supersymmetry - Mass spectrum of Type I string theory

The massless fields of the Type I string theory are the described by:

$$\begin{array}{*{20}{c}} {{\rm{Sector}}}&{{\rm{Massless fields}}}\\ {{\rm{R - R}}}&{{C_0}}\\ {{\rm{NS - NS}}}&{{g_{\mu \nu }},\Phi }\\ {{\rm{R - NS}}}&{{\Psi _\mu }}\\ {{\rm{NS - R}}}&{\lambda'}\\ {\rm{R}}&{}\\ {{\rm{NS}}}&{} \end{array}$$

1. Are there any (massless) fields in the R and NS sectors (open strings)?


2. What is the projection of state vectors from the Type IIB string theory to the Type I string theory?


3. What's the significance of the ' in $\lambda'$?


4. What exactly are the spectra of state vectors (in terms of $\mathbf{8}_s$, $\mathbf{8}_v$ etc.) in the Type I string theory?


5. If the Type I string theory is a projection of the Type IIB string theory, where do the open strings come from?


6. What is the mass spectrum of the Type I string theory?