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Tianwen-1 completes the First Midcourse Correction of Earth-Mars Transfer Orbit
Under the control of scientific research personnel from Beijing Aerospace Control Center and China Aerospace Science and Technology Corporation, Tianwen-1 Mars Probe succeeded in completing the first midcourse correction of Earth-Mars Transfer Orbitat 7:00 a.m. on August 2.
As of the first orbit correction, Tianwen-1 probe has flown in the outer space for about 230h, and is about 3 million km away from the earth, with excellent system status.
Why midcourse correction is necessary?
As introduced by Zhu Qinghua, Deputy Chief Technical Officer for Orbiter Technologies of Probe System for the First Mars Exploration Task, “lots of cars are equipped with lane-keeping functions, and if a car deviates from its lanes, the direction can be automatically corrected, so that it can return to the original lane. This is similar to the orbit correction of Mars probe, but the difference is what should be corrected by Mars probe includes not only the flying direction, but also variables, such as the flying speed.However, in the vast space, since no road marks can be used as references for the probe, there can be huge difficulties.”
In the Earth-Mars transfer orbit flying course, the probe may be influenced by orbit injection error, control precision error, etc. Since the probe is under long-term unpowered flight, tiny location speed error will be accumulated and amplified gradually. In case of failing to make correction, the probe will miss Mars and cause severe consequences, just as the saying goes, “a little error may lead to a large discrepancy”. Therefore, when executing the flying mission, midcourse correction control strategies for Earth-Mars transfer orbit shall be formulated, including the right time for each correction, the increment and direction of each correction speed. In the actual task, scientific research personnel shall complete corresponding probe attitudes and orbit controls based on midcourse correction strategies, and ensure that the probe can always fly on the pre-set orbit.
The key of midcourse orbit correction is to select the right time for correction, and control the precision to implement each correction.Scientific research personnel have taken the current actual orbit differences, navigation differences and thrust differences into comprehensive considerations, to confirm the right time for correction, and adopt on-orbit calibration technologies, to ensure the control precision of each midcourse correction.
The first midcourse orbit correction task of the Mars probe was implemented by China Academy of Space Technology and Shanghai Academy of Spaceflight Technology through close cooperation. Long March 5 SeriesLaunch Vehicle has succeeded in sending the Mars probe to the preset orbit, so the main objective of the orbit control is not to correct the injection accuracy, but to complete the first work and on-orbit calibration of 3000N main engine based on orbit control. Meanwhile, midcourse correction will also be applied in the constant calibration of engine thrust and direction, etc. as per the actual flying status of the probe. In addition, the iterative optimization of midcourse correction strategies will also be implemented, to finally ensure that the probe can accurately enter the Mars capture corridor.
Photos are originated from the internet
Author: Yang Lu, Li Boyang, Wang Shuying, and Duan Xun