Tag: GLONASS-K2

Directions 2022: A new epoch for GLONASS
Figure 1. GLONASS high inclined space complex. (Image: Institute of Navigation Technology JSC)

The digital transformation of the global economy requires precise time synchronization and valid object position information. Global navigation satellite systems (GNSS) are the most accurate tool for such tasks.

This year will be 40th anniversary of the launch of the first GLONASS satellite, and we see that the quality of navigation services is driven by the characteristics of today’s satellite navigation signals.

The first fourth-generation Glonass-K2 #13L satellite is scheduled for launch in 2022. It will broadcast a full ensemble of navigation signals — both Frequency Division Multiple Access (FDMA) signals in the L1 and L2 bands and Code Division Multiple Access (CDMA) signals in the L1, L2 and L3 bands. This long-awaited launch will cap a 10-year effort and begin to provide a new platform by broadcasting all the CDMA signals through a single antenna array on the satellite’s geometric axis.

The FDMA antenna array is displaced by 0.9 m from this axis, but this arrangement is done on only two satellites. The next Glonass-K2 satellites, which will be launched beginning in 2024, will have a single antenna array for all navigation signals.

The final second-generation Glonass-M satellite, scheduled to be placed in orbit next year, will provide services by open FDMA signals in the traditional bands at 1.6 GHz and 1.25 GHz. This satellite will be the seventh Glonass-M vehicle able to broadcast GLONASS L3 CDMA signals. There are only two Glonass-K satellites broadcasting this signal now, but more satellites with such a signal will be activated by the end of testing of the GLONASS modernized ground control facility.

We expect the number of satellites able to provide this service to increase by two per year as we replace Glonass-M satellites with Glonass-K and Glonass-K2 satellites.

As of this writing, 15 satellites (62% of the constellation) are working past their guaranteed life times, limiting our ability to increase the system’s accuracy. For the last decade, the signal-in-space range error (SISRE) was 1.4 m, despite the fact that newly launched satellites provide a SISRE of about 0.8 m.

Glonass-K satellites will be launched to maintain the orbit constellation within the next three years, and the accuracy of their signals will be the same or even better. These satellites have a single antenna array for all three bands and could broadcast either FDMA or CDMA signals.

In 2022, the constellation orbits will increase to six satellites in three planes, as we aim to increase the navigation service accuracy and availability (FIGURE 1). See TABLE 1 for satellite orbit parameters. This constellation will make it possible to increase navigation accuracy in the Eastern Hemisphere by about 25% through decreasing the value of the geometric factor.

Table 1. Augmented orbit constellation parameters.

Additionally, this will greatly improve the availability of the GLONASS navigation service in difficult conditions, such as locations where current users can only receive navigation signals from satellites at least 25° above the horizon. New constellation satellites will be based on the Glonass-K platform, which has passed in-orbit qualification and proved it can provide SISRE at 0.3 m. The preliminary design proved that satellites on this platform could provide an in-orbit SISRE below 0.4 m with standard cesium on-board clocks. This signal-in-space accuracy level with valid ionospheric and tropospheric model data from the navigation signal will allow users to receive a position determination error below 2 m in the plane. Navigation services from these satellites will be provided by the CDMA signal in three frequency bands.

The new satellite will weigh about 1,000 kg and be launched into orbit from both Russian spaceports (northern Plesetsk and eastern Vostochny) by the highly reliable Soyuz-2 rocket. The first launch is scheduled for 2026.

