UVIS Calibration Update
Greg Holsclaw
Jan 8, 2014
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Outline
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Calibrations since the last meeting
Future calibrations
Calibration update
Status of new calibration routine
Website updates
A restructured calibration routine
CDAP update
PDS label correction and user’s guide implications
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Calibrations since last meeting were
successful
• Standard calibration:
– FUV2013_230_14_40_13_UVIS_196IC_SPICARAST001
_PRIME
• SteFFL-style flat-field:
– 14 files, with each file containing 10 readouts
representing one pass of the star along the slit at a
different cross-slit position.
– First file:
FUV2013_230_15_47_33_UVIS_196IC_SPICARAST001
_PRIME
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Comparison of two most recent
standard calibrations
• This is the
total signal
on the
detector as a
function of
image
position
• There is no
evidence for
any change in
sensitivity or
worsening of
the starburn
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Future calibrations
• Mike Evans will be looking for a slot in the late
2014 XD segments for the SteFFL-style
(+standard) calibration. Tentative:
– UVIS_207IC_SPICASTAR001_PRIME, 2014223T11:30:00 (start)
• Standard cals:
– UVIS_204IC_ALPVIR001_PRIME, 2014131T11:41:00 (start)
– UVIS_214IC_ALPVIR001_PRIME,2015102T01:25:00 (start)
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Calibration schedule
Standard+
SteFFL
Standard
• Recall the nominal cadence is two standard
calibrations/year and one SteFFL/year.
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Slight differences in scan pattern
2003
B = Beginning of observation
Green symbol = start of integration period
Red symbol = end of integration period
Blue / orange lines = alternating colors of 14 passes
Shaded area represents the field of view of the FUV-lores slit
2013
Plots show the position of the
star (Alp Vir) in the FUV lores
frame.
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2003
8
2013
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At the last team meeting, a slightly revised
calibration approach was proposed
• Currently:
– Fractional change in each pixel is calculated from
Spica scans, then an exponential fit determined to
provide interpolation over time
– Disadvantages:
• introduced high-frequency artifacts
• difficult to adjust for slow decline in sensitivity
• Proposed:
– The ratio of each Spica spectrum to the first is
calculated and smoothed spectrally, then linearly
interpolated in time
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From June, 2013
Ratio to first Spica observation
count rate
year
150
c/s
2012
100
50
2010
0
120
140
160
wavelength (nm)
180
ratio
2008
1.4
1.2
1.0
2006
0.8
0.6
120
140
160
180
2003
ratio smooth
1.4
2001
ratio
1.2
1.0
0.8
0.6
120
140
160
180
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From June, 2013
Ratio to first Spica observation
count rate
year
150
100
50
2010
0
120
140
160
wavelength (nm)
180
ratio
2008
8
6
4
2006
2
120
140
160
180
2003
ratio smooth
8
6
ratio
c/s
2012
2001
4
2
120
140
160
180
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From June, 2013
Sensitivity-1 comparison at 2012-358
3.0
current
new
(ph/s/cm^2/angstrom) / (c/s)
2.5
2.0
1.5
1.0
0.5
0.0
120
140
160
wavelength (nm)
180
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From June, 2013
Comparison of most recent standard
Spica scan with IUE and SOLSTICE
8•104
ph/s/cm^2/nm
ph/s/cm^2/nm
8•104
IUE
current cal
new cal
6•104
4•104
2•104
4•104
2•104
0
140
160
wavelength (nm)
0
100
180
1.4
1.4
1.2
1.2
ratio
ratio
120
1.0
0.8
SOLSTICE
current cal
new cal
6•104
120
140
160
wavelength (nm)
180
200
120
140
180
200
1.0
0.8
0.6
120
140
160
180
wavelength range: 116-187nm
mean
sdv
current
0.93
0.12
new
1.05
0.12
0.6
100
160
wavelength range: 130-187nm
mean
sdv
current
0.85
0.06
new
0.95
0.04
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Calibration adjustment for small
sources now included
• At previous meetings it has been shown that for
unresolved sources (stars, moons) the flat-field
correction should not be applied
– The apparent variation in row-to-row sensitivity
appears to be due to a geometric effect, rather than
QE
• But this is problematic for observations at or near
the starburned rows, as the flat-field correction
also adjusts for the starburn
• The starburn and the flat-field correction have
now been separated
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Test the new cal routine for small
sources
• Try calibrating each frame of a standard cal
(star slewed along the slit for a total of ~78
readouts)
• Three cases:
– 2010 cal with flat-field corrector
– 2010 cal without flat-field corrector
– 2013 cal without flat-field corrector
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The new routine corrects for the
starburn without the FF applied
Normalized
total signal
Max deviation
(max-min)/mean
31 %
28 %
7%
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Total signal vs image row position
15% systematic increase in apparent signal due to revised calibration approach
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Restructured calibration routine?
• There are two calibration routines, one for each
channel
– Get_euv_2010_lab_calibration
– Get_fuv_2013_lab_calibration
• Proposal to combine these into one routine, with
the channel specified by a keyword
– Get_uvis_2013_calibration, channel=‘fuv’
• This will allow for more efficient software
maintenance, and eliminate confusion regarding
the version each channel’s calibration.
