************************************************************************ ******* Non-VLBA stations please follow the CHECKLIST below. ******** ************************************************************************ RDV04 (Astrometric/geodetic VLBA-04) 1997 July 24 Notes prepared by Nancy Vandenberg, NVI/GSFC Schedule name: RDV04.SKD on CDDIS Pointing files: rdv04crd.br, rdv04crd.fd, rdv04crd.hn, rdv04crd.kp, rdv04crd.la, rdv04crd.mk, rdv04crd.nl, rdv04crd.ov, rdv04crd.pt, rdv04crd.sc on aspen PCFS files: RDV04gc.snp, RDV04kk.snp, RDV04mc.snp, RDV04gn.snp, RDV04on.snp, RDV04gg.snp, RDV04wf.snp RDV04gc.lst, RDV04kk.lst, RDV04mc.lst, RDV04gn.lst, RDV04on.lst, RDV04gg.lst, RDV04wf.lst on CDDIS in [VLBIDATA.RD97] Nominal Start: 20:00 U.T. on July 24 (day 205) first observation at 19:30 U.T. on 0552+528 for Gg-Gc-Wf first observation at 20:00 U.T. on NRAO512 for Br-Hn-Mc Gn-On-La-Nl first observation at 20:00 U.T. on 1803+784 for Sc-Kk-Kp- Mk-Ov-Pt-Fd Duration: 24 hours + 1 hour for Gc-Gg-Wf Nominal Stop: 20:00 U.T. on July 24 (day 206) last observation at 19:57 U.T. on 0742+103 for Br-Fd-Hn-Wf- La-Mk-Nl-Ov-Pt-Sc-Gn-Kk last observation at 19:57 U.T. on CTA102 for Mc-On last observation at 20:16 U.T. on 4C39.25 for Gg-Gc-Wf Correlator: VLBA Summary file for correlator: RDV04.sksum on aspen Stations: 17 Station Codes # of tapes # of obs Occupation Code Brewster B Br 2.2 (TT) 299 76149901 Fort Davis D Fd 2.2 (TT) 323 76139801 Gilcreek A Al 6.5 (HD) 277 40476601 Hancock H Hn 2.2 (TT) 295 76185001 Kokee K Kk 6.0 (HD) 293 72983001 Kitt Peak L Kp 2.2 (TT) 319 76109401 Los Alamos M La 2.2 (TT) 322 76119601 Medicina C Mc 7.0 (HD) 246 72308801 Mauna Kea N Mk 2.2 (TT) 294 76175501 North Liberty O Nl 2.3 (TT) 305 76129701 Green Bank 20m P Gn 2.6 (TT) 309 72484701 Onsala T On 6.1 (HD) 260 72137701 GGAO (MV3) Z Gg 2.1 (TT) 277 71085301 Owens Valley Q Ov 2.2 (TT) 301 76165401 Pie Town R Pt 2.2 (TT) 322 72348601 St. Croix E Sc 2.2 (TT) 280 76159001 Westford F Wf 2.3 (TT) 304 72097301 Note: This is the last experiment for which we will have thick (HD) tapes sent to the VLBA correlator. For the next and following RDV0x experiments, all stations will be using thin tapes. Purpose ======= This is the third of six bi-monthly coordinated astrometric/geodetic experiments in 1997 that use the full VLBA plus geodetic stations capable of recording in VLBA format. 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 VLBA stations demonstrate high peculiar transverse velocities, i.e., residual motion after accounting for gross plate tectonic models. All of the VLBA stations also exhibit anomalous vertical motions. Analysis of a long-term data set will enable us to tell whether these motions are measurement artifacts, are of geophysical significance, or represent localized subsidence problems at the VLBA sites. The data will incorporate the VLBA stations into the VLBI reference frame through the inclusion of other geodetic stations in the network. 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 experiment were selected from a list of 106 sources with repeated observations by the geodetic networks in the last two years. It was decided that sources observed in these experiments should meet the standards imposed by Alan Fey in his imaging survey using the VLBA, of at least three scans and 135 total observations. It was also decided that this requirement would be relaxed for sources South of -25 degrees declination. After much discussion, it was also decided that a small number of sources with definite structure would be included, to better test the ability to apply image