UVIS Calibration Update Greg Holsclaw Jan 8,

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

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

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

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, T11:30:00 (start) Standard cals: – UVIS_204IC_ALPVIR001_PRIME, T11:41:00 (start) – UVIS_214IC_ALPVIR001_PRIME, T01:25:00 (start) 5

Calibration schedule Recall the nominal cadence is two standard calibrations/year and one SteFFL/year. 6 Standard+ SteFFL Standard

Slight differences in scan pattern 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.

8 2003

9 2013

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

Ratio to first Spica observation 11 From June, 2013

Ratio to first Spica observation 12 From June, 2013

Sensitivity -1 comparison at From June, 2013

Comparison of most recent standard Spica scan with IUE and SOLSTICE 14 wavelength range: nm mean sdv current new wavelength range: nm mean sdv current new From June, 2013

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

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

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 %

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

Website updates IDL SPICE kernel finder (bug fixes) – site/tools_software/SPICE_kernel_finder.htm site/tools_software/SPICE_kernel_finder.htm Visualize and animate data cubes – site/tools_software/AnimateDataCube.htm site/tools_software/AnimateDataCube.htm UVIS IDL PDS reader – site/tools_software/UVIS_PDS_data_reader.htm site/tools_software/UVIS_PDS_data_reader.htm 19

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

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

Example animation 22

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

Label file metadata 24 IDL> help, label ** Structure, 36 tags, length=416, data length=392, refs=1: RECORD_BYTES LONG FILE_RECORDS LONG 1511 PRODUCT_ID STRING 'EUV2008_054_15_36' SPACECRAFT_CLOCK_START_COUNT STRING '1/ ' SPACECRAFT_CLOCK_STOP_COUNT STRING 'UNK' START_TIME STRING ' T15:36:49.751' STOP_TIME STRING ' T17:42:44.751' 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 MISSION_PHASE_NAME STRING 'TOUR' PRODUCT_CREATION_TIME STRING ' ' 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 CORE_MULTIPLIER FLOAT 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

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

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

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