Leaving the Earth’s orbit and running towards Mars, Tianwen-1 will rendezvous with Mars in 4 months

　　"Tianwen No.1" officially left "mother's arms."

　　At 23:00 on October 9, 2020, under the control of the flight control team of my country's first Mars exploration mission, the main engine of the Tianwen-1 probe ignited for more than 480 seconds, successfully completing the deep space maneuver.

　　The orbital control performed by changing the current orbit of the probe into a new orbit is called maneuvering.

The orbital maneuver was carried out in deep space approximately 29.4 million kilometers from the earth.

　　For the "Tianwen-1" Mars exploration mission, this orbit change is of great significance.

　　At this point, the orbit of the probe becomes an orbit that can be accurately captured by Mars and intersect with Mars.

The probe will rendezvous with Mars about 4 months after its current orbit, during which two or three midway corrections will be implemented.

What is deep space maneuvering?

What is the difference with track correction?

　　According to the Mars Orbiter Team of the Eighth Academy of Aerospace Science and Technology Group (also known as Shanghai Aerospace Technology Research Institute), the paper told The Paper (www.thepaper.cn) that a deep-space maneuver refers to an orbital change maneuver implemented in the transfer section of a ground fire.

　　Schematic diagram of the probe's deep space maneuvering track

　　Through deep space maneuvering, the original flight speed and direction of the probe can be changed, so that it can fly smoothly to Mars along the orbit after the change.

　　Performing deep space maneuvers is the result of the joint optimization of the carrier’s orbital ballistics and the ground-fire transfer trajectory, which can enhance the launch capability of the carrier and increase the launch quality of the detector, so that the detector can carry more propellant and better complete the detection. task.

　　Different from the conventional midway correction where the speed increment is small and the engine work is shorter, during the deep space maneuver, the probe changes its orbit from the escape transfer orbit that is launched into orbit to the orbit that accurately reaches Mars. The speed increment is large and the engine works time. Long, extremely high requirements are placed on the detector control and propulsion system.

"Three Benefits" of Deep Space Maneuvering

　　By using deep-space maneuvers for orbit design and orbit control, the Mars Orbiter team of the Eight Institutes not only successfully increased the probe's propellant carrying capacity, but also achieved three goals.

　　First of all, deep space maneuvering decomposes a large capture speed increment into two relatively small speed increments, which is conducive to reducing the single working time of the engine and ensuring the reliability of engine operation.

　　At the same time, during the implementation of deep-space maneuvers, the thrust and specific impulse of the 3000N large engine can be calibrated, and the precise engine calibration parameters can better ensure the accuracy of Mars capture.

　　Through deep-space maneuvering, the Eighth Academy Mars Orbiter development team optimized the arrival time of the probe, which was able to obtain more favorable lighting conditions and communication conditions at the capture point, and also allowed the probe to experience the Naruto time during capture (the probe enters sunlight) The shadow area occluded by Mars) and the communication blind area are shorter.

How to achieve deep space maneuver?

　　The Paper (www.thepaper.cn) reporter learned that the implementation of deep space maneuvering missions requires the Eighth Academy Mars Orbiter team to formulate an orbit change strategy based on the scheduled arrival time to Mars, orbit parameters, and real-time measurement and control orbit determination parameters to complete the corresponding probe attitude And orbit control to ensure that the probe is in an orbit that accurately intersects Mars after maneuvering in deep space.

　　In order to complete the precise orbit determination of ground-based measurement and control and the precise and autonomous orbital control on the instrument, in this deep-space maneuver, the task of determining the orbit of the ground-based detector was jointly completed by my country’s deep-space measurement and control station and the observatory, which accurately ensured that the Precise orbit determination requirements.

　　In order to be able to accurately and autonomously control the orbit, the Mars Orbiter is equipped with a high-precision gyroscope, accelerometer, and an on-board computer with fault recognition and autonomous processing capabilities, which fully guarantees the accuracy and reliability of orbit control.

300 million kilometers aiming accuracy is better than the design index

　　In this deep space maneuver, the position of Mars during the braking capture of the orbiter was about 300 million kilometers away from the orbiter, and the error control was about 200 kilometers, which is equivalent to aiming at a diameter of about 0.8 meters in a distance of about 1200 kilometers from Beijing to Shanghai. The goal.

　　With the unremitting efforts of the Mars Orbiter team of the Eight Institutes, the actual accuracy of the deep space maneuver control is better than the design index.

　　In the follow-up, the team will iteratively optimize the midway correction strategy based on the actual flight status of the probe, and use midway correction to continuously correct the orbit to Mars to ensure that the probe can accurately enter the Mars capture corridor as planned, and be captured by Mars gravity into the ring fire. Orbit, prepare for landing on Mars and follow-up scientific exploration.

　　(This article is from The Paper. For more original information, please download the "The Paper" APP)

　　The Paper, reporter Yu Kai, correspondent Xie Pan