| Date: | 1997-11-04 20:00:00 | |
| Sender: | Van S. Husson <###FROM###> | |
| Subject: | [SLR-Mail] No. 92: SLR Performance Report Card | |
| Author: | Van S. Husson | |
| Content: | ******************************************************************************** SLR Electronic Mail 1997-11-04 20:00:00 UTC Message No. 92 ******************************************************************************** Author: Van S. Husson Subject: SLR Performance Report Card This is the first SLR global performance report card for the period (October 1, 1996 through September 30, 1997). During the November 1996 Shanghai SLR Workshop, Mike Pearlman presented some guidelines for high performance SLR systems. The intent was to establish metrics so that system performance could be measured and regularly reported. The metrics will provide the systems with a goal, however, these numbers are intended as a measure of minimum performance. These performance guidelines were divided into two categories, data quantity and data quality. The high performance guidelines are 1000 Low Earth Orbit (LEO) satellites passes per year, 400 LAGEOS passes per year, and a bias stability at the 20 millimeter level (mm). In this report, in order to give a more complete picture, we have extended these performance specifications to include high satellite tracking, measures of system precision, data delivery, status of configuration files, and version number of the CSTG normal point format. Data quality is measured in terms of data precision and data stability. Data precision is divided into 2 categories (LAGEOS single shot RMS, and LAGEOS normal point RMS). LAGEOS single shot RMS is the average LAGEOS RMS provided in the normal point data over this reporting period (i.e. bytes 48-51). This computation is not standardized because different stations may apply different editing levels(i.e. 2.5 vs. 3 sigma). The LAGEOS normal point RMS is based on The Center for Space Research (CSR) weekly LAGEOS report and is the average precision estimate of the normal point data set. Neither of these two precision statistics are influenced by system biases or errors in station position. The bias stability information is based on CSR weekly LAGEOS analysis. Bias stability is measured in both the short term (3 months) and long term (one year). The short term bias stability is the standard deviation about the station´s mean pass-by-pass range bias in the CSR weekly LAGEOS report for the past 3 months. The long term bias stability is the standard deviation about the CSR 15-day LAGEOS-1 mean bias for the past 12 months. It should be noted that stations that have very low LAGEOS data yield or poor quality LAGEOS data make it difficult to determine accurate station positions, which will further degrade bias stability determination. During the November 1996 Shanghai CSTG meeting, Andrew Sinclair and Van Husson proposed that all stations provide up-to-date station configuration information. The details of the format and management of this configuration information are provided in SLRMail message #48. This report contains the configuration file status report. In addition, modifications to the normal point format were also approved earlier this year and are contained in SLRMail message #47. Below is the matrix of performance statistics and status information. Column 1 is the station location name. Column 2 is the monument marker number. Column 3 is the LEO pass total. Column 4 is the LAGEOS pass total. Column 5 is the high satellite pass total. Column 6 is the single-shot LAGEOS RMS, in mm. Column 7 is the LAGEOS normal point RMS, in mm. Column 8 is the measure of short term bias stability, in mm. Column 9 is the measure of long term bias stability, in mm. Column 10 is the average data delivery time, in days, to the data centers. Column 11 is the CSTG normal poin ******************************************************************************** |