Due to the large columns of gas and dust in the core of the rho Oph cloud 
and the high density of sources, ground-based and spaceborne infrared           
observations have thus far been insensitive to two important populations of     
embedded stars.  The first is the low-luminosity Class I objects (<1 L(sun))    
which are in an early, deeply embedded phase of evolution and display strong    
infrared excesses.  The second group is the diskless Class III sources, which   
are usually strong x-ray emitters, but have no near-infrared excesses and can   
be difficult to distinguish from background stars.  Yet these diverse           
populations have something in common: they both emit weak radio continuum       
emission.  We propose to use ISOCAM at 6.75 and 11.5 microns to identify the    
infrared counterparts to a sample of weak radio sources in the rho Oph core.    
These data, when combined with existing near-infrared observations, will allow  
us to determine the amount of circumstellar dust present and to distinguish     
between Class I and Class III sources.  Using the microscanning mode we will    
reach required sensitivity levels of 1 mJy and 0.6mJy (S/N=10), respectively,   
which is 8 times the sensitivity achieved by the guaranteed time program of     
Nordh et al. at 6.75 microns.  Mid-infrared wavelengths are necessary since     
they are much more sensitive to thermal emission from circumstellar dust than   
near-infrared. Our program will reveal the extents and distributions of the low 
luminosity Class I and Class III populations embedded throughout the depth of   
the cloud core. The numbers and luminosities of Class I sources with L<1 L(sun) 
are of critical importance to explore the age, mass function, and accretion     
rate in rho Oph relative to other well-studied regions of low mass star
formation.  There is strong evidence that the Class III sources in the core     
are contemporaries of the T Tauri stars but have shorter timescales for disk    
dissipation.  Our data will allow us to determine the masses of their remnant   
disks for direct comparison with their ages determined from infrared spectra.