F OS INSTR UMENT AND CALIBRA TION ST A TUS ANURADHA - - PDF document

SLIDE 1 F OS INSTR UMENT AND CALIBRA TION ST A TUS

• ANURADHA

K ORA TKAR Sp ac e T elesc

• p

e Scienc e Institute

• San

Martin Drive Baltimor e MD

• Abstract

The F ain t Ob ject Sp ectrograph F OS is

• p

erating w ell and all its instrumen tal mo des are functional There has b een an enhancemen t for the pip eline calibration that accoun ts for scattered ligh t correction temp

• ral

c hanges in the instrumen t sensitivit y and fo cus c hanges These calibration c hanges can b e applied to preCOST AR data p

• stfacto

The calibration c hanges to the CALF OS soft w are will b e a v ailable for p

• stCOST

AR data in Septem b er

• and

will b e incorp

• rated

in to the HST calibration pip eline In addition to c hanges to the calibration pro cedure new mo des

• f
• p

eration that ha v e b een added to enhance target acquisition capabilities The F OS assisted GHRS target acquisition tec hnique has b een dev elop ed primarily to allo w guest

• bserv

ers GOs acquire fain t targets and

• btain

GHRS sp ectroscop y

• The

reusetargetoset acquisition capabilit y w as dev elop ed to so that a program could ha v e more ecien t target acquisitions if there w as more than

• ne

visit to the same target Key w

• rds

F OS

• Status
• Calibration
• F

OS Calibration Status

• Dead

Diodes Occasionally

• ne
• f

the

• dio

des

• n

either

• f

the F OS detectors b ecomes noisy

• r

ceases to collect data When suc h a dio de is disco v ered the dio de is monitored to determine its b eha vior If the dio de is dead

• r

the noisy b eha vior p ersists the dio de is disabled and dio de n um b er is added to a list

• f

dead dio des with a particular eectiv e date Presen tly

• sev

eral dio des are under scrutin y

• but

no new additions ha v e b een made to the dead dio de tables DDT since Decem b er

• Curren

tly

• F

OSBL and

• F

OSRD dio des are disabled The latest DDTs are giv en in a pap er b y Christensen and Martin in these pro ceedings Since the DDTs are

• nly

up dated p erio dically

• it

is p

• ssible

that some data can b e pro cessed through the CALF OS calibration pip eline without correction for newly disco v ered dead dio des An uncorrected dead dio de pro duces a c haracteristic signature in the data whic h can b e corrected F

• r

details consult the F OS section

• f

the HST Data Handb

• k

The latest v ersion

• f

the DDTs are a v ailable via the F OS home page

• n

the w

• rld

wide w eb WWW These should b e consulted to insure that data ha v e b een pro cessed with the most appropriate dead dio de reference le Summary Dead

• r

noisy dio des ma y not b e corrected for in some F OS datasets All

• bserv

ers and arc hiv e users should consult the latest v ersion

• f

the DDTs to ensure that data ha v e b een pro cessed with the most appropriate dead dio de reference le

• Ba

ck gr

• und

Subtra ction The F OS sp ectral bac kground is particleinduced A bac kground correction for all F OS gratings is no w included in the CALF OS calibration pip eline Note that F OS

SLIDE 2 A K ORA TKAR sp ectra suer also from grating scatter and require a scattered ligh t correction Please see the subsection b elo w

• n

scattered ligh t for details In the last calibration w

• rkshop

Rosa

• had

rep

• rted

a discrepancy

• f
• b

et w een the

• bserv

ed particle induced bac kground and the predicted pip eline bac k ground W e ha v e a substan tial baseline

• f

new dark bac kground measuremen ts that ha v e b een in v estigated b y Ha y es see his pap er in these pro ceedings The analysis indicates that the measured bac kground coun t rates are

• ctssdio

de for F OSBL and

• ctssdio

de for F OSRD F

• r

more details

• n

geo magnetic latitude and longitude dep endence please refer to the ab

• v

e men tioned pap er in these pro ceedings These bac kground coun t rates indicate that

• bserv

ations

• f

fain t

• b

jects are aected Summary All F OS

• bserv

ations ha v e a particleinduced bac kground subtraction applied to them

• Fla

t Fields The F OS at elds correct for the dio detodio de v ariations

• n

the scale

• f
• pixels
• r

less Sp ectral at elds are pro duced for all usable F OS detectorap erturedisp erser com binations A more complete discussion

