!  File:  4277C.PROP
!  Database:  PEPDB
!  Date:  20-FEB-1994:20:02:04

coverpage:

  title_1:         CALIBRATION OF NEARBY GALAXY TYPE IA SUPERNOVAE AS STANDARD CANDLES:
    title_2:       NGC 5253: CYCLE3HIGH
    sci_cat:       GALAXIES & CLUSTERS
    sci_subcat:    DISTANCE SCALE
    proposal_for:  GO
    pi_fname:      ALLAN
    pi_mi:         R
    pi_lname:      SANDAGE
    pi_inst:       OBSERVATORIES OF THE CIW
    pi_country:    USA
    hours_pri:     31.50
    num_pri:       1
    wf_pc:         Y
    time_crit:     Y
    funds_length:  12
    off_fname:     JOHN
    off_lname:     LIVELY
    off_title:     DIRECTOR OF ADM&FIN
    off_inst:      1660
    off_addr_1:    CARNEGIE INSTITUTION OF WASHINGTON
    off_addr_2:    1530 P STREET, NW
    off_city:      WASHINGTON DC
    off_state:     DC
    off_zip:       20005
    off_country:   USA
    off_phone:     202-387-6406
! end of coverpage

abstract:

    line_1:        We propose to proceed to the next step in the program (cycle 1 GO-2547) to
    line_2:        determine Cepheid distances to nearby, highly resolved galaxies that have produ-
    line_3:        ced Type-Ia supernovae (SNIa). The feasibility of the program has been
    line_4:        demonstrated by our results for IC 4182. The prediction in the Cycle 1 proposal
    line_5:        that many Cepheids would be found in IC4182 brighter than V=25.5 with periods
    line_6:        as short as 3 days has been confirmed (Fig. 1 here). Based on the P-L relation
    line_7:        from 27 Cepheids found from the Cycle 1 data, the apparent distance modulus to
    line_8:        IC4182 is 28.47, and the peak absolute magnitude in V for SNIa 1937C = -19.92
    line_9:        +/- 0.1, independent of everything but differential absorption between the SN
    line_10:       and the Cepheids. It is necessary to measure this
    line_11:       value for several SNIa to determine the mean value and intrinsic dispersion of
    line_12:       M(max) for SNIa. For the next target we propose to observe the amorphous galaxy
    line_13:       NGC 5253 that produced the two SNIa 1895B and 1972E. Photometry in V, R, and I
    line_14:       will determine the internal absorption of the Cepheids individually, giving
    line_15:       the true modulus of NGC 5253. The internal absorption of SN1972E is known to be
    line_16:       small, as shown by the blue color of (B-V)=-.08. Based on our experience with
    line_17:       IC 4182, accounting for the similar predicted distance for NGC 5253, and noting
    line_18:       that ground observations show the presence of many luminous blue supergiants,
    line_19:       we expect to find a similar number of Cepheids as found in IC 4182. This
    line_20:       project is therefore feasible with HST in its present status.

!
! end of abstract

general_form_proposers:

  lname:           SANDAGE
    fname:         ALLAN
    title:         PI
    mi:            R
    inst:          OBSERVATORIES OF THE CIW
    country:       USA

!

  lname:           PANAGIA
    fname:         NINO
    inst:          STSCI
    country:       USA
    esa:           Y

!

  lname:           MACCHETTO
    fname:         F
    mi:            D
    inst:          STSCI
    country:       USA
    esa:           Y

!

  lname:           TAMMANN
    fname:         GUSTAV
    mi:            A
    inst:          UNIVERSITAT BASEL
    country:       SWITZERLAND
    esa:           Y

!

  lname:           SAHA
    fname:         ABHIJIT
    inst:          STSCI
    country:       USA

!

  lname:           LABHARDT
    fname:         LUKAS
    inst:          UNIVERSITAT BASEL
    country:       SWITZERLAND
    esa:           Y

!
! end of general_form_proposers block

general_form_text:

  question:        3
    section:       1
    line_1:        Observations will be carried out with the WFC. Properly time
    line_2:        spaced observations in the V band with an accuracy of 0.1mag
    line_3:        will be required. If about 10 to 20 Cepheids are observed
    line_4:        and their period is determined to 10 percent
    line_5:        accuracy, the overall mean V will be known to better than
    line_6:        5 percent. In addition 3 observations in the I
    line_7:        band will permit us to reconstruct the I light curves
    line_8:        and to derive mean I.
    line_10:       The observing plan is to obtain
    line_11:       a sequential series of 10 images in the V band at time
    line_12:       intervals of 5/8 days (=15hr), immediately followed by 6
    line_13:       images taken at 17/8 day (=50hr) intervals, and finally 5
    line_14:       more images at 50/8 day (=150hr)intervals.
    line_17:       This strategy ensures that the light curve of
    line_18:       each Cepheid is defined by not less than 8 points, rather
    line_19:       regularly spaced in time. The additional images in the I
    line_20:       band will be obtained at 3 epochs. It is
    line_21:       preferable that these be made as close in time as possible to
    line_22:       the V exposures, and about 12.5, 22, and 30.7 days after the
    line_23:       first V observation.