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Website updates
• IDL SPICE kernel finder (bug fixes)
– http://lasp.colorado.edu/cassini/teamsite/tools_software/SPICE_kernel_finder.htm
• Visualize and animate data cubes
– http://lasp.colorado.edu/cassini/teamsite/tools_software/AnimateDataCube.htm
• UVIS IDL PDS reader
– http://lasp.colorado.edu/cassini/teamsite/tools_software/UVIS_PDS_data_reader.htm
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SPICE kernel finder
• Identify and download the complete set of
required SPICE kernels for the UVIS instrument
for year 2005, day-of-year 65.
– CASSINI_SPICE_KERNEL_LIST, 2005,
65, fkernel_cg, fkernel,
kernel_list,
local_kernel_path='/Users/holsclaw
/Cassini/UVIS/SPICE/’
• If the ftp connection fails, try setting the
keyword FTP_CONNECTION_MODE=0
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Visualization and animation
• Restore a data cube and plot the geometry for a
single readout:
– restore,'FUV2009_110_01_12_34_UVIS_1
09TI_FIRLMBAER002_CIRS.sav’
– window,0,xs=800,ys=800
– uvis_sim2, datastruct2[0], img,
body='Titan’
• Create an animation of all readouts:
– uvis_sim_animate, datastruct2,
body='Titan', /radec_grid,
filename_out=fdata
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Example animation
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PDS data reader
• Example:
– Filename = 'EUV2008_054_15_36.DAT’
– UVIS_PDS_READ_DATA, Filename, Data, Label
– UVIS_PDS_EXTRACT, Data, Databin
• Requires that the PDS label file (.LBL) is present in the same location
as the file
– This is necessary as the dimensionality of the array is contained in the
label
• ‘Data’ contains the detector readout as a 1024x64xN* array
– *If there is only one spatial element, the array is 1024x1xN
• ‘Label’ contains a subset of the metadata given in the ASCII label file
• ‘Databin’ contains the data in its native format
– For this example, Data has dimensions [1024,64,1511] while Databin
has dimensions [512,5,1511]
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IDL> help, label
** Structure <191ea08>, 36 tags, length=416, data length=392, refs=1:
RECORD_BYTES
LONG
131072
FILE_RECORDS
LONG
1511
PRODUCT_ID
STRING
'EUV2008_054_15_36'
SPACECRAFT_CLOCK_START_COUNT
STRING
'1/1582474410.96'
SPACECRAFT_CLOCK_STOP_COUNT
STRING
'UNK'
START_TIME
STRING
'2008-054T15:36:49.751'
STOP_TIME
STRING
'2008-054T17:42:44.751'
DATA_SET_ID
STRING
'CO-S-UVIS-2-CUBE-V1.2'
TARGET_NAME
STRING
'STAR'
INSTRUMENT_HOST_NAME
STRING
'CASSINI_ORBITER'
INSTRUMENT_NAME
STRING
'ULTRAVIOLET IMAGING SPECTROGRAPH'
INSTRUMENT_ID
STRING
'UVIS'
OBSERVATION_ID
LONG
96140
MISSION_PHASE_NAME
STRING
'TOUR'
PRODUCT_CREATION_TIME
STRING
'2011-255'
INTEGRATION_DURATION
STRING
'5.000 <SECOND>'
COMPRESSION_TYPE
STRING
'SQRT_9'
HI_VOLTAGE_POWER_SUPPLY_STATE
STRING
'ON'
OCCULTATION_PORT_STATE
STRING
'CLOSED'
SLIT_STATE
STRING
'OCCULTATION'
TEST_PULSE_STATE
STRING
'OFF'
ODC_ID
LONG
1067
CORE_ITEMS
STRING
'(1024, 64, 1511)'
CORE_ITEM_BYTES
INT
2
CORE_ITEM_TYPE
STRING
'MSB_UNSIGNED_INTEGER'
CORE_BASE
FLOAT
0.00000
CORE_MULTIPLIER
FLOAT
1.00000
CORE_NULL
INT
-1
CORE_NAME
STRING
'RAW_DATA_NUMBER'
CORE_UNIT
STRING
'"COUNTS/BIN"'
UL_CORNER_LINE
INT
26
UL_CORNER_BAND
INT
512
LR_CORNER_LINE
INT
30
LR_CORNER_BAND
INT
1023
BAND_BIN
INT
1
LINE_BIN
INT
1
Label file
metadata
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CDAP to improve UVIS data declined
• Objectives:
– UVIS data enhancement (pre-calculated geometry,
additional metadata)
– Database construction for programmatic search
– Visualization tools
• Response:
– “The proposal did not adequately make the case
that currently available tools are inadequate.”
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PDS labels are being updated
• Units specified in the PDS calibration matrix labels are incorrect
• The following items are from the most recent (version 3) UVIS
calibration label file:
– CORE_NAME
– CORE_UNIT
= RAW_DATA_NUMBER
= KILORAYLEIGHS
• A suggestion for more accurate values is:
– CORE_NAME
– CORE_UNIT
1
= INVERSE_SENSITIVITY
= KILORAYLEIGHS*ANGSTROM**-1*COUNT**-
• At a minimum, chapters 1, 3, and 4 of the UVIS user's guide will
need to be modified.
• Chapter authors need to review their content to reflect this
change, if necessary.
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Summary
• Revised calibration schedule progressing well
• Real changes in sensitivity have been
separated from the flat-field correction in the
new calibration
– Thus, unresolved sources are properly handled
• New calibration routine nearly ready
– Need to finish consolidation into one routine
• PDS User’s guide needs to be revised to reflect
a correction in the labels
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