The connection between heaven and earth suddenly lost, how much do you know about emergency troubleshooting methods?

On July 25, power supply problems caused the United States to lose communication with the International Space Station, forcing it to ask Russia for help and activate the backup system. Unmanned/manned spacecraft need to maintain communication with the ground team, but it is inevitable that they will lose contact unexpectedly. So what factors may be behind this? What technical means can both the ground and the space station use to try to resolve the danger?

There are many reasons for the loss of contact

When it comes to communication loss, people's first reaction is that the communication equipment is broken. In fact, the communication link between the spacecraft and the ground team may be affected by many factors, including whether the equipment is operating normally, the strength and recognition of the signal, and natural and man-made interference.

Failure and damage of communication equipment is indeed one of the common reasons for communication interruption and loss of connection between the earth and the sky. The working environment of communication equipment on spacecraft is harsh. As the operation time increases, it is subtly affected by various environmental factors. Equipment aging is inevitable, which can easily lead to unstable communication links and irregular communication interruptions.

To cope with this situation, the spacecraft's communication system is usually designed with backup equipment or redundant communication links to ensure that even if the main equipment fails, a minimum communication connection with the ground team can be maintained, improving the reliability and stability of communications.

Power outage temporarily caused NASA to lose contact with the International Space Station

In addition to "hard damage" such as equipment failure, communication links may also be subject to "soft damage" such as signal interference. The so-called "signal interference" refers to the complex interaction between irrelevant signals from other devices or background environments and communication signals, resulting in a decrease in communication signal quality or transmission errors. For this reason, spacecraft communication systems usually apply anti-interference technology and improve signal processing algorithms to improve signal quality and anti-interference capabilities to avoid the embarrassing situation of "overshadowing the host".

As electronic devices in people's daily life become more diverse and complex, the electromagnetic background is no longer "clean", and electromagnetic wave "pollution" is getting worse. Electromagnetic interference has become one of the important factors leading to communication failures. In order to overcome this almost ubiquitous threat, spacecraft communication systems usually carefully consider electromagnetic compatibility issues during the design phase and select appropriate shielding measures and interference suppression technologies.

In fact, electromagnetic interference often comes from strong electromagnetic fields, which is not necessarily a negative consequence of human activities. Severe weather conditions, such as thunderstorms, can also generate strong electromagnetic energy, interfering with the normal operation of aerospace communication equipment, leading to poor signal transmission and communication interruption. In response to this "heavenly power" that seems difficult to confront head-on, spacecraft and ground teams generally use high-frequency radio communication technology to strengthen communication.

Even if all equipment is working properly and the interference factors in the Earth's atmosphere are not significant, the loss of communication between the ground and the spacecraft may still occur. When a spacecraft enters a specific orbit, it is unable to maintain real-time contact with the ground team due to the long distance or temporary obstruction by specific objects. Researchers generally prepare for the future and equip the spacecraft with the "skill" of autonomous navigation so that it can independently determine its own position and adjust its orbit as needed to restore smooth communication with the ground team as soon as possible.

It is not difficult to find that there are many factors that cause the loss of contact between the earth and the ground. When the spacecraft and the ground team encounter an emergency, it is necessary to verify clues from multiple sources, carefully determine the causes, and formulate a disposal plan that suits the actual situation as soon as possible.

A variety of means to overcome danger

In space missions, it is very important to ensure stable communication between the ground and the earth. Whether it is timely obtaining spacecraft status information and sending instructions, or the spacecraft sending back observation results, efficient and reliable communication lines are indispensable to ensure the smooth progress of the mission. Therefore, once an unexpected loss of contact between the ground and the earth occurs, contact must be restored as soon as possible. At the current level of technology, the ground team often bears a more important responsibility.

In order to improve the reliability of space-ground communications, ground teams often launch or resend relay communication satellites in advance to establish a "seamless" communication network. As signal relay sites, these satellites can receive signals and forward them to ground stations, overcoming the distance limitations between different locations on the earth and ensuring that the spacecraft maintains contact with the ground at as many locations as possible in orbit. This method can significantly expand the communication range and signal coverage of spacecraft in normal times, and increase the probability of successful "rescue" in emergencies.

