Ресейлік спутниктік навигациялық жүйе GLONASS

Russian satellite navigation system

GLONASS (ГЛОНАСС, ; ) is a Russian satellite navigation system operating as part of a radionavigation satellite service. It provides an alternative to Global Positioning System (GPS) and is the second navigational system in operation with global coverage and of comparable precision. Satellite navigation devices supporting both GPS and GLONASS have more satellites available, meaning positions can be fixed more quickly and accurately, especially in built up areas where buildings may obscure the view to some satellites. GLONASS supplementation of GPS systems also improves positioning in high latitudes (north or south). Development of GLONASS began in the Soviet Union in 1976. Beginning on 12 October 1982, numerous rocket launches added satellites to the system until the completion of the constellation in 1995. In 2001, after a decline in capacity during the late 1990s, the restoration of the system was made a government priority, and funding increased substantially. GLONASS is the most expensive program of the Roscosmos, consuming a third of its budget in 2010. By 2010, GLONASS had achieved full coverage of Russia's territory. In October 2011, the full orbital constellation of 24 satellites was restored, enabling full global coverage. The GLONASS satellites' designs have undergone several upgrades, with the latest version, GLONASS K2, launched in 2023. In 2020, Glonass BDD LLC checked the information system for analyzing and preventing traffic accidents and published a digital safety rating for 3,000 km of Russian roads.

GLONASS is a global navigation satellite system, providing real time position and velocity determination for military and civilian users. The satellites are located in middle circular orbit at altitude with a 64.8° inclination and an orbital period of 11 hours and 16 minutes (every 17 revolutions, done in 8 sidereal days, a satellite passes over the same location). GLONASS's orbit makes it especially suited for usage in high latitudes (north or south), where getting a GPS signal can be problematic. The constellation operates in three orbital planes, with eight evenly spaced satellites on each. In the original GLONASS design, only obfuscated high precision signal was broadcast in the L2 band, but starting with GLONASS M, an additional civil reference signal L2OF is broadcast with an identical standard precision code to the L1OF signal. The open standard precision signal is generated with modulo 2 addition (XOR) of 511 kbit/s pseudo random ranging code, 50 bit/s navigation message, and an auxiliary 100 Hz meander sequence (Manchester code), all generated using a single time/frequency oscillator. The pseudo random code is generated with a 9 stage shift register operating with a period of 1 milliseconds. The navigational message is modulated at 50 bits per second. The superframe of the open signal is 7500 bits long and consists of 5 frames of 30 seconds, taking 150 seconds (2.5 minutes) to transmit the continuous message. Each frame is 1500 bits long and consists of 15 strings of 100 bits (2 seconds for each string), with 85 bits (1.7 seconds) for data and check sum bits, and 15 bits (0.3 seconds) for time mark. Strings 1 4 provide immediate data for the transmitting satellite, and are repeated every frame; the data include ephemeris, clock and frequency offsets, and satellite status. Strings 5 15 provide non immediate data (i. e. almanac) for each satellite in the constellation, with frames I IV each describing five satellites, and frame V describing remaining four satellites. The ephemerides are updated every 30 minutes using data from the Ground Control segment; they use Earth Centred Earth Fixed (ECEF) Cartesian coordinates in position and velocity, and include lunisolar acceleration parameters. The almanac uses modified orbital elements (Keplerian elements) and is updated daily. The more accurate high precision signal is available for authorized users, such as the Russian military, yet unlike the United States P(Y) code, which is modulated by an encrypting W code, the GLONASS restricted use codes are broadcast in the clear using only security through obscurity. The details of the high precision signal have not been disclosed. The modulation (and therefore the tracking strategy) of the data bits on the L2SF code has recently changed from unmodulated to 250 bit/s burst at random intervals. The L1SF code is modulated by the navigation data at 50 bit/s without a Manchester meander code. The high precision signal is broadcast in phase quadrature with the standard precision signal, effectively sharing the same carrier wave, but with a ten times higher bandwidth than the open signal. The message format of the high precision signal remains unpublished, although attempts at reverse engineering indicate that the superframe is composed of 72 frames, each containing 5 strings of 100 bits and taking 10 seconds to transmit, with total length of 36 000 bits or 720 seconds (12 minutes) for the whole navigational message. The additional data are seemingly allocated to critical Lunisolar acceleration parameters and clock correction terms.

