Long March 4B lofts Yaogan-21 in surprise launch

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The Chinese have conducted another surprise launch, this time with the Long March 4B rocket reported to have lofted a new satellite in the Yaogan Weixing series. The Yaogan-21 satellite was launched at 03:22 UTC on Monday from the LC9 launch complex at the Taiyuan satellite Launch Center.

Chinese Launch:

As usual for this type of satellite, the Chinese media is referring to the new satellite as ‘a new remote sensing bird that will be used for scientific experiments, land survey, crop yield assessment, and disaster monitoring.’

As was the case with the last launches of the Yaogan Weixing series, Western analysts believe this class of satellites is being used for military purposes.

The previous launch in this series was on August 9, when a Long March-4C launch vehicle orbited a “satellite triplet” during the Yaogan Weixing-20 mission.

That mission was understood to be associated with the locating and tracking foreign warships – collecting the optical and radio electronic signatures of the maritime vessels that will be used in conjunction with other information valuable for the Chinese maritime forces.

Developed by the Chinese Academy of Space Technology (CAST), Yaogan Weixing-21 is possibly the third electro-optical 2nd generation satellite equipped with a short-angle observation system and a Phoenix Eye-2 based bus.

The satellite is likely to be in the previous Yaogan-5 and Yaogan-12 satellite series, which has the military designation Jianbing-8. Yaogan-5 reentered the Earth’s atmosphere on September 2.

Also on board was the Tiantuo-2 satellite. This small bird was developed by the National University of Defense Technology (NUDT) and will be used for data reception for the satellite-based Automatic Identification System, as well as for optical imaging and various space experiments in orbit.

This launch was the 203rd Chinese orbital launch and the 192nd launch of the Long March launch vehicle family. It was also the 47th successful orbital launch from the Taiyuan Satellite launch Center, the 2nd launch from this space center in 2014 and the 5th orbital launch for China this year.

Looking back to the Yaogan Weixing launch series:

The first Yaogan Weixing satellite (29092 2006-015A) was launched by a Long March 4C (Y1) from the Taiyuan Satellite Launch Center on April 27, 2006. Developed by Shanghai Academy of Spaceflight Technology (SAST), the details about this satellite were closely guarded, but later it was said that this was the first Jianbing-5 satellite, equipped with the first space-based synthetic aperture radar (SAR).

The second satellite on the series, the Yaogan Weixing-2 (31490 2007-019A), was launched on 25 May, 2007, by a Long March-2D (Y8) from the Jiuquan Satellite Launch Center. Details were also restricted, though it is claimed that this spacecraft is an electro-optical military observation satellite also known as JB-6 Jianbing-6, complementing the results of the Yaogan Weixing-1.

A Y-W SatelliteAnother SAR mission similar to Yaogan-1 was launched on November 11, 2007 – with the Yaogan Weixing-3 (32289 2007-055A) satellite orbited by a Long March -4C (Y3) launch vehicle from Taiyuan, as well as Yaogan Weixing-10 (36834 2010-038A) launch on August 9, 2010, by the Long March-4C (Y6) launch vehicle from Taiyuan.

Yaogan Weixing-4 (33446 2008-061A) was then launched on December 1, 2008. This was the second electro-optical satellite on the series and was launched by a Long March-2D (Y9) from Jiuquan.

Other satellites in the Jianbing-6 series were Yaogan Wexing-7 (36110 2009-069A), launched on December 9, 2009 from Jiuquan by a Long March-2D (Y10), and Yaogan Weixing-11 (37165 2010-047A) launched on September 22, 2010, by the Long March -2D (Y11) launch vehicle from Jiuquan.

The first second-generation electro-optical reconnaissance satellite developed by CAST, Yaogan Weixing-5 (33456 2008-064A), was launched on December 15, 2008. The launch took place from Taiyuan by the Long March-4B (Y20) rocket.

Yaogan Weixing-12 (37875 2011-066B) was other second-generation electro-optical reconnaissance satellite, launched on November 11, 2011, by the Long March-4B (Y21) launch vehicle from Taiyuan.

Yaogan Weixing-6 (34839 2009-021A), launched by the Long March-2C-III (Y19) from Taiyuan on April 22, 2009, was a second-generation SAR satellite developed by SAST, having a spatial resolution of 1.5m. Other second-generation SAR satellites were the Yaogan Weixing-13 (37941 2011-072A) launch on November 29, 2011, by the Long March-2C (Y20) launch vehicle from Taiyuan and the Yaogan Weixing-18 (39363 2013-059A) launch on October 29, 2011, by the Long March-2C (Y25) launch vehicle from Taiyuan.

