SPACE TELESCOPE
SCIENCE INSTITUTE
COS
Status Update
Cristina Oliveira
for the COS Team
13/05/2016
STUC - COS
Fermi Bubbles
A. Fox et al.
1
Overview
SPACE TELESCOPE
SCIENCE INSTITUTE
•
COS Cycle 23 Calibration Plan - Overview
•
COS FUV Detector Gain Sag
– Monitoring
– Planning for COS/FUV LP4
• Time of activities
• Different Phases
•
COS Wavelength Calibration
– NUV
• Mechanism position uncertainty
• Zero point offsets
• Special calibration plan
– FUV
• Slopes and zero points of dispersion solutions
• Walk correction >> Update in back-up slides
• Geometric distortion correction >> Update in back-up slides
13/05/2016
STUC - COS
2
Cycle 23 Calibration Plan
SPACE TELESCOPE
SCIENCE INSTITUTE
Activity
# External orbs
# Internal orbs
FUV Monitors
FUV Spectroscopic Sensitivity Monitor
23
FUV Detector Dark Monitor
260
FUV Internal/External Wavelength Scale Monitor
3
Pure Parallel Observations of Geocoronal Ly α
4
FUV Gain Maps after HV changes
4
NUV Monitors
COS Target Acquisition Monitor
2
NUV Spectroscopic Sensitivity Monitor
4
NUV Detector Dark Monitor
52
NUV Internal/External Wavelength Scale Monitor
2
NUV MAMA Fold Distribution
1
TOTAL Cycle 23 Request
13/05/2016
34 + 4 (parallel)
STUC - COS
317
3
Modal Gain FUV Detector – LP3
Segment A
Y=450.5
SPACE TELESCOPE
SCIENCE
INSTITUTE
12
Modal Modal
Gain Gain
10
10
8
8
6
6
4
40
Y=450.5
FUVA
167
167
167
167
167
167
167
167
167
167
167
167
5.0×103
0
5.0×10
3
X Pixel
1.0×104
1.5×104
4
1.5×104
Segment B1.0×10
X Pixel
Y=508.5
FUVB
12
2015-02-09
2015-04-06
2015-06-08
2015-08-10
2015-02-09
2015-10-20
2015-04-06
2015-12-21
2015-06-08
2016-01-18
2015-08-10
2016-01-18
2015-10-20
2016-03-19
2015-12-21
2016-01-18
2016-01-18
2016-03-19
Segment A
12
2015-02-09
2015-04-06
2015-06-08
2015-08-10
2015-02-09
2015-10-20
2015-04-06
2015-12-21
2015-06-08
2016-01-16
2015-08-10
2016-01-19
2015-10-20
2016-03-19
2015-12-21
2016-01-16
2016-01-19
2016-03-19
Segment B
Y=508.5
Modal Modal
Gain Gain
12
10
10
8
8
6
6
4
40
163
163
163
163
163
163
163
169
163
169
163
163
169
169
13/05/2016
13-Apr-2016 16:13
0
13-Apr-2016 16:13
5.0×103
5.0×10
X Pixel
STUC
- COS
3
X Pixel
1.0×104
1.5×104
4
4
1.0×10
1.5×10
4
COS FUV Detector
Gain Sag Monitoring – LP3
Segment A
Y=450.5
SPACE TELESCOPE
SCIENCE INSTITUTE
• Assuming 1.25x current usage
• Plot on bottom right
• Increase HV FUV in Aug 2016
• Move to LP4 in Feb 2017
10
8
167
167
167
8
167
6
167
167
167
6
167
4
167
167
167
1500
4
167
FUVA LP3
2000
PHA
• Assuming current rate of usage
• Increase HV FUVB in Oct 2016
• Move to LP4 in ~Summer 2017
12
10
Modal Modal
Gain Gain
• HV FUVB LP3 raised in mid-Jan 2016
• (Blue modes are at LP2)
• 5% flux loss when PHA=3
Y=450.5
1500
2000
2500
X Pixel
3000
3500
2500 B
Segment
3000
3500
