Message-ID: <3EAEA486.CA49FDC6@jpl.nasa.gov> Date: Tue, 29 Apr 2003 09:12:54 -0700 From: Dave Stowers Reply-To: dstowers@jpl.nasa.gov To: igsmail@igscb.jpl.nasa.gov Subject: [IGSMAIL-4358]: MCM4 (possible interference effect since 26nov2002) Sender: owner-igsmail Precedence: bulk ****************************************************************************** IGS Electronic Mail 29 Apr 09:12:55 PDT 2003 Message Number 4358 ****************************************************************************** Author: Seth White/Dave Stowers Dear Colleagues, On 11/26/02, an Iridium telephone testing system was installed near the IGS station MCM4. A separate GPS receiver, operated from the same antenna as MCM4, has shown L1/CA phase breaks that correlate in time with transmissions from the Iridium system. Although the MCM4 receiver and data has not outwardly appeared to have experienced similar problems, it is possible that MCM4 data may have experienced some level of corruption due to the Iridium signal since 11/26/02. The Iridium system operates intermittently throughout the day, but since it is transmitting a large majority of the time, any interference would be essentially continuous. The Iridium system continues to operate, however measures are being taken to modify this system to solve the known interference problem with the other GPS receiver. Once the interference has been eliminated, another notification will be sent and the sitelog updated, noting the period of likely interference. Seth White Science Technician McMurdo Station, Antarctica scitech@mcmurdo.gov