!   $Id: 6148,v 6.1 1995/02/09 16:54:40 pepsa Exp $
coverpage:


  title_1:         CROSS FILTER CALIBRATION
    proposal_for:  CAL/AST
    pi_fname:      WILLIAM
    pi_mi:         H.
    pi_lname:      JEFFERYS
    pi_inst:       UNIVERSITY OF TEXAS
    pi_country:    USA
    pi_phone:      512-471-1455
    hours_pri:     12.0
    num_pri:       1
    time_crit:     X
    pi_position:   PROFESSOR
    fgs:           Y
! end of coverpage

abstract:

    line_1:   This CAL test attempts to determine values for the positional
    line_2:   shift between the "clear" filter and the other filters in
    line_3:   the astrometer FGS (FGS3) to one milliarcsecond rms or better.

    line_4:   The calibrations are necessary to correct relative positions
    line_5:   of targets measured with different filters within one
    line_6:   observation set to within the measurement errors of
    line_7:   of a single FGS setting.

!
! end of abstract

general_form_proposers:

  lname:           JEFFERYS
    fname:         WILLIAM
    mi:            H.
    inst:          TEXAS, UNIVERSITY OF
    country:       USA

!

  lname:           NELAN
    fname:         EDMUND
    mi:            P.
    inst:          TEXAS, UNIVERSITY OF
    country:       USA

!

  lname:           BENEDICT
    fname:         GEORGE
    mi:            F.
    inst:          TEXAS, UNIVERSITY OF
    country:       USA

!

! end of general_form_proposers block

general_form_text:

   question:        2
   section:           1
line_1:  When measuring relative star positions within the FGS field of 
line_2:  view  (pickle), changing filters between target settings within 
line_3:  an observation set may produce offsets of several milliarcseconds. 
line_4:  Unless these "cross filter" offsets are calibrated and removed, they 
line_5:  will contribute significant systematic errors to the observed 
line_6:  positions, and hence to the desired observed quantities such as 
line_7:  separations, parallaxes, or proper motions. These systematic errors
line_8:  can be devastating to the end results: e.g. in cases where angular 
line_9:  separations between bright and faint objects are observed, or in 
line_10: cases where the parallax of a bright object, observed using the F5ND,
line_11: is measured with respect to faint reference stars (observed using
line_12: F583W). When the pickle is rotated 180 deg from one side of the 
line_13: earth's orbit to the other, the cross filter affect is to add or 
line_14: subtract an unreal systematic component to the measured parallax.
line_16: The nominal operating range of the FGS through the clear (F583W)
line_17: filter is between 8th and 16th magnitude. In a typical observing 
line_18: scenario, the reference stars are observed using the F583W since
line_19: this is the filter used to determine the primary calibrations for 
line_20: optical field angle distortions (OFAD) and plate scale are made
line_21: through the clear filter. There are conditions which demand use of a
line_22: different filter for a given object, such as a star of extreme color
line_23: or brightness. In such cases, the cross filter calibration is required.


  question:        3
    section:       1
line_1:  The method of observation will be to point the telescope so that the 
line_2:  calibration target field is positioned at the desired location in the 
line_3:  pickle. The star will be observed as many times as possible, limited
line_4:  only by the visibility window, in the alternating sequence
line_5:  F583W/F5ND/F583W/F5ND,...etc. The test will be performed 3 times, 
line_6:  once with the target field at pickle center, and once at each of 
line_7:  the "football" ends, providing a field dependent sample of the 
line_8:  cross filter effect at different pickle locations. A total of 3 
line_9:  orbits are required.


  question:        4
    section:       1
line_1: At the moment, the program which makes the most use of a filter is the
line_2: GO and GTO program to tie the Hipparcos Reference Frame to Extragalactic
line_3: Objects (EGOs). To date, over 100 observation sets have been obtained.
line_4: The stragety is to observe the separation of a Hipparcos Star and an 
line_5: EGO. When the Hipparcos star is brighter than about 8.2, the neutral 
line_6: density filter is required. The EGOs are always fainter than about 12.8 
line_7: and are always measured using F583W, as are the reference stars. To date
line_8: about 20% of the Hipparcos star observations required the ND filter.  
line_9: In order to measure the separations of bright Hipparcos stars with
line_10: respect to faint EGOs with an accuracy that is comparable to the 
line_11: Hipparcos internal random accuracy (1.7 mas for individual stars, 
line_12: 0.2-0.3 mas systematically with respect to the Hipparcos reference 
line_13: frame) the FGS observations of the Hipparcos star that use the ND 
line_14: filter MUST be corrected for the position shift with respect to the
line_15: FGS observations of the EGO, which is measured with F583W.