corrections. The same source list has been used during the all 1997 sessions. Schedule ======== This is a new schedule generated by Marshall Eubanks using the 9706 version of the NASA sked program which handles continuous tape motion. This will be the second geodetic experiment to use continuous tape recording. The benefits of continuous recording are 1) greatly increased SNR because most of the on-source time will be correlated, and 2) anticipated higher data quality from the correlator because the tapes need to be synchronized only once per pass instead of on every scan. The disadvantage of continuous recording is increased tape usage: 7 thick tapes or 3 thin tapes at each station. The previous RDV03 experiment was processed in under a month, which may be an indication of the ease of processing continuous recording. The increased SNR results from increased observing time. Much of the former "idle" time is converted directly into observing time, as shown in the comparison of RDV02 with RDV04 below. (The average and median SNRs in the table do not include the GGAO scans.) Session #obs #scans %obs %idle %slew AvgSNR MedianSNR RDV02 33042 582 33 39 23 99 70 RDV03 27318 464 52 21 23 128 85 RDV04 30268 511 51 22 22 110 70 The same criteria were used for generating this schedule as were used for the first two of these sessions. The schedule has a total of 85 sources, 65 of which meet the 3 scans / 135 observation criteria. All but 4 of the remaining sources are below -25 degrees declination where the criteria were relaxed. NRAO provided a list of 7 sources for which precise positions are desired. All of these sources were within 10 degrees of each other. Since it is not efficient in a geodetic/astrometric schedule to observe so many weak sources so close to each other, three of the list could be included in this schedule. The sources are: --- Source Name ---- #scans #obs assumed flux (Jy) J1924+154 B1922+155 6 428 0.4 J2145+11 B2142+110 2 136 0.3 J2147+08 B2145+082 2 48 0.16 With the indicated fluxes, and with good a priori source positions, there should be no problem obtaining fringes on these sources. Manual scheduling was needed to ensure that the two weaker sources were observed for the minimum two scans. 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. Due to its low sensitivity, MV3 was not included directly into the schedule because the necessarily longer scan lengths would have compromised the experiment results. Instead, after the schedule was made, MV3 was tagged along to the schedule. In the tagalong mode, MV3 observes with the longest scan duration of all the stations participating in each scan, to maximize SNR. MV3 will make fringes on about 2600 of the 4000 observations in which it participates. This amount of data will allow a good determination of MV3's position in the reference frame. Extra Part of Schedule ====================== Fairbanks, Westford, and MV3 will observe an extra 30 minutes at the start and end of the experiment. The purpose is to make long scans with MV3 to help the VLBA correlator find fringes very efficiently. There are two long scans at each end of the experiment, one on 0552+398 and one on 4C39.25. Recording Mode and Frequencies: same as previous experiments ============================================================ The data will be recorded using 8 channels in VLBA format, 1:4 fan-out, 16 MHz sample rate, 1-bit sampling. This mode is designated 128-8-1. The correlator gets a speed-up factor of 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. 