rdv38 (Astrometric/Geodetic VLBA-38) 2003 May 7 Notes prepared by John Gipson, NVI/GSFC Schedule name: rdv38.skd Pointing files: rdv38crd.br, rdv38crd.fd, rdv38crd.hn, rdv38crd.kp, rdv38crd.la, rdv38crd.mk, rdv38crd.nl, rdv38crd.ov, rdv38crd.pt, rdv38crd.sc ftp://vlbiobs@aspen.nrao.edu/home/aspen6/astronomy/may03/rdv38 Summary file for correlator: rdv38.sksum on aspen PCFS file: ftp://vlbigeo@cddisa.gsfc.nasa.gov/vlbigeo/mar03/rdv38.skd http://lupus.gsfc.nasa.gov/sess/2003/sesshtml/rdv38.html First observations Source Start Stations 1745+624 03127-174500| Br FD Hn Kp La Mk Nl Ov Pt Wf Gg 0059+581 03127-180000| Ss Ts 1244-255 03127-180000| Ma Mc 0552+398 03127-180000| On Tc 1642+690 03127-200000| Kk Wz =========================================================== Last observations Source Start Stations 2328+107 03072-173538| Kk Tc Ts 1826+796 03072-173731| Ma On 1145-071 03072-174451| Mc Wz 1745+624 03072-174842| Mk 2250+194 03072-175508| Br Fd Hn Kp La Nl Ov Pt Sc Wf Gg =========================================================== Correlator: VLBA at Socorro Station Codes scans obs tapes BR-VLBA B Br 392 3206 2.4 TT FD-VLBA D Fd 373 3341 2.4 TT HN-VLBA H Hn 387 3093 2.4 TT KOKEE K Kk 410 2064 2.0 TT KP-VLBA L Kp 385 3428 2.4 TT LA-VLBA M La 390 3559 2.4 TT MATERA I Ma 331 1910 2.2 TT MEDICINA C Mc 399 2150 2.2 TT MK-VLBA N Mk 440 2356 2.4 TT NL-VLBA O Nl 376 3373 2.4 TT ONSALA60 T On 311 1925 2.2 TT ORION_5M Z Gg 339 2366 2.4 TT OV-VLBA R Ov 392 3230 2.4 TT PIETOWN U Pt 387 3535 2.4 TT SC-VLBA E Sc 350 2534 2.4 TT TIGO Q Tc 245 1437 2.1 TT TSUKUB32 V Ts 370 1497 2.1 TT WESTFORD F Wf 327 2695 2.2 TT WETTZELL W Wz 328 1911 2.0 TT Total number of observations (delay measurements): 24805 Total number of scans in the schedule: 1268 Special Notes for this session: - NEW in RDV34: The stations with Mk4 formatters, and with updated formatter firmware, will use barrel roll. - The fluxes used our most current models. If we did not have models for the fluxes we used those determined by Alan Fey (USNO). - 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. - 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 (670 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. - GGAO was tagged along after the schedule was generated using the other 19 stations. No SNR requirements were placed on the GGAO scans. GGAO was added to each scan that the antenna could slew to in time, and the scan length for GGAO was set to the maximum of all the stations already participating in the scan. There will be some non-detections on the GGAO baselines. - Wettzell and Kokee will begin participating in this schedule at 20:00 after finishing intensive session i03127 - NEW since RDV35: 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. Purpose ======= This is the first of six bi-monthly coordinated astrometric/geodetic experiments in 2003 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 using sked. There were no requested sources in rdv38. The source 2335-027 was originally scheduled in rdv37. However it was too close to the sun, and hence was rescheduled for this rdv. Using the "yearly" sources: 1004+141 Last observed RDV30 October 29 2001 1418+546 Last observed RDV31 January 16 2002 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. NEW SCHEDULING ALGORITHMS This schedule uses several new scheduling algorithms which were first used in rdv37. The first of these tries to minimize antenna idle time by scheduling observations using sub-nets that are idle. The second tries to put a floor on the # of observations of some subset of the sources. The third tries to reduce the discrepancy in # of observations per source between strong and weak sources, and between sources visible over much of the network, and those which are only observable over a subset. For a detailed description of these algorithms, please see the notes for rdv37. 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 (2220-2245Mz.) 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 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, NOTO, 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, Wettzell, Tsukuba, Matera, GGAO, TIGO ================================================================== These stations have Mark IV formatters. Use the procedures generated by DRUDG. These must be generated for rdv38 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 Kokee ================================================== 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: may03 directory on vlbeer: may03 directory on aspen: /home/aspen6/astronomy/may03/rdv38 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.