/JIM: November 15, 2007
1
Updates on ACS-R
Marco Sirianni
October 18, 2007
TIPS - October 18 2007
Agenda
• ACS Status
• ACS-R
– Concept
– Schedule
– EVA activities
– Role of STScI
TIPS - October 18 2007
Status of ACS
o ACS Side 1 Failed on June 19, 2006
• The ARB identified a most probable candidate for the failure,
an Interpoint DC-DC Converter on LVPS 3 board in MEB1
• Precluded all WFC and HRC CCD imaging.
• Operations started on side-2 electronics on Jul 4 2006.
o ACS Side 2 failed on January 27, 2007
•
•
•
•
Short likely in the Hold Bus
Side-2 is completely inoperable
Side-2 is inaccessible to astronauts for repair
Side 2 is not part of repair mission
o ACS was configured for Side-1 SBC operations
only on February 15, 2007
TIPS - October 18 2007
ACS-R
• Immediately after the failure of Jan 2007 the HST project
assembled a team for the repair of ACS.
• At the end of February a specific option was select for
further study.
• On October 3 & 4 the ACS-R project passed the critical
design review.
TIPS - October 18 2007
ACS-R CDR
Name
Affiliation
Primary Disciplines
Dennis Dillman
NASA/NESC
Review Team Chair
Tom Akers
Consultant
EVA
John Grunsfeld
JSC Crew Office
STS-125 Crew
Richard Harms
HST SM4 SRB
Instrument Systems
Denny Holt
Consultant
Shuttle Mission Mgmt
Chris Iannello
KSC Engineering
Power Systems
Wes Ousley
GSFC AETD
Thermal Engineering
Joe Pellicciotti
GSFC AETD
Mechanical Systems
Pete Salerno
GSFC SRO
Electrical Systems
Steve Scott
GSFC Chief Engineer
Systems, C&DH, SW
TIPS - October 18 2007
ACS-R Team
ACS Repair Mgr
Peter Alea
(ATK )
System Safety
Willian Hill
(SRS)
Electrical Lead
Ike Orlowski
(J& T)
LVPS
Larry Trubell
(Ball)
Flight Software
Barbara Scott
(GSFC)
FPGA
Ed Cheung
(J& T)
CEB-R Team
)
Systems
Kevin Boyce (GSFC )
Becky Emerle (Ball )
Contamination
Radford Perry
(SGT)
Mechanical Dev Mgr
Mark Turczyn
(GSFC)
Thermal
Jeff Lasco
(Ball)
DCL
Augustyn Waczynski
(GST)
Yiting Wen
(MEI )
Mechanical
Operations / FSW
SIDECAR ASIC
Markus Loose
Raphael Ricar
(Conceptual Analytics
Mission Assurance
Carl Powell
(HTSI )
Parts Engineering
Noman Siddiqi
(GSFC )
Clock Boards
Ken Albin
(Ball )
ACS Repair PI
Ed Cheng
Steve Arsianian (HTSI )
Randy Stevens (LMTO)
SI FSW
Bev Serrano
(Raytheon)
SIDECAR Asy Code
Raphael Ricando
Markus Loose
(Teledyne )
SIDECAR V &V
Rob Lampereur (Ball)
Chris Dorato (Ball )
Greg Waligroski (Ball )
Drew Brown (Ball )
TIPS - October 18 2007
CCD Emulator
Matt Owens
(MEI )
EGSE
Mark Belz
(J&T )
Structural Analysis
Mike Beda (Ball )
John Leahey (Ball)
Tools
Torchia Kelly
(ATK )
I&T
Ed Shade
(LMTO)
GSE Software
Kathleen Mil
(J&T )
EVA
Ed Rezac
(LMTO )
STSci
Marco Sirianni
Alan Welty
Carriers
Minal Kashkari
(LMTO)
ACS Current state simplified
Electrical Block Diagram
PDU 20 Amp Fuse
PDU 20 Amp Fuse
WFC CEB
Side 1
Side 2
WFC CCD
HOLD Bus
APB
LVPS H
OPERATE Bus
HOLD Bus
HRC CEB
APB
HRC CCD
+15, -15, +35
+15, -15, +35
+5
LVPS O
+5
Failed Element
LVPS H
LVPS O
Suspect Element
MEB
Side 1 is fully operational except for the
LVPS power to the CEBs.
