************************************************************************** **** NOTE: Newer S-band frequency sequence. **** ************************************************************************** RDV36 (Astrometric/Geodetic VLBA-36) 2002 December 11 Notes prepared by John Gipson and Nancy Vandenberg, NVI/GSFC Schedule name: rdv36.skd Pointing files: rdv36crd.br, rdv36crd.fd, rdv36crd.hn, rdv36crd.kp, rdv36crd.la, rdv36crd.mk, rdv36crd.nl, rdv36crd.ov, rdv36crd.pt, rdv36crd.sc ftp://vlbiobs@aspen.nrao.edu/home/aspen6/astronomy/dec02/rdv36 Summary file for correlator: rdv36.sksum on aspen PCFS file: ftp://vlbigeo@cddisa.gsfc.nasa.gov/vlbigeo/dec02/rdv36.skd http://lupus.gsfc.nasa.gov/sess/2002/sesshtml/rdv36.html First observations Source Start Stations 1128+385 02345-174500| Br-Fd-Gc-Hn-Kp-La-Mk-Nl-Ov-Pt-Wf 2145+067 02345-180000| Ma-Mc-Sc-Tc 4C39.25 02345-180040| Ny-On 1726+455 02345-200000| Kk-Wz =========================================================== Last observations Source Start Stations VR422201 02346-172017| Ma-Mc-Ny-On 1144-379 02346-174029| Tc 0059+581 02346-174105| Sc-Wz 0919-260 02346-174950| Kk 1308+326 02346-175804| Br-Fd-Gc-Hn-Kp-La-Mk-Nl-Ov-Pt-Wf =========================================================== Correlator: VLBA at Socorro Station Codes # of tapes # of scans Brewster B Br 2.4 (TT) 166 Fort Davis D Fd 2.4 (TT) 173 Gilcreek A Al 2.1 (TT) 149 Hancock H Hn 2.4 (TT) 149 Kokee K Kk 1.8 (TT) 124 Kitt Peak L Kp 2.4 (TT) 167 Los Alamos M La 2.4 (TT) 172 Matera I Ma 2.0 (TT) 154 Medicina C Mc 2.0 (TT) 152 Mauna Kea N Mk 2.4 (TT) 157 North Liberty O Nl 2.4 (TT) 163 Ny Alesund P Ny 2.0 (TT) 149 Onsala T On 2.0 (TT) 149 Owens Valley R Ov 2.4 (TT) 161 Pie Town S Pt 2.4 (TT) 169 St. Croix E Sc 2.4 (TT) 157 TIGO Q Tc 2.0 (TT) 100 Westford F Wf 2.1 (TT) 152 Wettzell V Wz 1.9 (TT) 130 Total number of observations (delay measurements): 16721 Total number of scans in the schedule: 309 Special Notes for this session: - NEW with RDV36: This session has a NEWER S-BAND FREQUENCY SEQUENCE that avoids the direct broadcast satellite band of 2320-2345 MHz. We use the same frequency sequence as in RDV35, but shifted up 7 MHz to get further away from the satellite broadcast band. - NEW in RDV34: The stations with Mk4 formatters, and with updated formatter firmware, will use barrel roll. - The baseline-format flux models determined by Alan Fey (USNO) using data from RDV31 (observed in January) were used. - NEW since RDV31: The phase cal tones detected at VLBA stations will be 10 kHz and 5010 kHz. In previous sessions the higher tone was 7010 kHz. - Fairbanks, Westford, and most VLBA stations record two initial long (5-min) scans and two final 5-min scans. - TIGO, at Concepcion, Chile, participates in this session. Because of its small size, TIGO participates in about half as many scans as the other stations. SNR minimums on baselines to TIGO were set to the same values as for other stations (20/15 at X/S). Margins for SNR calculations are 13/8. This means that even a detection at SNR 7 would be acceptable at the maximum scan length (700 seconds), and all of the scans that include TIGO should result in fringes, though some will be weak fringes. This approach was used because TIGO would not be able to see many of the northern-source scans in a tag-along mode. Scans include TIGO were given more weight in the automatic scheduling process. - Wettzell and Kokee will begin participating in this schedule at 20:00 after finishing intensive session i02345. Purpose ======= This is the last of six bi-monthly coordinated astrometric/geodetic experiments in 2002 that use the full 10-station VLBA plus up to 10 geodetic stations capable of recording VLBA modes. This year's series is a continuation of the highly successful RDV series begun in 1997. These experiments are being coordinated by the geodetic VLBI programs of three agencies: USNO, NASA, and NRAO. The experiments have been designed so that the same data set may be used by each agency for its particular goals. USNO will perform repeated imaging and correction for source structure. These sources will establish a set of core reference sources with known structure and precisely known positions. These data will provide the basis