• f

at elds is giv en in this v

• lume

in a pap er b y Key es All p

• stCOST

AR at elds ha v e b een deriv ed using the sup erat tec hnique F

• r

details

• f

this tec hnique refer to the Instrumen t Science Rep

• rt

CALF OS Addi tional v ariations

• f

the sup erat tec hnique that describ e the curren tly installed p

• st

COST AR at elds are giv en in Instrumen t Science Rep

• rt

CALF OS T ypical p

• stCOST

AR at elds displa y deviations

• f
• ab
• ut

a mean v alue

• f

unit y

• but

some substan tial

• deviations

also

• ccur

Additional spatial v ariations do

• ccur

Details

• f

this in v estigation will b e discussed in a future Instrumen t Science Rep

• rt

T emp

• ral

v ariations

• f

the F OSRD GH GH and GL at elds ha v e b een

• bserv

ed Flat eld deviations as a function

• f

distance p erp endicular to the disp ersion direction are under in v estigation A discussion

• f

this is pro vided b y Key es in this v

• lume

Curren tly

• no

at eld corrections are applied in the pip eline for any paired ap er ture data There will b e corrections applied in the pip eline at a later date Ho w ev er at eld corrections will not b e applied to the pair and barred ap ertures All p

• stCOST

AR single ap erture high disp ersion data

• btained

prior to

• July
• need

to b e recalibrated b ecause preCOST AR at elds w ere used in the pip eline calibration All p

• stCOST

AR single ap erture lo w disp ersion data tak en prior to

• June
• need

to b e recalibrated Summary All p

• stCOST

AR at elds ha v e b een deliv ered No at eld correc tions will b e applied to the pair and barred ap ertures Curren tly

• no

at eld cor rections are applied in the pip eline for an y paired ap erture data All p

• stCOST

AR single ap erture high disp ersion data prior to

• July
• and

all p

• stCOST

AR single ap erture lo w disp ersion data tak en prior to

• June
• need

to b e re Calibr ating HST Post Servicing Mission

SLIDE 3 F OS ST A TUS calibrated Some spatial v ariations ha v e b een

• bserv

ed in p

• stCOST

AR at elds for the F OSBL GL grating and an appropriate UPPER ap erture is recommend ed for suc h

• bserv

ations to minim ize the eect

• f

the at eld feature T emp

• ral

v ariations ha v e b een

• bserv

ed for the F OSRD GH GH and GL at elds

• Absolute

Photometr y The F OS in v erse sensitivit y reference les are used to apply the absolute photometric calibration for an

• bserv

ation These reference les are pro duced for all usable F OS detectorsap erturedisp erser com binations A detailed discussion

• f

F OS absolute photometry is giv en in this v

• lume

b y Bohlin All p

• stCOST

AR in v erse sensitivit y les ha v e b een deliv ered F

• r

details

• f

the p

• stCOST

AR F OS photometry

• refer

to the Instrumen t Science Rep

• rt

CALF OS

• The

F OSRD GH and GH grating data sho w temp

• ral

c hanges in the p

• stCOST

AR p erio d All

• ther

detectordisp erser com binations ha v e b een stable at the

• lev

el during the p

• stCOST

AR era In the CALF OS pip eline no absolute photometry corrections are applied to the pair and barred ap ertures All Cycle

• data

prior to

• Marc

h

• need

to b e recalibrated b ecause unit y reference les w ere used in the pip eline calibration PreCOST AR photometry w as strongly dep enden t up

• n

the com bined eects

• f

Optical T elescop e Assem bly OT A fo cus c hanges and timedep enden t degradation

• f

the F OS sensitivit y

• The

pip eline calibration no w includes corrections for these eects Th us prop erly recalibrated preCOST AR data will impro v e the photometric accura cy

• f

these data Standard pip eline calibrations will include corrections for the inu ence

• f

time dep endence for the p

• stCOST

AR data from Septem b er

• The

cali bration c hanges are discussed in detail in the Instrumen t Science Rep

• rt

CALF OS

• as

the Av erage In v erse Sensitivit y AIS metho d Additional information is also a v ailable in the Instrumen t Science Rep

