Optimization Strategies for the
NIRSpec MSA Planning Tool
James Muzerolle
Special thanks to NIRSpec teamlet members and
APT developers:
Diane Karakla
Tracy Beck
Jason Tumlinson
Jeff Valenti
Tom Donaldson
Rob Douglas
Karla Peterson
Quick NIRSpec overview
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3 spectroscopic modes: MOS, fixed slit, IFU
3 resolutions: R ~ 100 (prism), 1000 and 2700 (gratings)
effective wavelength range 0.6 – 5 microns
FOV ~ 3.6’ x 3.4’
Microshutter Array (MSA)
4 x 365 x 171 shutters,
individually addressable
shutter pitch = 0.26” x 0.51”,
(actual FOV = 0.2” x 0.45”)
activated with magnet sweep
prism spectral layout
R=2700 spectral layout
MSA planning tool prototype
(APT v17.0.3)
Preliminary optimization study
• IDL code to simulate planning tool analysis of target
placement within MSA shutters
• heuristic iterative scheme to optimize the number of
targets per MSA configuration from an input
“candidate” target sample
– grid of MSA center pointings and position angles
– optimized solution = grid point with largest number of targets
– loop for multiple configurations
• test cases to evaluate various parameters:
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–
–
input sample size/spatial distribution
number of “sky” shutters
including known failed shutters
dithers
target priorities
Optimization results
# cand
Targ Set 1
Targ 1/2
Config 1/2
Fails?
Test case
1009
102
407
5
n
1 center
1009
102
534
6
n
3x3 center grid, 3-shutter slitlets
1009
80
508
8
y
1009
118
505
5
y
2-shutter slitlets
1009
76
545
9
y
shutter dither (0.26”)
1009
65
510
11
y
gap dither (17.9”)
1000
64
519
11
y
concentrated source distribution
25
9
16
2
y
sparse sample, 3 orients
1009 (99, 100)
71 (24, 11)
528 (88, 76)
8
y
target priorities
Default test case:
• UDF-derived input candidate target catalog (1009 objects)
• 3x3 center pointing grid, 20.1” x 36.2” offsets
• 3-shutter slitlet
• ideal MSA
• 1 configuration per target set (no cross-slitlet dithers)
Optimization results
# cand
Targ Set 1
Targ 1/2
Config 1/2
Fails?
Test case
1009
102
407
5
n
1 center
1009
102
534
6
n
3x3 center grid, 3-shutter slitlets
1009
80
508
8
y
1009
118
505
5
y
2-shutter slitlets
1009
76
545
9
y
shutter dither (0.26”)
1009
65
510
11
y
gap dither (17.9”)
1000
64
519
11
y
concentrated source distribution
25
9
16
2
y
sparse sample, 3 orients
1009 (99, 100)
71 (24, 11)
528 (88, 76)
8
y
target priorities
Default test case with failed shutters
Optimization results
# cand
Targ Set 1
Targ 1/2
Config 1/2
Fails?
Test case
1009
102
407
5
n
1 center
1009
102
534
6
n
3x3 center grid, 3-shutter slitlets
1009
80
508
8
y
1009
118
505
5
y
2-shutter slitlets
1009
76
545
9
y
shutter dither (0.26”)
1009
65
510
11
y
gap dither (17.9”)
1000
64
519
11
y
concentrated source distribution
25
9
16
2
y
sparse sample, 3 orients
1009 (99, 100)
71 (24, 11)
528 (88, 76)
8
y
target priorities
Default test case with failed shutters,
2-shutter slitlet
Optimization results
# cand
Targ Set 1
Targ 1/2
Config 1/2
Fails?
Test case
1009
102
407
5
n
1 center
1009
102
534
6
n
3x3 center grid, 3-shutter slitlets
1009
80
508
8
y
1009
118
505
5
y
2-shutter slitlets
1009
76
545
9
y
shutter dither (0.26”)
1009
65
510
11
y
gap dither (17.9”)
1000
64
519
11
y
concentrated source distribution
25
9
16
2
y
sparse sample, 3 orients
1009 (99, 100)
71 (24, 11)
528 (88, 76)
8
y
target priorities
Default test case with failed shutters,
1-shutter dither (0.26”) in dispersion direction
Optimization results
# cand
Targ Set 1
Targ 1/2
Config 1/2
Fails?
Test case
1009
102
407
5
n
1 center
1009
102
534
6
n
3x3 center grid, 3-shutter slitlets
1009
80
508
8
y
1009
118
505
5
y
2-shutter slitlets
1009
76
545
9
y
shutter dither (0.26”)
1009
65
510
11
y
gap dither (17.9”)
1000
64
519
11
y
concentrated source distribution
25
9
16
2
y
sparse sample, 3 orients
1009 (99, 100)
71 (24, 11)
528 (88, 76)
8
y
target priorities
Default test case with failed shutters,
detector gap dither (18”)
prism spectral layout
R=2700 spectral layout
Optimization results
# cand
Targ Set 1
Targ 1/2
Config 1/2
Fails?
Test case
1009
102
407
5
n
1 center
1009
102
534
6
n
3x3 center grid, 3-shutter slitlets
1009
80
508
8
y
1009
118
505
5
y
2-shutter slitlets
1009
76
545
9
y
shutter dither (0.26”)
1009
65
510
11
y
gap dither (17.9”)
1000
64
519
11
y
concentrated source distribution
25
9
16
2
y
sparse sample, 3 orients
1009 (99, 100)
71 (24, 11)
528 (88, 76)
8
y
target priorities
Optimization results
# cand
Targ Set 1
Targ 1/2
Config 1/2
Fails?
Test case
1009
102
407
5
n
1 center
1009
102
534
6
n
3x3 center grid, 3-shutter slitlets
1009
80
508
8
y
1009
118
505
5
y
2-shutter slitlets
1009
76
545
9
y
shutter dither (0.26”)
1009
65
510
11
y
gap dither (17.9”)
1000
64
519
11
y
concentrated source distribution
25
9
16
2
y
sparse sample, 3 orients
1009 (99, 100)
71 (24, 11)
528 (88, 76)
8
y
target priorities
Recommendations
• Tool should incorporate iterative scheme for optimizing the number
of targets in a configuration using a grid of center pointings and/or
position angles.
• Account for “acceptance zone” where flux losses are minimized.
• Failed shutters must be tracked and updated. No targets in failed
closed. Generate warnings for targets in rows with failed opens.
• Include an option for dithers requiring separate configurations (e.g.,
detector gap coverage), for an arbitrary number of dithers.
• Target priorities, with an arbitrary number of layers, should be a
key part of the optimization scheme.
• Include a diagnostic plot summarizing characteristics of all targets
in a given configuration, such as relative shutter position, priority,
dither status, user-defined properties (magnitude, redshift, etc).
To do
• optical distortion across the FOV must be included, with the ability
to update the distortion solution as needed
• better treatment of prism spectra (can fit more than one in the same
shutter row without overlap)
• target acquisition: visualization and selection of reference stars,
avoiding failed closed shutters
• explore more observing scenarios