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					                                                                           Elektronikas un    Institute of
                                                                              Datorzinātņu    Electronics and
                                                                                  Institūts   Computer Science




      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
                                                                            Elektronikas un    Institute of
                                                                               Datorzinātņu    Electronics and
                                                                                   Institūts   Computer Science
   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 IECS is 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
      with SATELLITE LASER RANGING (SLR). The research is conducted in Time
      Measurement Laboratory by scientific/ engineering group currently consisting of 10
      specialists where four of them have doctoral degree.



 ESA INSTITUTIONAL AND INDUSTRIAL CAPABILITIES AUDIT IN LATVIA. Riga, 22 March, 2010
                                                                           Elektronikas un       Institute of
                                                                              Datorzinātņu       Electronics and
                                                                                  Institūts      Computer Science
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.

                                                         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




         Our R&D activity is focused on the Time-Of-Flight (TOF) measurements that
                               represent an integral part of SLR


ESA INSTITUTIONAL AND INDUSTRIAL CAPABILITIES AUDIT IN LATVIA. Riga, 22 March, 2010
                                                                           Elektronikas un    Institute of
                                                                              Datorzinātņu    Electronics and
                                                                                  Institūts   Computer Science
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-scale projects in the former USSR. In
particular, in 1980ies we have cooperated with the Lebedev Physical Institute of 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.


                                                            ILRS laser network


ESA INSTITUTIONAL AND INDUSTRIAL CAPABILITIES AUDIT IN LATVIA. Riga, 22 March, 2010
                                                                           Elektronikas un    Institute of
                                                                              Datorzinātņu    Electronics and
                                                                                  Institūts   Computer Science
 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.


ESA INSTITUTIONAL AND INDUSTRIAL CAPABILITIES AUDIT IN LATVIA. Riga, 22 March, 2010
                                                                            Elektronikas un    Institute of
                                                                               Datorzinātņu    Electronics and
                                                                                   Institūts   Computer Science
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), allowing a wide application of typical
    DSP tools instead of intricate analog circuits. This results in high performance of event
    timers combined with high reliability in operation and 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).




 ESA INSTITUTIONAL AND INDUSTRIAL CAPABILITIES AUDIT IN LATVIA. Riga, 22 March, 2010
                                                                           Elektronikas un    Institute of
                                                                              Datorzinātņu    Electronics and
                                                                                  Institūts   Computer Science
 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.



  SERVICES
        They concern mainly development of customized event timer systems for
        various applications including but not limited to SLR.



ESA INSTITUTIONAL AND INDUSTRIAL CAPABILITIES AUDIT IN LATVIA. Riga, 22 March, 2010
                                                                             Elektronikas un    Institute of
                                                                                Datorzinātņu    Electronics and
                                                                                    Institūts   Computer Science
  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 30 units of such
                  product have been made and delivered for ILRS network.

  ESA INSTITUTIONAL AND INDUSTRIAL CAPABILITIES AUDIT IN LATVIA. Riga, 22 March, 2010
                                                                           Elektronikas un    Institute of
                                                                              Datorzinātņu    Electronics and
                                                                                  Institūts   Computer Science
    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 - March 2008 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.



ESA INSTITUTIONAL AND INDUSTRIAL CAPABILITIES AUDIT IN LATVIA. Riga, 22 March, 2010
                                                                           Elektronikas un    Institute of
                                                                              Datorzinātņu    Electronics and
                                                                                  Institūts   Computer Science
 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 daytime SLR.
   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.


ESA INSTITUTIONAL AND INDUSTRIAL CAPABILITIES AUDIT IN LATVIA. Riga, 22 March, 2010
                                                                           Elektronikas un    Institute of
                                                                              Datorzinātņu    Electronics and
                                                                                  Institūts   Computer Science
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
      Compact Riga Event Timer (experimental model) known to us.




  The mentioned ambitions can be satisfied only 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.


ESA INSTITUTIONAL AND INDUSTRIAL CAPABILITIES AUDIT IN LATVIA. Riga, 22 March, 2010

				
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