Misplaced Pages

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61-581: The maiden flight on 10 March 1967 carried a Soyuz 7K-L1 as part of the Zond program . During the so-called Moon Race these Proton/Soyuz/Zond flights consisted of several uncrewed test flights of Soyuz spacecraft to highly elliptical or circumlunar orbits with the unrealized aim of landing Soviet cosmonauts on the Moon . It was retired from service in favour of the modernised Proton-M , making its 310th and final launch on 30 March 2012. The baseline Proton-K

122-548: A Block DM4 . The Briz-M upper stage was used for four launches; three carrying payloads for the Russian Government, and one commercial launch with GE-9 for GE Americom . One launch was reported to have used a Block DM-3 upper stage, however this may have been a reporting error, and it is unclear whether this launch actually used a DM-3, DM3, or DM-2. Due to its rushed development, the Proton K launch vehicle had

183-412: A 38° cone, using right-hand circular polarization , at an EIRP between 25 and 27 dBW (316 to 500 watts). Note that the 24-satellite constellation is accommodated with only 15 channels by using identical frequency channels to support antipodal (opposite side of planet in orbit) satellite pairs, as these satellites are never both in view of an Earth-based user at the same time. The L2 band signals use

244-529: A commercial version of the DM-2, was used to launch Inmarsat-3 F2 . The Block DM2 upper stage was used to launch three groups of seven Iridium satellites, including Iridium 33 . This configuration was also used to launch INTEGRAL for the European Space Agency . Block DM3 stages were used on twenty five launches, almost exclusively carrying commercial satellites. Telstar 5 was launched with

305-633: A full suite of modernized CDMA signals in the existing L1 and L2 bands, which includes L1SC, L1OC, L2SC, and L2OC, as well as the L3OC signal. Glonass-K2 series should gradually replace existing satellites starting from 2023, when Glonass-M launches will cease. Glonass-KM satellites will be launched by 2025. Additional open signals are being studied for these satellites, based on frequencies and formats used by existing GPS, Galileo, and Beidou/COMPASS signals: Such an arrangement will allow easier and cheaper implementation of multi-standard GNSS receivers. With

366-734: A low success rate initially. However, the issues were rectified and it went on to become one of the most widely used heavy launch vehicle. Soyuz 7K-L1 Soyuz 7K-L1 "Zond" spacecraft was designed to launch cosmonauts from the Earth to circle the Moon without going into lunar orbit in the context of the Soviet crewed Moon-flyby program in the Moon race . It was based on the Soyuz 7K-OK . Several modifications reduced vehicle mass and increased circumlunar capability. The most notable modifications were

427-671: A modified Soyuz. This would be launched towards the Moon on a UR-500 topped with the Blok D stage under development by the OKB-1 Bureau. Korolev originally intended to piece together the lunar Soyuz in Earth orbit because he did not believe the UR-500 was powerful enough to launch the full vehicle or that it wouldn't be safe for the crew. However, when he died in January 1966, his successor as head of OKB-1, Vasily Mishin , argued that it

488-416: 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. A fully operational constellation with global coverage consists of 24 satellites, while 18 satellites are necessary for covering

549-472: A solar array span of 7.2 m (24 ft) 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

610-506: A velocity vector measuring within 100 mm/s (3.9 in/s), 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

671-481: 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

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732-456: Is a single-chamber engine and uses a staged combustion cycle. The first-stage guidance system was open-loop, which required significant amounts of propellant to be held in reserve. The third stage was powered by an RD-0210 engine and four vernier nozzles, with common systems. The verniers provided steering, eliminating the need for gimballing of the main engine. They also aided stage separation, and acted as ullage motors . Ducts built into

793-478: 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 15 m (49 ft),

854-695: 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 400 mm (16 in) 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