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 the first two RDV0x sessions. Geodetic stations: please read the special procedures in the next section! VLBA | Fairbanks | Kokee, GB 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 B 805.89| 7600 B 805.99 2 X 8475.99 10,12,14,16 7900 B 575.99| 7600.1 B 875.89| 7600 B 875.99 3 X 8790.99 18,20,22,24 7900 B 890.99| 8080.0 C 710.99| 8100 C 690.99 4 X 8895.99 26,28,30,32 7900 B 995.99| 8080.0 C 815.99| 8100 C 795.99 5 S 2220.99 3, 5, 7, 9 2900 A 679.01| 1540.1 A 680.89| 1500 A 720.99 6 S 2240.99 11,13,15,17 2900 A 659.01| 1540.1 A 700.89| 1500 A 740.99 7 S 2330.99 19,21,23,25 2900 A 569.01| 1540.1 A 790.89| 1500 A 830.99 8 S 2360.99 27,29,31,33 2900 A 539.01| 1540.1 A 820.89| 1500 A 860.99 Onsala, Medicina, VLBA | Westford, MV3 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 2220.99 3, 5, 7, 9 2900 A 679.01| 2020.0 2 200.99 9 L 6 S 2240.99 11,13,15,17 2900 A 659.01| 2020.0 2 220.99 10 L 7 S 2330.99 19,21,23,25 2900 A 569.01| 2020.0 2 310.99 13 H 8 S 2360.99 27,29,31,33 2900 A 539.01| 2020.0 2 340.99 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 will be different from normal start&stop schedules. Please read this section carefully so that you know what to expect. At the time the antenna gets on source, you should see the "Data start" comment from the SNAP schedule. This is the signal that the VLBA correlator will use to determine when to start correlating this scan. Please make notes in the log if your antenna is consistently late or early for the "Data start". We may need to adjust some antenna slewing parameters to correct the models in sked for the next schedule. At the time the antenna begins slewing to the next source, you will see the "Data stop" comment 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 (in the .lst file) has an extra 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. At the end of each pass a parity check is done. You will need procedures named "check2m1, check2m2" or "check2v1, check2v2". If you have not already done so for the first two sessions, please create these procedures as a copy of "check2c1, check2c2" and change the tracks to be "v0,v1,v2,v3". Check and adjust the timing of this procedure and then make sure it can complete in the 70 seconds that the schedule allows. If it cannot be completed, you could check the odd tracks in one direction and the even tracks in the other. If you have any questions or problems with these parity procedures, please contact Nancy Vandenberg as soon as possible. There could be some times when the tape reaches the end of a pass and you should still be observing. This should not happen, but since this is the first time we are trying continuous recording, it might. Please note in the log when this occurs, if your station is manned at that time. Special procedures for Onsala, Medicina, Westford, MV3 ====================================================== Onsala, Medicina, Westford, and MV3 have Mark IV formatters. You can use the same procedures as for the previous RDV0x sessions. Remember 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 currently have no barrel roll capability, so please verify that your FORM command has no 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. Special procedures for Fairbanks, Kokee, Green Bank =================================================== Fairbanks, Kokee, and Green Bank have VLBA back ends. You can use the same procedures generated for the previous sessions. You must swap your IF inputs so that BBCs 1-8 have the inputs shown in the table above. The unused BBCs 9-14 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. Make and check out parity check procedures. 