significant progress in our knowledge of the pluto-charon system has been obtained in the last decade. in particular, it was discovered that (i) pluto.s surface is not uniform, but presents variations in albedo (ii) methane, nitrogen and carbon monoxide ices are present at pluto.s surface (iii) pluto possesses an atmosphere of several microbars. from this set of outstanding results, a general picture of pluto.s surface and atmosphere and their interaction is beginning to appear. however ,a basic piece of the puzzle, namely the knowledge of the surface temperature and its possible spatial variations, is still essentially missing. the surface temperature is a key parameter because it controls the vapor pressure equilibrium of the volatiles, thereby defining the atmospheric composition, which remains quantitatively unknown. presently available surface temperature measurements, from iras (60 and 100 microns) and from submillimeter observations, give apparently inconsistent results (t = 53-58 k and t = 30-45 k respectively). the contradiction may be due to emissivity effects or to a strongly non-uniform surface temperature. this issue can be observationnally addressed in three different ways (i) repeat the iras measurements and extend them to shorter wavelengths, where the difference between warm and cold surface will appear even more distinctly (ii) measure the far-infrared spectrum (50-200 microns) in narrow photometric bands, allowing to study possible spectral emissivity effects (iii) repeat broad band photometric measurements to study variations with pluto.s orbital phase. a satellite like iso is obviously required given the wavelength range that must be probed and the faintness of the source. we expect to obtain a fairly complete description of pluto.s surface temperature distribution and thermal properties, that will allow us to firmly address such basic issues as the atmospheric composition and vertical structure, and the transport of volatiles across pluto.s surface.
Instrument
CAM01 , PHT22
Temporal Coverage
1997-02-06T12:26:50Z/1997-03-17T15:16:32Z
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.
