ACS Instrument Science Report 99-06
ACS calibration pipeline testing:
error propagation
Doug Van Orsow, Max Mutchler, Warren Hack, Robert Jedrzejewski
17 August 1999
ABSTRACT
This report details how CALACS, the calibration software pipeline for the Advanced Camera for Surveys (ACS), produces ERR (error) array output. From a standard error analysis
text we derive the equations which CALACS should use to propagate errors. Tests are then
run to verify the actual CALACS error array output equals the expected values from our
derived equtions. CALACS thereby propagates the errors to a final statistical uncertainty
for each pixel in the calibrated SCI (science) array.
1. Introduction
CALACS corrects the science array from any systematic type of noise source affecting
the true signal by subtracting or dividing the appropriate calibration reference files (see
ISRs 99-03 ”CALACS Operation and Implementation” by Hack and 99-04 “ACS calibration and pipeline testing: basic image reduction” by Mutchler). Each correction in itself
may then introduce some additional error, calculated using Poisson statistics, to be
included in the error array. The error array then represents the quality of the science obsevations and of the reference files used to calculate its values. In a statistical sense one
might use it as a weighting factor in photometric accuracy for a certain area of the CCD or
the entire field of view. It may also tell you if the pixels are dominated by the read noise,
the background, or some other type noise source.
However, since the error array is the same size as the science array, it will be very large
(64Mb) in the case of the WFC. Several fully calibrated WFC images will take nearly a
gigabyte of disk space. Those who are disk space limited can use the keyword WRTERR
to control whether the error array is included in the output of the CALACS steps.
1
2. Test images
Our test images for each channel consist of two types, STIS data and simulated data
created by the IRAF task imcalc. Each has its own advantages over the other, so both types
were used.
The STIS test image for the WFC consists of 16 different STIS CCD images. The
IRAF task imcopy was used to mosaic these STIS images into two 2kx4k imsets. The
WFC reference files also consist of the very same reference images listed in each STIS
primary header. The script used to create the WFC test images is listed in Appendix A. Six
pixels were chosen on the WFC image, three pixels on stellar sources with high DN, two
pixels on extra galactic sources with moderate DN, and one pixel chosen from the background with the lowest DN value in the image. These pixels represent a large dynamic
range of DN in order to test all possible ranges of ERR values. These six test pixels were
run incrementally through each step of the ACS pipeline and their ERR array values
recorded. This allows the change in the error array to be determined for each CALACS
step and compared with the expected values. It also confirms which steps which have no
affect at all on the error array.
The STIS test images for the HRC and SBC did not need mosaicing as their
1024x1024 pixel dimensions already match. Using STIS data is advantageous since it is a
close match to what actual ACS data is expected be. A disadvantage is that some of the
reference files have such small error values that the resultant ERR array is hardly changed
if at all.
The simulated test images for all three channels were created with the IRAF task
imcalc and are the same as used in ISR 99-04 (Mutchler). Again a large range of DN were
created using imcalc and the same range of pixels were followed throughout the ERR
propagation process. Simulated data is advantageous in that we can input our own exact
values for each pixel and then test whether the output exactly equals what was planned.
Running the IRAF task catfits on the raw WFC image shows both ERR extensions as
dimensionless placeholders:
EXT#
FITSNAME
FILENAME
EXTVE
DIMENSIONS
BITPIX
0
wf_sci1_raw.fits
wf_sci1_raw.fits
1
IMAGE
SCI
1
2
IMAGE
ERR
1
16
3
IMAGE
DQ
1
16
4
IMAGE
SCI
2
5
IMAGE
ERR
2
16
6
IMAGE
DQ
2
16
16
2
4144x2068
4144x2068
16
16
3. CALACS tasks and steps
Test images for all three channels of ACS were incrementally run through the steps in
each CALACS task. The ERR and SCI array values were then recorded from the appropriate reference and science files. Scripts similar to ones used in ISR 99-04 (Mutchler) were
used to analyze all three channels.