X Pixel
Y=508.5
2015-02-09
2015-04-06
2015-06-08
2015-08-10
2015-02-09
2015-10-20
2015-04-06
2015-12-21
2015-06-08
2016-01-16
2015-08-10
2016-01-19
2015-10-20
2016-03-19
2015-12-21
2016-01-16
2016-01-19
2016-03-19
Segment B
12
Y=508.5
12
10
Modal Modal
Gain Gain
Gain Sag Monitoring
2015-02-09
2015-04-06
2015-06-08
2015-08-10
2015-02-09
2015-10-20
2015-04-06
2015-12-21
2015-06-08
2016-01-18
2015-08-10
2016-01-18
2015-10-20
2016-03-19
2015-12-21
2016-01-18
2016-01-18
2016-03-19
Segment A
12
10
8
163
163
163
8
163
6
163
163
163
6
169
163
4
169
163
163
2016-01-19
169
2016-03-19
8000
4
2016-08-26
12 169
FUVB LP3
FUVB; Y = 508 to 509
8500
xpixel
9000
13-Apr-2016 16:13
8000
8500
9000
X Pixel
169
169
169
175
175
X Pixel
2016-08-26
2017-02-12
13-Apr-2016 16:13
9500
10000
9500
10000
10
12
Modal Gain
FUVB; Y = 508 to 509
8
6
** No hotspots since last STUC meeting
13/05/2016
4
STUC - COS
2
8000
12
2015-08-24
2015-10-20
2016-01-28
2016-01-28
2016-07-06
Model predictions
10
assuming 1.25 usage
F UVB; Y = 508 t o 509
15-Apr-2016 10:10
8500
9000
X Pixel
9500
2016-01-19
2016-03-19
2016-08-26
2016-08-26
2017-02-12
169
169
169
175
175
10000
163
163
163
169
169
5
COS FUV Detector
Gain Sag Monitoring – LP2
SPACE
TELESCOPE
Gain
Sag
Monitoring
SCIENCE INSTITUTE
Segment A
Y=522.5
• G130M/1055/1096
blue modes remain at LP2 (due to their wide cross-dispersion 2015-02-08
profile)
12
2015-07-16
2015-12-27
• No further HV increases – use of multiple FP-POS
crucial to overcome effect of gain
sag hole
Segment A
2016-03-17
Modal GainModal Gain
10
Y=522.5
12
2015-02-08
2015-07-16
2015-12-27
2016-03-17
FUVA
8
10
6
8
4
6
173
173
173
173
1500 173
173
4
173
173
2000
3000
3500
3000
2015-02-08 3500
2016-03-01
Segment B
FUVB
1500
12
2500
X Pixel
2000
Y=578.5
2500
X Pixel
Modal GainModal Gain
Segment B
13/05/2016
10
12
Y=578.5
2015-02-08
2016-03-01
8
10
6
8
4
6
175
175
8000
8500
4
175
13-Apr-2016 16:10
175
8000
8500
9000
9500
10000
9000
9500
10000
Pixel
STUC -XCOS
6
LP4 Move
SPACE TELESCOPE
SCIENCE INSTITUTE
•
LP4 will be at ~ -5”
–
–
–
–
Assuming current usage move will be in July 2017
LP3 will last ~ 2.5 years
Resolution is expected to be within ~ 10% from resolution at LP3
Will execute program over Summer 2016 to evaluate resolution with
adjusted focus
Light leak when
wavecal lamp used
Active area of
the detector
LP2 location
LP1 location
Geocoronal
Ly emission
+6”
+3”
0”
~ LP3 location
-3”
-6”
Wavecal
location
~ LP4 location
13/05/2016
STUC - COS
7
COS NUV Wavelength Calibration
•
SPACE TELESCOPE
SCIENCE INSTITUTE
NUV help desk
call – program 13846 (99 orbits), Cycle 22, PI: Todd Tripp
These)large)wavecal)errors)in)the)COS)NUV)
– Wavelength
offsets up to ~+2 Å in some cases and up to -1.5 Å in others...