Currently running on Side 1.
TIPS - October 18 2007
OPERATE Bus
MEB
Side 2 is inoperable.
ACS-R concept
Restore WFC functionality under side-1 (LVPS failed on 6/2006) by
replacing the WFC CEB cards with a new module (CEB-R)
powered by a new LVPS (LVPS-R)
Restore HRC functionality by backpowering the existing HRC CEB
(the success depends on the status of the existing wire harness
within ACS)
Requirement: do not harm SBC
TIPS - October 18 2007
ACS-R simplified Electrical Block Diagram
New Power Supply
PDU 20 Amp Fuse
PDU 20 Amp Fuse
New
CEB
Side 1
Side 2
WFC CCD
HOLD Bus
APB
LVPS H
OPERATE Bus
HOLD Bus
HRC CEB
+15, -15, +35
+15, -15, +35
+5
+5
LVPS O
MEB
APB
HRC CCD
Failed Element
LVPS H
LVPS O
Suspect Element
OPERATE Bus
MEB
New Element
Side 1 used to operate the entire instrument
except for the CEBs which are
replaced/powered by a new box.
TIPS - October 18 2007
Side 2 is inoperable.
ACS-R Design Concept
PIE = Power Intercept Element
CEB-R = CCD Electronic Box - Repair
LVPS-R= Low Voltage Power Supply - Repair
POE = Power Output Element
LVPS-R
POE
CEB-R
PIE
TIPS - October 18 2007
Astronaut Handrail
CEB
Electrical
Interface
Conector
TIPS - October 18 2007
CEB-R
Replace the original 4 boards with a new
element which contains 4 replacement
boards
Backplane
Timing Board
Clock A/X Board
Motherboard Mating
Connectors
Clock B/Y Board
ASPC/Bias Board
TIPS - October 18 2007
LVPS-R
PIE Connector
Cover with
Tether Ring
POE
Tether
Ring
Cable
Stowing
LVPS-R
Grounding
Plug
Handrail Post
ACS Handrail
Post Attachment
Clamp
TIPS - October 18 2007
HRC Backpowering
• The ACS-R design provides the option of
backpowering the existing HRC CEB through the
existing harness within the instrument.
• One of the main issue is the supply of the +35V.
If it can be provided by the original LVPS than it
will be sincronized (-> lower noise), but it must
be provided by the LVPS-R HRC could be
noisier.
• Preliminary tests with flight spare HRC CEB and
CCD show no difference
TIPS - October 18 2007
ACS-R Testing
Besides the single component testing the full ACS-R system
will be tested with:
•
•
Flight spare HRC CEB (backpowering testing)
Flight spare build for HRC and WFC
– Cannot be cooled as on-orbit
– Used for testing with hi-I preamp and detector
– Functional testing when lowest noise is not needed
•
WFC SITE spare CCDs (+custom cryostat)
– Can be cooled to -80 C, crosstalk testing
CCD emulator
– allows readout of a complete 4Kx4K image
– adjustable noise level:
•
• Match on-orbit detector level to determine expected performance
• Set noise level very low to verify noise contribution of CEB-R
TIPS - October
18 2007
• Set noise level high to optimize
timing
pattern and CDS for best results.
Schedule Highlights
•
Testing with the first engineering module of CEB-R and ACS flight
spare CCDs will start on Oct 25th.