CALACS - controlling task for entire pipeline
ACSCCD - ccd specific calibration task
doNoise - error array initialization step
Unlike other CALACS steps, there is no keyword switch in the input file’s primary
header that controls whether doNoise is run. This step automatically runs in the ACSCCD
task and checks the ERR array of the input file. If one exists and has non zero values,
doNoise will not alter the image. If an ERR array does not exist or has all zero values,
doNoise will initialize the error array with floating point values using a simple noise
model in electrons depending upon the channel:
σ ccd =
readnoise 2
DN – bias
max  --------------------------, 0  +  -------------------------- 
 gain
  gain 
σ mama = max ( 1, counts )
Several versions of HRC and WFC images were tested by varying the DN, bias, gain,
and readnoise values in the image headers and/or reference tables. These values were
changed by editing the CCDTAB reference table. Bias, gain and readnoise do not apply to
MAMA images. Its noise model is simply the square root of the counts, with a lower limit
of 1.
Running catfits on the WFC image after running doNoise shows both ERR extensions
have been expanded to match the size of the SCI and DQ extensions. Their integer values
have now also been replaced by floating point values as indicated by the -32 value in the
BITPIX column:
EXT#
FITSNAME
FILENAME
EXTVE
DIMENSIONS
BITPIX
0
wf_sci1_raw.fits
wf_sci1_raw.fits
1
IMAGE
SCI
1
4144x2068
-32
2
IMAGE
ERR
1
4144x2068
-32
3
IMAGE
DQ
1
4144x2068
16
4
IMAGE
SCI
2
4144x2068
-32
5
IMAGE
ERR
2
4144x2068
-32
6
IMAGE
DQ
2
4144x2068
16
16
3
After running doNoise, all cases of the expected ERR values agree with the CALACS
output ERR values, within roundoff error. Here are a subset of the test cases:
Channel
DN
Bias
Gain
Readnoise
Expected
error
CALACS
error
WFC real
33890
4493.9
1
3.4952
171.49
171.5
WFC real
1320
4493.9
1
3.4952
3.4952
3.495
WFC sim
65000
5493.9
1
5.4952
244.0
244
WFC sim
1000
5493.9
1
5.4952
5.4952
5.495
HRC real
33069
5000
1
3.4
167.57
167.6
HRC real
1378
5000
1
3.4
3.4
3.4
HRC sim
65000
4000
1
3.4
247.01
247
HRC sim
5000
4000
1
3.4
31.81
31.81
SBC real
1896
N/A
N/A
N/A
43.54
43.54
SBC real
1419
N/A
N/A
N/A
37.67
37.67
SBC sim
60000
N/A
N/A
N/A
244.95
244.9
SBC sim
0.50
N/A
N/A
N/A
31.62
1.0
doDQI - bad pixel determination step
doAtoD - analog to digital correction step
doBlev - bias level correction step
These preceeding three CALACS steps have no affect on the error array. The doBlev
code contains no error analysis in the fitting of the bias level correction since its not felt
the error values will be of any significance. However it may be worthwhile investigating in
the future since it can always be added to the pipeline.
Running catfits on the WFC image shows the doBlev step has trimmed the overscan
regions from the ERR extensions to match the SCI and DQ extensions:
EXT#
FITSNAME
FILENAME
EXTVE
DIMENSIONS
BITPIX
0
wf_sci1_raw.fits
wf_sci1_raw.fits
1
IMAGE
SCI
1
4096x2048
-32
2
IMAGE
ERR
1
4096x2048
-32
3
IMAGE
DQ
1
4096x2048
16
4
IMAGE
SCI
2
4096x2048
-32
5
IMAGE
ERR
2
4096x2048
-32
6
IMAGE
DQ
2
4096x2048
16
16
4
doBias - bias image subtraction step
The bias reference file is subtracted from the input science file for the CCDs only. This
includes both the SCI and ERR arrays. Bevington’s “Data Reduction and Error Analysis
for the Physical Sciences” chapter 3 provides the equations for us to derive the formula for
calculation of errors when datasets are arithmetically related:
σ u = sci [ err ] x = sci [ sci ] – ref [ sci ]
error
σ v = ref [ err ] σ x = output
u = sci [ sci ]
v = ref [ sci ]x
a = cons tan t
b = cons tan t
σ uv = correlation
error
The summ or difference in data u and v results in x:
2
x = au ± bv
The error output in x is then given by:
2
2
2
2
2
σ x = a σ u + b σ v + abσ uv
2
Since a=1 and u and v are uncorrelated:
σx =
2
2 2
σu + σv b
The constant b in the equation above refers to the fact that the bias reference file needs
to be scaled up to match the input science file. The exptime and gain below refer to values
from the input science file. These values are not included if the reference file itself has an
5
EXPTIME greater than 1, although in practice this should not be the case. Substituting in
the sci and err values:
σ ccd =
exp time
2
( s ci [ err ] ) +  ref [ err ]  ---------------------  

 gain  
2
Channel
sci[err]
ref[err]
Expected error
CALACS error
WFC real
171.5
0.7487
171.5
171.5
WFC real
3.495
0.7485
3.574
3.574
WFC sim
244
10
244.2
244.2
WFC sim
5.495
10
11.41
11.41
HRC real
167.6
0.0
167.6
167.6
HRC real
3.4
0.0
3.4
3.4
HRC sim
247.0
10
247.2
247.2
HRC sim
31.81
7
32.57
32.57
ACSREJ - cosmic ray rejection task
The cosmic ray removal task has no affect on the ERR array.
