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Availability: Archived at NSSDC, accessible from elsewhere

Time span: 1979-02-26 to 1979-03-24


This description was generated automatically using input from the Planetary Data System.

Data Set Overview ================= This data set consists of Voyager 1 Jupiter encounter ephemeris data in Heliographic coordinates covering the period 1979-02-26 to 1979-03-24. Two versions, both covering the same time period, but containing slightly different data, are provided. One version was generated by the Voyager MAG team from Voyager 1 SEDR, the other by the PDS/PPI node using the VG1_JUP.BSP and PCK00003.TPC SPICE kernels. Two versions of the spacecraft ephemeris data are provided as an attempt to correct some of the problems in the Voyager SEDR while preserving the ability to reproduce early results. The original SEDR data has a variety of problems which may affect the knowledge of the spacecraft position, or conversely, the timing associated with certain events such as ring plane crossings. The SPICE SPK kernel provided on this disk includes corrections to some, but not all, of the problems associated with the Voyager SEDR. The Navigation and Ancillary Information Facility (NAIF) at JPL may issue a new Voyager SPK kernel in the future that will further improve the knowledge of the spacecraft location in inertial space. There are other differences in the in the two versions of ephemeris data that are the result of improvements in the knowledge of some of the physical constants associated with Jupiter and its moons. Since the Voyager era, there have been updates to the orientation of the jovian spin axis right ascension and declination, the radius of Jupiter, as well as the orbital characteristic and other physical parameters of many of the moons of Jupiter. These changes affect the stated position of the spacecraft in jovigraphic coordinate systems like System III without changing the position of the spacecraft in inertial space. The spin rate of Jupiter is not changed from the System III (1965) rate of 9h 55m 29.71sec (870.536 deg/day). The SPICE planetary constants kernel (PCK) contains both the current IAU definitions of the physical constants for the bodies within in the jovian system (as data) as well as the older IAU definitions (as comments). This is an ASCII text file (PCK00003.TCP) and users of the ephemeris data are encouraged to review it. SEDR generated ephemeris -----------------------Data Supplier : NSSDC Data sampling rate : 96 seconds Data Set Start Time : 1979-02-26T00:00:35.897Z Data Set Stop Time : 1979-03-24T22:47:56.304Z SPICE generated ephemeris ------------------------Data Supplier : S. Joy Data sampling rate : 48 seconds Data Set Start Time : 1979-02-26T00:00:35.897Z Data Set Stop Time : 1979-03-24T22:49:32.304Z Parameters ========== SEDR generated ephemeris -----------------------PARAMETER RESOLUTION/ DESCRIPTION NAME UNITS time 96.0 Sec. time of the sample (UT) in the format yyyy-mm-ddThh:mm:ss.sssZ m65536 counts spacecraft clock counts mod60 fds_line sc_x AU heliographic cartesian coordinates sc_y position vectors: X, Y, and Z sc_z vel_x km/s heliocentric X, Y, and Z spacecraft vel_y velocity components vel_z sc_r AU heliographic spherical coordinates sc_lat degrees position vectors: range, latitude, and sc_lon degrees longitude SolEquatorial_to_HG solar equatorial to heliographic coordinates rotation matrix containing 9 1pe15.8 elements HG_to_EarthOrbTrue heliographic to earth orbit true coordinates rotation matrix containing 9 1pe15.8 elements Spacecraft_to_HG payload (spacecraft) to heliographic coordinates rotation matrix containing 9 1pe15.8 elements SPICE generated ephemeris ------------------------PARAMETER RESOLUTION/ DESCRIPTION NAME UNITS time 48.0 Sec time of the sample (UT) in the format yyyy-mm-ddThh:mm:ss.sssZ R AU heliographic spherical coordinates LAT degrees position vectors: range, latitude, and LON degrees and longitude LocTime hours angular separation between the meridian containing the sun and the one containing the spacecraft converted to a time. The sun meridian is defined to be noon (12.000), with midnight (0.000) opposite it. Dawn (6.000) and dusk (18.000) are where the sun rises and sets according to the planet's rotation Coordinate System ================= The Heliographic coordinate system is a heliocentric system defined in the reference epoch of 1950. The unit vectors which define the coordinate system are as follows: Heliographic cartesian coordinates X points towards the the first point of Aries in the solar equatorial plane on the vernal equinox of the reference epoch 1950 (positive away from the Sun) Y completes the right handed set (X x Z) Z points along the Sun's spin axis (positive above the equatorial plane) Heliographic spherical coordinates R (Range) the distance from the Sun's position at the reference epoch to the spacecraft in AU LAT (Latitude) the angle between the solar equatorial plane of the reference epoch measured in the plane containing the solar spin axis of that epoch (positive above the equatorial plane) LON (Longitude) longitude is zero in the direction of the ascending node at the reference epoch (X direction) and increasing in the direction of planetary orbital motion (note that LON does not rotate with the Sun) For the SPICE data, the definition used for astronomical units is 1 AU = 149674000 km. The longitude of the ascending node was calculated using the equation: LON = 74 [degrees] 22' + 0.84' * ( year - 1900 ). The inclination of the Sun's North pole measured relative to the ecliptic was defined as being 7 [degrees] 15' in 1950. Data Coverage ============= Filename Records Start Stop ------------------------------------------------------------------SEDR057 6046 1979-02-26T00:00:35.897Z 1979-03-04T23:58:11.925Z SEDR064 6071 1979-03-05T00:00:35.925Z 1979-03-11T23:59:08.059Z SEDR071 6065 1979-03-12T00:00:44.059Z 1979-03-18T23:58:20.235Z SEDR078 5303 1979-03-19T00:00:44.236Z 1979-03-24T22:47:56.304Z SPICE057 12093 1979-02-26T00:00:35.897Z 1979-03-04T23:59:47.925Z SPICE064 12142 1979-03-05T00:00:35.925Z 1979-03-11T23:59:56.059Z SPICE071 12131 1979-03-12T00:00:44.059Z 1979-03-18T23:59:56.236Z SPICE078 10607 1979-03-19T00:00:44.236Z 1979-03-24T22:49:32.304Z

These data are available on-line from the Planetary Data System (PDS) at:

Alternate Names



  • Planetary Science: Fields and Particles

Additional Information


Questions and comments about this data collection can be directed to: Dr. Edwin V. Bell, II



NameRoleOriginal AffiliationE-mail
Mr. Steven P. JoyGeneral ContactUniversity of California, Los
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