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UVIS Calibration Update Greg Holsclaw Jan 8, 2014 1
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Outline 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 2
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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 3
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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 4
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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, 2014- 223T11:30:00 (start) Standard cals: – UVIS_204IC_ALPVIR001_PRIME, 2014- 131T11:41:00 (start) – UVIS_214IC_ALPVIR001_PRIME,2015- 102T01:25:00 (start) 5
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Calibration schedule Recall the nominal cadence is two standard calibrations/year and one SteFFL/year. 6 Standard+ SteFFL Standard
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Slight differences in scan pattern 7 20032013 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 Plots show the position of the star (Alp Vir) in the FUV lores frame.
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8 2003
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9 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 10
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Ratio to first Spica observation 11 From June, 2013
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Ratio to first Spica observation 12 From June, 2013
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Sensitivity -1 comparison at 2012-358 13 From June, 2013
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Comparison of most recent standard Spica scan with IUE and SOLSTICE 14 wavelength range: 116-187nm mean sdv current 0.93 0.12 new 1.05 0.12 wavelength range: 130-187nm mean sdv current 0.85 0.06 new 0.95 0.04 From June, 2013
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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 15
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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 16
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The new routine corrects for the starburn without the FF applied Total signal vs image row position 15% systematic increase in apparent signal due to revised calibration approach 17 Normalized total signal Max deviation (max-min)/mean 31 % 28 % 7 %
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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. 18
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Website updates IDL SPICE kernel finder (bug fixes) – http://lasp.colorado.edu/cassini/team- site/tools_software/SPICE_kernel_finder.htm http://lasp.colorado.edu/cassini/team- site/tools_software/SPICE_kernel_finder.htm Visualize and animate data cubes – http://lasp.colorado.edu/cassini/team- site/tools_software/AnimateDataCube.htm http://lasp.colorado.edu/cassini/team- site/tools_software/AnimateDataCube.htm UVIS IDL PDS reader – http://lasp.colorado.edu/cassini/team- site/tools_software/UVIS_PDS_data_reader.htm http://lasp.colorado.edu/cassini/team- site/tools_software/UVIS_PDS_data_reader.htm 19
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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/U VIS/SPICE/’ If the ftp connection fails, try setting the keyword FTP_CONNECTION_MODE=0 20
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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_109TI_ 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 21
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Example animation 22
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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] 23
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Label file metadata 24 IDL> help, label ** Structure, 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 ' COMPRESSION_TYPE STRING 'SQRT_9' HI_VOLTAGE_POWER_SUPPLY_STATESTRING '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
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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.” 25
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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 = RAW_DATA_NUMBER – CORE_UNIT = KILORAYLEIGHS A suggestion for more accurate values is: – CORE_NAME = INVERSE_SENSITIVITY – CORE_UNIT = KILORAYLEIGHS*ANGSTROM**-1*COUNT**- 1 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. 26
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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 27
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