ACS2D - Basic MAMA and CCD calibration task
doNoise - error array initialization step
doDQI - bad pixel determination step
The preceeding two steps are performed if not already done in the ACSCCD task.
doNonLin - Linearity correction for MAMA data step. This step is strictly for for
MAMA images. The counts observed in the science data is a[sci]. The true rate however is
6
represented by N, which we cannot be solve for in closed form, but only in an itterative
technique.
x = au
±b
a [ sci ] mama = Ne
–( τ N )
N
σ mama = --------------- sci [ err ]
a [ sci ]
Channel
a[sci]
tau
N
sci[err]
Expected
error
CALACS
error]
SBC real
1896
-0.00693
1216
43.54
27.92
27.92
SBC real
1419
-0.00693
909.9
37.67
24.15
24.15
SBC sim
60000
-0.00693
34440
244.9
140.572
140.57
SBC sim
0.5
-0.00693
0.287
1.0
0.574
0.574
doDark - dark image subtraction step
The same equation for doBias is used for CCD data in doDark since subtraction is the
operator between the data. The MAMA equation again just excludes any gain value. The
7
dark reference file is once again scaled up to match the science input in the second term of
both equtions:
σx =
2
2 2
σu + σv b
exp time
2
( s ci [ err ] ) +  ref [ err ]  ---------------------  

 gain  
σ ccd =
2
σ mama =
2
( s ci [ err ] ) + ( ref [ err ] ( exp time ) )
2
Channel
sci[err]
ref[err]
Expected error
CALACS error
WFC sim
244.2
0.1
249.27
249.3
WFC sim
11.41
0.1
51.29
51.29
WFC real
171.5
0.001409
171.5
171.5
WFC real
3.574
0.001727
3.68
3.677
HRC real
167.6
0.001402
167.6
167.6
HRC real
3.4
0.001635
3.40034
3.404
HRC sim
247.2
0.01849
247.21
247.2
HRC sim
32.57
0.01849
32.62
32.59
SBC real
27.92
0.001
27.92
27.92
SBC real
24.15
0.001
24.15
24.15
SBC sim
60.18
0.001
60.21
60.21
SBC sim
0.574
0.001
2.081
2.081
doFlat - flat field image combination and division step
The flat field reference file is divided into the input science file, again for both the SCI
and ERR arrays. The error in dividing sci[err] by ref[err] is:
au
x = ± -----v
8
The error in x when dividing is:
2
2
2
2
σ uv
σx
σu
σv
---------=
+
–
------------------2
2
2
2
uv
x
u
v
Multiplying both sides by x squared and dropping the correlation term:
2 2
σx
2 2
σu x
σv x
= ------------- + ------------2
2
u
v
2
From the first equation above:
u = xv
Substituting xv in for u and u/v for x:
2 2
σx
2
2
2
2
σu x
σv ( u ⁄ v )
= ------------- + ---------------------------2 2
2
x v
v
Cancel the x’s in the first term and move both v squares to the denominator in the second term:
σx
2
2
2 2
2
2 2
σu
σv u
= ------+
------------2
4
v
v
Taking the square root of both sides:
σx =
σu
σv u
------- + ------------2
4
v
v
9
Substituting the sci and err values:
σ ccd, mama =
sci [ err ]
ref [ err ]sci [ sci ]  2
 -------------------+  ----------------------------------------2


 ref [ sci ]
ref [ sci ]
2
CALACS then calculates the error in division as follows. The flat reference file is normalized to the science file in the last term.