•
Flight LVPS ready Mid Jan
•
Flight CEB-R ready early March
•
Servicing Mission Ground Testing (SMGT) End of February (possibly
a second campaign with complete flight-hardware)
•
TV testing - April
•
Shipment to KSC - Jun 9
•
Launch - August 8
TIPS - October 18 2007
More Detailed Schedule
2/21 – 2/25/08
2/26 – 2/28/08
ACS Repair
System
Integration
ACS-R
Functional
Test
CEB Test Set
EICIT/IVT Tests
4/21/08
Deliver to I&T
2/29 – 3/6/08
CEB Test Set
4/22 –
4/28/08
3/7 – 3/20/08
ACS-R
Performance
Test
CEB Test Set
ACS Spare Detector
Kirby Cryostat/CCDs
4/29 – 5/5/08
ACS-R
EMI Test
CEB Test Set
5/13 – 5/14/08
3/21 –
4/17/08
ACS-R T/V
Test
CEB Test Set
ACS Spare Detector
T/V Test Fixture
5/16 – 5/22/08
Mechanical
Interface
Verifications
VEST
Performance
Test
SM4 System
Compatibility
Test
ACS-R Pre-Ship
Performance
Test
Envelope Metrology
HFMS Fit-Check
Carrier Fit-Checks
Crew Fams
VEST/Ops Bench
CCD Emulator
VEST/Ops Bench
CCD Emulator
CEB Test Set
ACS Spare Detector
Kirby Cryostat/CCDs
System I&T Tests using EM ACS Repair System hardware:
1/31 – 2/14/08
ACS Repair
VEST Tests
VEST/Ops Bench
CCD Emulator
EICIT/IVT
AT/FT
SFT
2/27 – 2/28/08
4/15 – 4/18/08
ACS Repair
SMGT
SM4 Mission
Timeline
Test
VEST/Ops Bench
CCD Emulator
VEST/Ops Bench
CCD Emulator
TIPS - October 18 2007
Ship to
Launch Site
Current Timeline
TIPS - October 18 2007
EVA Tasks
•
All ACS Repair EVA tasks have been evaluated by suited SM4 crew
•ACS Prep
•Install Guide Studs
•Remove the EMI Grid
Install grid cutter, actuate, remove grid cutter w/grid
•Remove WFC Access Cover Plate and CEB Top Plate
Install FCP, release fasteners, remove FCP
•Remove 4 WFC CEB electronic boards
•Install WFC CEB Replacement Module
•Install Power Supply Module to ACS handrail, mate PIE
connector to LVPS-R and POE connector to CEB-R
•ACS worksite clean-up
00:05
00:20
00:10
00:45
01:00
00:10
00:10
00:20
Total (w/o door operations) 03:00
•The EVA timeline will continue to be refined through upcoming scheduled NBL
crew training and test runs as well as 1-G activities to address open issues on
tool stowage, tool design, fastener access, etc.
TIPS - October 18 2007
EVA Tools
Screen Grid Cutter
Card Extraction Tool
Fastener Capture Plate
TIPS - October 18 2007
The role of STScI
• Support ground calibration to identify areas where
science operations may need modification
(commanding, proposal preparation, data
processing)
• Support IPT in the definition of the ACS-R AT/FT
• Support the scientific evaluation of the FT
• SMOV planning and on-orbit re-commissioning
TIPS - October 18 2007
ACS-R in SMOV
• ACS-06 CCD Functional Test\
• ACS-08 WFC CCD Cross Talk
•
SMOV WFC and HRC observations will be kept in separate proposals/visits
to facilitate operations in case of unforeseen problems with the HRC
backpowering.
•
Cycle 17 calibration programs will overlap with SMOV and will provide
further characterization of the instrument.
•
We will include, as part of cycle 17 calibration plan, a “CCD optimization”
program to investigate the benefits of operating the CCDs with a reduced
clocking rate and clamp and sample scheme. The full impact on science
operation (read noise, CTE, dynamic range, readout time) will be evaluated
before making new options available for GO science.
•
This program will be executed promptly if the noise characteristics of the
default configuration are not satisfactory.
TIPS - October 18 2007
Conclusion
• ACS-R successfully passed CDR
• More integrated testing will start soon
• STScI will be more involved in the future starting with the
ground testing
-----Original Message----From: Weiss, Mike
Sent: Thursday, October 04, 2007 10:33 PM
To: Smith, Hsiao
Subject: Way to Go!
The ACS Repair just pulled off a miracle! You should all feel
extremely proud of what you just accomplished, and I'm sure that you do.
Please pass on to Ed, Pete and the entire team gratitude from not only
the HST Program Office but from anyone in our Agency who may feel that
NASA no longer has the "Right Stuff." ACS Repair has just proved them
wrong.
Superb effort on the part of all!
