!  File:  5244C.PROP
!  Database:  PEPDB
!  Date:  24-FEB-1994:02:48:23

coverpage:

  title_1:         DISKS AROUND MAIN SEQUENCE STARS: CYCLE3 HIGH
    title_2:       PART 2
    sci_cat:       INTERSTELLAR MEDIUM
    sci_subcat:    CIRCUMSTELLAR MATTER
    proposal_for:  GO
    cont_id:       4393
    pi_fname:      CHRISTOPHER
    pi_mi:         J.
    pi_lname:      BURROWS
    pi_inst:       STSCI
    pi_country:    USA
    pi_phone:      (410) 338-4913
    hours_pri:     2.42
    num_pri:       1
    wf_pc:         Y
    time_crit:     Y
    off_fname:     HERVEY
    off_mi:        S.
    off_lname:     STOCKMAN
    off_title:     DEPUTY DIRECTOR
    off_inst:      3470
    off_addr_1:    SPACE TELESCOPE SCIENCE INSTITUTE
    off_addr_2:    3700 SAN MARTIN DRIVE
    off_city:      BALTIMORE
    off_state:     MD
    off_zip:       21218
    off_country:   USA
    off_phone:     410-338-4730
! end of coverpage

abstract:

    line_1:        We propose to examine the circumstellar disk around Beta Pictoris in
    line_2:        order to determine its radial profile, and hence (in combination with
    line_3:        IRAS data) to fix its albedo and temperature profile.  These
    line_4:        observations will extend previous extensive ground based coronagraphic
    line_5:        investigations, and modelling by the authors. The data will enable us
    line_6:        to understand better the central clearing in the  disk and whether it is
    line_7:        caused by sublimation or possible planet formation. The observations will
    line_8:        also constrain the geometric properties of the  disk including its
    line_9:        inclination angle, vertical thickness and radial profile.  Such
    line_10:       observations limit models for the dynamics of the disk, including its
    line_11:       velocity dispersion and hence mass distribution, and radial mass
    line_12:       transport mechanisms. If density waves or clear zones are observed, they
    line_13:       will give indirect evidence for the presence of massive bodies (planets)
    line_14:       in the disk.  The observations involve a judicious use of roll
    line_15:       deconvolution, polarizers, and PSF modelling in order to allow the
    line_16:       central stellar image and associated scattered light to be subtracted.

!
! end of abstract

general_form_proposers:

  lname:           BURROWS
    fname:         CHRISTOPHER
    title:         PI
    mi:            J.
    inst:          STSCI
    country:       USA
    esa:           Y

!

  lname:           ARTYMOWICZ
    fname:         PAWEL
    inst:          LICK OBSERVATORY
    country:       USA

!

  lname:           KRIST
    fname:         JOHN
    mi:            E.
    inst:          STSCI
    country:       USA

!
! end of general_form_proposers block

general_form_text:

  question:        3
    section:       1
    line_1:        For Beta Pictoris, the observations are designed to give the clearest possible
    line_2:        image of the disk. The basic observation is in reflected stellar light at 413nm
    line_3:        with the star directly on the center of PC6.  The bandpass chosen represents a
    line_4:        best compromise between resolution and scatter.  The central image is
    line_5:        saturated, but each exposure time is limited to 1 minute in order to avoid
    line_6:        blooming over the region beyond 1 arcsec from the target (apart from the
    line_7:        columns that contain it).
    line_8:        In order to penetrate within the crucial 2 arcsecond radius where the disk is
    line_9:        expected to disappear, but which is covered by the skirt from the spherical
    line_10:       aberration, similar exposures through polarizers will provide a differential
    line_11:       measurement (the disk is about 30% polarized), as well as providing the first
    line_12:       direct measurement of  the polarisation of the disk from 2.5 to 5 arcsec. The
    line_13:       total observation set is designed to take one orbit, and thus optimizes the
    line_14:       use of HST time. The observations on Beta Pictoris are repeated a number of
    line_15:       months later in order to allow roll deconvolution.
    line_16:       This technique avoids unpredictable scattered light and diffraction effects
    line_17:       caused by the focal plane masking with the pyramid used in GTO observations.

!

  question:        3
    section:       2
    line_1:        After the observations are taken at the first roll angle, they will be
    line_2:        analysed so that the exposures for the second roll angle observations can be
    line_3:        optimised.