σ ccd, mama =
sci [ err ]  2   ref [ err ]   sci [ sci ]   2
 -------------------+ --------------------- ------------------- ref [ sci ] 
  ref [ sci ]   ref [ sci ]  
This step involves an additional calculation if more than one flat field reference file is
applied. The ref[err] equation below is used if two or more of the pixel to pixel, delta, or
low order flat fields are referenced in the header file. If one flat field is applied, the ref[err]
value is taken from that file only. We have verified that the expected err values equal the
ouput err values when one or two flat field reference files are used. When data u and v are
multiplied, the result is x:
x = ± auv
The error in x will then be (the same as in dividing):
2
2
2
2
σ uv
σx
σu
σv
------- = ------- + ------- + 2 ---------2
2
2
uv
x
u
v
Except now u and v have these values when multiplying:
x
u = -v
x
v = --u
10
Multiplying both sides by x squared, substituting for u and v, and dropping the correlation term:
σx
2
2 2
2 2
2 2
2 2
2 2
2 2
σu x
σv x
= ------------+
-------------2
2
2
2
x ⁄v
x ⁄u
Canceling the x squareds:
2
σ x = σu v + σv u
Taking the square root of both sides:
σx =
σu v + σv u
Substituting in the sci and err values:
ref [ err ] ccd ,mama =
2
( x [ sci ]y [ err ] ) + ( y [ sci ] x [ err ] )
2
Channel
sci[err]
ref[err]
ref[sci]
sci[sci]
Expected
error
CALACS
error
WFC real
171.5
.004787
0.9959
32532
233.04
233.1
WFC real
3.677
.005042
1.008
-256.9
3.864
3.866
WFC sim
249.3
0.1
2
54990
1380
1380
WFC sim
51.29
0.1
2
-9010
226.7
226.7
HRC real
167.6
0.00474
1
31721.
225.1
225.1
HRC real
3.404
0.004754
1.004
124.2
3.44
3.44
HRC sim
247.2
.005
1
61000
392.60
392.6
HRC sim
32.59
.005
1
1000
32.97
32.97
HRC sim
247.2
0.0051
1
61000
397.35
397.3
HRC sim
32.59
0.0051
1
1000
32.98
32.98
11
Channel
sci[err]
ref[err]
ref[sci]
sci[sci]
Expected
error
CALACS
error
HRC sim
247.2
0.05025
1
61000
3075
3075
HRC sim
32.59
0.05025
1
1000
59.89
59.89
SBC real
27.92
0.01394
1
1116
31.96
31.96
SBC real
24.15
0.01414
1
809.9
26.73
26.73
SBC sim
60.21
0.01394
1
4309
85.05
85.05
SBC sim
2.081
0.01414
1
-2000
23.356
28.35
Table 1: Multiple flat reference files
x[err]
x[sci]
y[err]
y[sci]
ref[err]
.005
1
.05
1
0.05025
.005
1
.001
1
0.0051
doShad - shutter shading file correction step
The Shutter shading step for the CCD includes a short calulation to determine ref[sci]
and then uses it to divide the input error array values.
shad [ sci ]
ref [ sci ] = 1 +  ------------------------- 
 exp time 
sci [ err ]
σ ccd = -------------------ref [ sci ]
Channel
sci[err]
ref[sci]
shad[sci]
EXPTIME
Expected
error
CALACS
error
WFC real
233.1
1.002
1
500
232.6
232.6
WFC real
3.866
1.002
1
500
3.858
3.858
WFC sim
1380
1.2
100
400
1150
1150
WFC sim
226.7
1.2
100
400
188.92
189
HRC real
225.1
1.01
1
100
222.87
222.9
HRC real
3.44
1.01
1
100
3.406
3.406
HRC sim
397.3
1.01
1
100
393.37
393.4
12
Channel
sci[err]
ref[sci]
shad[sci]
EXPTIME
Expected
error
CALACS
error
HRC sim
32.98
1.01
1
100
32.65
32.66
doPhot - photometry keyword calculation step
doStat - image statistics determination step
ACSSUM - repeat obs summing task
These last two steps and single task have no affect on the error array.
