TIPS Meeting
17 July 2003, 10am, Auditorium
1. A new geometric distortion solution
for the STIS NUV MAMA
Jesús Maíz
2. CTE in ACS
Adam Riess
3. Description and Benefits of JWST
Commanding Operations Concept
Vicki Balzano
Next TIPS Meeting will be held on 21 August 2003.
A new geometric
distortion solution
for the STIS NUV MAMA
Jesús Maíz-Apellániz
Leonardo Úbeda
TIPS
17 July 2003
Why?
• Original motivation: NUV-MAMA
objective-prism utility
• Current implementation based on
Walsh et al. 2001 gives large
errors
• New approach: use well-known PC
geometric distortion to obtain
solution for NUV MAMA
Data
• Central region of NGC 4214
• WFPC2
– GO 6716, P.I.: Stecher
F170W
angle 1: u4190101r, 02r
angle 2: u4190201m, 02m
F336W
u4190103r , 04r
u4190203m , 04m
• NUV MAMA
– GO 9096, P.I.: Maíz-Apellániz
CN182
CN270
angle 1: o6bz02isq, iwq
o6bz02j7q , jbq
angle 2: o6bz01afq,(akq) (o6bz01b1q),(b3q)
Positions
of the PC
fields
Positions
of the
NUV-MAMA
fields
N
MAMA
angle 1
E
PC
angle 2
MAMA
angle 2
PC
angle 1
F336W PC mosaic
Technique
• Find stars and measure positions (and
photometry) with HSTphot in PC data
• Measure rotation and displacement
between PC fields and merge lists
• Measure rotation and displacement
between PC and MAMA fields
• Find stars in MAMA fields using merged
PC list and centroid positions
• Calculate and test geometric
distortion
Geometric distortion model
• Direct
– xc =
– yc =
(pixel  sky
)
Σi=0,k Σj=0,i ai,j·(x-xr)j·(y-yr)i-j
Σi=0,k Σj=0,i bi,j·(x-xr)j·(y-yr)i-j
• Inverse (sky
– x = xr +
– y = yr +
Σi=0,k Σj=0,i ci,j·xcj·yci-j
Σi=0,k Σj=0,i di,j·xcj·yci-j
• xr = yr = 512
• k = 3,4,5
 pixel)
Testing
•
•
•
•
Consistency check of the PC solution
F336W vs. F170W PC data
Polynomial degree
Weighting schemes
– Distance between 2 PC positions
– Magnitude cut
• Single-field vs. multi-field solutions
• CN182 vs. CN270 differences
• Comparison with Walsh et al. 2001
(ISR)
• External testing
Consistency
check of
the PC
solution
F336W
vs.
F170W
data
N
o: F170W + F336W
o: F336W
E
Polynomial
degree
Testing
•
•
•
•
Consistency check of the PC solution
F336W vs. F170W PC data
Polynomial degree
Weighting schemes
– Distance between 2 PC positions
– Magnitude cut
• Single-field vs. multi-field solutions
• CN182 vs. CN270 differences
• Comparison with Walsh et al. 2001
(ISR)
• External testing
CN182 vs. CN270 differences
Detector coverage
Comparison with Walsh et al. 2001
Walsh et al. 2001
Comparison
with Walsh
et al. 2001
uncorrected
Comparison
with Walsh
et al. 2001
original
correction
Comparison
with Walsh
et al. 2001
corrected
Comparison with Walsh et al. 2001
uncorrected
original correction
corrected
Plate scales
Result
x scale
(mas/pixel)
y scale
(mas/pixel)
CN182
24.53 ± 0.04 24.79 ± 0.04
CN270
24.54 ± 0.01 24.83 ± 0.05
Walsh et al. 24.53 ± 0.12 24.83 ± 0.13
2001
External
testing
Added bonus:
testing PC
photometry
Summary
• New geometric distortion solution for
NUV MAMA
• Provides positions with median
uncertainties of 0.4 MAMA pixels
(10 mas)
• No wavelength dependence detected in
plate scale or distortion but testing
not quite complete
• PC astrometry and photometry in the UV
is quite precise after all corrections
are applied
We have the first, direct measure of photometric loss
due to imperfect CTE on ACS
The measurements
are made employing
large scale dithers
(WFC) and varying
selection of read-out
amplifier (HRC)
Permutations:
F606W, F775W, F502N
1100 sec, 400 sec, 30 sec
to sample a wide-range
of sky and stellar flux
(total counts)
Example:
Difference mags
for individual stars
versus differential
transfers
A linear loss trend
with parallel transfer
is clear at low flux,
Indicating degraded
CTE.
Not so for serial
transfers
WFC
WFC: parallel CTE loss has strong dependence on stellar flux,
Weak dependence on sky (negligible at r=5, 7)
Correction formulae derived using power law
Power law fitting formula, time dependence uncertain,
but cosmic rays tails consistent with linear degradation
Predicted Photometric Losses for WFC from Parallel CTE
extrapolation
3e
30e
100e
M31 faint-end CMD
SN Ia at peak, z~1.8
PSF flux=zeropoint
_ orbit integration
3 example programs: source in middle of chip, y=1024
WFC: no evidence of serial transfer losses, versus sky, or flux
or in any explored configuration
HRC example: parallel CTE loss apparent, no serial transfer loss seen
HRC
HRC: parallel CTE loss has similar dependence on
stellar flux and sky level
Correction formulae derived using power law
HRC: no evidence of serial transfer losses, versus sky, or flux
or in any explored configuration
Internal data: charge deferred tails in dark frames
Indications appear consistent with direct data and provides
first guess at time dependence: linear
Implications
1) For WFC, post-flashing may be ineffective at mitigating CTE
This statement is a direct implication of the weak dependence of photometric loss
on sky background. However, it is too soon to know for sure if this holds at sky levels
much higher than those studied here but are readily achieved by post-flashing. Perhaps
sky levels of a few hundred electrons will mitigate CTE (though such behavior would
appear to conflict with the extrapolation of the WFC correction formula), but if the sky
levels required are too high, the added shot noise may make such post-flashing
undesirable.