mode)are)persistent)but)not)en5rely)consistent:)
– NUV absolute
wavelength calibration requirement is 15 km/s
• Five)sight)lines)from)my)program:)
2
FBQS0751+2919
Wavelength Error (Angstroms)
PG1148+549
PG1407+265
1
PG1630+377
PHL1377
0
!1
!2
1900
•
2000
2100
2200
Observed Wavelength (Angstroms)
2300
Issues with wavelength calibration tracked down to 2 different causes
1. OSM2 mechanism position uncertainty outside of allowed ranges
2. Zero points of dispersion relations not updated on-orbit for some NUV settings
13/05/2016
STUC - COS
8
OSM2 mechanism position uncertainty
SPACE TELESCOPE
INSTITUTE
•SCIENCE
OSM2
mechanism
•
position uncertainty removed by CalCOS by cross-correlating
lamp flash concurrent with science exposure, with lamp template
Range over which cross-correlation search takes place defined in reference file
(WCPTAB)
– It was historically +/- 1 FP-POS (57 pix) around zero
– Zero point of search range has been adjusted since SMOV to take into account secular
drift of mechanism
13/05/2016
STUC - COS
9
OSM2 mechanism position uncertainty
SPACE TELESCOPE
INSTITUTE
•SCIENCE
OSM2
mechanism
•
position uncertainty removed by CalCOS by cross-correlating
lamp flash concurrent with science exposure with lamp template
Range over which cross-correlation takes place defined in reference file (WCPTAB)
– It was historically +/- 1 FP-POS (57 pix) around zero
– Zero point of search range has been adjusted since SMOV to take into account secular
drift of mechanism
ORIGINAL SHIFTS
13/05/2016
STUC - COS
10
OSM2 mechanism position uncertainty
SPACE TELESCOPE
INSTITUTE
•SCIENCE
OSM2
mechanism
•
position uncertainty removed by CalCOS by cross-correlating
lamp flash concurrent with science exposure with lamp template
Range over which cross-correlation takes place defined in reference file (WCPTAB)
– It was historically +/- 1 FP-POS (57 pix) around zero
– Zero point of search range has been adjusted since SMOV to take into account secular
drift of mechanism
ORIGINAL SHIFTS
CORRECTED
SHIFTS
13/05/2016
STUC - COS
11
OSM2 mechanism position uncertainty
SPACE TELESCOPE
SCIENCE INSTITUTE
•
To correct problem, search range has been expanded to +/- 90 pix for
G185M and G225M
•
New WCPTAB delivered on Mar 25 2016
•
In the process of notifying all COS users through STAN (includes both
issues that surfaced in Tripp’s program)
•
In the process of notifying PIs of specific programs affected (few specific
datasets only, taken since July 31st 2013)
•
Will continue to monitor closely the OSM2 mechanism drift
•
The second issue highlighted by Tripp’s program is discussed next...
13/05/2016
STUC - COS
12
COS NUV Zero Point Offsets
•
•
SPACE TELESCOPE
NUVINSTITUTE
dispersion
SCIENCE
solutions in use were derived in TV03 (1st order poly)
Zero points, to place TV03 solutions in on-orbit frame of reference derived during
SMOV (2009)
– “d (pixel)” in DISPTAB -Table
cenwaveNUV
+ stripe dependent
(Oliveira
et al. 2010,
COS2.ISRNUV
2010-05)
Table
offsets determin
determi
Table 2.