915-429: 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

976-507: 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

1037-419: Is transmitted with each string; UTC leap second correction is achieved by shortening or lengthening (zero-padding) the final string of the day by one second, with abnormal strings being discarded by the receiver. The strings have a version tag to facilitate forward compatibility : future upgrades to the message format will not break older equipment, which will continue to work by ignoring new data (as long as

1098-616: The Fobos 1 , Fobos 2 and Mars 96 spacecraft. The Blok DM upper stage was used on 66 launches. The most commonly used upper stage was the Blok DM-2 , which was used on 109 flights, mostly with GLONASS and Raduga satellites. Fifteen launches used the modernised Block DM-2M stage, mostly carrying Ekspress satellites, however other satellites, including Eutelsat 's SESAT 1 , also used this configuration. Two Araks satellites were launched using Block DM-5 upper stages. The Block DM1 ,

1159-594: 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

1220-635: The L1 was based on. Chief Designer Sergei Korolev had originally envisioned a crewed lunar spacecraft launched in pieces by R-7 boosters and assembled in Earth orbit. The development of Vladimir Chelomei 's large UR-500 booster theoretically made it possible to do the job in a single launch. However, Chelomei also proposed his own, competing for lunar spacecraft, the LK-1, and Soviet premier Nikita Khrushchev gave his approval in August 1964. Two months later, Khrushchev

1281-565: The L1 was called "Saturn" and featured some differences from the standard 7K-OK "Sirius-7K" IDS. Along with the remaining 7K-L1S, the Soviet Moon-flyby program was closed in 1970 without the achievement of its crewed primary goal. The intended crewed use of L1/Zond spacecraft was documented in official Soviet sources for the first time but from 1968 until 1989 this and the Moon-landing N1-L3 programs were classified and

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1342-487: 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

1403-507: The Moon showed problems using their star sensors for navigation. These problems caused ballistic reentry due to failed guidance. One direct descent re-entry was performed on a steep ballistic trajectory with a deceleration of up to 20 Gs and splashed down in the Indian Ocean. Three others performed a maneuver known as " skip reentry " to shed velocity. One of those also performed an unsafe (for humans) descent of up to 20 Gs of deceleration,

1464-583: The Soviet government denied the existence of both. Near 1968 a rare open Soviet source ( Big Soviet Encyclopedia 's Yearbook, Kosmonavtika small encyclopedia) sporadically referred to Zonds as tests of space ships for lunar missions in contrast to the space apparate term used by the Soviets for spacecraft not capable of carrying a crew. As of 1967, the Soyuz 7K-L1 launch schedule was: Mission In July 1968, it

1525-461: The centimetre level, but ideally a conversion to ITRF2008 should be done. Since 2008, new CDMA signals are being researched for use with GLONASS. The interface control documents for GLONASS CDMA signals was published in August 2016. According to GLONASS developers, there will be three open and two restricted CDMA signals. The open signal L3OC is centered at 1202.025 MHz and uses BPSK(10) modulation for both data and pilot channels;

1586-455: The constellation still transmits old string types), but up-to-date equipment will be able to use additional information from newer satellites. The navigational message of the L3OC signal is transmitted at 100 bit/s, with each string of symbols taking 3 seconds (300 bits). A pseudo-frame of 6 strings takes 18 seconds (1800 bits) to transmit. A superframe of 8 pseudo-frames is 14,400 bits long and takes 144 seconds (2 minutes 24 seconds) to transmit

1647-586: The current satellite (string types 10, 11, and 12 in a sequence) and part of the almanac for three satellites (three strings of type 20). To transmit the full almanac for all current 24 satellites, a superframe of 8 pseudo-frames is required. In the future, the superframe will be expanded to 10 pseudo-frames of data to cover full 30 satellites. The message can also contain Earth's rotation parameters, ionosphere models, long-term orbit parameters for GLONASS satellites, and COSPAS-SARSAT messages. The system time marker

1708-501: 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. As on 22 September 2017, GLONASS-M No.52 satellite went into operation and