• rts

CALF OS and CALF OS All data

• btained

prior to

• Septem

b er

• need

to b e recalibrated using the new AIS calibration tec hnique The corrections due to recalibration using the AIS system will v ary dep ending

• n

the ap erture and grating Summary All p

• stCOST

AR in v erse sensitivit y les ha v e b een deliv ered No abso lute photometry corrections are applied to the pair and barred ap ertures All Cycle

• data

prior to

• Marc

h

• need

to b e recalibrated F urther all data prior to

• Septem

b er

• need

to b e recalibrated using the new AIS calibration system The F OSRD GH and GH grating in v erse sensitivities sho w temp

• ral

c hanges in the p

• stCOST

AR p erio d All

• ther

detectordisp erser com binations ha v e b een sta ble at the

• lev

el during the p

• stCOST

AR era The CALF OS pip eline calibration no w includes corrections for fo cus c hanges and timedep enden t degradation

• f

the F OS sensitivit y

• W

a velength Calibra tion All F OS w a v elengths are v acuum w a v elengths Calibr ating HST Post Servicing Mission

SLIDE 4 A K ORA TKAR Because

• f

the dieren t paths follo w ed b y ligh t from the in ternal calibration lamps and an external target w a v elength

• sets

b et w een the t w

• paths

ha v e to b e deter mined The w a v elength

• sets

b et w een the in ternal calibration lamps and a kno wn external p

• in

t source are curren tly based

• n
• bserv

ations

• f

the dw arf emission line star A U Mic On the red side the mean

• set

b et w een in ternal and external sources is

• dio

des On the blue side the mean

• set

is

• dio

des These

• sets

are included in the pip eline reduction w a v elength calibration More details

• n

in ternal w a v elength calibration are giv en in the pap er b y Dahlem in this v

• lume

An indep enden t tec hnique to determine the w a v elength

• set

for the F OSBL GH grating is to use the geocoronal Ly An analysis using this metho d see pap er b y Koratk ar and Ev ans in these pro ceedings indicates that the

• set

is

• dio

des for the F OS blue detector W a v elength calibration is aected also b y the ltergratingwheel rep eatabilit y

• The
• ltergratingwheel

rep eatabilit y is

• f

the

• rder
• f
• dio

des but deviations as large as

• dio

des are

• bserv

ed see pap er b y Koratk ar and Martin in this v

• lume

The relativ e uncertain t y

• f

the F OS w a v elength calibration can also b e estimated from the p

• sition
• f

the geocoronal Ly Results

• f

this analysis see pap er b y Koratk ar and Ev ans in this v

• lume

are consisten t with those determined from the ltergratingwheel rep eatabilit y test Summary The w a v elength calibration used in the CALF OS pip eline has not b een c hanged since science v erication The mean

• set

b et w een in ternal and external sources is

• dio

des for the red detector and

• dio

des for the blue detector The rep eatabilit y

• f

the w a v elength calibration

• f

the

• rder
• f
• dio

des but deviations as large as

• dio

des are

• bserv

ed

• Sca

ttered Light Scattered ligh t

• bserv

ed in the F OS data is pro duced b y the diraction patterns

• f

the F OS gratings the en trance ap ertures and the microroughness

• f

the grat ings extensiv e w

• rk

discussed in the Instrumen t Science Rep

• rt

CALF OS There is a routine pip eline calibration correction that is applied

• nly

for gr atings that have r e gions

• f

zer

• sensitivity

to disp erse d light The applied correction is wave length indep endent F

• r

details

• f

the correction please see the Instrumen t Science Rep

• rt

CALF OS Note that the scattered ligh t correction is in addition to the bac kground subtraction Since the scattered ligh t c haracteristics

• f

the F OS are w ell understo

• d

a scattered ligh t mo del is no w a v ailable for use as a p

• stobserv

ation parametric analysis to

• l

to estimate the amoun t

• f

scattered ligh t aecting a giv en

• bserv

ation Summary A w a v elengthindep enden t scattered ligh t correction is applied in the CALF OS pip eline for

• bserv

ations

• btained

using some gratings A more complete scattered ligh t mo del is a v ailable for use as a p

