| Date: | 2007-02-14 00:15:00 | |
| Sender: | Philip Gibbs and Graham Appleby <Graham Appleby <GAPP@nerc.ac.uk>> | |
| Subject: | [SLR-Mail] No. 1534: Range correction for station 7840 Herstmonceux | |
| Author: | Philip Gibbs and Graham Appleby | |
| Content: | ******************************************************************************** SLR Electronic Mail 2007-02-14 00:15:00 UTC Message No. 1534 ******************************************************************************** Author: Philip Gibbs and Graham Appleby Subject: Range correction for station 7840 Herstmonceux Colleagues. This message announces an upgrade to the hardware of the SLR facility at SGF Herstmonceux, UK, as part of a programme leading to kHz-rate ranging later this Spring. >From 2007 Sunday February 11 at 0hr UT the time-of-flight measurements for all satellite and calibration ranging are being made using our new Event Timer (HxET) that is based on ps-level clock modules. This migration follows a period of evaluation of HxET, which included a valuable re-calibration of the Stanford counters that have been used at the station since 1994. As a result of this re-calibration, we have determined a correction to all data taken at Herstmonceux since 1994 October 1, which follows from non-linear behaviour of the old counters at close range during target-board ranging, plus a very small optical path correction. In summary, ALL SATELLITE range data taken by Herstmonceux in the period 1994 October 1 to 2007 February 10 inclusive is 8.5 +/- 2 mm TOO SHORT. So for all data in this period, add 8.5mm (58 ps) to all range observations. This correction is in addition to the corrections, caused by counter non-linearity effects that are distance-dependent, that should be applied for the period 1994 October 1 to 2002 February 1 as announced in SLRMail 0891 (2002 Jan 30); they amount to ~10mm at the distances of LAGEOS and of ETALON. Please check this SLRMail for more details. Details of these corrections have already been communicated to the ILRS analysis community, with particular regard to the ongoing re-analysis effort of LAGEOS and ETALON data. >From 2007 February 11.0 the Stanford counters, which were working well within their specified accuracies, have been removed and we are confident that range data from Herstmonceux from that date onwards will be free of systematic effects greater than about 1 or 2mm. We are currently planning to carry out similar analyses on counters in use at a number of other, mainly European, observatories. Please contact the authors if you are interested in contributing to this work. Regards, Philip Gibbs and Graham Appleby Pgig@nerc.ac.uk Gapp@nerc.ac.uk -- This message (and any attachments) is for the recipient only. NERC is subject to the Freedom of Information Act 2000 and the contents of this email and any reply you make may be disclosed by NERC unless it is exempt from release under the Act. Any material supplied to NERC may be stored in an electronic records management system. From: ”Graham Appleby” ******************************************************************************** |