rdv44 (Astrometric/Geodetic VLBA-44) 2004 May 05 Notes prepared by John Gipson, NVI/GSFC Schedule name: rdv44.skd Pointing files: rdv44crd.br, rdv44crd.fd, rdv44crd.hn, rdv44crd.kp, rdv44crd.la, rdv44crd.mk, rdv44crd.nl, rdv44crd.ov, rdv44crd.pt, rdv44crd.sc ftp://vlbiobs@aspen.nrao.edu/home/aspen6/astronomy/dec03/rdv44 Summary file for correlator: rdv44.sksum on aspen PCFS file: ftp://vlbigeo@cddisa.gsfc.nasa.gov/vlbigeo/dec03/rdv44.skd http://lupus.gsfc.nasa.gov/sess/2004/sesshtml/rdv44.html First observations Source Start Stations 0607-157 180000 | AP Fd Hn Kp La Mc Nl Gg Pt Sc Tc Wf 0003-066 180000 | Br Gc Mk Ov 0955+476 180000 | On 0818-128 195833 | Wz =========================================================== Last observations Source Start Stations 0212+735 173843 | Ap Br Fd Gc Hn Kp La Mc Mk Nl On Gg Ov Pt Sc Wf Wz 0607-157 175811 | Tc =========================================================== Correlator: VLBA at Socorro Station Code Scans Obs Tapes ALGOPARK G Ap 220 1914 2.1 BR-VLBA B Br 228 2098 2.4 FD-VLBA D Fd 238 2262 2.4 GILCREEK A Gc 193 1461 2.5 HN-VLBA H Hn 227 2035 2.4 KP-VLBA L Kp 234 2182 2.4 LA-VLBA M La 233 2279 2.4 MEDICINA C Mc 268 1283 2.2 MK-VLBA N Mk 192 1367 2.1 NL-VLBA O Nl 238 2273 2.4 ONSALA60 T On 215 1152 2.2 GGAO7108 Z Gg 192 1438 2.1 OV-VLBA R Ov 224 2059 2.2 PIETOWN U Pt 234 2290 2.4 SC-VLBA E Sc 203 1637 2.4 TIGOCONC Q Tc 99 595 2.1 WESTFORD F Wf 192 1794 2.2 WETTZELL W Wz 234 1093 2.1 All stations use thin tape. Total number of observations (delay measurements): 15606 Total number of scans in the schedule: 638 Special Notes for this session: - NEW in RDV44. We have used a new algorithm for selecting the sources. - 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. - Most stations participate in 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 participates in this schedule. It was tagged along after the schedule was generated. - Wettzell will begin participating in this session at 20:00 after completing the intensive session IO4-126. - 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 second of six bi-monthly coordinated astrometric/geodetic experiments in 2004 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. SOURCE SELECTION The selection of sources in this session is somewhat different than in previous sessions. We have selected 30 sources that have been not been observed at least twice in the last 12-months. The remaining 60 sources were picked using the "Best-N" algorithm. This algoritm picks tries to pick the best sources based on sky distribution and strength. SCHEDULING ALGORITHMS This schedule was generated using ASTROMETRIC mode for the 30 under-observed sources. For each source in astrometric mode, sked has a target number of observations, expressed as a percentage of the total number of observations. If the source has not met its target, observations on this source are perferred. In our case the targets for the 30 under-observed sources was 1%-1.5%. This translates into observing each source about 200 times. This schedule also uses the "SRCEVN SQRT" mode. Sked will preferentially observe strong sources that have high visibility. This mode attempts to smooth out the number of observations per source. This schedule also uses SRCFLR. Sources that are observed less than 0.5% of the time are prefered in selecting new scans by sked. 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 H 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 rdv44 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: mar04 directory on vlbeer: mar04 directory on aspen: /home/aspen6/astronomy/may04/rdv44 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.