for evaluating the long term stability of the radio reference frame and the ultimate accuracy of wide angle astrometric measurements of extragalactic radio sources using VLBI. NASA will analyze this data to determine a high accuracy terrestrial reference frame. The data will incorporate the VLBA stations into the VLBI reference frame through the inclusion of other geodetic stations for which we have long histories. The data will also produce the most accurate Earth rotation results ever produced. We will use these data to make accurate absolute measurements of UT1. NRAO will use these sessions to provide a service to users who require high quality positions for small numbers of sources. While the quality of these results will be high, the observing and data reduction overhead required will be minimal because such sources can be incorporated into a session of the regular geodetic observations, instead of requiring special observations. Sources for this series of experiments will be selected using the proposed approach. For each experiment we will select a set of 70-80 sources out of the pool of ~400 Northern Hemisphere ICRF sources. About 40-50 of these will remain the same from experiment to experiment and will be chosen to optimize the goals of the three groups. Schedule ======== This is a new schedule generated by John Gipson and Nancy Vandenberg using sked. "Requested" Sources in rdv36 : Requested by J. Wrobel, to be observed in rdv34,35,36. The sources in RDV35 are: Name RA(J2000) Decl(J2000) Sp(8.5 GHz) 36 J0202-0559 02 02 06.86417 -05 59 00.1242 78 mJy 36 J0223-0205 02 23 13.03999 -02 05 07.9220 127 mJy Dan Lebach requested: 36 2250+194 22 53 07.36916 19 42 34.6284 Hiroshi Imai requested: 36 GT0032+61 00 35 24.82 61 30 30.7 300 mJy Using rotating sources same as in RDV21, yearly from RDV28 Y |1255-316 Y |CTA102 No sources from the "new" list this time. We continue rotating through the large list of candidate ICRF sources. The method was as follows: - Start with the list of 80 core RDV sources. - Add up to 20 sources from the list of candidates that already have some NEOS or VLBA data available (rotating sources). - Add 2 sources from the list of sources to be observed yearly. - Add 2 sources from the list of candidates that have never been observed with the VLBA (new sources). The candidate list has been completely observed once, as of RDV26. The same criteria were used for generating this schedule as were used during the first year of these sessions. The criteria for sources to be mapped are a minimum of 3 scans and 135 observations. These criteria are relaxed for sources below -25 degrees declination. Most of the sources in this schedule meet the mapping criteria. The schedule was made using a combination of automatic selection plus manual scheduling to improve the coverage of the sources. Automatically scheduled scans were selected first on their improvement of sky coverage in the previous 1 hour, and then the best 60% were evaluated for the minor options: minimize idle time, minimize slewing time, and maximize the number of observations. An individual source was not observed more often than every 180 minutes. An early start of 30 seconds was used for the first scan on a tape pass. The minimum scan length was 40 seconds. NEW: RDV21 was the first schedule made with a new version of sked that takes advantage of the automatic tape allocation at the VLBA stations. For these stations sked assumes that any scan will fit on the tape pass and there is no need to run the tape to the end of a pass if the scan is too long to fit in the remaining tape. The VLBA stations routinely use automatic tape allocation and automatic tape reversal. Recording Mode and Frequencies: same as previous experiments ============================================================ The data will be recorded using the following setup: 8 channels 1:4 fan-out 16 MHz sample rate 1-bit sampling This recording mode is designated 128-8-1. The correlator speed-up factor is 2. The frequency sequence covers 490 MHz in 8 channels. This span fits in one VLBA receiver passband but it uses both the high and low parts of the geodetic receivers. Because only 8 channels are available when observing with the VLBA