!

  question:        4
    section:       1
    line_1:        HST provides an order of magnitude contrast improvement relative to the ground
    line_2:        (Burrows et al. 1991 and see Figure 1). We believe that the reason that other
    line_3:        protoplanetary disks have not been seen despite extensive ground based searches
    line_4:        is probably  that they are not close to edge on, as in the case of the Beta
    line_5:        Pictoris disk.  The latter has a contrast relative to a typical seeing profile
    line_6:        of less than one, so it is clear that the other disks are likely to be
    line_7:        unobservable from the ground. However, if they are otherwise similar to the
    line_8:        observed disk, then they will be observable with HST.
    line_9:        Beta Pictoris saturates 200 pixels per second through F413m, but the bleeding
    line_10:       is predominantly along the columns. Four such exposures then yield a signal to
    line_11:       noise of almost 20 per pixel in the disk four arcseconds from the star along
    line_12:       the centerline, and still good signal to noise in the fainter outer regions.

!

  question:        5
    section:       1
    line_1:        The observations must occur when the Beta Pictoris disk is not aligned with
    line_2:        the V3 axis of the telescope, since that is the direction of bleeding in the
    line_3:        PC6 CCD.  The observations will be repeated later at a different roll angle,
    line_4:        so that the image of the disk will be rotated but the scattered light terms
    line_5:        will not.  Any features that rotate in the image will be associated with the
    line_6:        target, while any that do not will be associated with the telescope.

!

  question:        7
    section:       1
    line_1:        In order to supress scattered light from the central star, we propose to first
    line_2:        subtract model PSFs from the images.  We have performed extensive PSF fitting,
    line_3:        and have now refined the methods to  the point that the models agree with the
    line_4:        data with a mean pixel to pixel error of 15%. The models include spherical
    line_5:        aberration, focus,  other low order aberrations, spacecraft jitter, measured
    line_6:        mirror figure errors, pixel registration, the full aperture function of the
    line_7:        telescope, misalignemnts in the PC camera. The residual errors are correlated,
    line_8:        and look similar  from star to star, hence they can be shifted and subtracted
    line_9:        to further improve PSF subtraction. The parameters in the models include the
    line_10:       PSF registration relative to pixel boundaries, so this method does not require
    line_11:       that the stars and reference exposures be identically registered with respect
    line_12:       to the pixel boundaries.  Problems with the undersampled data which can be
    line_13:       serious with a reference star image are  automatically largely overcome, as
    line_14:       only residual images need to be resampled.
    line_15:       Thus we would expect that a subtraction accurate to about 5% should be possible
    line_16:       after the combination of modelling and reference image subtraction. This would
    line_17:       give a residual contrast of about a factor of 2 where the disk turns over. The
    line_18:       contrast outside 2.5 arcseconds is always about an order of magnitude even
    line_19:       without subtraction.

!

  question:        10
    section:       1
    line_1:        The authors have workstations and already have written the relevant computer
    line_2:        software to model the PSF, subtract the images, parameterize the disk, and fit
    line_3:        it to thermal and mass equilibrium models.  The authors will perform the data
    line_4:        reduction and analysis.

!
!end of general form text

general_form_address:

  lname:           BURROWS
    fname:         CHRISTOPHER
    mi:            J.
    category:      PI
    inst:          STScI
    addr_1:        SPACE TELESCOPE SCIENCE INSTITUTE
    addr_2:        3700 SAN MARTIN DRIVE
    city:          BALTIMORE
    state:         MD
    zip:           21218
    country:       USA
    phone:         410-338-4913

!
! end of general_form_address records

fixed_targets:

    targnum:       1
    name_1:        HD39060
    name_2:        BETA-PIC
    descr_1:       A,124,904
    pos_1:         RA = 5H 47M 17.1S +/- 0.1S,
    pos_2:         DEC = -51D 3' 59" +/- 0.1"
    equinox:       J2000
    comment_1:     EXPOSURE TIMES PROVIDE FOR A S-TO-N
    comment_2:     OF 20 IN THE DISK AT FOUR ARCSECS
    comment_3:     FROM STAR USING FOUR EXPOSURES. THE
    comment_4:     STAR WILL BE SATURATED.
    fluxnum_1:     1
    fluxval_1:     V=3.9,TYPE=A5V
    fluxnum_2:     1
    fluxval_2:     B-V=0.2

!
! end of fixed targets

! No solar system records found

! No generic target records found

exposure_logsheet:

    linenum:       1.000
    sequence_1:    DEFINE
    sequence_2:    IMAGES
    targname:      HD39060
    config:        PC
    opmode:        IMAGE
    aperture:      PC6-FIX
    sp_element:    F413M, F8ND
    num_exp:       1
    time_per_exp:  40S
    priority:      1
    param_1:       CLOCKS=YES
    comment_1:     THIS EXPOSURE USED FOR
    comment_2:     PIXEL REGISTRATION.

