Broadband infrared photometry of comet Hale-Bopp with ISOPHOT ?

摘要: Comet Hale-Bopp was observed ve times with ISOPHOT, the photometer on board ESA's Infrared Space Observatory (ISO) between 4.6 and 2.8 AU. Each time, broadband photometry performed using 4 dierent detectors, 5 apertures 10 lters covering range 3.6 170 m. Background ob- servations were identical instrument settings at same positions sky several days after comet observations. The observation strategy data reduction steps are described in some detail, including techniques to correct for variable detector responsivity. resulting inband power values of observations their uncertainties given. mean uncertainty is 25%. nal fluxes computed, taking into account zodiacal background, possible oset comet's position from center aperture, brightness distribution within coma, spectral energy emission. Strong thermal emission a broad size dust particles detected all sets, even r =4 :6{4:9 AU pre-perihelion 3.9 post-perihelion; total varied as 3 . 7.3{12.8 m color temperature was1.5 blackbody temperature, higher than that any other comet. Silicate features 25 prominent largest heliocentric distances silicate has been presence crystalline water ice grains suggested 60 excess 4.6{4.9 AU, consistent QOH if icy slightly warmer an equilibrium blackbody. average albedo P/Halley, but lower measurements nearer perihelion. There no evidence component cold, bright enhancing scattered light Simple models mixture absorbing t ISO spectra flux >100 mr equires which most mass concentrated large particles. Dust production rates order 1:5 kg s 1 have found. They correspond gas ratios 6 10.