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SCIENTIFIC ABSTRACT The IRAS discovery of far-infrared excesses among seemingly normal main-sequence star motivates this proposal. These have been interpreted in terms of disks of cold material. The aim of this proposal is to establish the true frequency for far-infrared excesses in a volume-limited sample of main sequence stars using PHT-P measurements, in order to address the success or failure of single stars in processes related to the forming of planetary systems. For brighter sources, more extensive wavelength coverage and spatial resolution will be attempted, again with PHT-P. Finally, observations of Kuiper Belt objects will be attempted. OBSERVATION SUMMARY This proposal is split into three parts: this is PART 3. It is planned to obtain more accurate coordinates for the sources in this proposal, beyond the SIMBAD information used so far. Part 1: Concerns PHT03 measurements of a volume-limited sample of main sequence and related stars. PART 2: Concerns spatial mapping of selected brighter far IR sources. itemize AOTs, exposure times and S/N expected PART 3: Concerns attempted local Kuiper Belt observations. KUIPER BELT OBSERVING PROGRAM We request photometry of lines of sight through the zodiacal dust into possible outer solar system (Kuiper Belt) material. To increase our chances of distinguishing KB emission from hotter foreground zody emission, we plan to observe: 1) at wavelengths from 3.6 to 200 microns; 2) at 2 epochs, such that the same VOLUME ELEMENT in the KB is observed through different pieces of the zody cloud; 3) at two ecliptic latitudes, on the assumption that the nearby and distant material will have different latitude distributions. Observation at 2 epochs is designed to help untangle foreground from background flux, not to look for moving objects. The volume sampled by ISO will not be large enough for practical hopes of detecting macroscopic KB objects. Schematic target definition: 2 volume elements with the following HELIOCENTRIC ecliptic coordinates: 1) longitude L = 0.0 deg, latitude B = 3.0 deg, distance R = 50.0 AU 2) 0.0 13.0 50.0 Ecliptic longitude of 0.0 degrees represents a region of the ecliptic in the neighborhood of the S. galactic pole, thus reducing galactic background. Symmetric to these locations at ecliptic longitude of 180 deg, are equivalently galactic-free locations which would also be acceptable for this experiment. The tolerance on the chosen longitude is large, 15 degrees. This tolerance is meant to provide flexibility in scheduling the initial observations. The second epoch observations must return as exactly as possible to whatever longitude was observed at the first epoch. The latitudes are chosen to lie on one side of the likely plane of symmetry of the outer solar system. Neptune's orbit, which is a reasonable first guess as to the location of that plane, is tilted 1.7 degrees relative to the earth's orbit. The range of longitudes is meant to allow comparison of the vertical gradients of warm and cold material. The GEOCENTRIC ecliptic coordinates of the chosen volume elements will depend on the earth's position in its orbit. These can in turn be converted to geocentric RA and dec. Trial scenario: A) observe both locations when their solar phase angle first falls within ISO's pointing tolerance, i.e. phi <= 120.0 deg. This occurs when the earth's heliocentric longitude is 59.00 deg, approximately Nov. 21. The GEOCENTRIC RA and dec of the 3 KB volume elements at this time will be: 1) RA = +2.11 deg dec = +2.39 deg 2) RA = +6.07 +11.34 B) observe the same two locations in the KB when the line of sight through the foreground zody dust differs as much as possible from the first epoch, i.e. heliocentric longitude of the earth = 90.00 degrees, solar phase angle = 88.85 degrees, **1 MONTH AFTER THE FIRST OBSERVATIONS The GEOCENTRIC RA and dec of the same two KB locations this time will be: 1) RA = +2.25 deg dec = +2.30 deg 2) +6.16 +11.16 Observing mode: Staring photometry AOT PHT03 (PHT-P: 3.6, 11.5, 25, 60 and 100 microns) and PHT22 (PHT-C: 200 microns); aperture = 180 arcsec (P1, P2, and P3). At each target latitude, there will be a 2nd observation at a chop position 330 arcsec away (maximum throw) at position angle = 90 or 270 degrees. Time on one target latitude: P1 - 3.6 microns 2 meas x 32 sec [2 meas. separated by 330 arcsec] P1 - 11.5 microns 2 meas x 32 sec P2 - 25 microns 2 meas x 32 sec P3 - 60 microns 2 meas x 128 sec P3 - 100 microns 2 meas x 128 sec C200 - 200 microns 2 meas x 128 sec TOTAL INT. TIME 960 seconds (= 1024 sec) Plus overhead times listed in section 6.4 of ISOPHOT manual: telescope slew 180 sec set-up 15 sec FCS exposures ? 12 sec wheel 70 sec heated detectors 90 sec TOTAL OVERHEAD 367 sec Thus, total time at one latitude (incl. chop to 2nd location), one epoch: 1391 seconds Total experiment = 2 epochs x 2 latitudes x 1391 se