post-sm4 sensitivity calibration of the stis echelle modes
DESCRIPTION
Post-SM4 Sensitivity Calibration of the STIS Echelle Modes. Azalee Bostroem With help from: Ralph Bohlin , Alessandra Aloisi , Charles Proffitt , Kenneth Hart, Phil Hodge. Echelle Modes. Increasing Order/ Decreasing Wavelength. Grating disperses light vertically - PowerPoint PPT PresentationTRANSCRIPT
Post-SM4 Sensitivity Calibration of the
STIS Echelle ModesAzalee Bostroem
With help from: Ralph Bohlin, Alessandra Aloisi, Charles Proffitt, Kenneth Hart, Phil Hodge
Echelle Modes• Grating disperses light
vertically• Higher orders are chosen
and dispersed horizontally• Orders have overlapping
wavelength ranges• Allows for broadband high
resolution spectroscopy• STIS has 4 modes
medium and high resolution modes
Incr
easin
g Or
der/
Decr
easin
g W
avel
engt
h
Increasing Wavelength
Photometric Conversion Table (PHOTTAB)
Convert net count rate to fluxModels the shape of the blaze function of each orderShape varies continuously with location on the
detector and timeTemporal component can experience a discontinuity
with instrument changes (e.g. switch from Side 1 to Side 2 electronics
Discontinuity expected following SM4Program 11866 executed in Cycle 17 to characterize
the echelle blaze function
Status following SM4
Pre-SM4 Flux Calibration on Post-SM4 Data (smoothed)
Net Counts
Making a new PHOTTABSteps:
Divide net counts of each order by a model spectrum
Fit each order with a spline Smooth splines across ordersRecord smoothed nodes for each order of every
central wavelength in a table
But its never that simple…First PHOTTAB created using STScI CalSTIS
calibrated dataCreated grating dependent bad pixel tablesCreated new ripple tablesLook for the E140H flux anomalyData not in current PHOTTAB not extracted
Bad Pixel TablesNUV Bad Pixel Table:
NUV corners are vignettedVignetting is grating dependentPreviously in flat fieldNow in bad pixel table
FUV Bad Pixel Table:Repeller wire across detectorPreviously in flat fieldLocation is grating dependentNow in bad pixel table
Ripple TablesEchelle 2D scattered light background subtractionNormalized blaze functionOnly delivered once
in 2002, no information on the creation
Solve issue in E140H data background subtraction
Flux AnomalyDecreased throughput directly following SM4 in
E140H and E230M
Flux Anomaly Cont.Observed again after MAMA shutdown in fall
2010Not observed in next monitoring Observation:
April 2010Echelle Flux calibration program executed
November 28, 2009 - January 6, 2010
Data not affectedIf affected, then flux of new data should be too
high
Edge OrdersWhen PHOTTAB was created in 2006, the program
was taken at extreme mode select mechanism positions
Monthly offsetting turned off for Echelle dataSome orders are off the detectorCalSTIS will not extract data not in the PHOTTAB
unless fluxcorr is set to omitThese orders were evaluated and included on an
individual basis
PHOTTAB CreationFind sensitivity for each order:
Sensitivity = Observed Net Count Rate/Model Flux
Exclude bad pixels and strong absorption lines
Sensitivity
PHOTTAB Creation Find sensitivity for each order:
Sensitivity = Observed Net Count Rate/Model Flux Exclude bad pixels and strong absorption lines
Fit a 7 (9 for E230M) node spline to sensitivity for each order
Spline
PHOTTAB Creation Find sensitivity for each order:
Sensitivity = Observed Net Count Rate/Model Flux Exclude bad pixels and strong absorption lines
Fit a 7 (9 for E230M) node spline to sensitivity for each order
Smooth spline nodes for each order in the cross dispersion direction
Smooth
PHOTTAB Creation Find sensitivity for each order:
Sensitivity = Observed Net Count Rate/Model Flux
Fit a 7 (9 for E230M) node spline to sensitivity for each order
Smooth spline nodes for each order in the cross dispersion direction
Back out the TDS to reflect sensitivity at Launch
Extrapolate to infinite aperture and extraction box height
Final Calibration
Changes in CalSTIS 2.38opt_elem cenwave sporder sensitivity pedigreeE140H 1343 287 DUMMYE140H 1343 288 DUMMYE140H 1343 289 DUMMYE140H 1343 290 INFLIGHT
opt_elem
cenwave
sporder
dq net net_err flux err
E140H 1343 289 dqarray
netarray
net_err array
0 0
E140H 1343 290 dqarray
netarray
net_err array
flux array
err array
Phottab: A DUMMY pedigree will still be extracted
X1D Table: Add net_err column, set flux, err = 0 for DUMMY pedigree
Future Work: Blaze Function Shift Evolution