2. NUV offsets
offsets determined
determined from
from program
program 11474
11474
Table
2. NUV offsets
– Derived by using STIS data of same target
Grating
Grating
Cenwave
Cenwave
Stripe
Stripe A
A
(pixel)
(pixel)
Stripe
Stripe B
B
(pixel)
(pixel)
– For some settings zero points never derived
G225M
no
G225M of 2186
2186
no overlap,
overlap, 35.412
35.412 no
no overlap,
overlap, 35.874
35.874
• All cenwaves
G185M
2217
no
overlap,
33.223
no
overlap,
2217
no overlap, 33.223 no overlap, 33.591
33.591
• G225M: 2186/2217/2233/2250
–
A,B
2233
no
overlap,
33.352
no
overlap,
33.733
2233
no overlap, 33.352 no overlap, 33.733
2250
no
no
overlap,
2250
no overlap,
overlap, 34.934
34.934 –
noA
overlap, 35.437
35.437
• G225M: 2268/2283/2306/2325/2339
2268
no
9.358,
2268
no overlap,
overlap, 32.670
32.670
9.358, 33.052
33.052
• G285M: 2996/3035/30573074/3094
2283
no
9.817,
2283
no overlap,
overlap, 29.375
29.375 – C
9.817, 29.681
29.681
2306
no
overlap,
29.905
11.108,
2306
no overlap,
30.331
• G230L: 2635/2950/3000
– A, B,29.905
3360 –11.108,
B, C30.331
2325
no
overlap,
29.952
11.651,
30.128
2325
no overlap, 29.952 11.651, 30.128
– Due to lack of overlap
with no
STIS
data
or low12.520,
S/N 33.548
2339
overlap,
33.193
2357
10.491,48
30.857
12.085,binary)
31.175
– Unsuitable target (G185M:
Feige
– pulsating
Stripe
Grating
Cenwave
Stripe C
C
Grating
Cenwave
(pixel)
(pixel)
d
Stripe
d AA
Stripe
(pixel)
(pixel)
(pixel)
(pixel)
Notes
Stripe
NotesBB
Stripe
(pixel)
(pixel)
10.296,
·· ··overlap,
··overlap,
,, ·· ·· ·· 35.412
,,35.412
-25.798
Vis
G225M 36.094
2186 no
no
nooverlap,
overlap,
10.296,
36.094
-25.798no
Vis 01
0133
G225M
2186
11.910,
·· ··overlap,
··overlap,
,, ·· ·· ·· 33.223
,,33.223
-21.873
Vis
2217 no
no
nooverlap,
overlap,
11.910, 33.783
33.783
-21.873no
Vis 01
0133
2217
12.379,
·· ··overlap,
··overlap,
,, ·· ·· ·· 33.352
,,33.352
-21.359
Vis
2233 no
no
nooverlap,
overlap,
12.379, 33.738
33.738
-21.359no
Vis 01
0133
2233
11.607,
·· ··overlap,
··overlap,
,, ·· ·· ·· 34.934
,,34.934
-24.069
Vis
2250 no
no
nooverlap,
overlap,
11.607, 35.676
35.676
-24.069no
Vis 01
0133
2250
9.817,
··no
·· ··overlap,
,, -23.694,
-23.324
Vis
01
2268 no
overlap,
32.670
9.358,
33
9.817, 33.141
33.141
-23.694,
-23.324 9.358,
Vis 33.
01
2268
32.670
12.990,
··no
·· ··overlap,
,, -19.864,
-16.895
Vis
01
2283 no
overlap,
29.375
9.817,
29
12.990, 29.885
29.885
-19.864,
-16.895 9.817,
Vis 29.
01
2283
29.375
14.653,
30.274
·
·
·
,
-19.223,
-15.621
Vis
01
2306
no
overlap,
29.905
11.108,
30
14.653, 30.274
· · ·overlap,
, -19.223,
-15.621 11.108,
Vis 01
2306
no
29.905
30
14.831,
··no
·· ··overlap,
,, -18.477,
-15.735
Vis
2325 no
overlap,
29.952
11.651,
30
14.831, 30.566
30.566
-18.477,
-15.735 11.651,
Vis 01
01
2325
29.952
30
13.989, 33.778
·no
· ·overlap,
, -21.028,
-19.789 12.520,
Vis 01
2339 no
overlap,
33.193
12.520,
33
2339
33.193
33
15.542, 31.462
-19.090,
-15.92012.085,
Vis 01
2357 -20.366,
10.491,
30.857
12.085,
31
2357
10.491,
30.857
31
2373
9.517, 32.645
12.897, 33.283
16.734, 33.267
-20.386,
Vis 01
2373 -23.128,
9.517,
32.645-16.53312.897,
12.897,
33
2373
9.517,
32.645
33
2390
10.172, 32.510
12.661, 33.024
16.801, 33.141
-20.363,
-16.34012.661,
Vis 01
2390 -22.338,
10.172,
32.510
12.661,
33
2390
10.172,
32.510
33
2410
11.335, 29.070
13.799, 29.420
18.073, 29.467
-15.621,
-11.39413.799,
Vis 01
2410 -17.735,
11.335,
29.070
13.799,
29
2410
11.335,
29.070
29
• Why has problem
has 2617
not surfaced
before?
