8737(  1) - 12/30/99 13:00  - [  1]

    PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS   ST ScI Use Only
                                                       ID:      8737
                                                       Version: 1
                                                       Check-in Date: 30-Dec-1999
                                                                      12:30:58

1.Proposal Title:
Geometric Distances of Globular Clusters (AR part)
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2. Proposal For  3. Cycle
AR               9
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4. Investigators
                                                                                     Contact?
    PI: Ivan King                         University of California, Berkeley
   CoI: Dr. Jay Anderson                  University of California, Berkeley            N
   CoI: Dr. Karl Gebhardt                 UCSC/Lick Observatory                         N
   CoI: Dr. Carlton Pryor                 Rutgers, the State Univ. of New Jersey        N

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5. Abstract

This is a proposal to establish a globular-cluster distance scale of unprecedented
accuracy and reliability, with far- reaching impact on the distance and time scales
of cosmology. Our method is to compare internal dispersions of proper motion with
ground-based determinations of the dispersion of radial velocities. The prospect is
a geometrically based distance scale with an accuracy of better than 2\ ability to
make such measurements, and we are progressing with the conversion of them to a
distance for the cluster. Our project has two parts: (1) Where possible, we use
archival observations for both astrometric epochs (the 2 clusters in the present
proposal). (2) The accompanying GO proposal covers 5 more clusters for which an
archival first epoch exists but we lack second-epoch observations. With this
proposal, the accompanying GO proposal, and other HST collaborations in which we are
involved, we expect to determine accurate distances for 13 clusters, with a large
range of metallicities and second-parameter characteristics. (Moreover, we intend to
cover additional clusters in future ACS proposals.)
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                                                8737(  1) - 12/30/99 13:00  - [  2]

            Summary Form for Proposal  8737

  Item                         Used in this proposal
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  Proposal Category            AR
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