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International Technical Workshop WPLTN-2012
- RUSSIAN LASER RANGING NETWORK AND ITS APPLICATION FOR GLONASS GEODETIC AND EPHEMERIS-TIME SUPPORT

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Future requirements for GLONASS geodetic and ephemeris-time support
In accordance with the Federal program "GLONASS" for 2012-2020 should be solved problem of increasing the accuracy of the following indicators: positioning accuracy with no additional systems............................................................................. < 0.6 m (2.8 m); positioning accuracy with additional systems (on-line operation)..................................................< 0.1 (1 ); (in the posterior mode)...................................... 0.03 (0.1 ); uncertainty in determining the time of the user in the system time scale....................................................< 1 (5 ); uncertainty of reference of the Federal Geocentric Coordinate System to the Earth center of mass............< 0.01 (0.5 ); uncertainty of translation of the Federal Geocentric Coordinate System by GLONASS ephemeris..............< 0.02 (0.2 )

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, - c The accuracy of geodetic, ephemeris and frequency-time parameters of GLONASS must be improved to the level of tenths of centimeter and tenths of a nanosecond


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Laser techniques to improve the accuracy of geodetic and ephemeris-time support GLONASS - , - In order to improve the accuracy of geodetic and ephemeris-time support GLONASS developed new laser measuring technology, which are realized through inter-satellite laser navigation and communications system and Russian laser ranging network
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Inter-satellite laser navigation and communications system

Russian laser ranging network


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The use of laser data to improve the accuracy of GLONASS ephemeris support

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Improving accuracy of the ephemeris support with two-way laser ranging
The result of applying in GLONASS Measurement method using SLR

GLONASS ephemeris control with millimeter level Comparison of laser range and the projection of the ephemeris data NSC to the inclined range. Comparison orbit of NSC obtained from accuracy
laser measurements and obtained from monitor stations

Control of translation of the Federal Geocentric Determination the coordinates of sites from laser observation of SC Coordinate System by GLONASS ephemeris with Lageos (Blits) and comparison with coordinates of the same site millimeter level accuracy obtained from laser observation of NSC Glonass and data of
navigation message


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The use of laser data to improve the accuracy of GLONASS geodetic support


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Improving accuracy of the geodetic support with two-way laser ranging
The result of applying in GLONASS Measurement method using SLR Refinement of coordinates of measurement means, Determination the coordinates of sites from laser observation refinement of reference FGCS to the Earth center of of SC Lageos (Blits) and network adjustment, including mass, refinement FGSC to ITRF translation parameters collocation data SLR and GMS with millimeter level accuracy Formation of combined solutions, harmonization of the Laser observation of SC Lageos (Blits) and NSC Glonass on measurement model of the orbit, Earth orientation collocation sites SLR, VLBI, GMS parameters and sites coordinates with millimeter level accuracy


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Stations of the Russian laser ranging network
Third-generation SLR station (in operation since 1982 in Komsomolsk-in-Amur)

Telescope with two optical systems with a diameter of 500 mm for laser ranging and angle measurements and technical building


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Stations of the Russian laser ranging network
Fourth-generation SLR station (in operation since 1999 in Moscow region)

Telescope with two optical systems with a diameter of 600 mm and 200 mm for laser ranging and angle measurements and its shelter


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Stations of the Russian laser ranging network

Fourth-generation SLR station (in operation since 2003 in Savvushka, Altay region)

Telescope with three optical systems for laser ranging, angular coordinates measurements and for obtaining detailed images. General view of the first stage of the Altay optical-laser center


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Stations of the Russian laser ranging network

Mobile version of the fourth-generation SLR station (in operation since 2006 at the Baikonur cosmodrome)


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Stations of the Russian laser ranging network
Serial fifth- generation compact SLR station (Observatory "Svetloe" of the Institute of Applied Astronomy of the Russian Academy of Sciences)

Telescope with two optical systems with a diameter of 250 mm in the mount with gearless drive and optical sensors for laser ranging and angle measurements and the tower


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Stations of the Russian laser ranging network

Fundamental site of collocation VLBI, SLR and GMS
(Observatory "Svetloe" of the Institute of Applied Astronomy of the Russian Academy of Sciences)


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Location of Russian laser ranging network stations
The main characteristics of the Russian network Number of stations (2012 / 2013 ) ............10 / 24 Operation range.............................> 25 000 km Normal point accuracy...........................3-8 mm Performance..............................50-100 NP/day

10 stations brought into service:
· · · · three stations (Altai, Moscow region and Komsomolsk-on-Amur) in the ground segment of GLONASS; three stations form a collocation with VLBI stations (Svetloe, Zelenchukskaya, Badary); two stations are part SVOEVP (Baikonur station and optical observations station Arkhyz); Two stations are placed on sites of VNIIFTRI (Irkutsk and Mendeleev).