Mike
TIPS - October 18 2007
TIPS/JIM
October 18, 2007
Agenda:
INS Division News (Kriss)
COS Update: The NUV Gratings (Keyes)
Updates on the ACS Repair (Sirianni)
Pyraf/Pipeline Removal of SAA Persistence from NICMOS Data (Barker)
Next TIPS/JIM: November 15, 2007
1
PyRAF/Pipeline Removal of
SAA Persistence from
NICMOS Data
Elizabeth A. Barker
Vicki Laidler
Eddie Bergeron
Anton Koekemoer
TIPS Meeting
18 October 2007
South Atlantic Anomaly
 Part of inner Van Allen radiation belt
 Higher density of charged particles
 8-9 times per day
 About half of all orbits
Cosmic Ray Persistence
Electrons trapped during SAA passage
Exponential decay for release of electrons
Lower SNR in short exposures means
persistence has smaller contribution to
total noise
 Persistence becomes a more significant
noise source in long exposures
 Fixed noise pattern per SAA passage
(different from pure random noise)



Persistence Removal
 “Post-SAA Darks” [Bergeron & Najita,
1998]
 Different from standard calibration dark
images
 2 images taken back-to-back
 First exposure starts 174 sec after SAA
exit
 Each 256 sec exposure
 BLANK filter
 Implemented as automatically scheduled
exposures since Cycle 11
Post-SAA Darks
Post-SAA Dark
Persistence Model
SAA-impacted Images
NIC1, F090M, 448 sec, 918 sec since SAA exit
Calibrated Image
SAAcleaned Image
SAA-impacted Images
NIC2, F215N, 1400 sec, 917 sec since SAA exit
Calibrated, Pedsub Image
SAAcleaned, Pedsub Image
Persistence Removal
Algorithm
 Recommend pedestal correcting calibrated image
 Use previously determined scale factor of decay
between post-SAA darks (0.54-0.56)
 [Bergeron & Dickinson, NICMOS ISR 2003-010]
 Create Image of Persistence
 Weighted combination of post-SAA darks
 CR rejection
 Remove pedestal
 Iteratively scale and subtract persistence image from
science image
 Fitting to the minimum total noise in image
 Repeat pedestal correction on final output image
High and Low Signal
Populations
 Long SAA
passage duration
 Widely varying CR
energies
 Earliest CR hits
have decayed
most
 Latest CR hits
have higher
persistence signal
Iteratively Fitting
Persistence Model
[Bergeron & Dickenson ISR 2003-010]
 Persistence level depends on:
 Length/depth of SAA passage
 Time since SAA exit
 Science exposure time
 Iteratively subtract scaled persistence model




Step through different multiplicative factors
Measure RMS width of pixel histogram for each factor
Minimum RMS width indicates best factor
Subtract persistence model from science exposure,
after scaling by best factor
Best Persistence Fit
Figure 12: Bergeron & Dickinson ISR 2003-010
~ (129-46)/129
Testing PyRAF SAAclean
 Conversion from IDL [Bergeron] to Python
by Vicki Laidler
 Data Included:




All cameras
SAA-impacted
Flat-fielded
Pedestal-corrected (pedsub)
 Data Excluded:
 Grism data (not flat-fielded)
 Polarizers
Testing SAAclean - Results
Maximum
Error Correction
Median
Error Correction
# of High Signal Low Signal High Signal Low Signal
Camera Images
Domain
Domain
Domain
Domain
1
415
49.08%
29.43%
1.818%
0.132%
2
1595
59.93%
53.94%
1.319%
0.122%
3
2133
31.63%
27.41%
3.171%
0.174%
PyRAF SAAclean - Input
calcimage =
targimage =
output =
clobber = no
(readsaaper = no)
saaperfile = saaper.fits
saaper.fits
(writesaaper = yes)
(flatsaaper = yes)
(darkpath = saaref$)
saaref$)
Input (usually ped)
ped) file to calculate correction
Input (ped
(ped or cal) file to correct
Output cleaned datafile (targimage with correction applied)
Overwrite output files if they already exist?
Read SAA persistence image from file (If no, construct it.)
Filename for SAA persistence image
Write SAA persistence image?
