Near Real-time UT1 Measurement by Using e-VLBI Technique

Recent progress of e-VLBI technique and the increase of network speed made rapid UT1 measurements possible. On June 30, 2004 we performed a one-hour e-VLBI session with the baseline between Kashima and Westford stations to estimate UT1 as rapid as possible. Observation data were recorded with the K5/VSSP system at Kashima and the Mark-5 system at Westford. Immediately after the session was finished, Mark-5 data were transferred to Kashima through the Internet. The Mark-5 data were then converted to K5 format data. In the next step, the converted data were correlated with those recorded at Kashima by using the K5 software correlator combined with the network-distributed processing system named VLBI@home. Finally we succeeded to obtain estimated UT1 value in as short as 4.5 hours after the session was over. To shorten the turn-around time of UT1 estimation further, we are improving the K5 software correlator so as to correlate K5 data with Mark-5 data directly. We are also developing software to send K5 data over network according to the standard data format (VSI-E). In addition to the rapid UT1 measurement results, we will report about current status of these software developments. IVS Products Status and Goals (some examples from WG2 Report) Products Status Goals(2002-2005) • polar motion accuracy xp ~100 μas, yp ~200 μas xp, yp: 50 25 μas xP, yP latency 1 4 weeks 4 months 4 3 days 1day resolution 1 day 1 day 1h 10min freq. of sessions ~3 d/week ~7 d/week • UT1-UTC accuracy 5 20 μs 3.2 μs latency 1 week 4 3 days – 1 day resolution 1 day 1 day 10 min • celest. pole accuracy 100 400 μas 50 25 μas ∆e, ∆ψ latency 1 4 weeks... 4 months 4 – 3 days 1 day resolution 1 day 1 day freq. of sessions ~3 d/week ~7 d/week • TRF (x,y,z) accuracy 5 20 mm 5 2 mm • CRF(a, d) accuracy 0.25 3 mas 0.25 mas (improved distribution) freq. of solution 1 year 1 year latency 3 6 months 3 1 month(s) Key Stone Project VLBI Network (1994-2001) Number of Days Required to Deliver Products Situations in 2002 (January to August) R1 & R4 Time Delay Over Time 0 5 10 15 20 25 30 35 40 45 50 55 60 65 1/3 /20 02 1/1 0/2 00 2 1/1 7/2 00 2 1/2 4/2 00 2 1/3 1/2 00 2 2/7 /20 02 2/1 4/2 00 2 2/2 1/2 00 2 2/2 8/2 00 2 3/7 /20 02 3/1 4/2 00 2 3/2 1/2 00 2 3/2 8/2 00 2 4/4 /20 02 4/1 1/2 00 2 4/1 8/2 00 2 4/2 5/2 00 2 5/2 /20 02 5/9 /20 02 5/1 6/2 00 2 5/2 3/2 00 2 5/3 0/2 00 2 6/6 /20 02 6/1 3/2 00 2 6/2 0/2 00 2 6/2 7/2 00 2 7/4 /20 02 7/1 1/2 00 2 7/1 8/2 00 2 7/2 5/2 00 2 8/1 /20 02 8/8 /20 02 8/1 5/2 00 2 8/2 2/2 00 2 September 11, 2002 CCT Bonn R1 Hays R1 Wash R1 Wash R4 EOP Estimation by KSP Network