Image Stability

ACS SMOV image stability test (prop 9017)
went from a cold soak (anti-solar pointing) for 8
orbits to a hot attitude (including off-nominal
roll)
– Nominal jitter (typically about 3 mas RMS
and 10 mas peak-to-peak)
– Smooth drift at rates up to about 6 mas/hr in
both the HRC and WFC (same direction).
– Drift may be due to FGS's or to rigid body
movement of the ACS wrt the OTA
– Similar to image drift rates for other SIs.
Calibration – Flat Fields

L-flat for the F555W filter, the plot is a 4th order
least-squares fit to the stellar photometry.
– ~10% gradient from upper left to lower right
– (Mack, van der Marel, Bohlin, Blakeslee, Cox)
Flat field – Sanity Checks

Ratio of the F555W photometry in the CRJ to the
DRZ image, corrected for distortion.
– White is 1.10 and black is 0.93.
Pixel Map from Geometric
distortion
– ratio produces 1% residual
Sensitivity
• Inflight sensitivity vs prediction from components
HRC
WFC
F892N
F850LP
F814W
F775W
F660N
F658N
F625W
F606W
F555W
F550M
F502N
F475W
F435W
F344N
F330W
F250W
F220W
F892N
F850LP
F814W
F775W
F660N
F658N
F625W
F606W
F555W
F550M
F502N
F475W
F435W
0.8
0.85
0.9
0.95
1
1.05
1.1
1.15
1.2
0.85
0.95
1.05
1.15
1.25
WFC Distortion Calibration
• 4th order 2D polynomial fit matches observed distortion well
- RMS residual 1.1 mas (.02 px)
- peak deviation ~ .2 px
WFC CCD Amplifier Cross-talk
• Low-level “ghosts” of extended objects mirrored in alternate quadrants
• Slight “droop” (fractional e-) in bias level of all 3 alternate amps
• Ghosts do not appear to be proportional to target signal
Hard (2 e-) stretch of
WFC UGC10214 image
WFC: Long wave halo
n
CC D P ac kag e C r o ss -se ctio n
B ac k s id e i llu m in ate d,
th in n ed C C D (~1 5 m m )
Al metal layer reflects long-l photons
S od a g l as s h e a d er
20 0 0 m m
H e ad e r m e ta liz atio n
F814w
F850LP
WFC: Long wave halo
F775W
F850LP
IR Encircled Energy Performance
FILTER
ETC Measured 80%
5x5 px 5x5 px Ensq (px)
F775W (I)
0.8
0.79
5.2
F850LP (z)
0.76
0.68
7.1
FR1016N-996 0.73
0.49
15
FR1016N - 996
Optical “Ghosts”
Two ghost features have been identified with >0.1% of target energy:
WFC CCD to window reflection
produces pairs of elliptical ghosts
with ~ 0.2% integrated energy
F660N [NII] filter produces halos
with ~2% of integrated energy due
to reflection between its surfaces
Cats-Eye Nebula
NGC 6543 (HRC)
[OII] 3727
[OIII] 5007
Ha 6563
Ramp filter
Coronagraph performance
• Target acquisition functions
• executed proposal second time with
dithering to determine optimum location
under each occulting spot
Coronagraph Dither Results
Coronagraph Performance
SBC – First Light Image
Globular star cluster
NGC6681. This
cluster, with [Fe/H] =
-1.5, is rich in Blue
Horizontal Branch
stars.The image
combines first light
data taken with three
filters F125LP,
F150LP, and F165LP.
Solar Blind Channel
CALACS
• First generation updates to CALACS & PyDrizzle
are complete, software is frozen for distribution in
next STSDAS
•Includes ST-ECF AXE software for grism/prism
Mosaic generated from 18
images of 47 Tuc
HDF-N: i+ z & grism
WFC
- 2x i
- 3x z orbits
- “HDF overlay”
Grism: 3 orbits
HDF-N ACS Grism examples
Emission-line galaxy with continuum and knots
- [OIII] 5007 and Ha 6563
Redshift z = 0.319
F814AB = 22.5
(WFC 2x i + 3x z orbits, 3 grism orbits)
HDF-N SN2002dc
• Identified from difference imaging with WFPC2 HDFN
WFC 2x i + 3x z orbits, 3 grism orbits
Galaxy & SN z=0.475
HDF-N SN2002dc
• Galaxy and SN at z=0.48
• SN mag. is 22.7 (i)
• Type I (probably Ia)
Galaxy & SN z=0.475
SN2002dd
•
Identified from
extracted spectra !
Galaxy
z=0.79
SnIa
z=1.06
HDF-N SN2002dd
• Follow-up with DD proposal
Cool Image – A1689
Courtesy
ACS Science Team
Image Stability