!

  question:        5
    section:       1
    line_1:        We have ascertained from test data that we can do better
    line_2:        than 10 percent photometry at V=25.0 with 70 minute F555W
    line_3:        exposures. Our estimate of the distance modulus to NGC 5253
    line_4:        is 28.4. Our timing scheme and photometric accuracy will
    line_5:        thus permit detection of Cepheids with absolute magnitudes
    line_6:        of -3 mag. The later exposures in the sequence are spaced
    line_7:        by 150 hours, and are aimed to cover the light curves for
    line_8:        longer period (and hence brighter) Cepheids.
    line_9:        The exposures in 785LP are all GROUPED with some F555W
    line_10:       exposure, and no extra visits are required for them.

!

  question:        6
    section:       1
    line_1:        1) Orientation -- Since the observations span a total of
    line_2:        about 50 days, the orientation should be chosen so that
    line_3:        all observations are possible at the same orientation.
    line_4:        This means that the first exposure will need to be at
    line_5:        off-nominal roll.
    line_7:        2) Timing --- Observations need to be done at planned
    line_8:        time intervals, as detailed in the Exposure Logsheet
    line_9:        to ensure adequate coverage of the Cepheids' light curves.
    line_11:       The exposure logsheet specifies the
    line_12:       middle of the series of exposures with an "AT" Spec_req.,
    line_13:       and defines all other exposure epochs relative to it.
    line_14:       If the exposure with "AT" is set at nominal roll, then
    line_15:       the other exposures should be possible at the same orient.
    line_16:       THE "AT" requirement CAN BE CHANGED in value subject to roll
    line_17:       restrictions, but the RELATIVE spacing of the other
    line_18:       exposures should remain the same.
    line_20:       The 70 minute exposures span 2 orbits -- it is expected that
    line_21:       these will be two equal sub-exposures like from CR-SPLIT=0.5.

!
!end of general form text

general_form_address:

  lname:           SANDAGE
    fname:         ALLAN
    mi:            R
    category:      PI
    inst:          Observatories of the CIW
    addr_1:        OCIW
    addr_2:        813 Santa Barbara Street
    city:          PASADENA
    state:         CA
    zip:           91106
    country:       USA
    phone:         818-304-0246

!
! end of general_form_address records

fixed_targets:

    targnum:       1
    name_1:        NGC5253-FIELD
    descr_1:       E,306
    pos_1:         RA=13H 37M 06.0S +/- 0.1S,
    pos_2:         DEC=-31D 24' 00.0" +/- 1"
    equinox:       1950.0
    pm_or_par:     NO
    fluxnum_1:     1
    fluxval_1:     V=25.0 +/- 0.1, TYPE=G0

!
! end of fixed targets

! No solar system records found

! No generic target records found

exposure_logsheet:

    linenum:       1.000
    targname:      NGC5253-FIELD
    config:        WFC
    opmode:        IMAGE
    aperture:      WFALL-FIX
    sp_element:    F555W
    num_exp:       1
    time_per_exp:  45M
    s_to_n:        5
    fluxnum_1:     1
    priority:      1
    param_1:       PURGE=NO
    req_1:         BEFORE 13 BY 525H +/- 20H;
    req_2:         CYCLE 3 / 1-24;
    req_3:         SAME ORIENT FOR 1-12 AS 13
    comment_1:     USE SAME GUIDE STARS FOR ALL
    comment_2:     OBSERVATIONS IN PROPOSAL.

!

    linenum:       2.000
    targname:      NGC5253-FIELD
    config:        WFC
    opmode:        IMAGE
    aperture:      WFALL-FIX
    sp_element:    F555W
    num_exp:       1
    time_per_exp:  60M
    s_to_n:        10
    fluxnum_1:     1
    priority:      1
    param_1:       PURGE=NO
    req_1:         BEFORE 13 BY 375H +/- 20H;
    req_2:         POS TARG +10, -10 /1-24

!

    linenum:       3.000
    targname:      NGC5253-FIELD
    config:        WFC
    opmode:        IMAGE
    aperture:      WFALL-FIX
    sp_element:    F555W
    num_exp:       1
    time_per_exp:  60M
    s_to_n:        10
    fluxnum_1:     1
    priority:      1
    param_1:       PURGE=NO
    req_1:         BEFORE 13 BY 225H +/- 10H

!