• stobserv

ation parametric analysis to

• l

Calibr ating HST Post Servicing Mission

SLIDE 5 F OS ST A TUS

• Sky

Lines The lines

• f

geocoronal Ly

• and

OI

• app

ear regularly in F OS sp ectra with a width determined b y the size

• f

the ap erture Occasionally

• the

sky lines

• f

OI at

• and
• f

OI I at

• can

also b e seen when

• bserving
• n

the da yligh t side

• f

the

• rbit

Second

• rder

Ly sometimes app ears at

• Polarimetr

y F OS p

• larimetry

with the GH and GH gratings after the in tro duction

• f

COST AR is p

• ssible

The instrumen tal p

• larization

in tro duced b y the COST AR reections is

• and

is w a v elength dep enden t More details

• n

accuracies can b e found in the pap er b y Allen in this v

• lume
• Aper

ture Loca tion The absolute VV lo cations

• f

the

• ap

ertures are kno wn to

• The

in ternal accuracy

• f

the ap erture lo cations is

• but

the absolute accuracy

• f
• is

limited b y the Fine Guidance Sensor F GS to F GS alignmen t The p

• sitions
• f
• ther

single small ap ertures smaller than the

• ap

erture relativ e to the

• ap

ertures are kno wn to

• The

relativ e p

• sitions
• f

all

• ther

ap ertures are kno wn to

• F
• r

details see the Instrumen t Science Rep

• rts

CALF OS and CALF OS

• Aper

ture Areas The

• ap

erture dimensions in the F OS X and Y co

• rdinate

frame ha v e b een measured b y doing X and Y scans F

• r

details see the Instrumen t Science Rep

• rt

CALF OS The photometric areas for a limited n um b er

• f

ap ertures ha v e b een measured from

• bserv

ations

• f

cen tered targets for the preCOST AR ep

• c

h and p

• stCOST

AR measuremen ts F

• r

details see the Instrumen t Science Rep

• rt

CALF OS

• New

T arget Acquisition Capabilities

• F

OS assisted GHRS t ar get a cquisition Due to the presence

• f

COST AR the F OS and GHRS ap erture lo cations are no w separated b y a small enough distance

• n

the sky that targets can sometimes b e

• set

from

• ne

instrumen t to the

• ther

using the same guide stars This tec hnique

• f

target acquisition is called an F OS

• r

GHRS assisted target acquisition The standard F OSassisted GHRS target acquisition uses the F OS blue detector to acquire the target and then

• sets

the target in to the GHRS large science ap erture LSA The separation

• f

the GHRS and F OS red detector ap ertures is large enough

• This

distance is large enough that

• nly

under v ery sp ecial situations will it b e p

• ssible

to nd guide stars whic h are within the eld

• f

view

• f

the F GSs from the b eginning to the end

• f

an

• p

eration in v

• lving

b

• th

the F OS red detector and the GHRS whic h is a requiremen t

• f

this target acquisition strategy

• Therefore

F OS Calibr ating HST Post Servicing Mission

SLIDE 6 A K ORA TKAR assisted target acquisitions from the F OS red detector ma y actually b e p

• ssible
• nly

in v ery few cases One can rev erse the target acquisition strategy and use the GHRS to acquire a target for an F OSBLueside science

• bserv

ation A F OSassisted GHRS target acquisition strategy is recommende d esp ecially for

• bserv

ations that are b est p erformed using the GHRS and for whic h the target cannot b e acquired with the GHRS ev en with Side

• Similarly
• a

GHRSassisted F OS target acquisition is recomme nded if the

• bserv

ations are b est p erformed using the F OS and for whic h the target cannot b e acquired at all with the F OS V arious considerations indicate that a GHRS assisted F OS target acquisition is recommended

• nly

for the

• ap

erture and the

• ap

erture See the F OS Instrumen t Handb

• k

v ersion

• for

details

• f

this acquisition capabilit y

• An

assisted target acquisition is a restricted resource since the n um b er

• f

a v ail able guide stars will b e limited as the t w

• instrumen

ts must b e used in the same

• bserv

ation setvisit A real gain in

• v

erhead times for an F OSassisted GHRS target acquisition is ac hiev ed

• nly

if a binary searc h acquisition can b e used If a p eakup has to b e used the

• bserv

er m ust decide if a stage p eakup acquisition is sucien t Otherwise the F OS target acquisition

• v

erhead is similar to the GHRS

• v

erhead if a Side acquisition is p

• ssible

Of course if a stage p eakup acquisition is the

• nly

w a y to acquire a particular target then there is no c hoice but to use that strategy