1769-622: The final assembly point near the pad. The first stage of the Proton-K consisted of a central oxidiser tank, and six outrigger fuel tanks. This separated as one piece from the second stage, which was attached by means of a lattice structure interstage. The second stage ignited prior to first stage separation, and the top of the first stage was insulated to ensure that it retained its structural integrity until separation. The first stage used six RD-253 engines, designed by Valentin Glushko . The RD-253

1830-731: The full almanac. The navigational message of the L1OC signal is transmitted at 100 bit/s. The string is 250 bits long and takes 2.5 seconds to transmit. A pseudo-frame is 1500 bits (15 seconds) long, and a superframe is 12,000 bits or 120 seconds (2 minutes). L2OC signal does not transmit any navigational message, only the pseudo-range codes: Glonass-M spacecraft produced since 2014 include L3OC signal Glonass-K1 test satellite launched in 2011 introduced L3OC signal. Glonass-M satellites produced since 2014 (s/n 755+) will also transmit L3OC signal for testing purposes. Enhanced Glonass-K1 and Glonass-K2 satellites, to be launched from 2023, will feature

1891-1171: The introduction of CDMA signals, the constellation will be expanded to 30 active satellites by 2025; this may require eventual deprecation of FDMA signals. The new satellites will be deployed into three additional planes, bringing the total to six planes from the current three—aided by System for Differential Correction and Monitoring ( SDCM ), which is a GNSS augmentation system based on a network of ground-based control stations and communication satellites Luch 5A and Luch 5B . Six additional Glonass-V satellites, using Tundra orbit in three orbital planes, will be launched starting in 2025; this regional high-orbit segment will offer increased regional availability and 25% improvement in precision over Eastern Hemisphere , similar to Japanese QZSS system and Beidou-1 . The new satellites will form two ground traces with inclination of 64.8°, eccentricity of 0.072, period of 23.9 hours, and ascending node longitude of 60° and 120°. Glonass-V vehicles are based on Glonass-K platform and will broadcast new CDMA signals only. Previously Molniya orbit , geosynchronous orbit , or inclined orbit were also under consideration for

Proton-K - Misplaced Pages Continue

1952-520: 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

2013-410: The latest version, GLONASS-K2 , launched in 2023. 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 19,100 km (11,900 mi) altitude with a 64.8° inclination and an orbital period of 11 hours and 16 minutes (every 17 revolutions, done in 8 sidereal days,

2074-520: The military "Cosmos-NNNN" designation. The true first generation of GLONASS (also called Uragan) satellites were all three-axis stabilized vehicles, generally weighing 1,250 kg (2,760 lb) 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

2135-598: The most complex) on a circumlunar flight and return them relatively safely to Earth. Zond 5 splashed down in the Indian Ocean after descending steeply with a 20 G deceleration rate. Although unsafe for humans, these high Gs apparently didn't affect the tortoises' health, and they were reportedly able to breed afterward. Two modifications of main Soyuz 7K-L1 "Zond" version was created: the powered (up to 7000 kg mass) Soyuz 7K-L1S "Zond-M" that were failed attempted to launch for Moon flyby on N1 rocket two times due to Soyuz 7K-LOK orbital ship-module of L3 lunar expedition complex

2196-545: 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

2257-407: 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

2318-531: The need for low-temperature–tolerant components, and allowed the rocket to sit on the pad fully fuelled for long periods of time. In contrast, cryogenic fuels would have required periodic topping-up of propellants as they boil off. The propellants used on the Proton, were, however, corrosive and toxic and required special handling. The Russian Government paid for the cleanup of residual propellant in spent stages that impact downrange. Proton components were built in factories near Moscow, then transported by rail to

2379-494: The open signals; this places peak signal strength away from the center frequency of narrow-band open signals. Binary phase-shift keying (BPSK) is used by standard GPS and GLONASS signals. Binary offset carrier (BOC) is the modulation used by Galileo , modernized GPS , and BeiDou-2 . The navigational message of CDMA signals is transmitted as a sequence of text strings. The message has variable size - each pseudo-frame usually includes six strings and contains ephemerides for