!

    linenum:       2.000
    sequence_1:    DEFINE
    sequence_2:    IMAGES
    targname:      HD39060
    config:        PC
    opmode:        IMAGE
    aperture:      PC6-FIX
    sp_element:    F413M
    num_exp:       4
    time_per_exp:  1M
    priority:      1
    param_1:       CLOCKS=YES
    comment_1:     IMAGE IS SATURATED.

!

    linenum:       3.000
    sequence_1:    DEFINE
    sequence_2:    IMAGES
    targname:      HD39060
    config:        PC
    opmode:        IMAGE
    aperture:      PC6-FIX
    sp_element:    F413M, POL0
    num_exp:       1
    time_per_exp:  4M
    priority:      1
    param_1:       CLOCKS=YES
    comment_1:     IMAGE IS SATURATED.

!

    linenum:       4.000
    sequence_1:    DEFINE
    sequence_2:    IMAGES
    targname:      HD39060
    config:        PC
    opmode:        IMAGE
    aperture:      PC6-FIX
    sp_element:    F413M, POL60
    num_exp:       1
    time_per_exp:  4M
    priority:      1
    param_1:       CLOCKS=YES
    comment_1:     IMAGE IS SATURATED.

!

    linenum:       5.000
    sequence_1:    DEFINE
    sequence_2:    IMAGES
    targname:      HD39060
    config:        PC
    opmode:        IMAGE
    aperture:      PC6-FIX
    sp_element:    F413M, POL120
    num_exp:       1
    time_per_exp:  4M
    priority:      1
    param_1:       CLOCKS=YES
    comment_1:     IMAGE IS SATURATED.

!

    linenum:       6.000
    sequence_1:    DEFINE
    sequence_2:    IMAGES
    targname:      HD39060
    config:        PC
    opmode:        IMAGE
    aperture:      PC6-FIX
    sp_element:    F569W, F8ND
    num_exp:       1
    time_per_exp:  4S
    priority:      1
    comment_1:     THIS EXPOSURE USED FOR
    comment_2:     PIXEL REGISTRATION.

!

    linenum:       7.000
    sequence_1:    DEFINE
    sequence_2:    IMAGES
    targname:      HD39060
    config:        PC
    opmode:        IMAGE
    aperture:      PC6-FIX
    sp_element:    F569W
    num_exp:       4
    time_per_exp:  6S
    priority:      1
    param_1:       CLOCKS=YES
    comment_1:     IMAGE IS SATURATED.

!

    linenum:       8.000
    sequence_1:    DEFINE
    sequence_2:    IMAGES
    targname:      HD39060
    config:        PC
    opmode:        IMAGE
    aperture:      PC6-FIX
    sp_element:    F569W, POL0
    num_exp:       2
    time_per_exp:  12S
    priority:      1
    param_1:       CLOCKS=YES
    comment_1:     IMAGE IS SATURATED.

!

    linenum:       9.000
    sequence_1:    DEFINE
    sequence_2:    IMAGES
    targname:      HD39060
    config:        PC
    opmode:        IMAGE
    aperture:      PC6-FIX
    sp_element:    F569W, POL60
    num_exp:       2
    time_per_exp:  12S
    priority:      1
    param_1:       CLOCKS=YES
    comment_1:     IMAGE IS SATURATED.

!

    linenum:       10.000
    sequence_1:    DEFINE
    sequence_2:    IMAGES
    targname:      HD39060
    config:        PC
    opmode:        IMAGE
    aperture:      PC6-FIX
    sp_element:    F569W, POL120
    num_exp:       2
    time_per_exp:  12S
    priority:      1
    param_1:       CLOCKS=YES
    comment_1:     IMAGE IS SATURATED.

!

    linenum:       11.000
    sequence_1:    USE
    sequence_2:    IMAGES
    req_1:         CYCLE 3;
    req_2:         SEQ 1-10 NO GAP;
    req_3:         ORIENT 255D +/- 30D

!
! end of exposure logsheet

! No scan data records found