GRAV01C (Preliminary experiment for measurements of speed of propagation of gravity) 2002 August 28 Notes prepared by Leonid Petrov, NVI/GSFC ( pet@leo.gsfc.nasa.gov ) Station CODE Code # tapes # of obs Start Time End Time Algonquin G Ap 2 107 August 28, 18:00 August 29, 18:01 UT Fairbanks A Gc 3 141 August 28, 18:00 August 29, 18:01 UT HartRAO J Hh 2 72 August 29, 03:52 August 29, 13:13 UT Kokee K Kk 2 114 August 28, 18:00 August 29, 18:00 UT Matera I Mc 3 101 August 29, 02:20 August 29, 15:25 UT Ny Alesund N Ny 5 187 August 28, 18:00 August 29, 16:35 UT Westford E Wf 2 108 August 28, 18:00 August 29, 18:01 UT Wettzell V Wz 2 103 August 28, 02:20 August 29, 16:06 UT Long gaps: Algonquin does not observe between August 28, 21:56 and August 29, 09:19 UT Fairbanks does not observe between August 29, 03:52 and August 29, 12:15 UT Kokee does not observe between August 29, 02:48 and August 29, 14:59 UT Westford does not observe between August 28, 21:32 and August 29, 08:54 UT Purpose ======= This is the first experiment in the series of two experiments for measurement of gravity speed propagation. The schedule is designed for precise measurement of the change of the angular distance between the target quasar, 0839+187, and two calibrators within a session. It is expected that this change should be zero in the grav01c experiment. During the event of 2002.09.08 when Jupiter will pass 3.7 arcmin from the target quasar 0839+187, the theory based on general relativity predicts ( Kopeikin, S.M. "Testing the relativistic effect of the propagation of gravity by very long baseline interferometry", ApJ Lett., vol. 556, p. L1-L5, 2001 ) a special term for the differences in phases between the target and two calibrators. This phase difference changes in the range of 3-15 degrees during 3-10 hours before and after passing Jupiter due to the fact that according to general relativity gravity propagates with the same speed as light in vacuum. Measurements of this term would allow confirmation of the validity of general relativity for a NON-STATIONARY gravitation field. Up to now, no direct tests of such kind have been done. Since Jupiter will be far away from the target quasar on 2002.08.28, variations in phase differences between the target and quasar should be due only to noise and unmodeled effects. The level of these variations sets the accuracy limit of the speed of gravity measurements on 2002.09.08. Refer to http://gemini.gsfc.nasa.gov/pet/discussion/grav/grav.html for more details. Schedule ======== THIS IS NOT A GEODETIC SCHEDULE! It was generated to observe mainly the target source and calibrators. Stations observe only when these sources are up. This experiment is done in "nodding mode". The primary observable is the phase difference between the target quasar 0839+187 and two calibrators, OJ287 and 0836+182. Several scans for atmosphere path delay calibration are added after 2-3 hours of nodding observations. Three sources are the most frequently observed: 1) the target, 0839+187 ( flux 0.33 Jy, Jupiter will pas in 3.7 arcmin from this quasar on 2002.09.08 ) 2) the calibrator 1, 0836+182 ( flux 0.17 Jy, 49 armin away from 0839+187 ) 3) the calibrator 2, OJ287 ( flux 2.8 Jy, 3d15 armin away from 0839+187 ) Three sequences, which just fit one tape pass, are observed 90% of time: target-cal1-target; cal1-target-cal2; target-(cal2-target)-(cal2-target)-(cal2-target) =================================================================== SKED Summary from file ./grv01c.skd for experiment GRV01C (all scans with at least one subnet station) Average number of obs. per baseline per source (normalized by up-time) = 1.6 Min = .0 Max = 82.5 (Baseline Hh-Ma on 0839+187) RMS = 8.1 Total time: 1441 minutes ( 24.0 hours). Key: Ap=ALGOPARK Gc=GILCREEK Hh=HARTRAO Kk=KOKEE Ma=MATERA Ny=NYALES20 Wf=WESTFORD Wz=WETTZELL Ap Gc Hh Kk Ma Ny Wf Wz Avg % obs. time: 40 51 30 38 42 71 40 41 44 % cal. time: 1 1 0 1 1 2 1 1 1 % slew time: 4 1 3 1 1 1 1 0 2 % idle time: 53 44 65 58 54 24 56 56 51 # of tapes : 2.0 2.7 1.6 1.9 2.0 4.0 2.0 2.0 total # scans: 107 141 72 114 101 187 108 103 116 # scans/hour : 4 5 2 4 4 7 4 4 4.9 Avg scan (sec): 329 318 364 295 361 331 327 345 333 tape change times (hhmm): 1150 0015 0950 0015 0854 2315 1150 0854 0000 1347 0000 0000 0000 0423 0000 0000 0000 0000 0000 0000 0000 0950 0000 0000 # OF OBSERVATIONS BY BASELINE | Ap Gc Hh Kk Ma Ny Wf Wz StnTotal ---------------------------------------------- Ap|107 82 28 60 45 82 103 44 444 Gc| 141 6 109 32 118 78 33 458 Hh| 72 0 71 67 31 66 269 Kk| 114 4 88 59 6 326 Ma| 101 91 48 93 384 Ny| 187 81 96 623 Wf| 108 47 447 Wz| 103 385 Number of 2-station scans: 14 Number of 3-station scans: 59 Number of 4-station scans: 66 Number of 5-station scans: 40 Number of 6-station scans: 37 Number of 7-station scans: 6 Number of 8-station scans: 0 Total # of scans, observations: 222 1668