NICMOS SMOV Update
September 30 2009
Agenda
1. Recent & Upcoming Activities
2. NICMOS SMOV Program Status
3. Recent Results and Analysis
- Dark Monitoring
1
Recent Activity:
• NCS Set-Point changed from 75K to 77K on Thursday September 24 (day 267)
• Daily dark monitoring (prog 11947)
Planned activities:
— Decision on final NCS set-point (Thu Oct 1)
— NCS set-point change (Friday Oct 2?)
—11947 Dark Monitoring to continue with daily darks
— 11408 278:10:51 Monday October 5 Focus/Tilt part 1 (PAM focus), visits 1, 2, 3
— 11408 281:09:33 Thursday October 8 PAM upload if needed (visit 4)
— 11408 281:11:17 Thursday October 8 Focus/Tilt part 2 (PAM Tilt) visits 5, 6, 7
2
NICMOS SMOV Status
Activity
Prop ID
Title
PI
Visits
Done
Total Visits
Status
NIC03
11406
DC Transfer Test
Schneider
2
2
Completed
NIC04
11407
Filter Wheel Test
Wheeler
4
4
Completed
NIC05
11408
Focus/Tilt Test
Wiklind
0
8
waiting
NIC06
11409
FOM Functional
Dahlen
0
1
waiting
NIC07
11410
Aperture Location
Koekemoer
0
3
waiting
NIC08
11411
Optical Plate Scale
Wiklind
0
3
waiting
NIC09
11412
Geometric Stability
Wiklind
0
2
waiting
NIC10
11413
Mode-2 Coronagr. Target Acquisition
Schneider
0
10
waiting
NIC11
11414
Optimum Coronagraphic Focus
Schneider
0
2
waiting
NIC12
11415
Coronagr. Performance Assessment
Schneider
0
8
waiting
NIC13
11416
Thermal Characterization*
Barker
0
100
waiting
NIC14
11417
Detector Read Noise and Dark Current*
Dahlen
0
86
waiting
New
11947
Dark Monitoring (C17 Cal Program)
Dahlen
21
(59)
Running
*) will start after NIC06 (FOM Functional)
3
Recent Results
• Dark Monitoring
— A series of darks (8) were obtained at a NCS set-point of 75 K
— The increase in linear dark current was ~60% for NIC1 and NIC2
— For NIC3 the increase was ~170%
— The NCS set-point was increased to 77K on Thursday Sep 24
— The increase in linear dark current was ~125% for NIC1 and NIC2
— For NIC3 the increase was ~380%
— All three cameras show an increase in the number of hot/warm pixels as
well as changes in the structure of the dark current variation
• The reason for the unexpectedly large increase in the linear dark current for
NIC3 is presently unknown. Potentially indicating a larger temperature gradient
within the dewar than previously.
• Increased dark current levels increase the noise contribution for deep
observations but have a marginal impact on short exposures (read-noise limited)
• The NICMOS Team is evaluating the impact on science operation for Cycle 17
4
Recent Results
5
Recent Results
75K
77K
6
Recent Results
Linear Dark Current [e-/s]
Camera
NCS Set Point
72.4 K
Ratio
75 K
Ratio
77 K
Ratio
NIC1
0.09 ± 0.02
1.0
0.14 ± 0.02
1.6 ± 0.4
0.19 ± 0.03
2.2 ± 0.6
NIC2
0.08 ± 0.02
1.0
0.12 ± 0.02
1.6 ± 0.5
0.18 ± 0.03
2.3 ± 0.7
NIC3
0.13 ± 0.03
1.0
0.35 ± 0.03
2.7 ± 0.7
0.61 ± 0.09
4.8 ± 1.4
7
Recent Results
72.4K
75K
77K
Increase in number of warm/hot pixels
72.4 => 75K
72.4 => 77 K
NIC1
+97%
+145%
NIC2
+109%
+163%
NIC3
+93%
+130%
NIC1
Warm/hot pixel definition:
– Subtract the smoothed image from
the unsmoothed
NIC2
–Define the level comprising 10% of
the warmest pixels in the subtracted
72.4K image
– Count pixels above this level for 75
and 77K
[Preliminary: Most of the increase in linear
dark current due to increase in warm pixels
for NIC1/NIC2, while NIC3 has an increase
in the general dark current.]
NIC3
8
Noise contributions
• Sky background
– Low for narrow band
– High for broad band
• Thermal background
– Low for λ<2µm
– Dominates for λ>2µm
• Read-noise
– 26/26/29 e- for NIC1/NIC2/NIC3 (pre-SM4)
• Dark current
– Increased contribution for long/deep exposures
9