    linenum:       4.000
    targname:      NGC5253-FIELD
    config:        WFC
    opmode:        IMAGE
    aperture:      WFALL-FIX
    sp_element:    F785LP
    num_exp:       1
    time_per_exp:  60M
    s_to_n:        10
    fluxnum_1:     1
    priority:      1
    param_2:       PURGE=NO
    req_1:         GROUP 3-4 NO GAP

!

    linenum:       5.000
    targname:      NGC5253-FIELD
    config:        WFC
    opmode:        IMAGE
    aperture:      WFALL-FIX
    sp_element:    F555W
    num_exp:       1
    time_per_exp:  60M
    s_to_n:        10
    fluxnum_1:     1
    priority:      1
    param_1:       PURGE=NO
    req_1:         BEFORE 13 BY 175H +/- 10H

!

    linenum:       6.000
    targname:      NGC5253-FIELD
    config:        WFC
    opmode:        IMAGE
    aperture:      WFALL-FIX
    sp_element:    F555W
    num_exp:       1
    time_per_exp:  60M
    s_to_n:        10
    fluxnum_1:     1
    priority:      1
    param_1:       PURGE=NO
    req_1:         BEFORE 13 BY 125H +/- 10H

!

    linenum:       7.000
    targname:      NGC5253-FIELD
    config:        WFC
    opmode:        IMAGE
    aperture:      WFALL-FIX
    sp_element:    F555W
    num_exp:       1
    time_per_exp:  60M
    s_to_n:        10
    fluxnum_1:     1
    priority:      1
    param_1:       PURGE=NO
    req_1:         BEFORE 13 BY 75H +/- 3H

!

    linenum:       8.000
    targname:      NGC5253-FIELD
    config:        WFC
    opmode:        IMAGE
    aperture:      WFALL-FIX
    sp_element:    F555W
    num_exp:       1
    time_per_exp:  60M
    s_to_n:        10
    fluxnum_1:     1
    priority:      1
    param_1:       PURGE=NO
    req_1:         BEFORE 13 BY 60H +/- 3H

!

    linenum:       8.500
    targname:      NGC5253-FIELD
    config:        WFC
    opmode:        IMAGE
    aperture:      WFALL-FIX
    sp_element:    F785LP
    num_exp:       1
    time_per_exp:  60M
    s_to_n:        10
    fluxnum_1:     1
    priority:      1
    param_1:       PURGE=NO
    req_1:         GROUP 8-8.5 NO GAP

!

    linenum:       9.000
    targname:      NGC5253-FIELD
    config:        WFC
    opmode:        IMAGE
    aperture:      WFALL-FIX
    sp_element:    F555W
    num_exp:       1
    time_per_exp:  60M
    s_to_n:        10
    fluxnum_1:     1
    priority:      1
    param_1:       PURGE=NO
    req_1:         BEFORE 13 BY 45H +/- 3H

!

    linenum:       10.000
    targname:      NGC5253-FIELD
    config:        WFC
    opmode:        IMAGE
    aperture:      WFALL-FIX
    sp_element:    F555W
    num_exp:       1
    time_per_exp:  60M
    s_to_n:        10
    fluxnum_1:     1
    priority:      1
    param_1:       PURGE=NO
    req_1:         BEFORE 13 BY 30H +/- 3H

!

    linenum:       11.000
    targname:      NGC5253-FIELD
    config:        WFC
    opmode:        IMAGE
    aperture:      WFALL-FIX
    sp_element:    F555W
    num_exp:       1
    time_per_exp:  60M
    s_to_n:        10
    fluxnum_1:     1
    priority:      1
    param_1:       PURGE=NO
    req_1:         BEFORE 13 BY 15H +/- 3H

!

    linenum:       12.000
    targname:      NGC5253-FIELD
    config:        WFC
    opmode:        IMAGE
    aperture:      WFALL-FIX
    sp_element:    F785LP
    num_exp:       1
    time_per_exp:  60M
    s_to_n:        10
    fluxnum_1:     1
    priority:      1
    param_1:       PURGE=NO
    req_1:         GROUP 12-13 NO GAP

!

    linenum:       13.000
    targname:      NGC5253-FIELD
    config:        WFC
    opmode:        IMAGE
    aperture:      WFALL-FIX
    sp_element:    F555W
    num_exp:       1
    time_per_exp:  60M
    s_to_n:        10
    fluxnum_1:     1
    priority:      1
    param_1:       PURGE=NO
    req_1:         AT 24-JUN-1993 +/- 3D;
    req_3:         POS TARG 0, 0 /1-24

!

    linenum:       14.000
    targname:      NGC5253-FIELD
    config:        WFC
    opmode:        IMAGE
    aperture:      WFALL-FIX
    sp_element:    F555W
    num_exp:       1
    time_per_exp:  60M
    s_to_n:        10
    fluxnum_1:     1
    priority:      1
    param_1:       PURGE=NO
    req_1:         AFTER 13 BY 15H +/- 3H