2) The future photometric losses for WFC can now be predicted and are
expected to grow faster than for WFPC2
Assuming the linear time-dependence justified by the internal data is correct,
predictions can be made. In N years, the typical/worst case losses will be N*(2%/10%).
By the end of life for HST (2010), 8 years after launch, we can anticipate typical case
losses of 16% and worst case losses of 50%-80% (here the range of predictions reflects
the difference given by linear and power-law time dependence). For comparison
WFPC2 had typical/worst case losses of 6%/40% 7 years after launch (Whitmore et al
2000). Such a faster rate of degradation for WFC is expected from the greater number
of transfers edge-to-amplifier (2048 for WFC versus 800 for WFPC2).
Description and Benefits of JWST Commanding
Operations Concept
TIPS/JIM Meeting
17 July 2003
Vicki Balzano
1
Description and Benefits of JWST Commanding
Operations Concept
Three main components of JWST Commanding
Operations Concept:
– Event-Driven
– High-Level Ground-to-Flight Interface
– Human-Readable Uplink Format
2
Description and Benefits of JWST Commanding
Operations Concept
• What is Event-Driven Operations?
– The ability to react to on-board events without ground
interaction
• For HST:
[Primarily absolute time based]
» Flight Software monitors health and safety
» SI Operational Software has limited ability to
react through use of “event flags”
• For futuristic “robot” mission:
» Flight Software monitors health and safety
» Operational Software given proposal information and
does ALL the scheduling
3
Description and Benefits of JWST Commanding
Operations Concept
• What is Event-Driven Operations?
• For JWST:
» Flight Software monitors health and safety
» Ground Software does visit ordering and constraint
specification (for example: time windows)
» Flight Software initiates each visit in the list as its
constraints are met and after previous visit completes
» Operational Software has access to all telemetry so…
next operation occurs immediately after the previous
operation completes and execution strategy can be
based upon on-orbit events.
4
Description and Benefits of JWST Commanding
Operations Concept
• JWST Commanding Architecture
• Ground Software creates Visit Files
» An ordered list of ASCII high level statements
Similar to SMS statements but at “higher”
level and NO absolute time stamps
» Assigned a time window (earliest start, latest start,
latest end)
Visit statement example:
Activity, 07, MIRIMAGE, filter=F15W, sample=STEP24, exptime=1000 ;
5
Description and Benefits of JWST Commanding
Operations Concept
• JWST Commanding Architecture
• Ground Software creates Observation Plan
» An ordered ASCII list of visit files
• Ground System uplinks Observation Plan and
associated Visit Files once a week
6
Science Operations
- Observation Plan Graphic Visit 00301
E
e
l
f
Successful completion
Visit 05505
E
e
l
f
Successful completion
Visit 09008
e
e = earliest start time
l
l = latest start time
f
f = latest end time
7
Science Operations
- Observation Plan Graphic Visit 00301
x
e
l
f
Guide star acq failure
Visit 05505
E
e
l
f
Successful completion
Visit 09008
e
e = earliest start time
l
l = latest start time
f
f = latest end time
8
Description and Benefits of JWST Commanding
Operations Concept
• JWST Commanding Architecture
• Flight Software processes Observation Plan and
Visit Files
» Known as the OPE (Observation Plan Executive)
» Reads ASCII input, checks constraints, coordinates
parallel operations, manages interruptions
» When error is encountered, can skip items but
CANNOT reorder plan.
» Calls on-board operational software to execute visit
file activity statements
9
Description and Benefits of JWST Commanding
Operations Concept
• JWST Commanding Architecture
• On-board Operational Software
– In the form of ASCII JavaScript programs
– Similar to HST instructions but in robust software
language
» Each script contains operational rules and flight
software application requests necessary to accomplish
a high-level task (ex. Guide star acquisition,
NIRCAM exposure, MIRI alignment, wave-front
sensing)
10
Description and Benefits of JWST Commanding
Operations Concept
Benefits of JWST Event-Driven Operations
Takes advantage of L2 orbit, the hardware architecture, the absence
of many time-critical operational constraints and the capabilities
of modern flight computers
• Minimal task modeling in ground software
– Decreases size and complexity of ground software system
• Execution efficiency
• Minimizes down-time due to instrument safings
• Enables rapid workarounds to unexpected spacecraft
behavior
11
Description and Benefits of JWST Commanding
Operations Concept
Benefits of JWST High-Level Ground-to-Flight Interface
• Guarantees common scripts for both real-time and
planned operations
• Minimizes transition from I&T to Operations
• Decreases response-time to spacecraft and
instrument anomalies because programming in a
high-level scripting language
12
Description and Benefits of JWST Commanding
Operations Concept
Benefits of JWST Human-readable Uplink Format
• No bit-busting (binary command load verification)
• ASCII format corresponds to descriptions in usermanuals and user proposal forms
• It is human friendly: lowers risk of interpretation
errors
13