Regression Testing
ACS ISR 99-04 described basic image reduction in CALACS with emphasis on the
HRC science array values. That procedure has been duplicated here with the addition of
the HRC error array values.
13
Figure 1: Test science image
14
Figure 2: Test error image
The table below shows the same science values as recorded in ISR 99-04, but in
addition shows its error array values. They match the expected values exactly.
HRC image region
Image region
Raw image
hr_raw.fits
CALACS
output image
hr_flt.fits[sci,1]
CALACS
output image
hr_flt.fits[err,1]
Overscan
[1:19,1:1044]
5,000 DN
trimmed off
trimmed off
Background
[600:900,600:900]
15,000 DN
10,000 DN
100.1 DN
Objects
[650:850,415:445]
65,000 DN
60,000 DN
247 DN
SHAD isolation
[1:199,1:399]
10,000 DN
5,000 DN
56.04 DN
15
HRC image region
Image region
Raw image
hr_raw.fits
CALACS
output image
hr_flt.fits[sci,1]
CALACS
output image
hr_flt.fits[err,1]
BIAS isolation
[210:390,860:890]
10,000 DN
9,000 DN
100.6 DN
DARK isolation
[210:390,810:840]
10,000 DN
9,000 DN
100.6 DN
PFLT isolation
[210:390,760:790]
10,000 DN
5,000 DN
51.58 DN
DFLT isolation
[210:390,710:740]
10,000 DN
5,000 DN
51.58 DN
BIAS combination
[610:640,210:390]
10,000 DN
9,000 DN
100.6 DN
BIAS+DARK combination
[660:690,210:390]
10,000 DN
8,000 DN
101.1 DN
BIAS+DARK+PFLT combination
[710:740,210:390]
10,000 DN
4,000 DN
51.52 DN
BIAS+DARK+PFLT+DFLT combination
[760:790,210:390]
10,000 DN
2,000 DN
26.23 DN
IRAF scripts for testing CALACS ERR array
Several IRAF scripts below show a sample of how the WFC error array values werer
obtained. Most were adapted from ISR 99-04 (Mutchler) and changed to test the ERR
array values in place of the SCI array values.
#imset 1, chip 2, bottom row
imcopy o46p06010_raw.fits[sci,1,noinherit][1:1062,1:1044]wf_raw.fits[sci,1,overwrite][1:1062,1:1044]
imcopy o46p06010_raw.fits[sci,1,noinherit][1:1062,1:1044] wf_raw.fits[sci,1,overwrite][6:1067,1:1044]
imcopy o46p02010_raw.fits[sci,1,noinherit][20:1062,1:1044] wf_raw.fits[sci,1,overwrite][1049:2091,1:1044]
imcopy o46p4h010_raw.fits[sci,1,noinherit][20:1062,1:1044] wf_raw.fits[sci,1,overwrite][2073:3115,1:1044]
imcopy o46p8q010_raw.fits[sci,1,noinherit][20:1062,1:1044] wf_raw.fits[sci,1,overwrite][3097:4139,1:1044]
imcopy o46p8q010_raw.fits[sci,1,noinherit][1058:1062,1:1044] wf_raw.fits[sci,1,overwrite][4140:4144,1:1044]
#imset 1, chip 2, top row
imcopy o4y409010_raw.fits[sci,1,noinherit][1:1062,1:1044] wf_raw.fits[sci,1,overwrite][1:1062,1025:2068]
imcopy o4y409010_raw.fits[sci,1,noinherit][1:1062,1:1044] wf_raw.fits[sci,1,overwrite][6:1067,1025:2068]
imcopy o4y411010_raw.fits[sci,1,noinherit][20:1062,1:1044] wf_raw.fits[sci,1,overwrite][1049:2091,1025:2068]
