“7 Minutes of Terror” is a big problem in the Mars exploration mission.
It takes about 7 minutes for the Mars rover to gradually slow down from its original flying speed of nearly 7000m/s to zero. When it slows down, the attitude and angle of entering the atmosphere, and whether the parachute can work according to the program, precise control is required. However, in view of the lack of human knowledge of Mars and the delay of one-way radio signals between ground and fire, ground command can be said to be helpless.
At around 4:55 am on February 19, 2021, Beijing time, Perseverance landed on Mars successfully and reached the Jezero Crater (Jezero Crater) located at 18 degrees north latitude and 77 degrees west longitude on Mars.
And just a few hours ago, NASA heavily released a video, clearly showing the shocking process of landing on the surface of Mars.
What happened in 7 minutes of horror?
In the video, first is the opened parachute.
From the moment the parachute was opened, Perseverance’s camera system began to record the entire descent and landing process. The high-definition camera on the rover started shooting from a distance of 11 kilometers from the surface of Mars, so we can also see this thrilling video.
To protect Perseverance from the high temperatures during its entry into the Martian atmosphere, the heat shield was ejected.
The scarlet desolate land is getting closer and closer.
In a scene that resembles a science fiction work, the reverse thruster hoisted the rover out to ensure that it landed steadily on the surface of Mars, and then as far away from the rover as possible, and crashed on its own without hesitation. So far, the legendary “sky crane” landed smoothly. carry out.
And the next shot in the video is the cheering NASA ground staff.
Mike Watkins, head of NASA’s Jet Propulsion Laboratory, said:
This is the first time we have truly captured such a spectacular scene. By watching the performance of the rover in these videos, we will be able to learn a lot.
Not only the video, NASA also announced two audio segments today (one with machine noise and one with machine noise filtered out), which allows us on Earth to hear the real wind from Mars.
In the future, the team will continue to conduct preliminary inspections of the Perseverance system and its surrounding environment, and use the Mars Environmental Dynamics Analyzer to conduct the first weather observations.
NASA JPL reveals the secret UAV UAV
The above-mentioned precious audio and video, which NASA calls “epic”, are derived from the 23 cameras and 2 microphones onboard Perseverance-this time Perseverance also carried many black technologies to Mars, of which the most attractive There is nothing more eye-catching than the UAV WIT.
The Wit was placed on the belly of Perseverance, weighing 1.8 kilograms, height 0.5 meters, and propeller diameter 1.2 meters. The lift was provided by two counter-rotating propellers with a power of 350 watts.
This drone is charged by the solar panel on its top, and it can fly for about 90 seconds a day.
It will use the camera to track and estimate the speed to achieve visual navigation; it is equipped with Qualcomm Snapdragon 801 processor, Qualcomm flight control panel and Linux flight control system.
Recently, IEEE Spectrum also had a conversation with Tim Canham, the head of NASA JPL Mars drone operations, Lei Feng.(Public account: Leifeng.com)Compiled without changing its original intent. The following text may allow us to understand more in depth.
IEEE Spectrum: Can you briefly introduce the hardware of Gizwits?
Tim Canham: Since the witty number is a technical demonstration, JPL is willing to accept more risks.
For conventional deep-space exploration missions, the research team usually pays great attention to software and hardware, but we used a lot of ready-made consumer hardware this time. Although some electronic components are extremely sturdy and resistant to radiation, most of the technologies are commercial grade. of. For example, the processor we use is Qualcomm Snapdragon 801, which is essentially a mobile phone processor, but it is also much more powerful than the processor on the Mars rover, and its computing power is several orders of magnitude higher.
The reason is that to control the flight,The guidance loop needs to run at a frequency of 500hz. In addition, capturing images and analyzing features need to be tracked frame by frame at a frequency of 30hz. This requires considerable computing power, and NASA’s current avionics do not have enough power.
Can you describe the use of sensors in navigation?
What we use is a mobile phone-grade IMU (inertial sensor), a laser altimeter and a downward-pointing VGA (video graphics array) camera, which is mainly used for monocular feature tracking. The navigation method of the UAV is to compare dozens of features frame by frame, track the relative position, and calculate the direction and speed. In fact, this is done by estimating location, not memorizing features or creating maps.
There is also an inclinometer to determine the inclination of the ground during takeoff.
We also have a mobile-level 13-megapixel color camera, which is not used for navigation, but for taking some beautiful photos while flying. We call it RTE.
[Giz’s laser altimeter and navigation camera]
Does the witty number operate automatically?
At some levels, we can almost think of the Wit as a traditional spaceship. It has a sorting engine, we upload a series of written sequences and commands to the witty number, and it can execute these commands.In the ground simulation flight, we plan a series of waypoints as part of the navigation plan. We send the command sequence to the navigation software. When we want the drone to fly, the navigation software will start to run, execute take-off, and pass through. Pass different waypoints and then land.
Naturally, this means that the flight is planned very clearly in advance. This is not true autonomy, because if we don’t give it goals and rules, it can’t do any advanced reasoning.
We have no time in this project to develop a truly autonomous helicopter, but this “scripted flight” can prove that humans can successfully fly on Mars in the future.
Under what circumstances will wit deviate from the intended trajectory?
When all sensors are operating normally, the navigation software will produce good data. If there is a problem with the sensor, the witty will try to land in its current state, and then tell the ground what happened, and wait for us to deal with it. If the sensor fails, the helicopter will not continue to fly.
How should I decide where to fly the WIT?
We will conduct a so-called site selection process. This process starts with orbital images (a rough method for identifying possible locations), and then Perseverance will go to one of the locations for extensive surveys, based on rock, slope and even texture characteristics , Choose an operating location for the witty number.
According to the plan, what kind of flight will Wit do this time?
Because this is our first test, we have planned three major flights. During these three flights, the Wit will return to the take-off area and land because this place is a safe area that has been investigated.
We have a 30-day window period, and if we have time, we may try a fourth mission.
What are the things that engineers find interesting?
This is our first time using Linux on Mars.
We are actually running on the Linux operating system. The software framework we use is developed by JPL for the CubeSat and the instrument. We opened it up a few years ago. Therefore, engineers can get a software framework for flying on Mars helicopters and use it in their own projects. This is an open source victory.
This is also a new thing for JPL, because we tend to like very safe and verified things, but many people are very excited about it, and we are looking forward to doing it.
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