Ulymag_1sec_warning.txt                                        JPL 2004-03-30
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The following warning has been provided by Ed Smith of the Ulysses VHM/FGM Magnetometer team at the Jet Propulsion Laboratory for potential users of high resolution one-second interplanetary data:

So-called Interstellar Ion Waves are of particular interest from the high resolution data and we have published a couple of articles about them. However, in the course of analyzing these waves, we became aware that there were numerous intervals where "waves" were present that were actually spacecraft- generated interference. The identification of the interference (whose origin is unknown) is difficult because they are of the same amplitudes as the real waves and consist typically of a series of ascending and descending tones some of which are above our pass-band but are strong enough to be "aliased" and to then appear at low frequencies within our pass-band. 

No complete catalog of intervals affected by the interfering tones is available, but our team has developed software used to identify real versus false signals. However, the techniques used are rather complex and involve cross- spectra, frequency-time and polarization plots. Experience with the data is also needed to make a correct assessment. Anyone who makes use of the data and sees "waves" or other signals that might be interference should contact us so we can help make an accurate identification. 

Dr. Edward J. Smith
Mail Stop 169-506
Jet Propulsion Laboratory
4800 Oak Grove Drive
Pasadena CA 91109
Phone:  (818) 354-2248
Fax:  (818) 354-8895 
E-mail: Edward.J.Smith@jpl.nasa.gov