FIELD: well drilling; applicable in determination of various parameters and properties of formation near surface. SUBSTANCE: drill string is run into wellbore. Instrument has a tubular member made for axial connection with drill string, and a stabilizing member located round the tubular member for relative rotation of the stabilizing member and the tubular member. Connected with the stabilizing member are ribs and means for engagement of wellbore wall by friction forces. The stabilizing member supports the actuating system. One of ribs supports probe made for motion by actuating system between withdrawn position inside of one rib and extended position with engagement of wellbore wall so that probe gathers data on formation directly during drilling with use of drill string members to minimize number of round trip operations of drilling equipment. EFFECT: higher efficiency. 23 cl, 9 dwg