Flat-field SAA persistence image before analysis
Path to dark reference files
(scale = 0.54)
Scale factor for constructing persistence image
(wf1 = 0.7)
(wf2 = 0.3)
(crthresh = 0.3)
Weight for first SAA exposure
Weight for second SAA exposure
Threshold for CR rejection
(noisethresh = 1.0)
Noise reduction threshold (percent)
(binsigfrac = 0.3)
(stepsize = 0.008)
Stddev fraction for excluding narrow bins
Increment multiplier for SAA scale factor fitting
(fitthresh = yes)
(thresh = )
Solve for threshold value? (If no, uses value of thresh)
Threshold to separate high/low signal domain in SAA
persistence image
(histbinwidth = 0.001)
(nclip = 3)
(hirange = 0.4)
(lorange = 0.25)
(fitmult = yes)
(applied = )
(hi_nr = )
(lo_nr = )
alldiags = no
(diagroot = diag)
diag)
Bin width for histogram in threshold fitting
Number of clipping iterations for threshold fitting
Maximum multiplier for high signal domain
Maximum multiplier for low signal domain
Fit to determine multiplier for minimum noise?
Cleaning applied to which domains?
Noise reduction in high signal domain
Noise reduction in low signal domain
Write out all possible diagnostic files?
Root filename for diagnostic files
PyRAF SAAclean - Output
saaclean version 0.99dev
Input files: n8xw12n8q_subisr.fits n8xw12n8q_subisr.fits
sci image : using DQ extension for badpix
postsaa dark #1 : using DQ extension for badpix
failing over to /data/cdbs5/nref//m9c1047pn_msk.fits
postsaa dark #2 : using DQ extension for badpix
failing over to /data/cdbs5/nref//m9c1047pn_msk.fits
Using scale factor of 0.54 to construct persistence image
flatfile : using DQ extension for badpix
median used in flatfielding: 0.0379231178101
Coefficients for gauss-poly fit to persistence model histogram:
Gaussian (low signal component) terms:
Amplitude, Mean, Sigma: 1026.073392 17.503406 9.216971
Polynomial terms:
Constant, Linear, Quadratic:47.687849 0.422538 -0.003921
Threshold for hi/lo: 0.0995250821636
Npixels hi/lo: 9596 55940
Results summary for high domain:
chi2 for parabola fit = 0.000420518773132
min-noise (best) scale factor is: 0.311645043762
effective noise at this factor (electrons at gain 5.400000): 49.903919
noise reduction (percent) : 38.5484443442
Results summary for low domain:
chi2 for parabola fit = 4.05079716407e-05
min-noise (best) scale factor is: 0.189995821621
effective noise at this factor (electrons at gain 5.400000): 36.192606
noise reduction (percent) : 7.21719319318
Applying noise reduction in both domains
PyRAF SAAclean - Products
Files Output:
•SAA cleaned
image
•Persistence image
(if requested)
Keyword
SAAPERS
SCNPSCL
SCNPMDN
SCNTHRSH
SCNHNPIX
SCNLNPIX
SCNHCHI2
SCNHSCL
SCNHEFFN
SCNHNRED
SCNLCHI2
SCNLSCL
SCNLEFFN
SCNLNRED
SCNAPPLD
SAACNTAB
SAACPDGR
SAADFILE
SAADPDGR
SAACORR
SAADONE
Description
SAA persistence image
Scale factor used to construct persistence image
Median used in flatfielding persistence image
Threshold dividing high and low signal domains
Number of pixels in high signal domain (HSD)
Number of pixels in low signal domain (LSD)
HSD chi squared for parabola fit
HSD scale factor for min noise
HSD effective noise at SCNGAIN
HSD noise reduction (percent)
LSD chi squared for parabola fit
LSD scale factor for min noise
LSD effective noise at SCNGAIN
LSD noise reduction (percent)
To which domain(s) was SAA cleaning applied
Reference table (with task parameters)
Pedigree of reference table
SAA dark reference image file
Pedigree of reference image
Correct for SAA signature
Status of SAA signature correction
PyRAF SAAclean in Pipeline
 To be implemented in OPUS 2008.1
 After calnica ⇒ *_cal.fits
 Pedsub *cal.fits file → SAAclean
 SAAclean correction applied to
*_cal.fits file (without pedestal
correction)
 Outputs modified *_cal.fits file