High-Performance Event Timers for Satellite Laser Ranging

1. HIGH-PERFOMANCE EVENT TIMERS FOR SATELLITE LASER RANGING Jurijs Artjuhs /Yuri Artyukh/ Head of Time Measurement Laboratory Institute of Electronics and Computer Sciences Riga, LATVIA artyukh@edi.lv www.edi.lv ESA INSTITUTIONAL AND INDUSTRIAL CAPABILITIES AUDIT IN LATVIA. Riga, 22 March, 2010

2. ESA INSTITUTIONAL AND INDUSTRIAL CAPABILITIES AUDIT IN LATVIA. Riga, 22 March, 2010 ABOUT US Institute of Electronics and Computer Science(IECS) was founded 50 years ago (jubilee!), and was the largest scientific institution in Latvia for long time. Currently IECSis a public research institution with staff about 90 specialists, and provides applied research in the following basic directions: • Advanced Digital Signal Processing (randomized, event-driven, etc.), • Smart sensors and networked embedded systems, • Image acquisition and real-time processing, • UWB signal generation and high-sensivity acquisition, • Wired/wireless network management • and INNOVATIVE TECHNOLOGIES FOR HIGH-PRECISION EVENT TIMING The last direction of the research is the most closely related with the Space, namely withSATELLITE LASER RANGING(SLR). The research is conducted in Time Measurement Laboratoryby scientific/ engineering group currently consisting of 10 specialists where four of them have doctoral degree.

3. Satellite Distance Near < 500 km Middle < 1 500 km Distant (geodetic) ~ 6 000 km Very distant (GPS) ~ 20 000 km Geo-stationary 36 000 km SLR single shot RMS resolution: currently 1-2 cm in the near future 2-5 mm ESA INSTITUTIONAL AND INDUSTRIAL CAPABILITIES AUDIT IN LATVIA. Riga, 22 March, 2010 FOCUS OF OUR ACTIVITY WITHIN SLR In SLR a global network of stations measure the instantaneous round trip time of flight of ultra-short laser pulses to satellites. This provides instantaneous range measurements of very high precision, which can be accumulated to provide accurate orbits and a lot of important products for a wide range of scientific,engineering, and operational applications. Our R&D activity is focused on the Time-Of-Flight (TOF) measurements that represent an integral part of SLR

4. ILRS laser network ESA INSTITUTIONAL AND INDUSTRIAL CAPABILITIES AUDIT IN LATVIA. Riga, 22 March, 2010 SHORT HISTORY OF OUR ACTIVITY IN SLR We conduct R&D activity related with TOF measurement for more than 30 years. As a leader in this field, we were in a number of large-scaleprojects in the former USSR. In particular, in 1980ies wehave cooperated with the Lebedev Physical Instituteof RAS in development of the laser network «Crimea» for the Lunar and satellite ranging. Starting in 2000,our activity in SLR area was re-oriented to the demands worldwide. Specifically,the main efforts in development of Riga event timers were directed to meet the current demands of “International Laser Ranging Service” (ILRS) in high-performance timing instruments for ILRS laser network.

5. ESA INSTITUTIONAL AND INDUSTRIAL CAPABILITIES AUDIT IN LATVIA. Riga, 22 March, 2010 OUR CURRENT SPECIALIZATION As known, the SLR performance considerably depends on the performance of TOF measurements. Currently it is generally recognised that the epoch event timers should be used for TOF measurement to reach millimetre precision in range: • “If we truly wish to have 1mm systems we must migrate away from the interval timers in common use amongst the SLR community and convert to epoch timers.However epoch timers are very expensive and time consuming to build. …” • (from Summary of “International Laser Ranging Service” Workshop, Eastbourne,UK, October 2005) In view of that, our field of specialization is development and design of high-performance and reasonably priced epoch event timers for SLR and related applications. Scientific background of such activity is R&D results concerning innovative technologies for high-precision event timing.

6. ESA INSTITUTIONAL AND INDUSTRIAL CAPABILITIES AUDIT IN LATVIA. Riga, 22 March, 2010 WHY WE ARE THE BEST IN THE WORLD IN THIS FIELD • Experience • We have long experience of collaboration with SLR community. That allows well to understand the current problems in TOF measurement and find the best solution of them. Over many years we support close relationships with specialists of Riga SLR station that is the main proving ground for testing and applying of our devices. • Innovative technology • In the 2000-ties we invented and applied a completely new technology for designing high-performance event timers.Unlike traditional technologies,the new technology is based on special Digital Signal Processing (DSP), allowinga wide application of typical DSP tools instead of intricate analog circuits. This results in high performance of event timerscombined with high reliability in operationand low unit cost. • Growing demand • SLR community defines the Riga event timers as the best ones for SLR.In 2002, the fraction of Riga event timers in ILRS laser network was 8%. Currently it is about 30%. Subsequent growing of this percentage is expected as well as widening the application area of Riga event timers (e.g., on absolute gravimetry).

