Journal of Geodesy manuscript No. (will be inserted by the editor) Thomas Hobiger · Tetsuro Kondo · Yasuhiro Koyama · Kazuhiro Takashima · Harald Schuh Using VLBI fringe-phase information from geodetic experiments for short-period ionospheric studies Received: 09/05/2006 / Accepted: 05/02/2007 T. Hobiger Kashima Space Research Center National Institute of Information and Communications Technology (NICT) 893-1 Hirai, Kashima, 314-0012 Ibaraki, Japan Tel.: +81-0-299-84-7136 Fax: +81-0-299-84-7159 E-mail: hobiger@nict.go.jp T. Kondo Kashima Space Research Center National Institute of Information and Communications Technology (NICT) 893-1 Hirai, Kashima, Ibaraki 314-0012 Japan Tel.: +81-299-84-7137 Fax: +81-299-84-7159 E-mail: kondo@nict.go.jp Y. Koyama Kashima Space Research Center National Institute of Information and Communications Technology (NICT) 893-1 Hirai, Kashima, Ibaraki 314-0012 Japan Tel.: +81-299-84-7143 Fax: +81-299-84-7159 E-mail: koyama@nict.go.jp K. Takashima