China launched three more reconnaissance satellites Saturday, via a Chang Zheng 2D launch out of the Xichang Satellite Launch Center. Lifting off at 03:00 UTC (11:00 Beijing Time), Chang Zheng deployed three Yaogan 35 satellites into low Earth orbit.
Yaogan Weixing – meaning “remote sensing satellite” and usually shortened to Yaogan – is a name that China gives to many of its military satellites, akin to the “Kosmos” and “USA” designations used by Russia and the United States. The individual spacecraft under the Yaogan umbrella carry out different surveillance and national security missions for the Chinese government, although officially they are all remove sensing payloads operated by the Ministry of Agriculture.
Very few details of the individual satellites’ operations are disclosed by the Chinese government, with analysis of spacecraft in orbit and comparisons to western missions and previous Chinese satellites helping to build an understanding over time. As Yaogan 35 appears to represent a new type of payload, it is likely to be some time before its purpose becomes clear.
The Yaogan 35 satellites launched aboard a Chang Zheng 2D (CZ-2D) rocket. Also known as Long March 2D, this is a two-stage vehicle that is part of China’s heritage Chang Zheng series of rockets. The Chang Zheng 2, 3, and 4 lines of rockets are interconnected, originally deriving from the Dongfeng 5 (DF-5) ballistic missile.
The CZ-2 rockets use two stages – although they can also fly with small optional upper stages – for mostly low Earth orbit missions. Chang Zheng 2C, 2D, and 2F versions are currently in service.
The CZ-2D rocket climbs away from Xichang
The Chang Zheng 3 series takes the CZ-2C as its core, stretching it and adding a high-energy upper stage to enable launches into geostationary transfer orbit. The Chang Zheng 4 features a more modest stretch of the original vehicle, with a storable-propellant third stage that makes it well-suited for placing satellites into sun-synchronous orbits.
Chang Zheng 2D is an improved version of the original CZ-2 design – which remains in service as the Chang Zheng 2C. The 2D is essentially a Chang Zheng 4 without its upper stage, incorporating the enhancements made for that program back into the two-stage vehicle. It first flew in 1992, with the initial three launches being derived from the Chang Zheng 4A rocket. Since 2003, subsequent flights have used versions of the rocket derived from the CZ-4B.
With its design originating from China’s ballistic missile programs, both stages of the Chang Zheng 2D burned storable hypergolic propellants: unsymmetrical dimethylhydrazine and dinitrogen tetroxide. While this propellant combination allowed the DF-5 missile to be kept ready to launch for extended periods of time, it is highly toxic and inefficient compared to other options. The older members of the Chang Zheng rocket family are slowly being phased out in favor of newer rockets that burn cleaner propellants, such as the Chang Zheng 5, 6, 7, and 8.
Saturday’s launch marked the fifty-sixth flight of the Chang Zheng 2D, using the vehicle with serial number Y63. It is only the second CZ-2D to launch from the Xichang Satellite Launch Center, with most of its previous launches having taken place at Jiuquan and Taiyuan. China primarily uses Xichang for geosynchronous launches, although the CZ-2D is not capable of reaching such an orbit. Airspace restrictions published ahead of the launch indicated that the rocket was going to follow a south-easterly track after liftoff.
CZ-2D at the launch pad ahead of the Yaogan 35 mission
Xichang has two launch pads for Chang Zheng rockets – pads 2 and 3 – which are separated by about 300 meters. The larger Chang Zheng 3 rockets can fly from either launch pad, but when smaller Chang Zheng 2 rockets fly from Xichang, they usually use Pad 3, and Saturday’s launch was no exception.
Pad 3 was originally built for the first Chang Zheng 3 rockets in the 1980s, before being completely rebuilt in the mid-2000s to support the Chang Zheng 3A. As China’s launch rates increased and demand for the larger Chang Zheng 3B and 3C rockets grew, Pad 3 underwent significant work between 2012 and 2015 to provide an additional launch platform for those vehicles.
The only previous Chang Zheng 2D mission from Xichang lifted off in February of last year with four experimental Xinjishu Shiyan (XJS) satellites aboard. This reached an orbit about 480 kilometers in altitude at an inclination of 35 degrees. Saturday’s launch targeted a similar trajectory, with the first objects from the launch being tracked in a 495-kilometer orbit at the same inclination.
The earlier XJS launch was reported to be testing inter-satellite communications technologies and earth observation systems for future missions, with two of the satellites built by the Shanghai Academy of Spaceflight Technology (SAST) and one by the China Academy of Space Technology (CAST) through its DFH Satellite Company subsidiary. Two of the Yaogan 35 satellites were reported to have been constructed by CAST, with the third built by SAST, so the XJS satellites may have served as pathfinders for the new Yaogan spacecraft.
Even if they build on technology demonstrated by the XJS satellites, the Yaogan 35 satellites follow a different design, with a larger payload fairing required to carry the three spacecraft aboard Saturday’s mission compared to the four satellites on last year’s launch. This marks the first flight of a new extended fairing for the Chang Zheng 2D rocket – measuring 13.4 meters in length, it protected the satellites from the Earth’s atmosphere as Chang Zheng 2D climbed towards orbit.
Yaogan 35 being transported within the extended payload fairing
The official announcement of Saturday’s successful launch described the satellites as belonging to the “Yaogan 35 family,” implying that further missions of this type might be expected in the future. When carrying out follow-up launches in the Yaogan series, China has sometimes allocated new numbers to the spacecraft – such as Yaogan 9 and 16. Other times they have been given the same designation as their predecessors, such as Yaogan 30, which has now seen ten separate groups of satellites launched. If the latter model is followed with Yaogan 35, the satellites launched on Saturday will become known as Yaogan 35 Group 01 as their constellation begins to grow.
Saturday’s launch comes during a busy period for China’s space industry, which has seen launches from all three of China’s heritage major launch sites within 72 hours. It follows a Chang Zheng 2C launch from the Jiuquan Satellite Launch Center on Wednesday which deployed the twin Yaogan 32 Group 02 satellites, and a Chang Zheng 6 launch out of the Taiyuan Satellite Launch Center on Friday with the Guangmu, or SDGSAT-1, satellite on board.
Overall, 2021 has seen a significant uptick from China in terms of launches, with Yaogan 35 marking the country’s forty-third launch of the year. This has already exceeded the highest number of launches for China in the course of a year, with almost two months remaining for the total to grow further.
(Lead Image: Liftoff of Yaogan 35 aboard Chang Zheng 2D – via CASC)