stations, a wider spanned bandwidth is not advisable. With the 1:4 fanout at 16 MHz sample rate, all 32 tracks are recorded in one pass, so there will be 14 passes on a tape. Special note for sessions starting with RDV36: The S-band frequency sequence was increased by 7 MHz from RDV35. This was done to put the third S-band channel 7 MHz above the DARS band (2220-2245 MHz) These tables list the setup for the VLBA stations, the geodetic stations with VLBA back ends, and the geodetic stations with Mark IV back ends. These are the SAME frequencies used in all the standard RDV sessions. Geodetic stations: please read the special procedures in the next section! VLBA Fairbanks,Algonquin Kokee Chan Sky Tracks LO IF BBC | LO IF BBC #| LO IF BBC # 1 X 8405.99 2, 4, 6, 8 7900 B 505.99| 7600.1 A 805.89 3| 7600 A 805.99 3 2 X 8475.99 10,12,14,16 7900 B 575.99| 7600.1 A 875.89 4| 7600 A 875.99 4 3 X 8790.99 18,20,22,24 7900 B 890.99| 8080.0 C 710.99 5| 8100 C 690.99 5 4 X 8895.99 26,28,30,32 7900 B 995.99| 8080.0 C 815.99 6| 8100 C 795.99 6 5 S 2232.99 3, 5, 7, 9 2900 A 667.01| 1540.1 B 692.89 9| 1500 B 732.99 9 6 S 2262.99 11,13,15,17 2900 A 637.01| 1540.1 B 722.89 10| 1500 B 762.99 10 7 S 2352.99 19,21,23,25 2900 A 547.01| 1540.1 B 812.89 13| 1500 B 852.99 13 8 S 2372.99 27,29,31,33 2900 A 527.01| 1540.1 B 832.89 14| 1500 B 872.99 14 VLBA | Tsukuba Chan Sky Tracks LO IF BBC | LO IF BBC # 1 X 8405.99 2, 4, 6, 8 7900 B 505.99| 7680 A 725.99 3 2 X 8475.99 10,12,14,16 7900 B 575.99| 7680 A 795.99 4 3 X 8790.99 18,20,22,24 7900 B 890.99| 8080 A 710.99 5 4 X 8895.99 26,28,30,32 7900 B 995.99| 8080 A 815.99 6 5 S 2232.99 3, 5, 7, 9 2900 A 667.01| 1600 B 632.99 9 6 S 2262.99 11,13,15,17 2900 A 637.01| 1600 B 662.99 10 7 S 2352.99 19,21,23,25 2900 A 547.01| 1600 B 752.99 13 8 S 2372.99 27,29,31,33 2900 A 527.01| 1600 B 772.99 14 Medicina, Wettzell, Matera, GGAO, TIGO VLBA | Westford, Ny Alesund, HartRAO, Onsala Chan Sky Tracks LO IF BBC | LO IF VC VC# Patch 1 X 8405.99 2, 4, 6, 8 7900 B 505.99| 8080.0 1 325.99 3 H 2 X 8475.99 10,12,14,16 7900 B 575.99| 8080.0 1 395.99 4 H 3 X 8790.99 18,20,22,24 7900 B 890.99| 8580.1 3 210.89 5 L 4 X 8895.99 26,28,30,32 7900 B 995.99| 8580.1 3 315.89 6 H 5 S 2232.99 3, 5, 7, 9 2900 A 667.01| 2020.0 2 212.99 9 L 6 S 2262.99 11,13,15,17 2900 A 637.01| 2020.0 2 242.99 10 H 7 S 2352.99 19,21,23,25 2900 A 547.01| 2020.0 2 332.99 13 H 8 S 2372.99 27,29,31,33 2900 A 527.01| 2020.0 2 352.99 14 H Procedures ========== With continuous tape motion, the tape starts moving and recording at the beginning of the first scan of a pass. The tape runs and records continuously thereafter to the end of the tape (EOT or BOT). A parity check is done after the tape reaches this point. The tape starts moving in the opposite direction at the early start time (30 seconds) before the next scan. There will be a variable length of time between tape passes. For the VLBA stations, there will normally be a long enough time gap between passes for playback. Special procedures for non-VLBA stations ======================================== The tape motion in this experiment is different from normal start&stop schedules. At the time the antenna gets on source, you should see the command "data_valid=on" from the SNAP schedule. This is the signal that the VLBA correlator will use to determine when to start correlating this scan. At the time the antenna begins slewing to the next source, you will see the command "data_valid=off" from the schedule. This is the signal the correlator will use to stop correlating that scan. There will be no "et" command at the end of a scan. The DRUDG listing has a column that lists the time that the tape will stop. Note the "Start Tape" and "Stop Tape" columns list times only when the tape will start or stop, otherwise the time is blanked out because the tape is moving. For each scan, the "Start Data" column will be the time when the antenna is expected to be on source. The "Stop Data" column is the time when the antenna starts slewing to the next source. After the setup procedure, the tape is started at the beginning of each pass and will continue to move, at record speed, until it reaches the end of the pass. There are no fast tape motions in this schedule. The