China launches Gaofen-3-03 payload on CZ-4C from Jiuquan – NASASpaceFlight.com

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China launched another Gaofen satellite Thursday morning to a Sun-Synchronous Orbit (SSO). The launch was carried out on a Chang Zheng 4C from the Jiuquan Satellite Launch Center in China. The liftoff time was confirmed to be 7:47 AM local time on April 7 (23:47 UTC on April 6).

The destination of today’s mission is a 738 x 745 km orbit with an inclination of 98.4°.

The Gaofen 3 satellites were developed and constructed by the China Academy of Space Technology (CAST). CASt is part of the China Aerospace Science and Technology Corporation (CASC), which is the primary state-owned contractor for activities regarding the Chinese space program.

With the Gaofen satellites, China developed its own high-resolution Earth-imaging satellite constellation. It is part of the China High-resolution Earth Observation System (CHEOS), and an extension of the initial High-Definition Earth Observation satellite program (HDEOS).

The initial HDEOS received full funding in 2010 with the main goal of launching six HDEOS satellites to improve observation for disaster prevention, climate change observation, and resource survey. It is also suspected that the program has been used for military purposes.

In 2010, the government also proposed and approved the CHEOS program which would launch more spaceborne systems that could survey the world. It is overviewed by the Earth Observation System and Data Center – China National Space Administration (EOSDC-CNSA) and is also officially used for geographical and environmental mapping, including disaster prevention and disaster area monitoring.

Today’s launch was a Gaofen 3 C-band satellite, based on the CS-L3000B bus. They are equipped with Synthetic Aperture Radar (SAR), Control Moment Gyros (CMGs), and a data transmission system. The satellite will be able to monitor with an image resolution of one meter. It is designed for a lifetime of 8 years and is suspected to mass close to 2,800 kg. As usual for the Chinese space program, more details about today’s payload were not released for this launch.

Chang Zheng 4C lifts off with Gaofen-3-03

The first launch of Gaofen happened in April 2013 on board a Chang Zheng 2D rocket. Since then, 23 more Gaofen satellites launched on a wide range of Chinese rockets, including CZ-4, CZ-3, Kauizhou-1A, and CZ-11. Of these, two were not successful, both launching on variants of the Kuaizhou rockets.

The launch vehicle for this flight was the Chang Zheng 4C (Long March 4C is used internationally). It is a three-stage orbital rocket and part of the early generation of Chinese rockets that use N2O4 and UDMH as oxidizer and fuel for the first stage. Compared to its processor, the CZ-4B, it features a larger payload fairing and an upgraded upper stage with restart capabilities.

So far it has launched 42 times and is used for SSO and Low Earth Orbit (LEO) missions. It will be replaced down the line with modern rockets of the Chinese fleet, such as the recently debuted Chang Zheng 6A, once they reach the cadence and reliability to support the launch efforts of China.

Besides two failures, it has an otherwise reliable launch history. The two failures happened with the Gaofen 10 mission in August 2016, and the Yaogan 33 mission in May 2019.

The rocket stands 45.8 meters tall with a diameter of 3.35 meters and a liftoff mass of about 250,000 kg. It can handle payloads up to 4,200 kg to LEO and 2,800 kg to SSO. Reports indicate that the payload mass of this satellite pushes the SSO capability of the CZ-4C to its limit.

The first stage is the majority of the mass and size of the launcher, standing 27.91 meters tall and having a liftoff mass of 182,000 kg. It is powered by four YF-21C engines, providing a liftoff thrust of 2,961.6 kN together with a specific impulse of 260 seconds.

The Chang Zheng 4C launch vehicle on the pad at Jiuquan prior to launch

Above the first stage is the second stage. After detaching from the first stage in an event called Main Engine Cutoff (MECO), the second stage ignites its engines.

It is 10.9 meters long, uses the same diameter as the first stage, and utilizes a single YF-22C engine that produces a thrust of 742.04 kN, with a specific impulse of about 300 seconds. The four YF-23C vernier engines are used to steer and control the second stage in this phase of the flight. The propellants used for this stage are the same as in the first stage, UDMH and N2O4. The mass of the second stage is 52,700 kg.

At this point in the flight, the payload fairing also gets dropped from the rocket. The fairing’s capabilities to shield the payload from aerodynamics and heating are no longer needed as the rocket leaves the atmosphere. To save weight, it is deployed and exposes the payload to the vacuum of space.

The third stage is only 2.9 meters wide and has a length of 14.79 meters. It is powered by a single YF-40 engine that also runs on UDMH. As it is only used for the last maneuvers and sometimes performs relights for accurate orbital insertion, it only has a thrust of 100 kN with a specific impulse of 412 seconds. After it’s done its job, the payload is released from the payload adapter and can now perform its own maneuvering and deployment process.

The JSLC was opened in 1958. It is one of the biggest Chinese spaceports, currently hosting CZ-2, CZ-4, and CZ-11 rockets. It has three launch areas and six pads and is one of the four major spaceports of the Chinese space program. With its inland location, the falling rocket stages from launches regularly endanger villages and citizens in the flight path, as the rockets fly over populated areas.

This was the 414th flight of the Chang Zheng family. It was the ninth launch this year from China and already the fourth CZ-4C launch of 2022. Previously this year, it launched the Yaogan 34-02 payload and the L-SAR 01A and 01B payloads. All of these missions were a success.

(Lead photo: CZ-4C lifts off from the Jiuquan Satellite Launch Center with Gaofen-3-03.)

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