Directions 2018: GLONASS focuses on user needs

By Sergey Karutin, GLONASS designer general;
Nicolay Testoedov, Director General, SC Information Satellite Systems;
and Andrey Tulin, Director General, SC Russian Space Systems

This year has marked the 35th anniversary of the first GLONASS launch. During these years, the world has made great strides through high tech, and now no modern society can progress without satellite-based navigation.

Today’s urban resident can hardly do without a smartphone planning his route through traffic, determining the paid parking site location or getting a reminder of parking session completion once he has left the parking lot.

The search for the nearest pharmacy, gas station, restaurant or any other point of interest is of vital necessity today. The growing dependence of modern society on navigation signals-in-space increases the responsibilities of GNSS providers. At the same time, users long for simplicity in getting quality services. That is why this year the GLONASS team is going to set up its most ambitious program: improving the quality of the GLONASS services at a user level.

The traditional GLONASS conception of signal-in-space accuracy is now being augmented by the user level performance estimation. Due to the fact that the signal propagation environment contributes a lot to the positioning error budget, it is obvious that users need information that would reduce the influence of signal propagation path on the positioning accuracy.

Glonass-M satellites currently form the core of the GLONASS constellation, and with six ground spares now in stock, they will continue to do so for at least the next eight years. Therefore, in 2018 the new edition of L1 and L2 FDMA Interface Control Documents are to be published which will include the ionospheric and tropospheric models recommended in the recently released GLONASS CDMA Signals ICDs.

Glonass-K2 satellite (artist’s rendering).

We plan to use the spare bits within the navigation superframe of FDMA signals to transmit ionospheric parameters described in the General Description of the GLObal NAvigation Satellite System with the Code Division Multiple Access Signals ICD.

Studies being performed demonstrate up to 70 percent reduction in impact of ionospheric refraction when using the adaptive model transmitted by the three parameters: the numerical factor for the peak TEC (Total Electron Content) of F2 ionosphere layer, the solar activity index and the daily geomagnetic activity index. In the new CDMA signal message, these parameters are initially provided.

To enable the unanimity of technologies for reducing the hydrostatic component of the tropospheric delay, which accounts for 80 percent of its value, the both FDMA and CDMA Signals ICDs will include the latitudinal tropospheric model based on the preliminary set tabular values.

The preliminary design review for the technical baseline of the fourth-generation Glonass-K2 satellite has been passed this year. The new cubic arrangement of the platform enables mitigation of unmodeled forces and transition of propellant tank to the satellite’s center of mass.

This provides for the relative position constancy for the satellite’s center of mass and the satellite’s antenna phase center during the satellite’s lifetime. This platform arrangement also accommodates the whole ensemble of navigation signals (both CDMA and FDMA) on the single phased-array antenna system.

Glonass-K2 is equipped with the new atomic frequency standard composed of the legacy quantum frequency standard based on the cesium beam tube and the passive hydrogen maser. The miniature PHM with the relative daily stability of 5×10^-15 will be installed onboard the satellite to be launched in 2020.

Introduction of the new satellite will enable a new constellation sustainment strategy — through the both dual launches by Angara-A5 launcher from Vostochny and single launches by Soyuz from Plesetsk — to provide on-demand replenishment of the constellation.

By 2020, when we celebrate the 25th anniversary of GLONASS full operational capability, all the efforts mentioned above will offer new quality of services to GLONASS users prioritized as per their needs.