The Yaogan Weixing-8 (36121 2009-072A), launched on December 15, 2009, by the CZ-4C (Y4) from Taiyuan was a new generation of optical reconnaissance satellite. Similar to the Yaogan-8 was the mission of Yaogan Weixing-14 launched on May 10th, 2012 by the Long March-4B (Y12) from Taiyuan.

The YaoGan Weixing-9 mission, launched March 5, 2010 from Jiuquan, had an architecture different from the previous missions on the series. Launched by Long March-4C (Y5) rocket, the mission put not one but a triplet of satellites in Earth orbit. Flying in formation this three satellites form what looks like a type of NOSS system. Similar missions were the Yaogan-16, Yaogan-17 and Yaogan-20, all launched from Jiuquan.

The Yaogan Weixing-15 was a optical reconnaissance satellite launched on May 29, 2012 by the Long March-4C (Y10) from Taiyuan. This vehicle also used a 3.35m diameter fairing for the Yaogan 15 ride uphill. Another mission similar to Yaogan-15 was the Yaogan Weixing-19 (39410 2013-065A) launched on November 20, 2013, by the Long March-4C (Y14) from Taiyuan.

The Launch Vehicle:

The feasibility study of the CZ-4 Chang Zheng-4 (Long March-4) began in 1982 based on the FB-1 Feng Bao-1 launch vehicle. Engineering development was initiated in the following year.

Initially, the Long March-4 served as a back-up launch vehicle for Long March-3 to launch China’s communications satellites.

After the successful launch of China’s first DFH-2 communications satellites by Long March-3, the main mission of the Long March-4 was shifted to launch sun-synchronous orbit meteorological satellites. On other hand, the Long March-4B launch vehicle was first introduced in May 1999 and also developed by the Shanghai Academy of Space Flight Technology (SAST), based on the Long March-4.

The rocket is capable of launching a 2,800 kg satellite into low Earth orbit, developing 2,971 kN at launch. With a mass of 248,470 kg, the CZ-4B is 45.58 meters long and has a diameter of 3.35 meters.

SAST began to develop the Long March-4B in February 1989. Originally, it was scheduled to be commissioned in 1997, but the first launch didn’t take place until late 1999.

The modifications introduced on the Long March-4B included a larger satellite fairing and the replacement of the original mechanical-electrical control on the Long March-4 with an electronic control.

Other modifications were an improved telemetry, tracking, control, and self-destruction systems with smaller size and lighter weight; a revised nuzzle design in the second stage for better high-altitude performance; a propellant management system for the second stage to reduce the spare propellant amount, thus increasing the vehicle’s payload capability and a propellant jettison system on the third-stage.

The first stage has a 24.65 meter length with a 3.35 meter diameter, consuming 183,340 kg of N2O4/UDMH (gross mass of first stage is 193.330 kg). The vehicle is equipped with a YF-21B engine capable of a ground thrust of 2,971 kN and a ground specific impulse of 2,550 Ns/kg. The second stage has a 10.40 meter length with a 3.35 meter diameter and 38,326 kg, consuming 35,374 kg of N2O4/UDMH.

The vehicle is equipped with a YF-22B main engine capable of a vacuum thrust of 742 kN and four YF-23B vernier engines with a vacuum thrust of 47.1 kN (specific impulses of 2,922 Ns/kg and 2,834 Ns/kg, respectively).

The third stage has a 4.93 meter length with a 2.9 meter diameter, consuming 12,814 kg of N2O4/UDMH. Having a gross mass of 14,560 kg, it is equipped with a YF-40 engine capable of a vacuum thrust of 100.8 kN and a specific impulse in vacuum of 2,971 Ns/kg.

The Launch Center:

Situated in the Kelan County in the northwest part of the Shanxi Province, the Taiyuan Satellite Launch Center (TSLC) is also known by the Wuzhai designation. It is used mainly for polar launches (meteorological, Earth resources and scientific satellites).

Z114The launch center has two single-pad launch complexes, a technical area for rocket and spacecraft preparations, a communications centre, a mission command and control centre, and a space tracking centre.

The stages of the rocket are transported to the launch centre by railway, and offloaded at a transit station south of the launch complex. They are then transported by road to the technical area for checkout procedures.

The launch vehicles are assembled on the launch pad by using a crane at the top of the umbilical tower to hoist each stage of the vehicle in place. Satellites are airlifted to the Taiyuan Wusu Airport about 300km away, and then transported to the centre by road.

The TT&C Centre, also known as Lüliang Command Post, is headquartered in the city of Taiyuan, It has four subordinate radar tracking stations in Yangqu (Shanxi), Lishi (Shanxi), Yulin (Shaanxi), and Hancheng (Shaanxi)

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