G285M
3.297, 33.766
5.260, 33.960
9.754,
34.344
-30.469,
-28.700,
-24.590
Vis
01
G285M
2617
3.297,33.766
33.766
5.260,33.
33
G285M
2617
3.297,
5.260,
– NUV has very low usage
2637
3.948, 35.125
6.405, 35.652
11.178, 35.883
-29.247,
Vis 35.
01
2637 -31.177,
3.948,
35.125-24.7056.405,
6.405,
35
2637
3.948,
35.125
2657
4.208, 30.183
7.395, 30.546
8.697, 30.664
-23.151,
Vis 30.
01
2657 -25.975,
4.208,
30.183-21.9677.395,
30
30.183
– Tripp had FUV data which
allowed
him to predicted
expected
NUV2657
data (Ly4.208,
series
at z ~ 7.395,
2676
4.368, 33.161
6.815, 33.391
10.653, 33.871
-26.576,
Vis 33.
01
2676
4.368,
33.161
2676 -28.793,
4.368,
33.161-23.2186.815,
6.815,
33
aa
a
1)
2695
5.019,
-106.233
8.827,
2695
5.019, -106.233
8.827, -108.190
10.631, -110.788
117.017,
121.419
Vis-108
01
2695 111.252,
5.019,
-106.233
8.827,
-108
13/05/2016
STUC
COS
13
2709
4.913,
34.826
2709
4.913, 34.826
9.043, 35.237
11.110, 35.488
-26.194,
Vis 35.
01
2709 -29.913,
4.913,
34.826-24.3789.043,
9.043,
35
2719
5.460, 40.373
8.355, 40.900
12.177, 41.262
-34.913,
-32.545,
-29.083
Vis
02
2719
5.460,
40.373
8.355,
40.
2719
5.460, 40.373
8.355, 40
2739
4.892,
38.412
9.163,
2739
4.892, 38.412
9.163, 38.925
9.502, 39.545
-33.520,
-29.762,
-30.043
Vis 38.
02
2739
4.892, 38.412
9.163,
38
What are we doing
to fix NUV λ issue?
SPACE TELESCOPE
SCIENCE INSTITUTE
•
•
•
•
•
G225M/2217/A/B/C offsets derived using AG DRA data (E230M)
Missing offsets: use value from the nearest stripe for the same cenwave
(except for G185M, not perfect but reduces offset)
Updated NUV DISPTAB has been produced and delivered
STAN is being prepared to warn all COS users as well as PIs of all COS
NUV programs that used settings not updated on-orbit
Tripp’s data has been reprocessed by COS team, and PI was given
access to it
Ø Special NUV wavelength calibration program do update zero points has
been created and approved for execution by HSTMO
– 3 special calibration programs (1 COS + 2 STIS, for a total of 5 orbits)
• COS/G185M/NGC330-B37, STIS/E230M + G430M/HD187691 to update G225M + G285M
zero points, STIS/G230MB + G230M/HD6655 to update G285M + G230L zero points
– Program expected to execute over the next couple of months time frame
– Once data analyzed and updated file delivered, STAN will be released
13/05/2016
STUC - COS
14
COS/FUV Wavelength Calibration
SPACE TELESCOPE
SCIENCE INSTITUTE
•
Current requirement for wavelength calibration is 1 resolution
element (~6 pixels, 1 σ)
•
Can be improved to 3 pixels RMS by revising dispersion solutions
– Working ongoing also to improve walk correction and geometric
correction
•
Dispersion solutions are given by polynomials that transform pixels
to wavelengths using a zero point and a linear coefficient (slope)
•
Next slides walk us through different steps adopted to determine
updated zero-points and slopes for dispersion solutions
– Examples shown are all for LP1 data (G130M + G160M)
13/05/2016
STUC - COS
15
Steps to Improve λ dispersion
Solutions - I
SPACE TELESCOPE
INSTITUTE
1 SCIENCE
Cross-correlate
COS spectra with STIS spectra, used as a reference
wavelength, and derive wavelength offsets in pre-defined spectral
windows where ISM lines are identified with good S/N. Fit the COS-STIS
offsets vs XFULL to a linear solution (green line) to derive new dispersion
solutions. This allows us to derive updated slopes and zero-points.