One of GLONASS’ important tasks is to transmit the UTC (SU) national time scale to consumers. Over the past few years, significant results have been achieved in this area.
- A complex of high-precision measuring instruments to compare the national coordinate timescale UTC (SU) with the GLONASS timescale was put into operation. These instruments include a transported quantum clock that provides timescale storage with an uncertainty of no more than 1 ns at an observation interval of one day, and with a transportation time of no more than 12 hours. It also provides duplex comparisons of timescales, comparing objects with the permissible uncertainty of ±1.5 ns.
- Timescale storage complexes of secondary and working standards of time and frequency VET1-5 (Irkutsk), VET 1–19 (Novosibirsk), VET 1–7 (Khabarovsk) and RET1-1 (Petropavlovsk-Kamchatsky) were modernized and put into operation, providing an overall uncertainty of 3 · 10^-15 and with a maximum permissible shift of the timescale of the complex relative to the national timescale UTC (SU) of ± 10 ns.
- An optical ground-based frequency reference on cold strontium atoms was developed with an uncertainty of reproduction of the frequency unit and time of no more than 1 · 10^-17 .
- A keeper of time and frequency units was developed on the basis of a “fountain” of rubidium atoms having a frequency instability of no more than 2 · 10^-16 for equipping the standards of time and frequency units and subsequent transmission of more accurate time-frequency information to precision ground and onboard equipment and GLONASS systems.
- A developmental prototype of the national timescale storage complex of the Russian Federation was developed on the basis of a new generation of hydrogen keepers.
The application of the newly developed technical equipment made it possible to significantly reduce the maximum displacement of the national timescale relative to the International Coordinated Time Scale (UTC), which in 2020 was less than ± 3 ns (FIGURE 2). The UTC (SU) timescale ranks among the best national implementations of UTC, according to the International Bureau of Weights and Measures (BIMP).

Figure 2. Displacement of national timescales relative to Universal Coordinated Time (UTC). (Image: VNIIFTRI FSUE)

Many important events are coming for GLONASS users in 2022. They will improve the user characteristics and lay the foundation for further development of the system.

Sergey Karutin is general designer of the Russian GNSS program GLONASS.

Nicolay Testoedov is CEO of JSC Information Satellite Systems Reshetnev (ISS JSC), a Russian satellite manufacturing company.

Sergey Donchenko is general director of the Federal State Unitary Enterprise, Russian metrological institute of technical physics and radio engineering, VNIIFTRI FSUE.
January 18, 2022
Directions 2021: GLONASS on the verge of a new decade
By Yury Urlichich, first deputy director general of Roscosmos State Space Corporation
Sergey Karutin, designer general of GLONASS
Nikolay Testoedov, director general, Information Satellite Systems JSC
Sergey Koblov, director general, Central Research Institute of Machine Building JSC

The year 2020 heralds the end of another 10-year stage of development of the Russian GLObal NAvigation Satellite System (GLONASS). Reconstruction of our orbital constellation, started in 2006, is bearing its fruit. Today, it is hard to imagine one’s daily life without the continuous artificial radio-navigation field provided to users globally by the GLONASS orbital constellation since 2011.

GLONASS signals are employed to perform a wide range of tasks, such as
- Saving lives in road accidents
- Air, ground and naval traffic monitoring and control
- Network synchronization of mobile cellular communications
- Monitoring and enabling the energy grid, road travel, agricultural equipment operation, and more.
Our orbital constellation is built upon a base of second-generation spacecraft (SC) — Glonass-M SC — that was developed in 2003 and has demonstrated outstanding operational capacity: 14 SC are already operating well beyond their expected lifetimes, and four SC celebrate their 13th birthday in orbit this year. Activities focused on improving GLONASS accuracy have not stopped for a single day.

If we go back to 2014, the SC-based ranging offset (which specialists refer as equivalent ranging deviation) was 1.4 m. We managed to achieve 0.9 m offset on Jan. 30, 2020, and during the same week the offset did not exceed 1.15 m. Furthermore, the penultimate series-produced Glonass-M SC (Cosmos-2545), which was launched on March 30, demonstrated basic service ranging accuracy of 0.38 m on a daily interval and 0.63 m accuracy on the “best week” interval.

Glonass-K No. 15 was launched into orbit on Oct. 25. (Photo: Roscosmos)

It was Glonass-M SC development that enabled users around the world to gain access to the first dual-frequency navigation service, which is necessary for decreasing the effects of the ionosphere on navigation accuracy.

The third generation of GLONASS SC — Glonass-K — was successfully launched from the Plesetsk launch site on Oct. 25. This SC will provide users with a broader range of capabilities — and a more accurate and informative signal in the L3 frequency band. Further gradual rejuvenation of the GLONASS constellation will ensure the ever-improving quality of our navigation services.

Two Glonass-K2 SC are planned for the launch campaign in 2021, and all the experience accumulated during the development of third-generation GLONASS SC (Glonass-K) will be implemented in the fourth-generation SС. Glonass -K2 is a unique SC: It will provide users with five navigation signals, its accuracy will be within 0.3–0.5 m, and its assured expected lifetime will be at least 10 years.

