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, with pht-p, pht-c and sws. finally, observations of kuiper belt material will be attempted. observation summary this proposal is split into three parts: this is part 2. it is planned to obtain more accurate coordinates for the sources in this proposal, beyond the simbad information used so far. exposure times were estimated using the pht and sws cookbooks. 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. extended sources program scientific abstract we request micro-scanning observations with aot pht32 (c100) at a wavelength of 60 microns of the brightest and nearest vega-like sources to measure the characteristic sizes of the emitting regions and glean some information regarding their shapes and orientations. the sample is limited to main sequence stars found to have ir excesses in iras data, with total 60-micron flux greater than virgul0.5 jansky and parallax distances less than 20 parsecs, plus a few very nearby stars of special interest, plus a few stellar point source standards. the observing plan in each case will be to perform photometry with the p32-c100 detector and filter and 3x the diffraction limited step size, 15 arcseconds. the goal originally was to use pht12 super-res mode and scan profiles along 3 position angles which could be deconvolved to find the intrinsic size and shape of the fwhm contour of the emitting region. we would have done a first integration at the target position, then a series of micro-scan steps by the focal plane chopper extending radially away from the target position in 3 legs of a y at position angles 0, 120, and 240 degrees. the removal of pht12 leaves us with pht32 mapping as the only available comparable approach. an integration time as short as 32 or 64 sec seems possible given that successive measurements along the raster scan will be viewing almost exactly the same source flux and background, thus settling time of the detector after each measurement should be small. the signal/noise ratio in 32 sec on a 0.5 jy source at 60 microns with p32-c100 with pessimistic background assumptions (ecliptic lat = 0 deg) should be about 32. observation summary aot p32 (microscan), detector c100 - 60 micron filter, 15 arcsec stepsize n the z-axis, 60 arcsec in y, integration time per raster scan point = 32 or 64 seconds no peakup, no repeat/reverse scans, and either 3 x 3 or 5 x 5 raster, centered on target. time spent integrating = 5 x 5 raster x 32 sec/substep = 800 sec time spent integrating = 3 x 3 raster x 64 sec/substep = 586 sec overhead time expected from section 6.6.5 of isophot manual: telescope acquisition and slewing 180 sec instrument set-up 15 sec time for fcs exposures for 3 scans ? 18 sec time for wheel positioning (3 wheels) 30 sec time for stabilizing heated detector 90 sec est. settle time per chop move x 30 90 sec total overhead 423 sec total time per source, integration + overhead = 1223 5x5 or 1009 3x3 sec number map lines z = 3; oversampling = 3; number samples in y = 3. part 3: concerns attempted local kuiper belt observations. linked observations: yes fixed time observations: no concatenation: no
Instrument
PHT32
Temporal Coverage
1996-02-14T08:48:05Z/1997-09-09T06:45:50Z
Version
1.0
Mission Description
The Infrared Space Observatory (ISO) was the worlds first true orbiting infrared observatory. Equipped with four highly-sophisticated and versatile scientific instruments, it was launched by Ariane in November 1995 and provided astronomers world-wide with a facility of unprecedented sensitivity and capabilities for a detailed exploration of the Universe at infrared wavelengths.
European Space Agency, Stencel et al., 1999, 'The Birth and Death of Planetary Systems comma Part 2 of 7', 1.0, European Space Agency, https://doi.org/10.5270/esa-7t89d1o
