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