Remote Sensing satellite launched from Taiyuan
A Long March-4B (CZ-4B serial number Y55) rocket launched the Gaofen-11 04 observation satellites from Taiyuan Satellite Launch Center (platform LC9), north China's Shanxi Province, Dec. 2022, at 15:37 Beijing time (07:37 UTC). According to official sources, Gaofen-11 04 (高分 十一 号 04, Gāo Fēn Shíyī hào04, “GF11-04”) entered the initial target orbit as planned, and a network with Gaofen-11 01, 02 and 03 will be added to “improve the efficiency of Earth observation and make greater contributions for social development in the areas of land survey, urban planning, land ownership, road network design, crop estimation and disaster prevention and mitigation.” The common initial orbit for GF 11 spacecraft is 248 km x 694 km, inclined at 97.4° to the equator.
According to reports, the Gaofen 11 spacecraft may be able to achieve a ground image resolution of 10 cm or less. If this conjecture can be confirmed, China confirms that it has a satellite image capacity second only to that of the United States. Even with a civilian name, the Gaofen 11 clearly demonstrate their military use: they can provide information for the implementation of major national strategies such as the “Belt and Road” and the modernization of Chinese national defense. The satellite imaging system allows “reading a newspaper headline in the hands of someone on the ground”.
The satellite is sometimes compared to the Key Hole KH-11 KENNEN of the Americans, and the diameter of the optical telescope aperture is 1.7 meters – which may indicate the presence of a large mirror used by a Dobsonian-type telescope. The largest mirror carried by a commercial observation satellite is the 1.1 m mirror on the Worldview 3 & 4, manufactured in the USA by ITT Exelis. For non-commercial satellites, the French have published images of their Helios 2, suggesting they have a 1.4 m mirror. The GF-1 is better than all of them and is only surpassed in its optical imaging category by two US devices, the Hubble Space Telescope, which has a 2.4 m mirror working at optical wavelengths; the KENNEN spies which must have a mirror size similar to that of Hubble.
As the GF-11s are positioned at 247 × 693 km (parameters converted to a circular orbit of 470 km later), a 1.7 m mirror would give a terrestrial resolution of 8 to 10 cm at perigee, around 10:00 am local solar and 20°N, directly over India and the South China Sea. The resolution released in November 2020 by academic Li Deren, in fact, is 0.1 meter. At an average altitude of 470km the resolution is still 15 to 20 cm, surpassing all commercial and most reconnaissance satellites. This puts China in the select club of countries that can acquire NIIRS 8-9 resolution qualities which means the resolution is high enough to identify handheld small arms. Supposedly, the only members of this club are the US and now China, and this will continue to be the case for the foreseeable future, with perhaps Russia joining them later if the Razdan program lives up to its promises.
No further details of the satellite released, continuing Chinese reticence with this type of Gaofen. To date, China has launched sixty-two orbital rockets, with 60 of them successful. The rocket and satellite used in this launch were developed by the Fifth Academy of China Aerospace Science and Technology Corporation – CASC and manufactured by Aerospace Dongfanghong Satellite Co. According to official media, this was the 457th flight of a rocket that uses the Long March name, counting all models.
The Taiyuan Launch Center experiences very cold weather in December, with temperatures reaching minus 30 degrees Celsius. In order to ensure that the rocket was not affected by environmental conditions and was launched within the allotted time, safeguard measures were taken: on the one hand, low temperature protection for winter, and the combination of insulation layer and pumped hot air is used; on the other hand, preparations in order to improve the trajectory in relation to the load of high altitude winds, when the wind conditions reach a certain limit, the trajectory is modified increasing the probability of launch in the predetermined window.
The Long March 4B is developed by the Aerospace Science and Technology Group, capable of operating at room temperature as a three-stage rocket, capable of launching various types of satellites in different orbit capacity requirements, placing a single satellite or multiple payloads. in sun-synchronous orbit or in geosynchronous orbit. The CZ-4B is developed by the Aerospace Science and Technology Group, capable of launching various types of satellites in different orbit capacity requirements, placing a single satellite or multiple payloads, in sun-synchronous orbit or geosynchronous orbit. The orbital payload capacity can reach 2.5 tons.