imcopy o4y406010_raw.fits[sci,1,noinherit][20:1062,1:1044] wf_raw.fits[sci,1,overwrite][2073:3115,1025:2068]
imcopy o4y406010_raw.fits[sci,1,noinherit][20:1062,1:1044] wf_raw.fits[sci,1,overwrite][3097:4139,1025:2068]
imcopy o4y406010_raw.fits[sci,1,noinherit][1058:1062,1:1044] wf_raw.fits[sci,1,overwrite][4140:4144,1025:2068]
chip 1, top row
imcopy o46p5a010_raw.fits[sci,1,noinherit][1:1062,1:1024] wf_raw.fits[sci,2,overwrite][1:1062,1045:2068]
imcopy o46p5a010_raw.fits[sci,1,noinherit][1:1062,1:1024] wf_raw.fits[sci,2,overwrite][6:1067,1045:2068]
imcopy o46p5d010_raw.fits[sci,1,noinherit][20:1062,1:1024] wf_raw.fits[sci,2,overwrite][1049:2091,1045:2068]
imcopy o46p9r010_raw.fits[sci,1,noinherit][20:1062,1:1024] wf_raw.fits[sci,2,overwrite][2073:3115,1045:2068]
imcopy o46p1u010_raw.fits[sci,1,noinherit][20:1062,1:1024] wf_raw.fits[sci,2,overwrite][3096:4138,1045:2068]
imcopy o46p1u010_raw.fits[sci,1,noinherit][1057:1062,1:1024] wf_raw.fits[sci,2,overwrite][4139:4144,1045:2068]
#imset 2, chip 1, bottom row
imcopy o46p3x010_raw.fits[sci,1,noinherit][1:1062,1:1024] wf_raw.fits[sci,2,overwrite][1:1062,21:1044]
imcopy o46p3x010_raw.fits[sci,1,noinherit][1:1062,1:1024] wf_raw.fits[sci,2,overwrite][6:1067,21:1044]
imcopy o46p4r010_raw.fits[sci,1,noinherit][20:1062,1:1024] wf_raw.fits[sci,2,overwrite][1049:2091,21:1044]
imcopy o46p5s010_raw.fits[sci,1,noinherit][20:1062,1:1024] wf_raw.fits[sci,2,overwrite][2073:3115,21:1044]
imcopy o46p5t010_raw.fits[sci,1,noinherit][20:1062,1:1024] wf_raw.fits[sci,2,overwrite][3096:4138,21:1044]
imcopy o46p5t010_raw.fits[sci,1,noinherit][1057:1062,1:1024] wf_raw.fits[sci,2,overwrite][4139:4144,21:1044]
20 overscan rows at bottom
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imcopy o46p3x010_raw.fits[sci,1,noinherit][1:1062,1025:1044] wf_raw.fits[sci,2,overwrite][1:1062,1:20]
imcopy o46p3x010_raw.fits[sci,1,noinherit][1:1062,1025:1044] wf_raw.fits[sci,2,overwrite][6:1067,1:20]
imcopy o46p4r010_raw.fits[sci,1,noinherit][20:1062,1:1024] wf_raw.fits[sci,2,overwrite][1049:2091,1:20]
imcopy o46p5s010_raw.fits[sci,1,noinherit][20:1062,1:1024] wf_raw.fits[sci,2,overwrite][2073:3115,1:20]
imcopy o46p5t010_raw.fits[sci,1,noinherit][20:1062,1:1024] wf_raw.fits[sci,2,overwrite][3096:4138,1:20]
imcopy o46p5t010_raw.fits[sci,1,noinherit][1057:1062,1:1024] wf_raw.fits[sci,2,overwrite][4139:4144,1:20]
Similar scripts were used to create the SCI, ERR and DQ extenstions of the WFC bias,
dark, and flat field reference files.
This script sets the appropriate header keywords, runs CALACS, and analyzes its output using imstat:
print ("Removing old output...")
