scientific abstract comets comprise the most primitive material in the solar system. observations of their composition are diagnostic of the environment during their formation. phenomena to be studied are bare cometary nuclei and onset of activity at large heliocentric distances and gas and dust emissions in the inner solar system. objectives of observations of gas and dust are to characterize the physical parameters of the dust (total production, sizes and surface properties) and to analyze the chemical composition of both volatile and refractory constituents with special emphasis on organic compounds. the first priority target, p/kopff, is most productive among the here proposed comets: not only in dust, but also in gas production (oh up to 5x10^28). also, a cometary trail of this comet was observed by iras. results from this observational programme have to be compared with the results from the programme properties of solar system dust and other cp-comet observations by cam, sws and lws. observation summary observations of active comets (p/kopff and p/churyumov-gerasimenko or p/wild 2) should be made through 4 apertures (13.8 to 120 arcsec at three wavelengths between 12.8 and 25 microns) centered on maximum brightness and through 9 filters (3.6 to 160 microns) to obtain thermal energy spectrum of the dust emission. spectra in the 2-12 micron range will be obtained with pht-s, in order to determine the strength and shape of features due to organic grains, silicate grains and various molecular species (h2co, co, co2, ch-x, etc.). observations of cometary nuclei and onset of activity (chiron and p/schwassmann-wachmann 1) should be made in several sets of flux measurements from 25 to 160 microns with pht-p and pht-c. observations through 3 different apertures (52 to 99 arcsec) with the 60 micron filter may allow separation of a dust coma from the nucleus. linked observations: active comets have high proper motion. they are tracked in the solar system objects mode. no ephemeris are given here. the astrometric observation of the target objects shortly before launch and during the iso operation should be used for ephemeris improvement. background is determined by a subsequent (a few days later) staring observation at the mid-term position of the previous observation (shadow object). targets for observations of bare nuclei are in the outer solar system and hence have slow proper motion (< 0.1./h). they are observed as solar system objects with staring mode. in order to determine the background, the method of shadow object is also used. fixed time observations: the active comet observations are time-critical (within a few days) because of the time-variable activity. it is planned to specify the accurate observation time after the exact ephemeris are known and an analysis of the background has been made. concatenation: each comet observation starts with a peaking-up of the tracked comet. for time-economy this is done only once per observation which includes several filters-, apertures- and one spectrometer-observation. in addition the 3.6 micron observation has to be concatenated with the pht-s observation in order to provide absolute calibration of the spectra.
Instrument
PHT03 , PHT04 , PHT22 , PHT40
Temporal Coverage
1996-05-19T04:40:52Z/1997-12-30T01:28:43Z
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, Gruen et al., 1999, 'Comet observations with ISOPHOT: Study of bare nuclei comma onset of activity comma composition of comets and dust production Part 3 ', 1.0, European Space Agency, https://doi.org/10.5270/esa-khr0fto