2440-455: The orbital grouping has again increased to 24 space vehicles. GLONASS-K is a substantial improvement of the previous generation: it is the first unpressurised GLONASS satellite with a much reduced mass of 750 kg (1,650 lb) versus the 1,450 kg (3,200 lb) of GLONASS-M. It has an operational lifetime of 10 years, compared to the 7-year lifetime of the second generation GLONASS-M. It will transmit more navigation signals to improve

2501-432: The other suffered main parachute failure, and only one flight - Zond 7 - would have been safe for cosmonauts. Instrumentation flown on these missions gathered data on micrometeor flux, solar and cosmic rays , magnetic fields , radio emissions, and solar wind . Many photographs were taken and biological payloads were also flown. Zond 5 was the first spacecraft to carry a group of terrestrial creatures (tortoises being

Proton-K - Misplaced Pages Continue

2562-470: The program's cancellation. It was also intended for Chelomey's 20-ton LKS spaceplane that was never realised. Like other members of the Universal Rocket family, the Proton-K was fuelled by unsymmetrical dimethylhydrazine and nitrogen tetroxide . These hypergolic propellants ignite on contact, avoiding the need for an ignition system, and can be stored at ambient temperatures. This avoids

2623-402: 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

2684-735: The ranging code transmits at 10.23 million chips per second, modulated onto the carrier frequency using QPSK with in-phase data and quadrature pilot. The data is error-coded with 5-bit Barker code and the pilot with 10-bit Neuman-Hoffman code. Open L1OC and restricted L1SC signals are centered at 1600.995 MHz, and open L2OC and restricted L2SC signals are centered at 1248.06 MHz, overlapping with GLONASS FDMA signals. Open signals L1OC and L2OC use time-division multiplexing to transmit pilot and data signals, with BPSK(1) modulation for data and BOC(1,1) modulation for pilot; wide-band restricted signals L1SC and L2SC use BOC (5, 2.5) modulation for both data and pilot, transmitted in quadrature phase to

2745-600: The regional segment. 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

2806-419: The replacement of the orbital module with a support cone and a high-gain parabolic antenna, the removal of a reserve parachute, and the addition of the gyro platform and star navigation sensors for the far space navigation. The spacecraft was capable of carrying two cosmonauts . At the start of flight testing, there were serious reliability problems with the new Proton rocket , the 7K-L1, and the Soyuz 7K-OK that

2867-460: The same FDMA as the L1 band signals, but transmit straddling 1246 MHz with the center frequency 1246 MHz + n × 0.4375 MHz, where n spans the same range as for L1. 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

2928-421: The same code as their standard-precision signal; however each transmits on a different frequency using a 15-channel frequency-division multiple access (FDMA) technique spanning either side from 1602.0 MHz , known as the L1 band. The center frequency is 1602 MHz + n × 0.5625 MHz, where n is a satellite's frequency channel number ( n =−6,...,0,...,6, previously n =0,...,13). Signals are transmitted in

2989-453: 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

3050-597: The structure channelled vernier exhaust before stage separation. The third stage guidance system was also used to control the first and second stages earlier in flight. Many launches used an upper stage to boost the payload into a higher orbit. Blok D upper stages were used on forty flights, the majority of which were for the Luna and Zond programmes. Ten flights used the Blok D-1 , mostly to launch spacecraft towards Venus . Blok D-2 upper stages were used three times, with

3111-649: The successful United States Apollo 8 crewed flight around the Moon, the Soviet crewed Moon-flyby missions lost political motivation. The first crewed flight of the L1/Zond spacecraft with Alexei Leonov and Valery Bykovsky planned for the end of 1970 was cancelled. In addition, the Proton booster was far from being human-rated and its poor launch record made it undesirable for crewed flights. All L1/Zond spacecraft made only uncrewed flights from 1967 to 1970, from ( Zond 4 to Zond 8 ), and four of these five Zond flights suffered malfunctions. Test flights conducted around

