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13th International Laser Ranging
Workshop
"Toward Millimeter Accuracy"
Submitted
Abstracts
Timing Devices (E. Samain and P. Gibbs)
| Title | Primary Author |
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| Range comparison results for various Eurolas SR timers | Philip Gibbs |
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NERC SGF F. Koidl and G. Kirchner SR timers are very stable, easy to use timing devices. Unfortunately they are non-linear over the full range of measurements required by SLR, although they are very stable in their non-linearily. Each SR timer would appear to have its own individual behavioral pattern. This paper will present comparisons made between SR timers from San Fernando, Potsdam, Graz, Borowiec, Zimmerwald and Herstmonceux against one of the Herstmonceux SR timers. It will also present the results of comparisons carried out at Graz between the Graz SR timers and the Graz event timer. Oral presentation; received August 6, 2002 |
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| A010 Family of Time interval Counters Adapted to SLR Applications | Yuri Artyukh |
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Institute of Electronics and Computer Science, University of
Latvia . Bespalko, E. Boole, K. Lapushka Presented by: K. Lapushka At present the A010 family includes three models (A011, A012 and A013) of high-precision PC-based time interval counters, which are tailored to meet different special requirements of SLR applications. Specifically, all models are capable of measuring continuously either a sequence of time intervals (up to 4680 in each cycle) between separate Start pulse and Stop pulses or between adjacent Start-stop pulses at the common input. Measurement of time intervals in every cycle is attended by Start pulse timing using internal real time clock (12.5 ns LSD). Measurement process can be controllable both by external signals (input pulse gating, measurement cycle synchronization) and by a user?s program. The counter?s models differ mainly by offered single shot RMS resolution (A011 - <40 ps and A012 - <20 ps; both in the measurement range from 100 ns to 209 ms). Compared to the A012, the model A013 offers additional operating mode allowing <10 ps RMS resolution in the measurement range from 1 mcs. Every counter is available both as a ready-to-use instrument (including custom-made options) and a set of hardware-software tools for embedding the counter in more complex measurement system. Operation of the counters is based on high-speed (<100 ns "dead time") single-channel event timing. Since both Start and Stop events are sequentially timed by the same hardware means, this provides high linearity and temporal stability of time interval measurement under time-varying operating conditions. Some experimental data, which characterize the main features of the counters, are presented. Oral presentation; received August 21, 2002 |
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| ILRS Timing Devices: Specifications, Error Analysis, BEST Calibration Practices | Van Husson |
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HTSI L. Stewart The time-of-flight measurement device is a key component in satellite laser ranging and is a limiting factor in absolute data accuracy, especially at the one millimeter level. Therefore; optimizing ILRS station timing performance is critical to achieving new scientific objectives. There are two different types of timing devices in use within the ILRS network of approximately 35 sites; the time interval counter and the epoch event timer. The time interval counter measures the time between two intervals (i.e., laser fire and satellite echo return). The event timer records the epochs of events, from which a time interval between laser fire and satellite echo events is derived. The systematic error sources of both timing principles are very similar; however, the magnitude of the absolute errors can vary significantly depending upon manufacturer specifications, calibration procedures, maintenance practices and the external timebase (i.e. the oscillator). Currently, more than ú of the ILRS sites have time interval units, which were manufactured by either Stanford Research, Hewlett-Packard, or the Latvian University. Less than ÿ of the ILRS sites have event timers, which were manufactured by either Peso Consulting andThales (formerly Dassault), Electro-Optics Systems, Honeywell Technology Solutions Inc. or EG&G. Based on manufacturer specifications and ILRS network performance in the areas f single shot precisions and long-term range bias stabilities, pico-second event timers can achieve one mm absolute ranging accuracies. Oral paper; received August 22, 2002 |
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| An ultra stable event timer | Etienne Samain |
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OCA An ultra stable event timer has been designed at OCA (Observatoire de la CÙte d'Azur). It includes a vernier, a logic counter, and a 100 MHz frequency synthesis. The event timer has a precision of 2 ps and a linearity in the range of 1 ps. The thermal drift of the 100 MHz synthesis is very low. The dead time between two consecutive events is 10 µs. The device has a RS422 serial port to exchange data. An automatic internal calibration permits to improve the long-term time stability. A prototype of the device is actually working at OCA. A space design is also under study for the space segment of the T2L2 Project (Time Transfer by Laser Link). Oral paper; received August 23, 2002 |
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| Counter Calibrations at Zimmerwald | Werner Gurtner |
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Astronomical Institute, University of Bern Johannes Utzinger The paper describes the Stanford timer calibration procedures performed at Zimmerwald after the Herstmonceux reference calibration during the EUROLAS workshop in March 2002. One of the surprising results was the problem two out of the three Zimmerwald counters showed when driving the counters with an external 5 MHz reference frequency. The calibration values have been applied to the submitted ranges since end of May 2002. Oral paper; received August 26, 2002 |
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| Portable - Pico Event Timer Upgrade | Karel Hamal |
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Czech Technical University Ivan Prochazka To reach the millimeter satellite laser ranging accuracy the Portable - Pico Event Timer (P-PET, London) was upgraded to < 3 picoseconds jitter and advanced range gating. The capability to cooperate with the multi kiloHertz laser ranging systems was added. Oral paper; received August 22, 2002 |
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| Operational Performance of GPS Steered Rubidium Oscillators | Loyal Stewart |
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NASA Satellite Laser Ranging, Sustaining Engineering The use of the GPS Steered Rubidium Oscillator as a Time and Frequency Standard for the NASA Satellite Laser Ranging Network had been proposed as early as 1994. This is when initial field-testing was done at the Greenbelt station, operating a custom GPS Steered Rubidium Oscillator concurrently with the stations Cesium Beam Standard (HP 5061A). As this technology made steady improvements, it was decided in May of 1999 to replace all of the networks aging Cesium Beam Standards with the TrueTime XL-DC GPS Time and Frequency Receiver. This poster will describe the basic theory of operation of the GPS Steered Rubidium Oscillator. It will offer examples of actual system performance of the XL-DC units installed at various NASA SLR Stations. Also it will show pre and post Selective Availability performance, as well as laboratory data detailing Allan Deviation and phase performance of various GPS steered oscillators. Poster presentation; received August 19, 2002 |
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Last Updated:
September 20, 2002