New goal
+/- 3 pix
Original req.
+/- 6 pix
13/05/2016
STUC - COS
16
Resul&ng)dispersi
Steps to improve λ dispersion
solution - II
SPACE TELESCOPE
SCIENCE INSTITUTE
2 New dispersion slopes are consistent with ray-trace models when plotted
vs. OSM position. Ray-trace models have arbitrary focus reference,
resulting in arbitrary vertical offset. χ2 minimization performed between
ray-trace slopes and COS-STIS dispersion slopes vs. OSM position
allows us to determine vertical offset. Provides us with set of robust
dispersion slopes (red dotted line) based on both COS-STIS cross-correlation
and ray-trace modeling.
Resul&ng)dispersion)solu&ons)
13/05/2016
STUC - COS
New)dispersions)are)in)agree
17
LP1 Dispersion Solutions (Slopes)
SPACE TELESCOPE
SCIENCE INSTITUTE
Adopted slopes for new
dispersion solutions
13/05/2016
STUC - COS
18
Steps to improve λ dispersion
o%point*determina.on ** solution - III
on*
e*
els*
gle*
aves*
djust*
SPACE TELESCOPE
SCIENCE INSTITUTE
3 Because of TA uncertainties in COS spectra, the zero-points derived from
COS-STIS cross-correlations
are only accurate to +/- 3 pix. (ray-trace
1327*vs*1291*
model does not predict zero
points). To correct for this, we perform crossFUVB*
NEW*dispersion*
correlations between COS
spectra obtained within single visits with
New*zero%point*
different cenwaves. We adjust the COS-STIS derived zero-points so that
the mean cross-correlation offsets between different cenwaves become
Zero%point*determina.on **
zero.
• Due*to*target*acquisi.on*
1327*vs*1291*
FUVB*
uncertainty,*COS%STIS*
NEW*dispersion*
derived*zero%points*are*
OLD*zero%point*
only*accurate*to*3*pixels*
• Use*COS%COS*cross%
correla.ons*within*single*
visits*to*align*all*cenwaves*
with*each*other*and*adjust*
zero%points*
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1327*vs*1291*
FUVB*
NEW*dispersion*
New*zero%point*
1327*vs*1291*
FUVB* 19
NEW*dispersion*
OLD*zero%point*
Steps to improve λ dispersion
solution - IV
TELESCOPE
4 SPACE
Re-run
the COS-COS cross-correlations with the COS-STIS + ray-trace based
SCIENCE INSTITUTE
dispersion slopes, and the zero-points adjusted to align cenwaves together (from
step 3). Mean and RMS offsets in the COS-COS cross-correlations are improved
compared to what is in the pipeline now
FUVB 1309 vs. 1291
Old
Old
Old
New
Wavelength (Å)
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New
Residual Shift (pix)
20
COS-STIS Comparison: Old vs. New
SPACE TELESCOPE
SCIENCE INSTITUTE
OLD
13/05/2016
NEW
STUC - COS
21
COS-COS Comparison – Summary
SPACE TELESCOPE
SCIENCE INSTITUTE
13/05/2016
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22
Plan Forward
SPACE TELESCOPE
SCIENCE INSTITUTE
•
Dispersions for LP1/G130M and LP1/G160M are been delivered to
HST Data Processing (all data retrieved after May 5 2016 will use new DISPTAB)
– STAN informing users and explaining how new coefficients were derived
has been released (extensive content)
http://www.stsci.edu/hst/cos/documents/newsletters/
cos_stis_newsletters/full_stories/2016_05/new_disptab
– FUV dispersion reference files are now lifetime dependent
•
LP2 and LP3 dispersion solutions not as well constrained from COSSTIS comparison. As with LP1, will deliver COS-STIS + ray-trace
based updated solutions after testing
– In the process of finalizing COS-COS cross-correlation windows for LP2
data
– Plan to deliver updated dispersion solutions for LP2 + LP3 by Summer
2016
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23
SPACE TELESCOPE
SCIENCE INSTITUTE
BACK-UP SLIDES
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24
X-Walk Correction - Update
SPACE TELESCOPE
SCIENCE INSTITUTE
•
Detector X-walk limits wavelength accuracy to a ~3 pixels
•
Progress made on characterizing X-walk as a function of X and PHA
– Use data from 12793, which took lamp exposures at different HV
(and Y positions)
– Cross-correlate lamp lines in different PHA bins and X regions
– Correct for drift of OSM mechanism during lamp exposures
– Fit X-shifts as a function of X and PHA with polynomial
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25
X-Walk Correction: Results
SPACE TELESCOPE
SCIENCE INSTITUTE
HVA/HVB
143/142
143/142
143/142
143/142
143/142
143/142
Polynomial
fitting is
reasonable
but we still
need to work
out the
edges in X/
PHA space
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26
X-Walk Correction: Plan Forward
SPACE TELESCOPE
SCIENCE INSTITUTE
•
X-walk currently implemented as list of polynomial coefficients in
CalCOS
– Dependent on x, y location and PHA
– Mechanics of X-walk correction never tested
• Need for 64 bit identified during preliminary testing => HSTDP June build
• Mechanics testing ongoing
• The plan is to mplement any other fixes from mechanics testing in HSTDP
June build
•
Test the scientific content of the new X-walk reference file
– Earliest date for HSTDP implementation is build in Fall 2016
•
Once satisfied with scientific validation can just deliver reference file.
