Ground state conformation of dimethyl disulfide

What is the ground state conformation of dimethyl disulfide ? 


The two which seem reasonable to me are trans to avoid methyl-methyl gauche interactions or gauche due to sulfur donation into the S-Me sigma antibonding orbital. 


I found a discussion in [this paper](http://pubs.acs.org/doi/abs/10.1021/j100547a013) but it doesn't seem to really answer the question definitely. 