• ReuseT

ar getOffset If an F OS

• bserving

program requires more than

• ne

visit to a target within

• w

eeks and the target acquisition sequence is time consuming then the reusetargetoset pro cedure can b e used This pro cedure requires that the same guide star p

• sitions

in the F GS eldofview b e used for the rep eat visits F

• r

this target acquisition pro cedure the rst return visit m ust b e at least

• da

ys after the initial acquisition F urthermore the pro cedure can b e used

• nly

if the target acquisition scenario for the rst visit is a p eakup acquisition It is recomme nded that in subsequen t return visits a singlestage p eakup b e p erformed to impro v e the p

• in

ting accuracy

• See

the F OS Instrumen t Handb

• k

v ersion

• for

the details

• f

this acquisition capabilit y

• F

OS Cycle

• Calibration

Plan After the deplo ymen t

• f

COST AR an extensiv e calibration program w as carried

• ut

during SMO V and Cycle

• and

the p erformance

• f

the p

• stCOST

AR F OS has b een c haracterized in detail A summary

• f

the Cycle

• calibration

as completed through No v em b er

• is

presen ted in Instrumen t Science Rep

• rt

CALF OS Instrumen t Science Rep

• rt

CALF OS pro vides further calibration information In Cycle

• w

e exp ect to main tain the routine calibration for the F OS Our cali bration program is divided in to t w

• parts
• a

set

• f

monitoring tests whic h aim to v erify the stabilit y

• f

the instrumen t Calibr ating HST Post Servicing Mission

SLIDE 7 F OS ST A TUS p erformance and to monitor those asp ects

• f

the F OS p erformance that are kno wn to sho w time v ariation and

• a

set

• f

sp ecic tests designed to maximi ze the instrumen tal p erformance and to c haracterize those asp ects

• f

the F OS p erformance that ha v e b een sp ecially requested b y Cycle

• GOs

See the F OS Instrumen t Handb

• k

v ersion

• and

the Instrumen t Science Rep

• rt

CALF OS for the details

• f

the Cycle

• calibration

program

• F

OS WWW P age The F OS W eb page can b e accessed via the follo wing URL httpwwwstscie duftpinstrument newsF OStopfoshtml Instrumen t related do cumen tation including man y Instrumen t Science Rep

• rts

are no w a v ailable

• n

the W eb An ything new andor imp

• rtan

t can b e found under the Advisories button All

• f

the curren tly recomme nded reference les for an y

• bserv

ation date are listed under the Calibration Pro ducts button A list

• f

F OS team con tacts and their sp ecialties are can b e accessed through these pages References Bushouse HA Recalibrating PreCOST AR F OS Data CALF OS

• Bohlin

R

• Colina

L P

• stCOST

AR F OS Ap erture T ransmissions for P

• in

t Sources CALF OS

• Ev

ans IN Koratk ar A Key es C

• T

a ylor CJ SMO V Rep

• rt

VI F OS Ap erture Align men ts

• I

Large Ap ertures CALF OS

• Ev

ans IN Koratk ar A Key es C

• T

a ylor CJ SMO V Rep

• rt

VI I F OS Ap erture Align men ts

• I

I Small Ap ertures and Adopted Alignmen ts CALF OS

• Ev

ans IN P

• stCOST

AR F OS Small Ap erture Relativ e Throughputs Deriv ed from SMO V Data CALF OS

• Key

es C Koratk ar A

• Kinney
• AL

Calibratio n Pro duct Review for the F ain t Ob ject Sp ectrograph CALF OS

• Kinney
• AL
• Bohlin

R Bac kground Due to Scattered Ligh t CALF OS

• Koratk

ar AKey es C Dahlem M Ha y es J Christensen J

• Martin

S F OS Calibration Plan for Cycle

• CALF

OS

• Lindler

D Bohlin R Hartig G

• Key

es C F OS Flats F rom Sup er Sp ectra CALF OS

• Rosa

M R Scattered Ligh t in the F OS An Assessmen t Using Science Data CALF OS

• T

a ylor CJ F OS PreCOST AR T arget P

• in

ting Ana ylsis CALF OS

• Key

es CD Flat Fields CALF OS

• Bohlin

RC Lindler D

• Key

es CD Cycle

• Photometric

calibration

• f

the F OS CALF OS

• Calibr

ating HST Post Servicing Mission