On the trail of tails. openParImaging the trails of comets P/Kopff comma P/Gunn and P/Churyumov-Gerasimenko with CAMclosePar

scientific abstract: isocam images of cometary dust trails are proposed to determine trail structure at various positions along the trails of two periodic comets. primary targets are p/kopff and p/churyumovgerasimenko for autumn 95 and p/kopff and p/gunn for a spring 96 launch. p/encke and p/ponswinnecke are considered as alternates depending on launch date. observations from iras (davies et al, nature 309 p315 1984) discovered an extended infrared tail (also referred to as a debris trail) associated with comet p/tempel2. sykes et al (science 232 p115 1986) independently discovered the tempel2 tail and subsequently identified a number of similar features in the iras skyflux plots.these trails may represent the main source of mass loss from comets yet they are too faint for ground based infrared observation. isocam images at various positions close to the nucleus will probe the fine structure of the trail and, by determining its width, place constraints on the ejection velocity of the particles and provide inputs to theoretical models of dust ejection. observation summary: we have modelled various trails at the time of the mission and find the trail of p/kopff to be about 1.5*10**5 jy/arc sec**2 at 12um. in a few min/frame isocam would get s/n10 in the lw10 filter (815 microns) using 6 arc sec pfov. since the comet moves these must be done as fixed time observations. the trails usually appear no more than 4 arc minutes wide so three frames at right angles to a trail taken with the 6 arcsec pfov should be enough to cover one trail at one position around the comet.s orbit and to get far enough away to reach the background. to obtain best sensitivity to these extended sources we will use the microscanning option in cam aot1 to scan across a trail at each position using the offsets to extend the coverage approx 2 iso fields along the trail. we require similar scans through the trail at posi trunca [truncated!, Please see actual data for full text]