1983 IRAS Thermal Image of Comet Tempel 1

The earth orbiting infra-red sensing spacecraft IRAS made an early observation of Comet Tempel 1 on June 18th 1983, sensing at nominal infra-red wavelengths of 12, 25, 60 and 100µm.

At that time Tempel 1 was at a distance of 1.51 AU from the sun, and 0.85 AU from the earth. Space scientists in the Physics Laboratory at the University of Kent at Canterbury in England analysed the data and generated images, including this false colour map of the temperatures in the image. They concluded that the darkest regions corresponded to a temperature of 220K (-53C) and the brightest regions to 280K (+7C). The original comet image was of low resolution, and this image was Gaussian interpolated to re-construct the likely original temperature distribution.

Integrating the thermal emission over the whole comet for the 12 and 25 µm bands, the blackbody temperature was estimated as 251K +/-10K, which is higher than the 225K expected for a blackbody at this distance from the sun. The difference (26K) was assumed to be due to small (~ 1µm) dust grains adsorbing solar energy.

This analysis and a grey-scale copy of this image were presented at a conference in 1985:

A preliminary analysis of IRAS AO's (additional observations) of comet Tempel 1. J.C. Zarnecki, S. Chakaveh, D. Bowen and J.A.M. McDonnell. Asteroids, Comets, Meteors II; Proceedings of the International Meeting, Uppsala, Sweden, June 3-6, 1985 (A87-11901 02-90). Ed. Lagerkvist, C.I., B.A. Lindblad, H. Lundstedt, H. Rickman, p403-406, Uppsala, Sweden 1986.

Original Article (PDF Format)

J.C. Zarnecki, S. Chakaveh, D. Bowen and J.A.M. McDonnell.
1985 graphic image processing and rendering, Beau Webber.