VHM / FGM User Notes - Ulysses
VHM/FGM - User Notes
VHM/FGM Contact (1 Hour Data):
Dr. Adam Rees
The Blackett Laboratory
Imperial College of Science and
Technology, Prince Consort Road
London SW7 2BZ
UK
Phone: (44) 20 7594-7774
Telefax: (44) 20 7594-7772
E-mail: adam.rees@ic.ac.uk
The file contains hourly averages of the magnetic field for the in-ecliptic
cruise, timed at mid-interval (i.e. on the half hour). There are eight columns:
1) Year (two digit integer)
2) Decimal day no. (January 1 = Day 1, fractional part completely
specifies the timing of the data point)
3) Decimal hour (actually redundant but aids readability of the file)
4) Magnetic field hour average of R component (nT)
5) Magnetic field hour average of T component (nT)
6) Magnetic field hour average of N component (nT)
7) Magnetic field hour average magnitude (nT) (note that this is the
average of the magnitudes of the individual full resolution vectors
as opposed to the magnitude of the vector formed by the hourly
averaged components)
8) Number of full resolution vectors that have contributed to the
average (as a crude statistical validity check)
I have not flagged data gaps in any way - if there were no available data in a
particular hour then there is no entry for that hour in the file.
VHM/FGM Contact (1 Minute and 1 Second Data):
Dr. J. E. Wolf
MS 169-506
Jet Propulsion Laboratory
4800 Oak Grove Drive
Pasadena, CA 91009
USA
Phone: (1) 818 354-7361
Telefax: (1) 818 354-8895
E-mail: jwolf@jplsp.jpl.nasa.gov
Data Set Description:
This data set contains one minute averages of the interplanetary magnetic field
measured by the Ulysses Magnetic Field experiment. Field vector components are
given in units of nanoteslas and in RTN coordinates, where R is the sun-s/c
axis, T is the cross product of the solar rotation axis and R, and N is the
cross product of R and T. The field magnitudes in nT are averages of scalar
magnitudes at higher time resolution. Times are computed at the mid-point of
each minute interval and expressed in Spacecraft Event Time - UT (SCET-UT).
Data gaps have not been flagged in any way - if there were no available data in
a particular hour then there is no data record for that hour. No data from the
Feb. 1992 encounter with Jupiter are included. Most files cover 10-day
intervals, except that the first file of each year covers days 1-9, and the
last file of each year covers days 360-365 (or 366). Further details on the
magnetic field measurements can be found in the following reference: Balogh,
A., et al., Astron. Astrophys. Suppl. Ser., 92(2), 221, 1992. This data set is
available on-line in the NSSDC Anonymous FTP directory and will also be put on
the NDADS near-line system. See NSSDC's Ulysses flight project page under URL
http:/nssdc.gsfc.nasa.gov/space/space_physics_home.htm for further details.
Data Set Files:
ULYMAGMN.FMT - this file
UyydddMINSH.DAT - minute average data files (ASCII) starting at day yyddd
Parameter Format for File UyydddMINSH.DAT:
IY SCET-UT year (yy)
IDOY SCET-UT day of year (ddd), IDOY = 1 for Jan. 1
IHR SCET-UT hour of day
IMIN SCET-UT minute of hour
ISEC SCET-UT second of minute
BR Radial component (RTN system) of vector magnetic field in nT
BT Transverse component (RTN system) of vector magnetic field in nT
BN Normal component (RTN system) of vector magnetic field in nT
B Scalar magnitude of magnetic field in nT
The data records are read in ASCII FORTRAN format as follows:
READ(10,110) IY, IDOY, IHR, IMIN, ISEC, BR, BT, BN, B
10 FORMAT (1X,I2,I4.3,3I3.2, 4F8.3)
Acknowledgement:
Please acknowledge the Ulysses Data System and the Principal
Investigator, A. Balogh of Imperial College, London, UK.
File: ULYMAG_1SEC_FMT.txt Version: NSSDC 2003-07-18 JFC ========================================================================= ULYSSES HIGH RESOLUTION INTERPLANETARY CRUISE MAGNETIC FIELD DATA ------------------------------------------------------------------- Data Set Coverage (yyy-mm-dd): 1990-10-25 to 1991-12-31 Data Set Contact: Joyce Wolf, NASA Jet Propulsion Laboratory Data Set Description: This data set contains high resolution samples at about one-second intervals of the interplanetary magnetic field measured by the Ulysses Magnetic Field experiment. Field vector components are given in units of nanoteslas and in RTN coordinates, where R is the sun-s/c axis, T is the cross product of the solar rotation axis and R, and T is the cross product of R and T. The field magnitudes in nT are averages of scalar magnitudes at higher time resolution. Times are computed at the mid-point of each minute interval and expressed in Spacecraft Event Time - UT (SCET-UT). Data gaps have not been flagged in any way - if there were no available data in a particular hour then there is no data record for that hour. No data from the Feb. 1992 encounter with Jupiter are included. Each file includes one day of data. Further details on the magnetic field measurements can be found in the following reference: Balogh, A., et al., Astron. Astrophys. Suppl. Ser., 92(2), 221, 1992.
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.
Data Set Files: ULYMAG_1SEC_FMT.txt - this file UyydddSH.asc - high resolution data file (ASCII) for day yyddd Parameter Format for File UyydddSH.asc: IY SCET-UT year (yy) IDOY SCET-UT day of year (ddd), IDOY = 1 for Jan. 1 IHR SCET-UT hour of day IMIN SCET-UT minute of hour SEC SCET-UT second of minute BR Radial component (RTN system) of vector magnetic field in nT BT Transverse component (RTN system) of vector magnetic field in nT BN Normal component (RTN system) of vector magnetic field in nT B Scalar magnitude of magnetic field in nT The data records are read in ASCII FORTRAN format as follows: READ(10,110) IY, IDOY, IHR, IMIN, SEC, BR, BT, BN, B 110 FORMAT (1X,I2,I4.3,2I3.2,F6.2,4F8.3) NSSDC Data Set ID: 90-090B-08?? Acknowledgement: Please acknowledge the National Space Science Data Center and the Principal Investigator, A. Balogh of Imperial College, London, UK.