• Data Set Overview

• =================

• Data Set Description

• ====================

This Data Set consists of Voyager 2 Saturn Encounter Ephemeris Data in Kronographic (L1) Coordinates covering the Period from 1981-08-23 to 1981-08-29.

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 2 SEDR, the other by the PDS/PPI Node using the VG2_SAT.TSP and PCK00006.TPC SPICE Kernels.

Due to Inaccuracies in Voyager SEDR, as well as Changes in the Values of some Key Parameters (e.g., the Radius of Saturn) the Timing is improved for the SPICE generated Data. However, since much of the original Analysis was based upon the SEDR generated Ephemeris, these Data have been included as well.

• SEDR Generated Ephemeris
• ========================

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

| Instrument P.I. | N/A |
| Data Supplier | NSSDC |
| Data Sampling Rate | 96 SECONDS |
| Data Set Start Time | 1981-08-23T10:34:23.645Z |
| Data Set Stop Time | 1981-08-29T23:57:35.078Z |
+------------------------------------------------------+

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

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

| Instrument P.I. | N/A |
| Data Supplier | S. JOY |
| Data Sampling Rate | 96 SECONDS |
| Data Set Start Time | 1981-08-23T10:34:23.645Z |
| Data Set Stop Time | 1981-08-29T23:57:35.078Z |
+------------------------------------------------------+

• 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[S] | Kronocentric (L1) Spacecraft Position, Cartesian Coordinates, X Component |
| sc_y | R[S] | Kronocentric (L1) Spacecraft Position, Cartesian Coordinates, Y Component |
| sc_z | R[S] | Kronocentric (L1) Spacecraft Position, Cartesian Coordinates, Z Component |
| vel_x | km/s | Kronocentric (L1) Spacecraft Velocity, Cartesian Coordinates, X Component |
| vel_y | km/s | Kronocentric (L1) Spacecraft Velocity, Cartesian Coordinates, Y Component |
| vel_z | km/s | Kronocentric (L1) Spacecraft Velocity, Cartesian Coordinates, Z Component |
| sc_r | R[S] | Kronocentric (L1) Spacecraft Position, Spherical Coordinates, Radial Distance from Saturn |
| sc_lat | degrees | Kronocentric (L1) Spacecraft Position, Spherical Coordinates, Latitude |
| sc_lon | degrees | Kronocentric (L1) Spacecraft Position, Spherical Coordinates, Longitude |
| CartSys3_to_SphSys3 | | Cartesian System L1 to Spherical System L1 Coordinate Rotation Matrix containing nine 1PE15.8 Elements |
| SC_to_CartSys3 | | Payload (Spacecraft) to Cartesian System L1 Coordinate Rotation Matrix containing nine 1PE15.8 Elements |
| SC_to_SphSys3 | | Payload (Spacecraft) to Spherical System L1 Coordinate Rotation Matrix containing nine 1PE15.8 Elements |
+--------------------------------------------------------------------------------------------------------------------------------------------------+

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

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

| time | 96 s | Time of the Sample (UT) in the Format YYYY-MM-DDTHH:MM:SS.SSSZ |
| R | AU | Kronocentric (L1) Spacecraft Position, Spherical Coordinates, Radial Distance (Range) |
| LAT | degrees | Kronocentric (L1) Spacecraft Position, Spherical Coordinates, Latitude |
| LON | degrees | Kronocentric (L1) 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 Kronographic (L1) Coordinate System is a Saturn centered Spherical Coordinate System, defined by using the Saturn Longitude System (Voyager Measurements of the Rotation Period of Saturn's Magnetic Field of Saturn, Desch, M. D. and M. L. Kaiser, Geophys. Res. Lett., 8, 253-256, 1981). In this Coordinate Syatem, Longitude increases with Time as viewed by a stationary Remote Observer.

• Cartesian Coordinates
• =====================

• X points along the Saturn-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 Saturn, positive

• Spherical Coordinates
• =====================

• R gives Saturn to Spacecraft Range, positive away from Saturn
• LAT completes the left-handed, Orthogonal Set
• LON gives East Longitude, with Longitude increasing eastward from a specific Saturnian Prime Meridian

SPICE Ephemeris were generated using the current Definition of the Saturnian Radius, 60,268 km. The Spin Rate used in generating these Data is the same as that used for System III (1965), 870.536° per Day.