  question:        4
  section:         2
line_1: We need to determine the cross filter calibration (F583W to 
line_2: F5ND or other filter) to 1 mas or better, if at all possible, so 
line_3: that the calibration will not be a major contributor to the 
line_4: error budget of an astrometric measurement.  The internal 
line_5: precision of an FGS reading (averaged over one setting) may 
line_6: be as high as a few tenths of a milliarcsecond.  The external 
line_7: accuracy of a single setting is around 2-3 milliarcseconds, 
line_8: based on global astrometric solutions and comparisons with 
line_9: ground-based data, for example.  A cross filter calibration 
line_10: consists of differencing the measurements of a star with two 
line_11: filters.  Thus, if we had a single measurement accuracy of 
line_12: 2mas, a single difference accuracy would be SQRT(2) larger or 
line_13: about 3mas.  Therefore, to get to the 1 mas level formal error 
line_14: in the calibration, we need 9 single difference measurements.  
line_15: Because the 2 mas accuracy includes uncertainties in the local 
line_16: optical field angle distortion with respect to the global FGS 
line_17: frame, and because the cross filter measurements are all 
line_18: made within a tiny patch of the FGS, we expect the cross filter 
line_19: calibration to be better than that indicated using the 2mas 
line_20: number for the single setting formal rms error.  However, the 
line_21: observations must be performed in such a manner that the 
line_22: FGS drift is removed at the same level of accuracy, and that 
line_23: will probably reduce the accuracy.  The drift will be discussed below.

!

  question:        5
    section:       1
line_1: We expect that the cross filter correction will show a slight
line_2: rotation across the pickle with the positional dependence 
line_3: predicted by the theoretical model of the optics of the FGS.
line_4: However, because of the complex OTA/FGS optical aberations the model is
line_5: suspect, and since the Hipparcos observations are made with the 
line_6: Hipparcos star at various positions within the pickle, we need measure
line_7: the field dependence of the cross filter calibration. We need to monitor
line_8:  the drift in such a way as to remove it at the level of accuracy we
line_9: we are attempting to reach in the calibration. Analysis of the OFAD 
line_10: data indicates that the FGS reference frame drift is adequately
line_11: modeled by simple second order polynomials with time in x,y. Therefore,
line_12: the repeated measurement of a single star should suffice to give the 
line_13: drift in x and y in the pickle with high accuracy. By concentrating 
line_14: on one or two stars, with multiple measurements in any filter, the 
line_15: drift will be monitored at the location of the calibration measurements
line_16: with a frequency and time span unequaled in any other FGS3 observation
line_17: set. By alternating between filters, the cross filter measurements 
line_18: will give us the best statistical value because of the repeated 
line_19: settings. Therefore, with this proposed observation stragety, we will
line_20: obtain more detailed drift information than we have had in the past, 
line_21: as well as obtain the best cross filter calibration.  

!


  question:        7
    section:       1
line_1: The data will be processed through the standard astrometric 
line_2: pipelines and analyzed using the standard astrometric reduction 
line_3: software, including dejittering and drift correction software.  The 
line_4: reduction and analysis will be performed at both STScI and Austin.
line_5: 
!

  question:        8
    section:       1
line_1: The Fine Guidance Sensors have filter wheels with five filter 
line_2: positions.  The Astrometer FGS (FGS 3) filter set comprises the 
line_3: following filters:
line_4: 
line_5:  F583W  --  the "clear" filter
line_6:  F5ND   --  the "neutral density" filter (with an intensity 
line_7:             reduction equivalent to 5 magnitudes)
line_8:  F605   --  the "astrometry clear" filter
line_9:  F550W  --  the "yellow" filter, and
line_10: PUPIL --   an aperture stop "filter" with a clear circular 
line_11:            aperture with a radius of 2/3 of the full "clear" filter.


!
!end of general form text

general_form_address:

    lname:         JEFFERYS
    fname:         WILLIAM
    mi:            H.
    category:      PI
    inst:          UNIVERSITY OF TEXAS
    addr_1:        ASTRONOMY DEPARTMENT
    city:          AUSTIN
    state:         TX
    zip:           78712
    country:       USA
    phone:         (512) 471-4461
    telex:         TEXASTRO

!
! end of general_form_address records


fixed_targets:

TARGNUM: 1
NAME_1: XFILTER
NAME_2: (GSC 509)
DESCR_1: J,701
POS_1: RA = 92.2354792D +/- 0.5",
POS_2: DEC = 24.35992D +/- 0.5"
EQUINOX: 2000
FLUXNUM_1: 1
FLUXVAL_1: V = 8.08 +/- 0.1

! end of fixed targets

exposure_logsheet:

!

LINENUM: 1
SEQUENCE_1: DEFINE
SEQUENCE_2: POSMODE
TARGNAME: #
CONFIG: FGS
OPMODE: POS
APERTURE: 3
SP_ELEMENT: #
PARAM_1: DATA-RATE=32
PARAM_2: ACQ-MODE = SEARCH
NUM_EXP: 1
TIME_PER_EXP: 20S
S_TO_N: 10
FLUXNUM_1: 1
PRIORITY: 1
COMMENT_1: FINE LOCK GUIDING

!

