• Data Set Overview

• =================

• Version 1.1

• ===========

The SEDR based Data provided as Part of this Data Set were originally reviewed and archived with the NSSDC and PDS as Version 1.0 (DATA_SET_ID=VG1-J-POS-4-48.0SEC). Version 1.1 includes additional Columns not present in the previous Version, 96 s Time Samples rather than 48 s Time Samples, Times converted to "PDS Style" or ISO Standard, and upgrading of PDS Labels and Templates to Version 3.2. The SPICE based Data that are also Part of this Data Set were not previously archived with the PDS. This Version 1.1 Data Set replaces previously archived Versions.

• Data Set Description
• ====================

This Data Set consists of Voyager 1 Jupiter Encounter Ephemeris Data in System III (1965) left-handed Coordinates covering the Period from 1979-03-03 to 1979-03-16.

Two Versions, both covering the same Time Period, but containing slightly different Data, are provided. One Version was generated by the Voyager Magnetometer (MAG) Team from Voyager 1 SEDR, the other by the PDS/PPI Node using the VG1_JUP.BSP and PCK00003.TCP 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 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 expressed via its 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 9 h 55 min 29.71 s (870.536° per 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
• ========================

+------------------------------------------------------+
| Parameter Characteristics | Value |

| Instrument P.I. | N/A |
| Data Supplier | NSSDC (Voyager MAG Team) |
| Data Sampling Rate | 96 SECONDS |
| Data Set Start Time | 1979-03-03T00:00:35.978Z |
| Data Set Stop Time | 1979-03-16T23:59:08.185Z |
+------------------------------------------------------+

• SPICE Generated Ephemeris
• =========================

+------------------------------------------------------+
| Parameter Characteristics | Value |

| Instrument P.I. | N/A |
| Data Supplier | S. JOY |
| Data Sampling Rate | 48 SECONDS |
| Data Set Start Time | 1979-03-03T00:00:35.978Z |
| Data Set Stop Time | 1979-03-16T23:59:56.185Z |
+------------------------------------------------------+

• Parameters

• ==========

• SEDR Generated Ephemeris

• ========================

+----------------------------------------------------------------------------------------------------------------------------------------------------+
| Parameter Name | Resolution/Units | Description |

| time | 96 s | Time of the Sample (UT) in the Format YYYY-MM-DDTHH:MM:SS.SSSZ |
| m65536 | counts | Spacecraft Clock Counts, mod 65536 |
| mod60 | counts | Spacecraft Clock Counts, mod 60 |
| fds_line | counts | Spacecraft Clock Counts, fds_line |
| sc_x | R[J] | Jovicentric (System III) Spacecraft Position, Cartesian Coordinates, X Component |
| sc_y | R[J] | Jovicentric (System III) Spacecraft Position, Cartesian Coordinates, Y Component |
| sc_z | R[J] | Jovicentric (System III) Spacecraft Position, Cartesian Coordinates, Z Component |
| vel_x | km/s | Jovicentric (System III) Spacecraft Velocity, Cartesian Coordinates, X Component |
| vel_y | km/s | Jovicentric (System III) Spacecraft Velocity, Cartesian Coordinates, Y Component |
| vel_z | km/s | Jovicentric (System III) Spacecraft Velocity, Cartesian Coordinates, Z Component |
| sc_r | AU | Jovicentric (System III) Spacecraft Position, Spherical Coordinates, Radial Distance (Range) |
| sc_lat | degrees | Jovicentric (System III) Spacecraft Position, Spherical Coordinates, Latitude |
| sc_lon | degrees | Jovicentric (System III) Spacecraft Position, Spherical Coordinates, Longitude |
| CartSys3_to_SphSys3 | | Cartesian System III to Spherical System III Coordinates Rotation Matrix containing nine 1PE15.8 Elements |
| SC_to_CartSys3 | | Payload (Spacecraft) to Cartesian System III Coordinates Rotation Matrix containing nine 1PE15.8 Elements |
| SC_to_SphSys3 | | Payload (Spacecraft) to Spherical System III Coordinates Rotation Matrix containing nine 1PE15.8 Elements |
+----------------------------------------------------------------------------------------------------------------------------------------------------+

• SPICE Generated Ephemeris
• =========================

+-----------------------------------------------------------------------------------------------------------------------------------------------------+
| Parameter Name | Resolution/Units | Description |

| time | 48 s | Time of the Sample (UT) in the Format YYYY-MM-DDTHH:MM:SS.SSSZ |
| R | AU | Jovicentric (System III 1965) Spacecraft Position, Spherical Coordinates, Radial Distance (Range) |
| LAT | degrees | Jovicentric (System III 1965) Spacecraft Position, Spherical Coordinates, Latitude |
| LON | degrees | Jovicentric (System III 1965) Spacecraft Position, Spherical Coordinates, Longitude |
| LocTime | hours | Angular Separation between the Meridian containing the Sun and the one containing the Spacecraft converted |
| | | 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 Rotation of the Planet. |
+-----------------------------------------------------------------------------------------------------------------------------------------------------+

• Coordinate System
• =================

The System III (1965) is a Jovicentric left-handed Coordinate System defined such that Longitude increases with Time as viewed by a stationary Remote Observer.

• Jovicentric (Jupiter Fixed) Cartesian Coordinates
• =================================================

• X points along the Jupiter-Sun Line in the Solar Equatorial Plane, positive towards the Sun
• Y completes the right-handed Set, Y = X ⨯ Z
• Z points along the Spin Axis of Jupiter

• Jovicentric System III (1965) Spherical Coordinates
• ===================================================

• R gives the Jupiter to Spacecraft Range, positive away from Jupiter
• LAT completes the left-handed, Orthogonal Set
• LON gives the System III (1965) East Longitude with Longitude increasing eastward from a specific Jovian Prime Meridian

SPICE Ephemeris were generated using the current Definition of the Jovian Radius, 71,492 km. The Spin Rate used in generating these Data is the same as that used for System III (1965), 870.536° per Day.

• Data Coverage
• =============

+--------------------------------------------------------------------------+
| Filename | Records | Start Date and Time | Stop Date and Time |

| SEDR062 | 1623 | 1979-03-03T00:00:35.978Z | 1979-03-04T23:58:59.925Z |
| SEDR064 | 6071 | 1979-03-05T00:00:35.925Z | 1979-03-11T23:59:08.059Z |
| SEDR071 | 4370 | 1979-03-12T00:00:44.059Z | 1979-03-16T23:59:08.185Z |
| SPICE062 | 3246 | 1979-03-03T00:00:35.978Z | 1979-03-04T23:59:47.925Z |
| SPICE064 | 12142 | 1979-03-05T00:00:35.925Z | 1979-03-11T23:59:56.059Z |
| SPICE071 | 8740 | 1979-03-12T00:00:44.059Z | 1979-03-16T23:59:56.185Z |
+--------------------------------------------------------------------------+