PDS_VERSION_ID = PDS3 RECORD_TYPE = FIXED_LENGTH RECORD_BYTES = 80 OBJECT = TEXT PUBLICATION_DATE = 1999-09-30 NOTE = "VG1 Titan Tapes - Time-Ordered List and Anomalies" END_OBJECT = TEXT END Names of ODR files indicate only the sequential order in which CCTs were generated from original MBODRs. This document shows the relationships among file name, times covered, recorder, frequency, and polarization. It should be helpful to persons interested in processing specific parts of the full data set. Titan data were collected using one S-band (2295 MHz) and one X-band (8415 MHz) receiver, each connected to a right-circularly polarized antenna feed. The two receiver outputs (SR and XR) were sampled (8-bits) and recorded in parallel on high-speed video tapes using analog technology. Each analog tape (a Medium-Band Original Data Record, or MBODR) could hold approximately 60 minutes of Titan data. Because about 15 minutes was required to reload, two recorders were required in order not to have gaps in the data. Operations of Recorder A and Recorder B were staggered so that at least one drive would always be running. During overlap times, the user may select from between data collected on the two recorders. The MBODRs were shipped to JPL where data were extracted and written to the VJ series of computer-compatible tapes (CCTs). Each CCT from Titan was a 1600-bpi tape containing (nominally) 6000 records of 5056 bytes each. Each CCT contained 8-bit sample data from only one receiver. Both receiver channels were originally sampled at 300 ksps; S-band CCTs contained "decimated" samples (rate reduced to 100 ksps), while X-band CCTs retained the original (300 ksps) rate. As a result each S-band digital tape covers 300 seconds, while each X-band digital tape covers only 100 seconds. Analog tape recording suffers from occasional signal drop-outs; hence there are times when the digital sample stream coming from the MBODR was interrupted. Tracking the "sample count" in header words 27-28 is the best way to detect these anomalies. Synchronization was usually recovered only when the other recorder started. When both recorders were operating (07:25:00-07:29:59 and 07:45:00-07:49:59) tapes can be swapped to recover data lost to drop-outs. CCTs had names of the form VJnnnn, where nnnn was the sequence number in which the CCTs were generated. For Titan and Saturn data, nnnn began at 6000 and ended at about 6660. Data files in the ODR directory of the archival CD have file names VJnnnnCC.ODR, where C is a single letter denoting the order of file 'fragments'. Occasional records on VJnnnn tapes were lost because of damage to or deterioration of the media. When a single record (or one group of contiguous records) was lost, the first part of the file was named VJnnnnAA.ODR and the second became VJnnnnnBB.ODR. In cases where there were more errors, the succeeding file fragments were given names VJnnnnCC.ODR, VJnnnnDD.ODR, etc. Each fragment contains only integral records, but only the first fragment is likely to begin on an integral second mark. The user may choose how to recombine these file fragments before processing the data. The tape and record format is described in document RSC-11-6. Figure RSC-11-6-2 in the document is a sketch of record organization. Pages 2-13 give details on each field. Note that "source station" (word 4, bits 9-16) will be "21" because the CCTs were generated at JPL's CTA 21; there is no indicator within the tape of the source DSN antenna (63). First order analysis of the raw data could be achieved by stripping the first 56 bytes from each record, then concatenating the blocks of 5000 8-bit sample values into files of 30 MB. In fact, several tapes could be concatenated in the same way. Table Description ----------------- Left column gives nominal time of first sample on tape. Columns 2-9 give tape number, where prefix "VJ" is understood (that is, tape VJ6281 starts at 06:35:00). SR = S-band right-circularly polarized; XR = X-band right-circularly polarized. An asterisk (*) beside the tape number indicates the recommended (original) tape choice for processing. A pound sign (#) beside the tape number indicates a tape with at least one known lost record (two file fragments on the CD). Data collected between 06:35:00 and 08:30:00 were from the Titan occultation. Data collected between 23:00:00 and 23:30:00 were for testing and calibration of the data acquisition system. 1980 Recorder A Recorder B 12 Nov ------------------------- ------------------------- ERT--UTC SR SL XR XL SR SL XR XL -------- ---- ---- ---- ---- ---- ---- ---- ---- 06:35:00 6281* 6292* 06:36:40 6293* 06:38:20 6294* 06:40:00 6282* 6295* 06:41:40 6296* 06:43:20 6297* 06:45:00 6283* 6298* 06:46:40 6299* 06:48:20 6300* 06:50:00 6284* 6301* 06:51:40 6302* 06:53:20 6303* 06:55:00 6285* 6304* 06:56:40 6305* 06:58:20 6306* 07:00:00 6286* 6307* 07:01:40 6308* 07:03:20 6309* 07:05:00 6287* 6310* 07:06:40 6311* 07:08:20 6312* 07:10:00 6288* 6313* 07:11:40 6314* 07:13:20 6315* 07:15:00 6289* 6316* 07:16:40 6317* 07:18:20 6318* 07:20:00 6290* 6319* 07:21:40 6320* 07:23:20 6321* 07:25:00 6291* 6322* 6361 6366 07:26:40 6323* 6367 07:28:20 6324* 6368 07:30:00 6362* 6369* 07:31:40 6370* 07:33:20 6371* 07:35:00 6363*# 6372* 07:36:40 6373* 07:38:20 6374* 07:40:00 6364* 6375* 07:41:40 6376* 07:43:20 6377* 07:45:00 6325* 6334* 6365 6378 07:46:40 6335* 6379 07:48:20 6336* 6380 07:50:00 6326* 6337* 07:51:40 6338* 07:53:20 6339* 07:55:00 6327* 6340* 07:56:40 6341* 07:58:20 6342* 08:00:00 6328* 6343* 08:01:40 6344* 08:03:20 6345* 08:05:00 6329* 6346* 08:06:40 6347* 08:08:20 6348* 08:10:00 6330* 6349* 08:11:40 6350* 08:13:20 6351* 08:15:00 6331* 6352* 08:16:40 6353* 08:18:20 6354* 08:20:00 6332* 6355* 08:21:40 6356* 08:23:20 6357* 08:25:00 6333* 6358* 08:26:40 6359* 08:28:20 6360* 23:02:00 6589* 6595* 23:03:20 6596* 23:05:00 6590* 6597* 23:06:40 6598* 23:08:20 6599* 23:10:00 6591* 6600* 23:11:40 6601* 23:13:20 6602* 23:15:00 6592* 6603* 23:16:40 6604* 23:18:20 6605* 23:20:00 6593* 6606* 23:21:40 6607* 23:23:20 6608* 23:25:00 6594* 6609* 23:26:40 6610* 23:28:20 6611*