2. Get .snp file and .lst file from CDDIS. You cannot make .snp files for this experiment and you cannot make the Option 5 listings because the distributed version of drudg does not support continuous or adaptive tape motion yet. 3. Set up your system to monitor the clocks with the "gps-fmout" or "fmout-gps" commands, per Ed Himwich's messages. If you have questions or problems, please contact Ed as soon as possible. 4. Send a "ready" message an hour or so before the experiment to the ops mail list. Copy Peggy Perley at the VLBA (pperley@nrao.edu) on the message. 5. Send a "start" message soon after you have started recording. Copy Peggy Perley on this message. 6. During the experiment, please try to note any times when the antenna is not on source at the "Data start" times. Also note any times that the tape stops before the "et" command is issued at BOT or EOT. 7. At the end of the experiment, send a "finish" message summarizing how the experiment was conducted. 8. *IMPORTANT* Transfer your log files BOTH to aspen.nrao.edu and to CDDIS. Remember that you have to use different naming conventions! on CDDIS: RDV04xx.log in [vlbidata.rd97] on aspen: RDV04log.xx in directory "jul97" We have been reminded by VLBA ops that some stations have not followed their conventions. Please double check! If you put the log file into the wrong directory by mistake, you can delete it in ftp, but please don't leave it there. Remember that you will have to telephone Socorro to get the new password for aspen. 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. SKED Summary from file ./rdv04.skd for experiment RDV04 (all scans with at least one subnet station) SOURCE |0 6 12 18 | #SCANS #OBS #Obs/bl 0003-066I x x x x x x x x I 8 352 6.2 0014+813I x x x x x x x x x x x x I 12 1632 12.0 0048-097I x x x x I 4 297 5.5 0059+581I x x x x x x x x x x x I 11 1112 9.3 0104-408I x x x x x I 5 71 4.1 0111+021I x x x I 3 197 3.1 0119+115I x x x x x x x x I 8 485 7.0 0119+041I x x x I 3 232 3.6 0133+476Ix x x x x x x x x x I 10 812 7.9 0201+113I x x x x I 4 302 4.3 0202+149I x x x x x I 5 367 5.1 0208-512I xx I 2 2 .2 0229+131I x x x x I 4 179 2.5 0234+285I x x x x x x x x xI 9 780 9.5 NGC1052 I x x x x x I 5 195 3.7 CTA26 I x x x I 3 199 3.3 0402-362I x x xx x I 5 104 3.6 3C120 I x x x x xI 5 395 6.0 0454-234I x x x x x x x I 7 187 4.6 0458-020I x x x x I 4 221 3.7 0528+134I x x x x x x I 6 364 5.1 0537-441I x x x x x I 5 39 2.5 0552+398I x x x x x x xx x I 9 448 4.7 0556+238I x x x x x I 5 421 5.4 0642+449Ix x x x x x x x I 8 902 9.1 0727-115I x x x x x x x I 7 329 6.0 0742+103I x x x x x x x x xI 9 508 7.4 0804+499I x x x I 3 347 3.3 0823+033I x x x x x x x I 7 291 4.5 OJ287 I x x x x x x x x xI 9 541 7.1 0919-260I x x x x x x x I 7 189 5.1 0920-397I x x x x I 4 43 1.9 4C39.25 Ix x x x x x x xxx x I 11 834 9.0 OK290 I x x x x x I 5 190 2.4 0955+476I x x x x x x x x x x I 10 623 6.0 1004+141I x x x x I 4 316 4.4 1034-293Ix x x I 3 142 4.1 1044+719I x x x x x x x x x x xx x I 13 1291 9.9 1101+384Ix x x I 3 227 2.5 1124-186I x x x x xI 5 172 3.8 1128+385I x x x x x x I 6 558 6.1 1144-379I x x x I 3 84 3.7 1145-071I x x x x x x x I 7 369 6.6 1156+295I x x x x x I 5 334 4.1 1219+044I x x xI 3 172 2.6 1226-028I x x x I 3 118 1.9 3C274 I x x x x x x I 6 375 5.3 3C279 I x x x x I 4 329 5.7 1255-316I x x x I 3 130 4.1 1300+580Ix x x x I 4 276 2.3 1308+326I x x x x x x x I 7 447 5.2 1313-333Ix x x x I 4 133 4.4 1334-127I x x x x x xx x x x I 10 234 4.8 1351-018I x x x I 3 30 .5 1357+769Ix x x x x x x x I 8 788 5.8 OQ208 I x x x x