Airborne P-band Signal of Opportunity (SoOP) demonstrator instrument; status update. - Joseph J. Knuble; Jeffrey Piepmeier; Manohar Deshpande; Cornelus Du Toit; James L. Garrison; Yao-Cheng Lin; Georges Stienne; Stephen J. Katzberg; George Alikakos (IGARSS, 2016)