– No need to redo wavelength dispersion solution
– Updated WALKTAB should reduce scatter in residuals of wavelength cal.
– Expect to deliver updated WALKTAB by Fall
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27
Geometric Correction: Update (I)
SPACE TELESCOPE
SCIENCE INSTITUTE
•
Procedure
– Use same pre-launch data originally used to derive distortion solution.
– Derive differential geometric correction by fitting wavelengths of lines in
FLT images produced with current reduction, using a model lamp spectrum
based on NIST wavelengths.
• Include multiple lamp lines in fits where needed
– Next will compute differential distortion table based on global map of offsets
and use as a lookup table to update original distortion solution
– Will allow tuning of distortion solution to take into account updates to the
walk correction
•
Have refined algorithm for measuring shifts without allowing strong
features to bias results for close but weaker lines
– Global maps for shifts show distortion solution mostly pretty good, but with
some larger errors near left and right edges, and in the detector region
below the current Lifetime Position (LP3)
– Still need to produce updated distortion table and verify reduction of
residuals (next on agenda)
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28
Geometric Correction: Update (II)
SPACE TELESCOPE
SCIENCE INSTITUTE
•
Example of lines
fitted as blend
– Histogram shows
data
– Dotted lines show
predicted spectrum
– Dash dot line shows
fit to individual
combined line
•
Next 2 pages show
offsets measured
from all fits
–Height of arrow
corresponds to
measured offset in X
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29
FUVA: line offsets from
expected X location
SPACE TELESCOPE
SCIENCE INSTITUTE
x offsets shown
along y axis for
better visualization
Blue: PSA region
Red: WCA region
Up: line found to
the right of
expected location
Down: line found to
the left of expected
location
Note outlier with
shift of 12 pixels in
yellow box
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30
FUVB: line offsets from
expected X location
SPACE TELESCOPE
SCIENCE INSTITUTE
x offsets shown
along y axis for
better visualization
Blue: PSA region
Red: WCA region
Up: line found to
the right of
expected location
Down: line found to
the left of expected
location
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31
Distribution of Offsets
SPACE TELESCOPE
SCIENCE INSTITUTE
•
Most points within 2 pixels, but occasional outliers are real
– Note particularly large outlier on FUVA near X = 11500 and Y = 430
which corresponds to a very localized 12 pixel distortion
• Fortunately such large offsets are rare
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Geometric Correction: Plan Forward
SPACE TELESCOPE
SCIENCE INSTITUTE
•
Offsets derived from analysis described in previous slides will be
incorporated in the current GEOTAB
• Will then proceed with scientific validation of updated GEOTAB
•
Will iterate ~couple of times between walk correction and geometric
distortion correction
– Will need to scientifically validate every iteration
– Once satisfied with both will need to redo wavelength dispersion
solutions for all Lifetime Positions
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33
LP4 Move Timeline
•
SPACE TELESCOPE
SCIENCE
INSTITUTE
Exploratory
phase during August-September 2016
Aug/Sep
2016
– Gain map
– Fine optimization of Y position via evaluation of gain-sag effects at LP3/LP4 overlap
– Mini focus sweep (1 setting) followed by resolution measurements, to evaluate impact
on resolution (data taken without focus adjustment shows up to ~30% R degradation)
•
Enabling phase during December 2016
– Full focus sweep (only for settings not done before)
– Aperture placement
– TA verification
•
Calibration phase (part I) during March 2017
– Need cross-dispersion profiles ready to calibrate data at move date
– Flux + flat calibration program
•
Dec
2016
Mar
2017
Estimated move date is July 2017 (~2.5 yrs at LP3)
– Prediction based on past usage
– Will adjust move date after Cycle 24 results
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Jul
2017
34
Planning for COS/FUV LP4 - FSW
SPACE TELESCOPE
•COS
Software
SCIENCEFlight
INSTITUTE
(FSW) Update : LV0058
•
SCR C367 covers the updates to pcmech_ApMXDispPosition, the aperture
mechanism position table for moves in cross-dispersion. The FUV values for LP5 –
LP8 are now the same as FUV LP3.