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Main tasks and technical tools of the frequency-time support of GLONASS
Main tasks of the frequency-time support of GLONASS
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SC «Glonass»

Formation GLONASS system time scale, measurement and maintenance of its differences from UTC (SU); Measurement of differences between onboard time scale and system time scale and the formation of time-frequency corrections.

SC «Glonass»

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Onboard synchronizing device

Onboard synchronizing d e v ic e

UTC (SU)
Calibration tools

GNSS monitor station

Two-way RF rangefinder

GNSS monitor station

Central synchronizer (main) Calibration tools

GNSS monitor station

Central synchronizer (backup)
Calibration tools

SVO EVP

System control center


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- : The accuracy of existing tools and methods of frequency-time support
· · · · · · ...................2-3 ; .....................2-5 ; ..................1-10 . Accuracy of comparison of onboard and ground time scales at the time of measurement.................2-3 ns; Accuracy of comparison of the time scales of remote time and frequency standards.........................2-5 ns; Calibration accuracy of the GNSS monitor stations......................................................................1-10 ns.

- : · · ...................< 0.1 ; ......................< 0.1 .

Experimental laser system for GLONASS synchronization control will improve the accuracy of time-frequency information: · · Accuracy of comparison of onboard and ground time scales at the time of measurement................< 0.1 ns; Accuracy of comparison of the time scales of remote time and frequency standards ........................< 0.1 ns.


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Principle of laser measurements of differences of onboard and on-ground time scales
Onboard module
Onboard synchronizing device

Time interval counter

Photoreceiver SC Glonass-M

t

stop (time of pulse arrival in onboard time scale)

T

(differences of time scales)

Laser retroreflector

SLR station

Telemetry radiolink

t
On-ground module Photoreceiver Laser transmitter SLR station photoreceiver Time interval counter two-way pulse delay

stop



Time interval counter Local or central synchronizer

t

start (pulse start time in ground time scale)

Data processing center

Link

L aser pseudorange

L aser range

Differences o f t im e s c a le s

S = c(ts

top

­ tstart)

R = c / 2

T = ( R ­S) / c


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Composition and principle of operation of on-ground module of one-way SLR station

On-ground module
Op t i c a l t i m e s t a m p

L a s e r p u ls e

F ib e r lin k a n d lo o p

Photoreceiver

Laser transmitter Time interval counter
T wo - wa y t i m e d e l a y T o lin e o f communication with data center

Interface equipment

Time interval counter
Time of laser pulse starts

Computer

Photoreceiver

Central synchronizer

Composition of module: interface equipment, fiber link with fiber loop, measurement photoreceiver and time interval counter. Principle of operation: start time of the laser pulse is measured in the scale of CS using time interval counter by measuring intervals between optical time stamp and laser pulse with the calibration correction continuously measured using fiber loop. Uncertainties of a single measurement start time of the laser pulse...............................................................................................not more than 90 ps. Uncertainties of a multiple measurement time scales differences.........................................................................................................less than 10 ps.


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Composition and principle of operation of onboard module of one-way SLR station
1 PPS

Controlled oscillator 200 MHz

Time interval counter

Processor

Memory

Onboard synchronizer device

Phase lock loop
Synchronization unit

Mosaic photoreceiver

Onboard module
L a s e r p u ls e of SLR station to telemetry radiolink

Composition of module:

mosaic photoreceiver device, time interval counter, processor with memory, synchronization unit with controlled oscillator and phase lock loop. arrival time of the laser pulse in time scale of onboard synchronizer is measured using time interval counter of the relative to stable time scale synchronized with onboard synchronizer device.

Principle of operation:

Uncertainties of a single measurement of arrival time of the laser pulse.........................not more than 130 ps. Uncertainties of a multiple measurement of time scales differences.......................................less than 10 ps.

Onboard module, mounted on the SC Glonass-M


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Application of one-way SLR for improvement of accuracy of the time-frequency support of GLONASS


- 0.1 0.1



The result of applying in GLONASS
Frequency-time correction control with accuracy 0.1 nc Remote on-ground time scales control with accuracy 0.1 nc

Measurement method using SLR
Determination of difference of laser range and laser pseudorange

Comparison of on-ground time scales with a time scale of the same NSC Calibration of monitor stations with centimeter level Comparison of laser pseudorange and RF pseudorange accuracy Calibration of two-way RF rangefinders with millimeter level Comparison of laser range and radiofrequency range accuracy


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