LINENUM: 100.01
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F583W
REQ_1: SEQ 100.01-100.23 NON-INT;
REQ_2: POS TARG -290, -60;
REQ_3: CYCLE 4/100.01-300.23;
COMMENT_1: THIS PROPOSAL MAY SPECIFY;
COMMENT_2: MORE OBSERVATIONS THAN;
COMMENT_3: CAN BE FIT INTO THE VISIBILITY;
COMMENT_4: PERIOD. IF SO, STARS CAN BE ;
COMMENT_5: DROPPED FROM THE END OF THE ;
COMMENT_6: EXPOSURE LOG LIST

LINENUM: 100.02
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F5ND
REQ_1: SAME POS FOR 100.02-100.23 AS 100.01;


LINENUM: 100.03
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F583W

LINENUM: 100.04
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F5ND

!

LINENUM: 100.05
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F583W

LINENUM: 100.06
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F5ND

!

LINENUM: 100.07
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F583W

LINENUM: 100.08
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F5ND

!

LINENUM: 100.09
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F583W

LINENUM: 100.10
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F5ND

!

LINENUM: 100.11
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F583W

LINENUM: 100.12
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F5ND

!

LINENUM: 100.13
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F583W

LINENUM: 100.14
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F5ND

!

LINENUM: 100.15
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F583W

LINENUM: 100.16
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F5ND

!

LINENUM: 100.17
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F583W

LINENUM: 100.18
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F5ND

!
!

LINENUM: 100.19
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F583W

LINENUM: 100.20
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F5ND

!

LINENUM: 100.21
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F583W

LINENUM: 100.22
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F5ND

!

LINENUM: 100.23
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F583W

!

LINENUM: 200.01
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F583W
REQ_1: SEQ 200.01-200.23 NON-INT;
REQ_2: POS TARG 0,0;
COMMENT_1: THIS PROPOSAL MAY SPECIFY;
COMMENT_2: MORE OBSERVATIONS THAN;
COMMENT_3: CAN BE FIT INTO THE VISIBILITY;
COMMENT_4: PERIOD. IF SO, STARS CAN BE ;
COMMENT_5: DROPPED FROM THE END OF THE ;
COMMENT_6: EXPOSURE LOG LIST

LINENUM: 200.02
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F5ND
REQ_1: SAME POS FOR 200.02-200.23 AS 200.01;


LINENUM: 200.03
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F583W

LINENUM: 200.04
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F5ND

!

LINENUM: 200.05
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F583W

LINENUM: 200.06
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F5ND

!

LINENUM: 200.07
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F583W

LINENUM: 200.08
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F5ND

!

LINENUM: 200.09
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F583W

LINENUM: 200.10
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F5ND

!

LINENUM: 200.11
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F583W

LINENUM: 200.12
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F5ND

!

LINENUM: 200.13
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F583W

LINENUM: 200.14
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F5ND

!

LINENUM: 200.15
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F583W

LINENUM: 200.16
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F5ND

!

LINENUM: 200.17
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F583W

LINENUM: 200.18
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F5ND

!
!

LINENUM: 200.19
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F583W

LINENUM: 200.20
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F5ND

!

LINENUM: 200.21
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F583W

LINENUM: 200.22
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F5ND

!

LINENUM: 200.23
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F583W

!

LINENUM: 300.01
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F583W
REQ_1: SEQ 300.01-300.23 NON-INT;
REQ_2: POS TARG +290, -60;
COMMENT_1: THIS PROPOSAL MAY SPECIFY;
COMMENT_2: MORE OBSERVATIONS THAN;
COMMENT_3: CAN BE FIT INTO THE VISIBILITY;
COMMENT_4: PERIOD. IF SO, STARS CAN BE ;
COMMENT_5: DROPPED FROM THE END OF THE ;
COMMENT_6: EXPOSURE LOG LIST

LINENUM: 300.02
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F5ND
REQ_1: SAME POS FOR 300.02-300.23 AS 300.01;


LINENUM: 300.03
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F583W

LINENUM: 300.04
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F5ND

!

LINENUM: 300.05
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F583W

LINENUM: 300.06
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F5ND

!

LINENUM: 300.07
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F583W

LINENUM: 300.08
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F5ND

!

LINENUM: 300.09
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F583W

LINENUM: 300.10
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F5ND

!

LINENUM: 300.11
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F583W

LINENUM: 300.12
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F5ND

!

LINENUM: 300.13
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F583W

LINENUM: 300.14
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F5ND

!

LINENUM: 300.15
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F583W

LINENUM: 300.16
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F5ND

!

LINENUM: 300.17
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F583W

LINENUM: 300.18
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F5ND

!
!

LINENUM: 300.19
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F583W

LINENUM: 300.20
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F5ND

!

LINENUM: 300.21
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F583W

LINENUM: 300.22
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F5ND

!

LINENUM: 300.23
SEQUENCE_1: USE
SEQUENCE_2: POSMODE
TARGNAME: XFILTER
SP_ELEMENT: F583W

!
! end of exposure logsheet

! No scan data records found