tape is continuously recording from the initial "st" command at the start of the pass. There are no other "st" commands during a pass and there are no other setup procedures called. If you have to re-start the schedule for a problem or emergency, you will be able to do it either 1) at the beginning of a pass or 2) in the middle of a pass by entering the setup and start tape commands manually. The problem is that the heads cannot be positioned reliably when the tape is moving if there is recorded data on the tape. If the tape is moving the reproduce power level can cause cross-talk with the head positioner and give false indications of position. Another problem is that the data disappears on tape while the formatter resets itself, thus largely eiliminating the benefits of continuous motion. At the end of each pass a parity check is done. You will need procedures named "checkf80" and "checkr80". Check and adjust the timing of this procedure and then make sure it can complete in the 100 seconds that the schedule allows. Special procedures for Medicina, Westford, Onsala, Ny Alesund, Wettzell, HartRAO, Tsukuba, Matera, GGAO, TIGO ================================================================== These stations have Mark IV formatters. Use the procedures generated by DRUDG. These must be generated for rdv36 because of the new S-band frequency sequence. Note that the patching for VC10 must be changed from L to H for this session. This is a non-standard setup. There are 8 video converters used: 3, 4, 5, 6, 9, 10, 13, and 14. These were selected so that you will NOT have to change the standard geodetic IF patching. The 6 unused VCs 1, 2, 7, 8, 11, and 12 should be set to frequencies which do not occur in any of the passbands. Any value in the 100-200 MHz range is OK. The Mark IV formatters now have barrel roll capability, so please verify that your FORM command has specification for barrel roll. The IF3 command in the procedure IFDSX assumes that VC3 will be patched to High. Please verify that the switches for your IF3 module are wired this way, and if they are not please edit the IF3 command to change the switches. If you have questions about the wiring, please contact Brian Corey at Haystack. Special procedures for Fairbanks, Kokee, Algonquin ================================================== These stations have VLBA back ends. Use the procedures generated by DRUDG. BBCs 3,4,5,6 are used at X-band with IFs A and C. BBCs 9,10,13,14 are used at S-band with IF B. The unused BBCs 1,2,7,8,11,12 should be set to frequencies which do not occur in any of the passbands. Any value in the range 500-600 MHz is OK. The formatter should be set up to use barrel roll. Please verify that you are using the same barrel roll as you used in previous sessions correlated at the VLBA. CHECKLIST for non-VLBA stations =============================== Please follow the checklist below to ensure you have done all the necessary steps for this experiment: 1. Make .prc file with DRUDG and check them out, or use the procedures from last session. Check out parity check procedures. 2. Make .snp file and listings using DRUDG options 3 and 5. 3. Set up your system to monitor the clocks with the "gps-fmout" or "fmout-gps" commands. If you have questions about this, please contact Ed Himwich as soon as possible. 4. Send a "ready" message an hour or so before the experiment to the ivs-ops mail list. Copy analysts@nrao.edu on your ready message. 5. Send a "start" message soon after you have started recording. Copy analysts@nrao.edu on the message. 6. At the end of the experiment, send a "finish" message summarizing how the experiment was conducted. Copy analysts@nrao.edu on your message. 8. Transfer your log files to your normal log file data center. The directories for three possible servers are listed below: directory on cddisa: dec02 directory on vlbeer: dec02 directory on aspen: /home/aspen6/astronomy/dec02/rdv36 NOTE: If you don't normally use aspen, you should not put your log file on that server. The VLBA correlator knows where to find your log files. Correlation =========== This experiment will be correlated at the VLBA Correlator. Tapes should be shipped to Socorro as soon after the experiment as practical.