7. ESA INSTITUTIONAL AND INDUSTRIAL CAPABILITIES AUDIT IN LATVIA. Riga, 22 March, 2010 OFFERING THE PRODUCTS Along with usual publishing of our basic R&D results (mostly – at the ILRS Workshops), we develop and offer the Riga event timers for SLR community for practical applications. The offered product is periodically updated in view of the latest R&D results. The product represents a spin-off of our basic activity. It is made in the form of prototype carefully implemented and tested and is available on contract basis. The contract conditions can include certain customizing of the product on user request. The basic way of dissemination of the data concerning our new timing products within SLR community is their placement at our web page (www.edi.lv) and ILRS web page (http://ilrs.gsfc.nasa.gov) as well as announcements at the ILRS Workshops. They concern mainly development of customized event timer systems for various applications including but not limited to SLR. SERVICES

8. ESA INSTITUTIONAL AND INDUSTRIAL CAPABILITIES AUDIT IN LATVIA. Riga, 22 March, 2010 PRODUCT DESCRIPTION • To meet different user demands, we have developed and offered an “adaptable-to-application” event timer that allows creating user-defined event timer systems in two basic configurations: • Networked system (event timer interacts with application via network) • Integrated system (timer’s software and application software are integrated) • Both systems are based on the same hardware and differ by software. • Main features: • Precision: 3-4 ps RMS • Event rate: • up to 20 MHz (in bursts) • up to 15 KHz continuously • Reasonable unit cost • Short manufacturing cycle • Customizing on user request The product performance is quite comparable with the best commercial products of such kind (e.g., with Advanced Event Timer from Honeywell). During 2005-2009 years 30units of such product have been made and delivered for ILRS network.

9. ESA INSTITUTIONAL AND INDUSTRIAL CAPABILITIES AUDIT IN LATVIA. Riga, 22 March, 2010 THE BEST PRACTICE OF APPLICATION • We have a number of ongoing agreements on scientific and technical collaboration with different European and Asian institutions from SLR community. Basically these agreements are aimed for the most efficient applications of Riga event timers. • The best results have been achieved in such collaboration with Chinese SLR stations where the Riga event timers are widely used in various applications, including but not limited to the conventional SLR*. • As an example, the experiment with time transfer by Laser link was carried out in July 2007 - March2008 at Chinese SLR stations. The experiment was directed to extremely precise synchronising of terrestrial clocks through Chinese satellite COMPASS-M1. In this experiment Riga event timers were used for onground measurements in parallel with onboard measurements, providing the data for clock comparison. * Reference: Zhang Zhongping et al., (Shanghai Astronomical Observatory, CAS), Yu. Artyukh (Institute of Electronics and Computer Science, Riga, Latvia ). Applications of Riga Event Timer at Shanghai SLR Station // Proceedings of the 16th International Workshop on Laser Ranging, Poznan, Poland, 2009, Vol.2, pp. 447- 453.

10. ESA INSTITUTIONAL AND INDUSTRIAL CAPABILITIES AUDIT IN LATVIA. Riga, 22 March, 2010 SERVICES We offer our knowledge, skill and experience for custom designs of high-performance event timer systems (including auxiliary electronics, application software, etc) strictly tailored to the specific user requirements. The Riga Event Timer System RTS-2006 represents an example of such system designed and built for Riga SLR station. Along with high-precision TOF measurement, the RTS-2006 provides pre-processing of STOP pulses to reduce the noise influence for daytimeSLR. Additionally the RTS-2006 precisely measures amplitude of each STOP-pulse to digitally correct the bias in satellite range.Embedded computer supports all real-time software functions, including satellite autotracking. Unlike the offering of almost completed product, such services are preferable for us, combining R&D and knowledge-based engineering. We hope to extend such activity, including our participation in International joint projects.

11. ESA INSTITUTIONAL AND INDUSTRIAL CAPABILITIES AUDIT IN LATVIA. Riga, 22 March, 2010 IS ONBOARD RIGA EVENT TIMER POSSIBLE? Some applications of satellite technologies (such as laser time transfer, one-way interplanetary laser ranging) need high-preformance onboard event timers. It seems that the Riga technology for event timing is well suited for onboard event timer design. • Achieved performance • Precision: 2 ps RMS • Event rate: 25 MHz • Size (one card): 160x175 mm • Power consumption: 7 W • is quite comparable with that for the high-precision onboard event timers known to us. Compact Riga Event Timer (experimental model) The mentioned ambitions can be satisfiedonly in close cooperation with experienced designers of space instrumentation. We are very interested to be in ESA programs and projects and in this way realise, among other ones, these ambitions.