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==> This proposal requests an upgrade from Priority 3 for ETEDESCO.ASTSFDIS
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The first two paragraphs below are an updated version of the abstract from the
original proposal.
The size-frequency distribution of asteroids with diameters < 10 km is
essentially unknown. We propose to use ISOCAM (LW10, CAM01) in microscanning
mode to test current predictions of the number of asteroids per square degree
down to sizes below 1 km. Our objective is to measure the number of asteroids
per unit area of sky observed as a function of IR brightness. (A 1 km main-belt
asteroid has a flux density at 12 microns of about 1 mJy.) From these data we
will be able to constrain, and perhaps decide among, current estimates for the
numbers of asteroids with diameters greater than 1 km. These estimates differ
by up to a factor of six. Any region of sky along the ecliptic is suitable for
this purpose and two such regions were identified during the previous Phase 2.
Each of the selected target regions contain no infrared sources from any of the
IRAS catalogs, including extra galactic, or FSS sources.
In addition to the solar system science resulting from this study, we will
provide data useful for assessing the "contamination" rate from asteroids in all
ISOCAM observations. We will also obtain data from which the brightness and
small-scale structure of the zodiacal background can be determined.
The additional images obtained by the proposed upgrade improve statistics and
probe deeper into the stellar point-source and zodiacal backgrounds. This
facilitates identification of asteroids.