PDS_VERSION_ID = PDS3 LABEL_REVISION_NOTE = "R. SIMPSON; 1999-08-11" RECORD_TYPE = FIXED_LENGTH RECORD_BYTES = 80 OBJECT = TEXT NOTE = "Voyager USO Frequencies for Giant Planet Radio Occultations" PUBLICATION_DATE = 1999-08-11 END_OBJECT = TEXT END This file documents S- and X-band frequencies transmitted by the Voyager spacecraft during radio occultation experiments (and tests) at or near Jupiter, Saturn, Uranus, and Neptune. Not all combinations of target and spacecraft have been documented. Frequencies transmitted by the Voyager spacecraft during radio occultation experiments were controlled by on-board UltraStable Oscillators (USOs). Critical elements of each USO were in temperature-controlled dewars so that frequency drift resulted primarily from aging of the crystal. Aging is accelerated by radiation (e.g., during the close approach to Jupiter); otherwise, each oscillator drifted approximately linearly at a rate on the order of 10 Hz per year. No unambiguous records exist within the Voyager Radio Science Team of USO frequencies during the Voyager encounters. However, by examining software and data files created after each encounter, we have accumulated circumstantial evidence that allows us to develop the table below of potentially useful USO frequencies. Values were obtained from archival computer files of P.A. Rosen and D.L. Gresh and from the personal documentation of D.P. Hinson. Note that the USO frequency was usually derived in an iterative procedure which also included solving for the spacecraft trajectory and the planetary gravitational field. The trend in the Neptune numbers (slowly decreasing USO frequency as the Gresh/Rosen file date increased) is consistent with such an evolution. The best solutions for USO frequencies were obtained during cruise phases of the mission when the spacecraft trajectory was not perturbed by planetary gravity fields and the oscillator crystal was not being damaged by intense radiation; but these were also the least relevant solutions for determining USO frequency during a planetary encounter. The precision shown in the table (tens of microhertz at X-band) is not supported by the data; the high precision is included only to preserve the historical record. D.P. Hinson feels that internally consistent numbers at the 1 Hz level have been sufficient for his work on planetary atmospheres. |============================================================================| | | | FREQUENCIES (HZ) | | |S/C|TARGET|---------------------------------| COMMENTS | | | | X-BAND | S-BAND | | |---+------+----------------+----------------+-------------------------------| |VG1|TITAN |8414995272.53000| |Hinson: 1980's to present | |---+------+----------------+----------------+-------------------------------| |VG1|SATURN|8414995272.37600|2294998710.64800|Rosen: December 1985 | |---+------+----------------+----------------+-------------------------------| |VG2|JUPITR|8420430593.44700| |Hinson: Ingr, 1990's | | | |8420430593.19000| |Hinson: Egr, 1990's | |---+------+----------------+----------------+-------------------------------| |VG2|SATURN|8420430462.00000|2296481021.00000|Rosen: December 1985 | |---+------+----------------+----------------+-------------------------------| |VG2|URANUS|8420430456.10000|2296481033.50000|Hinson, Rosen, Gresh: FEB-86 to| | | | | | present | | | |8420430448.54033|2296481031.42000|Rosen: for Egr rings AUG-89(?) | |---+------+----------------+----------------+-------------------------------| |VG2|NEPTUN|8420430410.33000|2296481021.00000|Gresh: 20-MAR-89 | | | |8420430402.63000|2296481018.90000|Rosen: 17-MAY-89 | | | |8420430401.87000|2296481018.69200|Rosen: 11-JUL-89 | | | |8420430399.04320|2296481017.92090|Rosen: 25-SEP-89 | | | |8420430397.13590|2296481017.40070|Rosen: 15-DEC-89 | | | |8420430398.42000| |Hinson: 1990's | |---+------+----------------+----------------+-------------------------------| |VG2|TRITON|8420430395.22850|2296481016.88140|Rosen, Gresh: SEP-89 | |============================================================================| The table below gives the complete list of USO frequencies found during our search of archival computer files. In most cases, the files located had names "occvecs.constants", a standard input to many Stanford programs computing observational geometries and Doppler shifts. "Source" gives the path on archival CD SCRA_1102 where the file was found. Subdirectory SCRA902 contains files used by D.L. Gresh; SCRA903 and SCRA904 contain files used by P.A. Rosen. No files were found in directories belonging to R.A. Simpson or H.A. Zebker. Source X-Band Frequency S-Band Frequency File Date/Context ------------------ ------------------ ----------------- ------------------ SCRA902/f00805.dat 8420430456.10000d0 2296481033.5000d0 29-OCT-86 GEOMETRY SCRA902/f00825.dat 8420430456.10000d0 2296481033.5000d0 17-FEB-87 NEPTUNE SCRA902/f00847.dat 8420430456.10000d0 2296481033.5000d0 17-FEB-87 NEP/POLAR SCRA902/f01887.dat 8420430410.33000d0 2296481021.0000d0 20-MAR-89 STEERING SCRA902/f02018.dat 8420430395.22850d0 2296481016.8814d0 01-SEP-89 TRITON SCRA903/f01337.dat 8420430401.87000d0 2296481018.6920d0 11-JUL-89 STEER SCRA903/f01338.dat 8420430402.63000d0 2296481018.9000d0 17-MAY-89 STEER SCRA903/f01378.dat 8420430397.13590d0 2296481017.4007d0 15-DEC-89 NEPTUNE SCRA903/f01379.dat 8420430399.04320d0 2296481017.9209d0 25-SEP-89 NEPTUNE SCRA903/f01380.dat 8420430402.63000d0 2296481018.9000d0 17-MAY-89 NEPTUNE SCRA903/f01409.dat 8420430448.54033d0 2296481031.4200d0 26-AUG-89 RINGSEGR SCRA903/f01423.dat 8420430395.22850d0 2296481016.8814d0 07-SEP-89 TRITON SCRA904/f01582.dat 8420430456.10000d0 2296481033.5000d0 31-JUL-86 GEOMETRY SCRA904/f01583.dat 8420430456.00000d0 2296481033.0000d0 23-FEB-86 GEOMETRY SCRA904/f01612.dat 8420430462.00000d0 2296481035.0000d0 03-DEC-85 GEOM/DLG SCRA904/f01651.dat 8420430462.00000d0 2296481035.0000d0 03-DEC-85 GEOM/DLG/V2 SCRA904/f01669.dat 8420430410.33000d0 2296481021.0000d0 20-MAR-89 NEPTUNE SCRA904/f01689.dat 8420430456.20000d0 2296481033.4200d0 10-MAR-86 GEOM/PAUL SCRA904/f01736.dat 8414995272.37600d0 2294998710.6480d0 22-MAY-85 SATURN SCRA904/f01909.dat 8414995272.37600d0 2294998710.6480d0 22-MAY-85 URANUS SCRA904/f01650.dat 8414995272.37600d0 2294998710.6480d0 03-DEC-85 GEOM/DLG/V1