RDV34 (Astrometric/Geodetic VLBA-31) 2002 July 24 Notes prepared by Nancy Vandenberg, NVI/GSFC Schedule name: rdv34.skd Pointing files: rdv34crd.br, rdv34crd.fd, rdv34crd.hn, rdv34crd.kp, rdv34crd.la, rdv34crd.mk, rdv34crd.nl, rdv34crd.ov, rdv34crd.pt, rdv34crd.sc ftp://vlbiobs@aspen.nrao.edu/home/aspen6/astronomy/jul02/rdv34 Summary file for correlator: rdv34.sksum on aspen PCFS file: ftp://vlbigeo@cddisa.gsfc.nasa.gov/vlbigeo/jul02/rdv34.skd http://lupus.gsfc.nasa.gov/sess/2002/sesshtml/rdv34.html First observations Source Start Stations 0552+398 02205-174500| Br-Fd-Gc-Hn-Kp-La-Nl-Ov-Pt-Sc-Wf 1313-333 02205-180000| Ma-Mc-Tc 0552+398 02205-180020| Mk-Ny-On =========================================================== Last observations Source Start Stations 4C39.25 02206-175341| Ma-Mc-On-Wz 0420+210 02206-175756| Kk-Mk-Ny 0528+134 02206-181622| Br-Fd-Gc-Hn-Kp-La-Nl-Ov-Pt-Sc-Tc-Wf =========================================================== Correlator: VLBA at Socorro Station Codes # of tapes # of obs Brewster B Br 2.4 (TT) 210 Fort Davis D Fd 2.4 (TT) 203 Gilcreek A Al 2.1 (TT) 214 Hancock H Hn 2.4 (TT) 175 Kokee K Kk 1.9 (TT) 169 Kitt Peak L Kp 2.4 (TT) 204 Los Alamos M La 2.4 (TT) 206 Matera I Ma 2.1 (TT) 188 Medicina C Mc 2.1 (TT) 194 Mauna Kea N Mk 2.4 (TT) 191 North Liberty O Nl 2.4 (TT) 194 Ny Alesund P Ny 2.4 (TT) 199 Onsala T On 2.1 (TT) 196 Owens Valley R Ov 2.4 (TT) 191 Pie Town S Pt 2.4 (TT) 205 St. Croix E Sc 2.4 (TT) 169 TIGO Q Tc 2.4 (TT) 91 Westford F Wf 2.2 (TT) 175 Wettzell V Wz 1.9 (TT) 159 Total number of observations (delay measurements): 19125 Total number of scans in the schedule: 408 Special Notes for this session: - NEW in RDV34: The stations with Mk4 formatters will use barrel roll. - New baseline-format flux models were used to make this schedule. The models were determined by Alan Fey (USNO) using data from RDV31, observed in January. Therefore the flux models should be fairly up-to-date. - 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. - Ny Alesund records 12 passes, instead of the usual 14, because they are having some recorder problems. It is hoped that this will minimize data loss. - Fairbanks, Westford, GGAO, and most VLBA stations record two initial long (5-min) scans and two final long (5-min) scans. - TIGO, based at Concepcion, Chile, will participate for the first time in an RDV 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) but the margins 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. - Due to TIGO's participation, using 19 instead of 20 stations, and the inclusion of four fairly weak requested sources, there are fewer observations in this schedule compared to other RDVs. - Wettzell and Kokee will begin participating in this schedule at about 20:00 after finishing intensive session i02205. - NEW since RDV27: This session has the NEW S-BAND FREQUENCY SEQUENCE that avoids the direct broadcast satellite band of 2320-2345 MHz. The new sequence was used in RDV27 and all following sessions, except for RDV32 in which the old sequence was inadvertantly used. Purpose ======= This is the next 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 Nancy Vandenberg using sked. "Requested" Sources in rdv34 : Requested by J. Wrobel, to be observed in RDV34,35,36 (as marked): Name RA(J2000) Decl(J2000) Sp(8.5 GHz) 36 J0202-0559 02 02 06.86417 -05 59 00.1242 78 mJy 34 J0209-0438 02 09 30.76627 -04 38 26.1423 172 mJy 34 J0210-0737 02 10 16.52894 -07 37 20.6965 93 mJy 34 J0213-0719 02 13 16.67062 -07 19 32.4590 102 mJy 34 J0215-0343 02 15 11.50555 -03 43 07.8693 93 mJy 35 J0216-0118 02 16 05.66268 -01 18 03.3886 143 mJy 35 J0216-0105 02 16 12.21194 -01 05 18.8485 85 mJy 35 J0217-0122 02 17 55.00002 -01 21 50.7221 129 mJy 36 J0223-0205 02 23 13.03999 -02 05 07.9220 127 mJy These are candidate phase calibrators for an approved VLBA program, BR081, to be observed in October 2002. BR081 is a survey of 106 FIRST sources in the Cetus field of the NOAO Deep Wide-Field Survey, making use of the strategies demonstrated in the Bootes field (Wrobel et al., 2001, VLBA Scientific Memo 28). These candidate calibrators are not in sources.vlba. They were selected as having flat spectra from the NVSS and PMN surveys, then observed with the VLA in the JVAS style during program AW574. Each candidate is core-dominated to the VLA at 200-mas resolution at 8.5 GHz. The quoted peak flux densities are accurate to a few percent. I expect that the quoted positions are accurate to a few tens of mas but I won't know for a couple more days, after I finish analyzing the few hundred sources in program AW574. Requested by A. Fey: 0420+210 4:20:04.839 +21:01:04.854 B1950 Flux(6 cm) = 0.75 Jy (assume it is flat spectrum) The position is for ongoing phase referencing observations of T Tau that we are making using MERLIN (Jodrell Bank's Multi-Element Radio Linked Interferometer Network). Using rotating sources same as in RDV20, yearly from RDV27 Y | 0953+254 OK290 Y | 1351-018 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 90 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 RDV27: The S-band frequency sequence was modified to reverse the sequence steps and raise the sequence by 5 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 2225.99 3, 5, 7, 9 2900 A 674.01| 1540.1 B 685.89 9| 1500 B 725.99 9 6 S 2255.99 11,13,15,17 2900 A 644.01| 1540.1 B 715.89 10| 1500 B 755.99 10 7 S 2345.99 19,21,23,25 2900 A 554.01| 1540.1 B 805.89 13| 1500 B 845.99 13 8 S 2365.99 27,29,31,33 2900 A 534.01| 1540.1 B 825.89 14| 1500 B 865.99 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 2225.99 3, 5, 7, 9 2900 A 674.01| 1600 B 625.99 9 6 S 2255.99 11,13,15,17 2900 A 644.01| 1600 B 655.99 10 7 S 2345.99 19,21,23,25 2900 A 554.01| 1600 B 745.99 13 8 S 2365.99 27,29,31,33 2900 A 534.01| 1600 B 765.99 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 2225.99 3, 5, 7, 9 2900 A 674.01| 2020.0 2 205.99 9 L 6 S 2255.99 11,13,15,17 2900 A 644.01| 2020.0 2 235.99 10 H << change 7 S 2345.99 19,21,23,25 2900 A 554.01| 2020.0 2 325.99 13 H 8 S 2365.99 27,29,31,33 2900 A 534.01| 2020.0 2 345.99 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 rdv34 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: jul02 directory on vlbeer: jul02 directory on aspen: /home/aspen6/astronomy/jul02/rdv34 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. Summary ======= The following listing is a summary of the observations in this schedule.