| Date: | 2003-05-22 10:21:00 | |
| Sender: | Werner Gurtner <Werner Gurtner <werner.gurtner@aiub.unibe.ch>> | |
| Subject: | [SLR-Mail] No. 1090: Reminder: Realtime Time Bias Distribution | |
| Author: | Werner Gurtner | |
| Content: | ******************************************************************************** SLR Electronic Mail 2003-05-22 10:21:00 UTC Message No. 1090 ******************************************************************************** Author: Werner Gurtner Subject: Subject: Reminder: Realtime Time Bias Distribution REMINDER: REALTIME TIME BIAS DISTRIBUTION ***************************************** Werner Gurtner May 22, 2003 TIME BIAS FUNCTIONS The NERC Space Geodesy Facility group at Herstmonceux is automatically and frequently collecting normal point data to compute updated time bias functions (with respect to all available IRV sets) for all ILRS satellites. In order to simplify the use of these updated time bias functions, a server program at Zimmerwald frequently accesses the latest time bias functions at NERC and computes time biases for the current epoch, including drag functions (if existing) for all available satellites and IRV sets. With one simple call SLR stations can get the best current estimate of time biases for all satellites from this server. REMINDER At the recent SLR meetings in Nice it was stated that - more stations should make use of this service and - the quality of the time bias functions could still be improved by further speeding up the submission of normal point data (of the lower satellites). USAGE There are several ways to download the current time biases: - Unix and DOS/Windows Systems: Use a C program (EUROSTAT), the code of which can be downloaded from ftp://ftp.unibe.ch/aiub/slr (see also program SLRMAIL 372), as follows: eurostat aiuas3.unibe.ch 7840 1 [>time_bias_file] The program connects to port 7840, receives the time bias values and writes them to the standard output (e.g., redirected into a file for subsequent interpretation). - On unix systems you can use telnet, too: telnet aiuas3.unibe.ch 7840 [>time_bias_file] (On DOS/Windows PC telnet usually cannot redirect the output to a file). - From a web browser: http://aiuas3.unibe.ch/cgi-bin/cgi-time_bias - Or you write your own program using socket library routines to connect to port 7840 and to receive the time bias message. The host disconnects the tcp/ip connection immediately after having sent the message. Using the codes for the IRV sets and the satellite names/numbers you can easily extract the corresponding time bias value to be applied to the raw predictions from the file. EXAMPLE ! ! Time biases at 20-May-2003 09:01 UT ! ! Satellite Total IRVset LstObs Passes SIC Drag ! TB[ms] [hhh:mm] used [ms] ! Ajisai 1 HON138 2:47 26 1500 0 Ajisai 1 HON139 2:47 26 1500 0 Ajisai 3 NSD039 2:47 26 1500 0 Ajisai 164 RGO105 2:47 114 1500 0 BeaconC -14 HON138 5:54 18 0317 0 BeaconC -6 HON139 5:54 18 0317 0 BeaconC -50 RGO058 5:54 56 0317 0 Champ -38 GFZ503 0:00 0 8002 -38 ERS2 47 GFZ477 23:54 91 6178 0 ERS2 7 HON138 5:39 13 6178 0 ERS2 4 HON139 5:39 13 6178 0 Recently NERC modified the time bias function procedures to also include ”yesterday´s” IRV sets to avoid application problems during the transition phase to a new IRV set. Further information about the time bias service (e.g., format description of the transmitted data) can be found in SLRMail 0921. We would like to invite all ILRS stations to test the service and incorporate it into their procedures. Please send any questions or comments to werner.gurtner@aiub.unibe.ch Werner Gurtner From: Werner Gurtner ******************************************************************************** |