High-Orbit Space Complex

GLONASS developers remain focused on user requirements. Recent surveys show a growing demand for high-quality navigation services in difficult conditions where the SC is visible at more than 25° above the horizon. To satisfy these needs with the implementation of new CDMA signals, development of the GLONASS High-Orbit Space Complex (HOSC) will begin in 2021. Its first SC will be launched in 2025, and complete deployment of the constellation including six SC in three or six planes will be finished by the end of 2027.

As a result, the accuracy and availability of navigation in difficult conditions will improve in the Eastern Hemisphere. But the major anticipated outcome of the HOSC implementation is assured two-fold coverage of the Northeastern segment of the globe with high-accuracy differential navigation data by GLONASS and other GNSS.

HOSC implementation will ensure 25% navigation accuracy improvement over the Eastern hemisphere. Glonass-K SC will be used as a base platform for HASC deployment due to its excellent record.

Ground Control at the Titov Main Test Space Center established a stable telemetry connection with the new satellite shortly after launch. (Photo: Roscosmos)

User Interface Harmony

One of the most important tasks for the year 2020 is harmonization of the GLONASS user interface. As we already mentioned, the signal propagation environment has a strong effect on navigation accuracy; therefore, new issues of GLONASS Interface Control Documents (ICD) are being prepared for publication.

We anticipate that GLONASS end-user accuracy improvement will be achieved through introducing additional information into reserve bits of navigation frames, including relevant parameters of an ionospheric model.

The ICD will contain operating methods with parameters of the ionospheric model and definite recommendations designed for compensation of ionospheric delays by both single-frequency and dual-frequency receivers, as well as generalized methods for compensating for tropospheric delays.

Changes in the ICD concerning FDMA and CDMA signals will ensure backward compatibility and uninterrupted operation for the existing range of user navigation equipment.
December 14, 2020
Directions 2019: High-orbit GLONASS and CDMA signal

Yury Urlichich, First Deputy Director General, Roscosmos. (Photo: Roscosmos)

By Yury Urlichich
First Deputy Director General, Roscosmos State Space Corporation

The year 2019 will bring GLONASS users many new opportunities. Improving navigation services specifically at the user level, primarily assessed in terms of signal accuracy and availability, is our primary goal. Improving navigation accuracy is based on space system development, including both the orbital constellation (space segment) and ground control segment.

CDMA Signal

A Glonass-K2 spacecraft (SC) launch followed by flight testing will be the most important event in space segment development. This SC will enable navigation not only using legacy FDMA signals available for users for more than 35 years, but simultaneously with a full row of CDMA signals in all GLONASS frequency bands: L1, L2 and L3.

Currently the major navigation error contributors are the radio signal trajectory and the user terminal receiving environment. The new signals will allow lowering the hardware-dependent SC-user ranging error by an order of magnitude, reducing the influence of signal reflections from buildings, constructions and landscape (multipath effect), thus enabling their effective use for high-precision navigation with real-time errors below 0.1 m.

We are also finalizing in 2019 the newest edition of the GLONASS Interface Control Document containing recommended models for evaluation of tropospheric and ionospheric delays. Our forecasts show two times navigation accuracy improvement for users of these models.

High-Orbit GLONASS

Improving signal availability is equally important. As large urban areas demonstrate growing use of navigation technologies, these users experience difficulties receiving signals from SC flying below the elevation angle of 25°. To provide a navigation solution in such environments, we will begin development of High-Orbit GLONASS in 2019.

High-Orbit GLONASS will consist of six SC distributed among the three orbital planes and forming two SC ground traces with 64.8° orbit inclination, eccentricity of 0.072, revolution period of 23.9 hours, geographical longitude of the ascendant angle – 60°, 120° (See figure below).

High-Orbit GLONASS — ground track in red. (Image: Roscosmos)

The new generation space segment will be populated with Glonass-B satellites designed on the proven Glonass-K platform, successfully providing services since 2012. Users will be offered the full spectrum of new CDMA signals in all three GLONASS frequency bands.

The first Glonass-B is planned for launch in 2023, with the full constellation of six SC to be deployed by the end of 2025, increasing by 25% the navigation accuracy in the Eastern hemisphere.