At peak efficiency, the standard precision signal offers horizontal positioning accuracy within 5–10 metres, vertical positioning within , a velocity vector measuring within , and timing within 200 nanoseconds, all based on measurements from four first generation satellites simultaneously; newer satellites such as GLONASS M improve on this. GLONASS uses a coordinate datum named "PZ 90" (Earth Parameters 1990 – Parametry Zemli 1990), in which the precise location of the North Pole is given as an average of its position from 1990 to 1995. This is in contrast to the GPS's coordinate datum, WGS 84, which uses the location of the North Pole in 1984. As of 17 September 2007, the PZ 90 datum has been updated to version PZ 90.02 which differ from WGS 84 by less than in any given direction. Since 31 December 2013, version PZ 90.11 is being broadcast, which is aligned to the International Terrestrial Reference System and Frame 2008 at epoch 2011.0 at the centimetre level, but ideally a conversion to ITRF2008 should be done.

The main contractor of the GLONASS program is Joint Stock Company Information Satellite Systems Reshetnev (ISS Reshetnev, formerly called NPO PM). The company, located in Zheleznogorsk, is the designer of all GLONASS satellites, in cooperation with the Institute for Space Device Engineering (:ru:РНИИ КП) and the Russian Institute of Radio Navigation and Time. Serial production of the satellites is accomplished by the company Production Corporation Polyot in Omsk. Over the three decades of development, the satellite designs have gone through numerous improvements, and can be divided into three generations: the original GLONASS (since 1982), GLONASS M (since 2003) and GLONASS K (since 2011). Each GLONASS satellite has a GRAU designation 11F654, and each of them also has the military "Cosmos NNNN" designation.

The true first generation of GLONASS (also called Uragan) satellites were all three axis stabilized vehicles, generally weighing and were equipped with a modest propulsion system to permit relocation within the constellation. Over time they were upgraded to Block IIa, IIb, and IIv vehicles, with each block containing evolutionary improvements. Six Block IIa satellites were launched in 1985–1986 with improved time and frequency standards over the prototypes, and increased frequency stability. These spacecraft also demonstrated a 16 month average operational lifetime. Block IIb spacecraft, with a two year design lifetimes, appeared in 1987, of which a total of 12 were launched, but half were lost in launch vehicle accidents. The six spacecraft that made it to orbit worked well, operating for an average of nearly 22 months. Block IIv was the most prolific of the first generation. Used exclusively from 1988 to 2000, and continued to be included in launches through 2005, a total of 56 satellites were launched. The design life was three years, however numerous spacecraft exceeded this, with one late model lasting 68 months, nearly double. Block II satellites were typically launched three at a time from the Baikonur Cosmodrome using Proton K Blok DM2 or Proton K Briz M boosters. The only exception was when, on two launches, an Etalon geodetic reflector satellite was substituted for a GLONASS satellite.

The second generation of satellites, known as Glonass M, were developed beginning in 1990 and first launched in 2003. These satellites possess a substantially increased lifetime of seven years and weigh slightly more at They are approximately in diameter and high, with a solar array span of for an electrical power generation capability of 1600 watts at launch. The aft payload structure houses 12 primary antennas for L band transmissions. Laser corner cube reflectors are also carried to aid in precise orbit determination and geodetic research. On board cesium clocks provide the local clock source. 52 Glonass M have been produced and launched. A total of 41 second generation satellites were launched through the end of 2013. As with the previous generation, the second generation spacecraft were launched three at a time using Proton K Blok DM2 or Proton K Briz M boosters. Some were launched alone with Soyuz 2 1b/Fregat. In July 2015, ISS Reshetnev announced that it had completed the last GLONASS M (No. 61) spacecraft and it was putting it in storage waiting for launch, along with eight previously built satellites.

According to Russian System of Differentional Correction and Monitoring's data, as of 2010, precision of GLONASS navigation definitions (for p=0.95) for latitude and longitude were with mean number of navigation space vehicles (NSV) equals 7—8 (depending on station). In comparison, the same time precision of GPS navigation definitions were with mean number of NSV equals 6—11 (depending on station). Some modern receivers are able to use both GLONASS and GPS satellites together, providing greatly improved coverage in urban canyons and giving a very fast time to fix due to over 50 satellites being available. In indoor, urban canyon or mountainous areas, accuracy can be greatly improved over using GPS alone. For using both navigation systems simultaneously, precision of GLONASS/GPS navigation definitions were with mean number of NSV equals 14—19 (depends on station). In May 2009, Anatoly Perminov, then director of the Roscosmos, stated that actions were undertaken to expand GLONASS's constellation and to improve the ground segment to increase the navigation definition of GLONASS to an accuracy of by 2011. In particular, the latest satellite design, GLONASS K has the ability to double the system's accuracy once introduced. The system's ground segment is also to undergo improvements. As of early 2012, sixteen positioning ground stations are under construction in Russia and in the Antarctic at the Bellingshausen and Novolazarevskaya bases. New stations will be built around the southern hemisphere from Brazil to Indonesia. Together, these improvements are expected to bring GLONASS' accuracy to 0.6 m or better by 2020. The setup of a GLONASS receiving station in the Philippines is also now under negotiation.