Author: Site Editor Publish Time: 2020-11-04 Origin: Site
At 22:00 on October 28, under the control of the flight control team of China's first Mars exploration mission, eight 25N engines of tianwen-1 spacecraft ignited at the same time, successfully completed the third orbit correction, and calibrated the actual performance of the 25N engine in orbit. The implementation of the third half way orbit correction is to adjust the transfer orbit again after deep space maneuver, so that the Mars probe will rendezvous with Mars according to the scheduled time. Up to now, tianwen-1 has been in orbit for 97 days, about 44 million kilometers away from the earth, and the flight distance is about 256 million kilometers.
At 23:00 on October 9, under the control of the flight control team of China's first Mars exploration mission, the main engine of tianwen-1 probe ignited for more than 480 seconds, successfully completing the deep space maneuver. The orbital maneuver was carried out in deep space about 29.4 million kilometers from the earth.
The reporter learned from the eighth Institute of China Aerospace Science and technology group that this orbit change is of great significance for the "tianwen-1" Mars exploration mission. At this point, the flight orbit of the probe becomes an orbit that can be accurately captured by Mars and intersects with Mars accurately. The probe will rendezvous with Mars about four months after its current orbit, during which it will implement two or three orbital midway corrections.
What is deep space maneuver? What's the difference between orbit correction and orbit correction? According to the Mars Orbiter team of the eighth Academy of Aerospace Science and technology group, the deep space maneuver refers to an orbit change maneuver implemented in the ground fire transfer phase. Through deep space maneuver, the original flight speed and direction of the probe can be changed, so that it can fly smoothly to Mars along the orbit after orbit change.
Deep space maneuver is the result of joint optimization of launch trajectory and ground fire transfer orbit. It can improve the launch capability of the carrier, increase the launch quality of the detector, and make the detector carry more propellant to complete the detection task better. Different from the conventional midway correction with small speed increment and short engine operation, during the deep space maneuver, the probe changes from an escape transfer orbit launched into orbit to an orbit that accurately reaches Mars, with large speed increment and long engine working time, which puts forward high requirements for the control and propulsion system of the probe.
Three advantages of deep space maneuver: through the use of deep space maneuver for orbit design and orbit control, the Mars Orbiter team of the eighth Institute not only successfully increased the propellant carrying capacity of the probe, but also achieved three goals.
First of all, deep space maneuver decomposes a large acquisition speed increment into two relatively small speed increments, which is conducive to reducing the single engine working time and ensuring the reliability of the engine.
At the same time, the implementation of deep space maneuver is conducive to the calibration of 3000n engine. In the process, thrust and specific impulse of 3000n large engine can be calibrated, and accurate engine calibration parameters can better ensure the accuracy of Mars capture.
Through deep space maneuver, the Mars Orbiter research team of the eighth Institute of research and development of the Mars Orbiter has optimized the arrival time of the probe, which can obtain more favorable lighting conditions and communication conditions at the capture point, and shorten the fire shadow time (the probe enters the shadow area covered by the sun light by Mars) and the communication blind area during the acquisition.
1How to realize deep space maneuver?
To carry out the deep space maneuver mission, the Mars Orbiter team of the eighth Academy of Sciences should formulate the deep space maneuver orbit change strategy according to the scheduled arrival time, orbit parameters and real-time measurement and control orbit parameters, and complete the corresponding attitude and orbit control of the probe, so as to ensure that the probe is in the orbit accurately intersecting with the fire star after the deep space maneuver.
In order to complete the precise orbit determination of ground-based TT & C and precise autonomous orbit control on board, the orbit determination task of ground surface detector is jointly completed by China's deep space TT & C station and the observatory, which ensures the precise orbit determination requirements of the detector's orbit change accurately. In order to control the orbit accurately and autonomously, the Mars Orbiter is equipped with high-precision gyroscopes, accelerometers and on-board computers with fault identification and autonomous processing capabilities, which fully ensure the accuracy and reliability of orbit control.
Aim 300 million kilometers away
In this deep space maneuver, Mars was about 300 million kilometers away from the orbiter during the braking capture, and the error control was about 200 kilometers, which was equivalent to aiming at a target with a diameter of about 0.8 meters in the distance of 1200 kilometers from Beijing to Shanghai. With the unremitting efforts of the Mars Orbiter team of the eighth Academy of Sciences, the actual accuracy of the deep space maneuver control is better than the design index.
In the future, the team will iteratively optimize the midway correction strategy according to the actual flight status of the probe, and use the midway correction to continuously correct the orbit to Mars, so as to ensure that the probe can accurately enter the Mars capture corridor as planned, be captured by Mars gravity and enter the ring fire orbit, and carry out preparations for landing on Mars and follow-up scientific exploration.