In the following, we propose to obtain additional observations
using the ISO spectrometers of 3C58 which is visible from 
now until March 16 1998. This short visibility window requres a fast 
turnaround time to enable the observations to be scheduled. We would like 
to transfer and upgrade time available from another programme 
(SUNGER PSR1259, 7200s) to assist in the time allocation required.

Observations of the SNR 3C58 and the Crab offer us the unique opportunity to
contrast two distinctly different young pulsars. According to models 
(based eg on radio filaments), a lot of thermal gas (much more than in 
the Crab) should exist within 3C58. Our LWS observations indicate that
the FIR lines in 3C58 are much weaker than the Crab. ISO offers us the 
unique opprotunity to determine the composition of this gas and its 
ionization state. For example, in Cas A it has long been a mystery
why no Neon is observed in the optical. Our SWS observations resolve 
this issue with the detection of \[NeII\], \[NeIII\], \[SIII\], \[ArII\], 
\[ArIII\] and \[SiII\]. 3C58 has not been observed with the SWS.
Perhaps it is in this wavelength range that 3C58 is cooling 
down, without looking we will not know the answer to this puzzle for a 
longtime!
VISIBILITY:

3C 58           2h 05m 34.4s  64d 49' 49.8"
784  08 Jan 98 -- 852  16 Mar 98