!rm wf_sci*_blv_tmp.fits
!rm wf_sci*_flt.fits
!rm wf.trl
print ("Setting header keywords through BLEVCORR")
hedit.add = no
hedit.delete = no
hedit.verify = no
hedit.show = no
hedit.update = yes
hedit wf_sci1_raw.fits[0] STATFLAG T
hedit wf_sci1_raw.fits[0] DQICORR PERFORM
hedit wf_sci1_raw.fits[0] ATODCORR OMIT
hedit wf_sci1_raw.fits[0] BLEVCORR OMIT
hedit wf_sci1_raw.fits[0] BIASCORR OMIT
hedit wf_sci1_raw.fits[0] DARKCORR OMIT
hedit wf_sci1_raw.fits[0] FLATCORR OMIT
hedit wf_sci1_raw.fits[0] SHADCORR OMIT
hedit wf_sci1_raw.fits[0] GEOCORR OMIT
hedit wf_sci1_raw.fits[0] PHOTCORR OMIT
hedit wf_sci1_raw.fits[0] CRCORR OMIT
hedit wf_sci1_raw.fits[0] EXPSCORR OMIT
hedit wf_sci1_raw.fits[0] RPTCORR OMIT
print ("Using TEST reference files...")
hedit wf_sci1_raw.fits[0] BPIXTAB /theta/data2/calacs/reftest/wf_bpx_id.fits
hedit wf_sci1_raw.fits[0] CCDTAB /theta/data2/calacs/reftest/wf_ccd_id.fits
hedit wf_sci1_raw.fits[0] OSCNTAB /theta/data2/calacs/reftest/wf_osc_id.fits
hedit wf_sci1_raw.fits[0] ATODTAB /theta/data2/calacs/reftest/wf_a2d_id.fits
hedit wf_sci1_raw.fits[0] BIASFILE /theta/data2/calacs/reftest/wf_bia_id.fits
hedit wf_sci1_raw.fits[0] DARKFILE /theta/data2/calacs/reftest/wf_drk_id.fits
hedit wf_sci1_raw.fits[0] PFLTFILE /theta/data2/calacs/reftest/wf_pfl_id.fits
hedit wf_sci1_raw.fits[0] DFLTFILE /theta/data2/calacs/reftest/wf_dfl_id.fits
hedit wf_sci1_raw.fits[0] LFLTFILE N/A
hedit wf_sci1_raw.fits[0] IDCTAB N/A
hedit wf_sci1_raw.fits[0] SHADFILE /theta/data2/calacs/reftest/wf_shd_test.fits
hedit wf_sci1_raw.fits[0] PHOTTAB /theta/data2/calacs/reftest/wf_pht_id.fits
hedit wf_sci1_raw.fits[0] CRREJTAB /theta/data2/calacs/reftest/wf_crr_id.fits
print ("Running CALACS...")
calacs.verbose = no
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calacs.savetmp = yes
calacs.quiet = yes
calacs wf_sci1_raw.fits
print ("Imstat on stellar pixel 1")
print ("sci DN")
imstat wf_sci1_raw.fits[sci,2][770,1646]
print ("sigma")
imstat wf_sci1_flt.fits[err,2][746,1626]
print ("Imstat on stellar pixel 2")
print ("sci DN")
imstat wf_sci1_raw.fits[sci,2][914,1714]
print ("sigma")
imstat wf_sci1_flt.fits[err,2][890,1694]
print ("Imstat on stellar pixel 3")
print ("sci DN")
imstat wf_sci1_raw.fits[sci,2][646,1180]
print ("sigma")
imstat wf_sci1_flt.fits[err,2][622,1160]
print ("Imstat on WFC galaxy nucleus pixel 1")
print ("sci DN")
imstat wf_sci1_raw.fits[sci,1][1848,1806]
print ("sigma")
imstat wf_sci1_flt.fits[err,1][1824,1806]
print ("Imstat on galaxy nucleus pixel 2")
print ("sci DN")
imstat wf_sci1_raw.fits[sci,1][494,491]
print ("sigma")
imstat wf_sci1_flt.fits[err,1][470,491]
print ("Imstat on WFC background pixel")
print ("sci DN")
imstat wf_sci1_raw.fits[sci,1][245,983]
print ("sigma")
imstat wf_sci1_flt.fits[err,1][221,983]
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print ("Imstat on WFC background pixel")
print ("sci[err]")
imstat wf_scierr_flt.fits[err,1][221,983]
print ("a[err]")
imstat wf_sci1_flt.fits[err,1][221,983]
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