The satellite mass below 1,000 kg allows Angara-A5, the new Russian heavy launch vehicle, to perform a dual launch from either Plesetsk or Vostochny launch sites.

Much attention is being paid to the signal characteristics’ stability throughout the whole system lifecycle. For this purpose, ROSCOSMOS developed the GLONASS Monitoring and Performance Assessment System for civil users, including the distributed network of monitoring stations abroad, and dedicated radio telescopes capable of analyzing the navigation signal structure and power on the Earth’s surface.

Currently the planned user range error (URE) for signal in space is 1.4 m. Feb. 26, with URE of 1.13 m, became the best day of the ten-month long monitoring in 2018. Moreover, this value tends to decrease as Glonass-M satellites operating beyond their guaranteed life period are being replaced. For instance, on Nov. 3, Glonass-M satellite No. 57 launched, replacing No. 16 after almost 12 years of operation in orbit.

As already mentioned, the Glonass-K2 is planned for launch in 2019. Compared to Glonass-M and Glonass-K satellites, Mission Definition Requirements for Glonass-K2 define URE to be 0.3 m, qualitatively improving GLONASS user performance.

The new on-board frequency standard based on passive hydrogen maser (PHM) will also contribute to better performance. This PHM is undergoing its ground tests and will be installed onboard the SC by the end of the year. Its relative 24-hour stability of better than 5×10-15 ensures the required URE.

December 12, 2018
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.

December 6, 2017
ISS Reshetnev to build 11 new GLONASS-K satellites

ISS Reshetnev has signed a contract with Russian space agency Roscosmos to build 11 new GLONASS satellites, according to the Roscosmos website. ISS Reshetnev is Russia’s leading spacecraft developer and manufacturer.

ISS Reshetnev will build nine GLONASS-K1 satellites and two GLONASS-K2 satellites. The GLONASS-K1 satellites will be transition satellites between the existing GLONASS-M satellites and the future GLONASS-K2 satellites.

GLONASS-K2 satellites will begin flight tests in 2018, with mass production of GLONASS-K2 satellites to begin in the 2019–2020 time frame.

The GLONASS-K1 satellites are expected to have a 10-year lifetime. The first of the new batch of GLONASS-K1 satellites will be launched in 2018.

Flight tests of the two GLONASS-K1 satellites now in orbit have been completed.

— written with assistance from Richard Langley, “Innovation” editor.

March 1, 2016
Final GLONASS-M Satellite Passes Tests

Artist’s rendering of the GLONASS-M satellite.

News courtesy of CANSPACE Listserv.

The last of the GLONASS-M satellites (serial number 61) has been built and has passed all acceptance tests, reports the July 20 issue of Sibirskii Sputnik (Siberian Satellite), the internal newspaper of ISS Reshetnev. It will join eight other GLONASS-M satellites in storage on the ground awaiting launch between now and 2017.

Following the launch of the last GLONASS-M satellite, 11 GLONASS-K1 satellites will be launched through 2020. The GLONASS-K2 model is currently under development and will be launched beginning in 2017, according to a presentation made by ISS Reshetnev at the Workshop on the Applications of Global Navigation Satellite Systems held in Krasnoyarsk in May 2015.

August 3, 2015
First Launch of GLONASS-K2 Satellite Planned for 2018

The first GLONASS-K2 spacecraft will be launched into orbit in 2018, said Nicholas Testoyedov, the CEO of Information Satellite Systems Reshetnev, as reported by the Assotsiatsiya GLONASS/GNSS Forum.

“In 2018, we are preparing to launch the first satellite of the series GLONASS-K2,” Testoyedov said. “This satellite has advanced features. In the development of the navigation functions, new code division signals will be emitted, so it will provide more accurate positioning for users and more accurate tethering in those systems where important accurate time reference is required, such as in computer systems, connected devices, and so on.”

Testoyedov added that the GLONASS-K2 satellite will have equipment installed that makes it compatible with the international search and rescue system Cospas–Sarsat.

Budget Cuts. The budget of the GLONASS federal target program (FTP) for 2015 will be cut by more than 5 billion rubles, according to Russian news reports. After spending cuts, the budget for the current year will amount to 42.5 billion rubles, a cut of more than 10 percent, which is the average size of cuts for the entire “Space activities of Russia for 2013-2020” budget group.

April 2, 2015