| Date: | 2002-01-30 08:34:00 | |
| Sender: | Graham Appleby & Philip Gibbs <slr@slrb.rgo.ac.uk (SLR Herstmonceux)> | |
| Subject: | [SLR-Mail] No. 891: Removal of systematic bias in Herstmonceux SLR range data | |
| Author: | Graham Appleby | |
| Content: | ******************************************************************************** SLR Electronic Mail 2002-01-30 08:34:00 UTC Message No. 891 ******************************************************************************** Author: Graham Appleby & Philip Gibbs Subject: Removal of systematic bias in Herstmonceux SLR range data NERC Space Geodesy Facility REMOVAL OF SYSTEMATIC BIAS IN HERSTMONCEUX SLR RANGE DATA REASON FOR CHANGE We are now confident that we understand the characteristics of a range-dependent range bias that has been in our SLR measurements since 1994 October 1. It is caused by subtle non-linear effects in the Stanford SR620 counters that we use to make the range measurements; the range bias values (amounting for example to some 8-10mm at the distance of LAGEOS) continue to be stable and predictable at a level of uncertainty of about 20ps (3mm in 1-way range). DATE OF CHANGE From 2002 February 1 00:00 UT we will apply range corrections to our data before they are submitted to EDC and CDDIS and no further corrections will be required by users. CONSISTENCY WITH PREVIOUS DATA For maximum accuracy in interpretation of Herstmonceux (7840) data obtained in the period 1994 October 1 until 2002 January 31 inclusive, the following table should be used to determine the appropriate range-dependent correction that must be ADDED TO the time-of-flight given in the normal point data. Range (ms) Correction (ps) to 2-way time-of flight 0 0 2 35 4 48 6 52 8 73 10 77 12 91 14 92 16 100 18 120 20 109 22 120 24 111 26 115 28 112 30 97 32 100 34 87 36 82 38 75 40 72 42 73 44 62 46 61 48 50 50 54 52 48 54 53 56 52 58 54 60 74 62 71 64 75 66 84 68 86 70 87 72 101 74 100 76 83 78 80 80 76 82 78 84 84 86 74 88 79 90 82 92 73 94 85 96 79 98 80 100 76 102 83 104 79 106 78 108 73 110 85 112 82 114 76 116 75 118 78 120 75 122 62 124 72 126 67 128 56 130 70 130 70 Please contact us if further details are required. | ========================================================= -O- ========= | NERC Space Geodesy Facility /| | | Herstmonceux Castle / | | Hailsham / | | East Sussex ( / / /) | | UK BN27 1RN ( /_/ / ) | | Tel: +44 (0)1323 833888 ( |O| / ) | | Fax: +44 (0)1323 833929 ================= | | Email: slr@slrb.rgo.ac.uk == == | | Web: http://nercslr.nmt.ac.uk/ = = | ======================================================================= From: slr@slrb.rgo.ac.uk (SLR Herstmonceux) ******************************************************************************** |