•
SCR C368 changes the initialization value for global variable ta_ApMLTPosition
from FUV LP3 to 0 (NUV & FUV LP1). Regardless of the initialization value,
ta_ApMLTPosition will be overwritten by LAPER, therefore setting it to 0 means the
value does not need to be maintained as the lifetime position evolves.
•
The LV0058 changes are being combined with the LV0057 changes for the planned
CS FSW release in September 2016.
•
LV0057 slightly changes one telemetry item, and adds three new ones. Ground
System and keyword rules are being modified to allow for seamless transition to
the enhanced telemetry format.
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35
LP4 Exploratory Phase
•
SPACE
LP4TELESCOPE
will be ~
SCIENCE INSTITUTE
-2.5” below LP3 or ~-5” below LP1
– No other detector real estate easily available without major changes to how we operate
– Resolution degradation at -5” has not been robustly quantified
• Data without focus adjustment shows ~30% degradation
– As part of exploratory phase need to measure resolution at -5”, after determining what is
the best focus at that position
• Requires mini-focus sweeps at -5” with target used before (Feige 48)
• Probably only 1 cenwave needed (G130M)
• Once best focus is determined, can determine resolution (G130M, AzV 75)
– Gain map (internal) will allows to determine exactly how close to LP3 can we place LP2
• If needed can observe external target to determine impact of LP3 gain sag on LP4
Light leak when
wavecal lamp used
Active area of
the detector
LP2 location
LP1 location
+6”
~ LP3 location
-3”
Geocoronal
Ly emission
+3”
0”
-6”
Wavecal
location
~ LP4 location
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36
COS/FUV TDS Update
Data upTELESCOPE
to March 2016 included
SPACE
SCIENCE INSTITUTE
LP1
•
LP2
LP3
•
•
Rate of decline of COS FUV
Time Dependent Sensitivity
(TDS) varies with time, detector,
and λ
Steeper TDS slopes in periods of
increased solar activity – likely
due to atomic O at HST’s orbit
reacting with CsI photocatode of
open-faced COS FUV detector
Increase in sensitivity with HV is
under study
10.7 cm radio flux
Breakpoints in slope
HV Increase
• New FUV/TDS ref file delivered early May, in use by HSTDP
• FUVA slopes slightly shallower (G130M -3.5% => -2.5%;
G160M -5.5% => -4.5%; G140L -4% => -3%).
• FUVB /G160M slightly steeper (-1.8% => -2.2%)
•No ETC updates for Cycle 24 phase II support
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37
COS/NUV TDS Update
SPACE TELESCOPE
SCIENCE INSTITUTE
~ -0.1%/yr
~ -0.1%/yr
~ -3%/yr
~ -12%/yr
COS NUV TDS trends continue to remain constant
- Delivered updated synphot files for use with the ETC 24.2
- ETC files had slopes based on data obtained up to 2011, and predictions for mid-Cycle 25
were off by as much as ~40% for a couple of G285M settings (most within a few %, lead to
lower predicted throughput)
- We are in the process of updating TDS ref file for use with the pipeline
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38