x I 5 121 1.5 1418+546I x x x x x x x I 7 540 4.7 1424-418I x x x I 3 25 1.2 1451-375I x x x x I 4 105 3.8 1514-241I x x x x x x x xI 8 214 5.3 1606+106Ix x x x x x x x x I 9 617 8.9 1611+343I x x x x xx x I 7 549 6.3 1622-253I x x x x x I 5 140 3.6 NRAO512 Ix x x x x x x I 7 422 4.5 1726+455I x x x I 3 97 .9 1739+522I x x x x x x x x xI 9 800 7.3 1741-038I x x x x x x x I 7 441 7.5 1745+624I x x x x x x I 6 454 3.7 1749+096I x x x x x x I 6 278 4.0 1803+784I x x x x x x x x x x x x I 12 980 7.2 1815-553I x I 1 1 .2 1908-201Ix x x x x x x x I 8 295 6.8 1922+155I x x x x x x I 6 455 6.3 1921-293I x x x x x x I 6 91 2.6 1954-388I x x x x I 4 87 4.0 2052-474I x x x x x I 5 14 1.3 2136+141I x x x x x x x xI 8 319 4.5 2142+110I x x I 2 160 2.3 2145+082I x x I 2 58 .9 2145+067Ix x x x x I 5 289 4.4 VR422201I x x x x x x x x x xx I 11 928 9.7 CTA102 I x x x xx x I 6 304 4.4 2234+282I x x x x x x I 6 253 3.1 2243-123I x x x x x x x x xI 9 354 6.5 2255-282I x x x x x x xx I 8 162 4.7 Total scans, obs: 511 30268 Average number of obs. per baseline per source (normalized by up-time) = 4.9 Min = .0 Max = 14.4 (Baseline Ov-Pt on 1606+106) RMS = 3.4 Total time: 1492 minutes ( 24.9 hours). Key: Br=BR-VLBA Fd=FD-VLBA Gc=GILCREEK Hn=HN-VLBA Kk=KOKEE Kp=KP-VLBA La=LA-VLBA Mc=MEDICINA Mk=MK-VLBA Nl=NL-VLBA Gn=NRAO20 On=ONSALA60 Gg=ORION_5M Ov=OV-VLBA Pt=PIETOWN Sc=SC-VLBA Wf=WESTFORD Br Fd Gc Hn Kk Kp La Mc Mk Nl Gn On Gg Ov Pt Sc Wf Avg % obs. time: 55 53 43 55 42 51 51 24 49 55 60 41 67 53 52 49 70 51 % cal. time: 3 3 3 3 3 3 3 2 3 3 3 2 3 3 3 3 3 3 % slew time: 25 27 18 24 14 26 27 29 23 25 17 17 9 24 27 22 14 22 % idle time: 15 15 35 17 39 18 17 42 23 15 18 37 19 18 17 24 12 22 # of tapes : 2.9 3.0 6.5 2.2 6.0 2.9 2.9 7.0 2.9 2.3 2.6 6.1 2.1 2.9 2.9 2.2 2.3 total # scans: 299 323 277 295 293 319 322 246 294 306 309 260 277 301 322 280 304 295 # scans/hour : 12 12 11 11 11 12 12 9 11 12 12 10 11 12 12 11 12 12.3 Avg scan (sec): 166 147 139 167 130 143 144 90 151 161 175 144 219 159 144 158 207 155 # OF OBSERVATIONS BY BASELINE | Br Fd Gc Hn Kk Kp La Mc Mk Nl Gn On Gg Ov Pt Sc Wf StnTotal ---------------------------------------------------------------------------------- Br|299 280 238 257 208 278 285 139 222 275 257 157 218 269 284 227 249 3512 Fd| 323 222 266 218 313 317 134 234 292 278 148 230 290 318 251 263 3627 Gc| 277 215 197 223 226 144 197 221 218 166 192 218 225 182 220 3796 Hn| 295 177 259 269 159 188 279 283 175 245 242 267 258 282 3560 Kk| 293 224 218 92 276 195 187 106 171 224 220 154 183 3379 Kp| 319 312 129 240 285 269 143 225 295 314 241 255 3471 La| 322 137 234 294 277 151 232 292 320 249 264 4017 Mc| 246 82 145 155 233 142 117 135 145 158 3405 Mk| 294 211 193 99 171 240 236 164 185 3629 Nl| 306 285 162 241 268 292 255 275 3364 Gn| 309 172 254 248 275 267 292 3651 On| 260 157 133 150 153 176 3392 Gg| 277 212 230 226 256 3599 Ov| 301 294 219 237 4022 Pt| 322 247 262 2755 Sc| 280 259 3838 Wf| 304 3503 Number of 2-station scans: 99 Number of 3-station scans: 40 Number of 4-station scans: 13 Number of 5-station scans: 9 Number of 6-station scans: 5 Number of 7-station scans: 22 Number of 8-station scans: 20 Number of 9-station scans: 22 Number of 10-station scans: 17 Number of 11-station scans: 14 Number of 12-station scans: 20 Number of 13-station scans: 14 Number of 14-station scans: 53 Number of 15-station scans: 78 Number of 16-station scans: 33 Number of 17-station scans: 52 Total # of scans, observations: 511 30268 Average baseline components for all observations Average XY = 3563. Average XZ = 3164. Average YZ = 2198. Average length = 3805.