9198(  1) - 12/20/00 23:39  - [  1]

    PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS   ST ScI Use Only
                                                       ID:      9198
                                                       Version: 1
                                                       Check-in Date: 20-Dec-2000
                                                                      23:31:53

1.Proposal Title:
Asteroid Trails in the HST Archive II
------------------------------------------------------------------------------------
2. Proposal For  3. Cycle
AR               10
------------------------------------------------------------------------------------
4. Investigators
                                                                                     Contact?
    PI: Robin Evans                       Gibbel Corporation
   CoI: Dr. Karl Stapelfeldt              Jet Propulsion Laboratory                     N

------------------------------------------------------------------------------------
5. Abstract

New images including the trails of small, main-belt asteroids are continuously being
added to the HST Archive. The telescope's small field of view and lack of
availability for follow-up observations are more than offset by a unique and
remarkable advantage: HST asteroid trails are curved due to the parallax induced by
the spacecraft's orbital motion. Using HST ephemerides to fit a trail's shape, an
asteroid's geocentric distance can be derived from as little as 10 minutes of
imaging data. The availability of accurate distances allows an absolute magnitude
(size) distribution histogram to be constructed down to a limiting magnitude of V=
24 (H= 20; diameter ~ 0.3 km) without need of full orbit determinations. Over the
past four years, we have surveyed 87, 000 WFPC2 images and 7, 000 STIS images for
asteroid trails and uncovered 491 images with trails from 206 distinct objects. We
propose to continue building the HST asteroid database in Cycle 10 by searching 110,
000 new images and combining the results with our previous work. The results will
provide fundamental constraints on models for collisional evolution of the main belt
and a census of a major source region of Earth-crossing objects.
------------------------------------------------------------------------------------
                                                9198(  1) - 12/20/00 23:39  - [  2]

            Summary Form for Proposal  9198

  Item                         Used in this proposal
------------------------------------------------------------------------------------------------------------------------------------
  Proposal Category            AR
------------------------------------------------------------------------------------------------------------------------------------