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3172-632: The system's accuracy — including new CDMA signals in the L3 and L5 bands, which will use modulation similar to modernized GPS, Galileo, and BeiDou. Glonass-K consist of 26 satellites having satellite index 65-98 and widely used in Russian Military space. The new satellite's advanced equipment—made solely from Russian components — will allow the doubling of GLONASS' accuracy. As with the previous satellites, these are 3-axis stabilized, nadir pointing with dual solar arrays. The first GLONASS-K satellite

3233-400: The territory of Russia. To get a position fix the receiver must be in the range of at least four satellites. GLONASS satellites transmit two types of signals: open standard-precision signal L1OF/L2OF, and obfuscated high-precision signal L1SF/L2SF. The signals use similar DSSS encoding and binary phase-shift keying (BPSK) modulation as in GPS signals. All GLONASS satellites transmit

3294-399: 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

3355-482: The view to some satellites. Owing to its higher orbital inclination , GLONASS supplementation of GPS systems also improves positioning in high latitudes (near the poles). 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

3416-743: Was a three-stage rocket. Thirty were launched in this configuration, with payloads including all of the Soviet Union's Salyut space stations , all Mir modules with the exception of the Docking Module , which was launched on the United States Space Shuttle , and the Zarya and Zvezda modules of the International Space Station . It was intended to launch Chelomey's crewed TKS spacecraft , and succeeded in launching four uncrewed tests flights prior to

3477-463: Was definitely possible to strip down the Soyuz enough to launch it with the UR-500 . With the first four uncrewed test starts (see below) being partially successful or unsuccessful, including two under the common open name " Kosmos " as for any Soviet test spacecraft, the mission of 2–7 March 1968 and subsequent ones were the flights of the L1 spacecraft under the open designation " Zond " that were given by Soviets for test missions to far space. After

3538-413: Was expelled from power and Chelomei lost his principal patron. At the end of the year, Korolev revived his proposal for the Soyuz spacecraft but concealed his true intentions by billing it as an Earth orbital vehicle for testing rendezvous and docking maneuvers. In October 1965, a mere three months before his death, Korolev was granted official approval for developing a crewed lunar spacecraft, which would be

3599-617: Was not ready; the Soyuz 7K-L1E "Zond-LOK" as dummy mockup of Soyuz 7K-LOK and were successfully launched on Low Earth Orbit on Proton rocket as Kosmos 382 and failed launched for Moon orbiting on third N1 rocket . No official name for crewed Soyuz 7K-L1 "Zond" was adopted. According to Mishin 's and Kamanin 's memoirs, the names "Rodina" ( motherland ), "Ural" ( Ural mountains ), "Akademik Korolyov" ( academician Korolyov ). Also, "Zarya" ( dawn ) and "Znamya" ( banner ) were proposed for both lunar Soyuz 7K-L1 flyby and Soyuz 7K-LOK orbital ships. The information display systems (IDS) on

3660-755: Was proposed that L1 spacecraft would be launched every month, and the first crewed mission would be in December 1968 or January 1969 after 3 or 4 successful uncrewed flights. In December 1968, dates for three crewed L1 missions were set to March, May, and July 1969. Finally, in September 1969 one crewed L1 mission was formally set for April 1970. Fifteen Soyuz 7K-L1 were built: GLONASS GLONASS ( ГЛОНАСС , IPA: [ɡɫɐˈnas] ; Russian: Глобальная навигационная спутниковая система , romanized : Global'naya Navigatsionnaya Sputnikovaya Sistema , lit. 'Global Navigation Satellite System')

3721-473: 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 1,480 kg (3,260 lb). They are approximately 2.4 m (7 ft 10 in) in diameter and 3.7 m (12 ft) high, with

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