!

    linenum:       15.000
    targname:      NGC5253-FIELD
    config:        WFC
    opmode:        IMAGE
    aperture:      WFALL-FIX
    sp_element:    F555W
    num_exp:       1
    time_per_exp:  60M
    s_to_n:        10
    fluxnum_1:     1
    priority:      1
    param_1:       PURGE=NO
    req_1:         AFTER 13 BY 30H +/- 3H;
    req_2:         SAME ORIENT FOR 14-24 AS 13

!

    linenum:       16.000
    targname:      NGC5253-FIELD
    config:        WFC
    opmode:        IMAGE
    aperture:      WFALL-FIX
    sp_element:    F555W
    num_exp:       1
    time_per_exp:  60M
    s_to_n:        10
    fluxnum_1:     1
    priority:      1
    param_1:       PURGE=NO
    req_1:         AFTER 13 BY 45H +/- 3H

!

    linenum:       17.000
    targname:      NGC5253-FIELD
    config:        WFC
    opmode:        IMAGE
    aperture:      WFALL-FIX
    sp_element:    F555W
    num_exp:       1
    time_per_exp:  60M
    s_to_n:        10
    fluxnum_1:     1
    priority:      1
    param_1:       PURGE=NO
    req_1:         AFTER 13 BY 60H +/- 3H

!

    linenum:       17.500
    targname:      NGC5253-FIELD
    config:        WFC
    opmode:        IMAGE
    aperture:      WFALL-FIX
    sp_element:    F785LP
    num_exp:       1
    time_per_exp:  60M
    s_to_n:        10
    fluxnum_1:     1
    priority:      1
    param_1:       PURGE=NO
    req_1:         GROUP 17-17.5 NO GAP

!

    linenum:       18.000
    targname:      NGC5253-FIELD
    config:        WFC
    opmode:        IMAGE
    aperture:      WFALL-FIX
    sp_element:    F555W
    num_exp:       1
    time_per_exp:  60M
    s_to_n:        10
    fluxnum_1:     1
    priority:      1
    param_1:       PURGE=NO
    req_1:         AFTER 13 BY 110H +/- 10H

!

    linenum:       19.000
    targname:      NGC5253-FIELD
    config:        WFC
    opmode:        IMAGE
    aperture:      WFALL-FIX
    sp_element:    F555W
    num_exp:       1
    time_per_exp:  60M
    s_to_n:        10
    fluxnum_1:     1
    priority:      1
    param_1:       PURGE=NO
    req_1:         AFTER 13 BY 160H +/- 10H

!

    linenum:       20.000
    targname:      NGC5253-FIELD
    config:        WFC
    opmode:        IMAGE
    aperture:      WFALL-FIX
    sp_element:    F555W
    num_exp:       1
    time_per_exp:  60M
    s_to_n:        10
    fluxnum_1:     1
    priority:      1
    param_1:       PURGE=NO
    req_1:         AFTER 13 BY 210H +/- 10H

!

    linenum:       21.000
    targname:      NGC5253-FIELD
    config:        WFC
    opmode:        IMAGE
    aperture:      WFALL-FIX
    sp_element:    F785LP
    num_exp:       1
    time_per_exp:  60M
    s_to_n:        10
    fluxnum_1:     1
    priority:      1
    param_1:       PURGE=NO
    req_1:         GROUP 20-21 NO GAP

!

    linenum:       22.000
    targname:      NGC5253-FIELD
    config:        WFC
    opmode:        IMAGE
    aperture:      WFALL-FIX
    sp_element:    F555W
    num_exp:       1
    time_per_exp:  60M
    s_to_n:        10
    fluxnum_1:     1
    priority:      1
    param_1:       PURGE=NO
    req_1:         AFTER 13 BY 360H +/- 20H

!

    linenum:       23.000
    targname:      NGC5253-FIELD
    config:        WFC
    opmode:        IMAGE
    aperture:      WFALL-FIX
    sp_element:    F555W
    num_exp:       1
    time_per_exp:  60M
    s_to_n:        10
    fluxnum_1:     1
    priority:      1
    param_1:       PURGE=NO
    req_1:         AFTER 13 BY 510H +/- 20H

!

    linenum:       24.000
    targname:      NGC5253-FIELD
    config:        WFC
    opmode:        IMAGE
    aperture:      WFALL-FIX
    sp_element:    F555W
    num_exp:       1
    time_per_exp:  45M
    s_to_n:        10
    fluxnum_1:     1
    priority:      1
    param_1:       PURGE=NO
    req_1:         AFTER 13 BY 660H +/- 20H

!
! end of exposure logsheet

! No scan data records found