The Voyager 2 probe has lost contact with the ground team recently

With the advancement of information technology, in the face of signal interference, spacecraft and ground teams can use technical means such as network delay compensation and error checking to improve communication quality. Network delay compensation technology can make corresponding adjustments based on the delay time of signal transmission to ensure the synchronization of communication signals. Error checking technology is expected to detect and correct errors that may occur in communication to ensure the accuracy and integrity of data.

In the face of meteorological interference in the Earth's atmosphere, high-frequency radio waves are favored by researchers. They have the special ability to penetrate the atmosphere and are particularly suitable for long-distance communications. Compared with radio waves in other frequency bands, they have less propagation loss in the atmosphere, especially being able to effectively penetrate clouds, thunderstorms, etc., helping spacecraft to try their best to maintain contact with ground teams in bad weather.

In this regard, designers can also consider equipping spacecraft with multiple receivers and transmitters to increase signal strength and coverage. At the same time, spacecraft can use antenna technology to adjust and enhance signals according to preset programs, and it is also expected to adapt to different weather conditions and environments.

Autonomous navigation technology is crucial for spacecraft positioning, changing orbits and restoring contact with the ground. At present, autonomous navigation is mainly achieved by means of laser ranging and onboard inertial navigation. Among them, the laser ranging system emits laser pulses to the target and calculates the distance between the spacecraft and the target based on the echo time of the pulse. The laser rangefinder on the spacecraft scans the surrounding environment in a timely manner, analyzes the distance information obtained, and can determine its own position and attitude relative to other objects.

The satellite-borne inertial navigation system uses inertial sensors (such as gyroscopes and accelerometers) to measure the linear acceleration and angular velocity of the spacecraft, and estimates the position and attitude changes of the spacecraft based on these data, providing high-precision position and attitude information, allowing the spacecraft to navigate independently in the absence of ground signals.

New technologies give rise to new solutions

With the advancement of technologies such as microelectronics and artificial intelligence, spacecraft can operate longer and fly to more distant targets. Although they face more challenges, there is also hope that more problems that have been traditionally difficult to deal with can be solved.

For example, the new generation of autonomous navigation technology can periodically update the position and attitude information of the spacecraft. Once the communication signal with the ground is weak or interrupted, it can deal with it according to its own positioning information. Obviously, this effectively improves the independence and flexibility of the spacecraft and reduces its dependence on ground control.

It is worth mentioning that autonomous navigation technology also provides better safety and accuracy for space missions. Spacecraft can adjust their orbits based on real-time position and attitude information to meet various mission requirements, such as satellite positioning and space exploration, thus bringing more possibilities to space exploration and resource utilization.

For a long time, problems with the internal systems of spacecraft have led to loss of communication between the earth and the sky, including computer system crashes, power supply failures, sensor failures, etc., and the only way out is to "hope for the best". However, with the advancement of technology and processes, the backup of spacecraft has been enhanced, and it is expected that they will gradually acquire the ability to resolve failures on their own.

For example, in the face of a computer system crash, the spacecraft will take emergency measures to promptly activate the internal backup power supply and backup communication equipment. The backup power supply can provide stable power to ensure the normal operation of other important equipment. The backup communication equipment uses different frequencies or uses satellites to restore contact with the ground team as soon as possible.

Before a spacecraft flies into space, the power system will be carefully checked by scientific researchers, but battery failure, circuit abnormalities and other factors may still cause power supply failures. In order to cope with such accidents, the spacecraft will be equipped with a backup power system, including solar panels, fuel cells, etc.

Spacecraft are equipped with various sensors to obtain environmental information and perform observation tasks. If some sensors fail to work properly, they may "involve" other equipment. For this reason, spacecraft can be equipped with multiple sensor redundancy systems. Even if a sensor fails, other sensors can still provide accurate data and keep in touch with the ground team through backup communication equipment.

Looking ahead, as the application of artificial intelligence technology becomes more extensive and in-depth, spacecraft control software will also have better modular and universal performance. Faced with the crisis of loss of connection between the earth and the sky caused by various factors, the spacecraft is expected to autonomously "isolate" the faulty part, rebuild the control system, and use relay communication satellites, autonomous navigation, backup systems and equipment to improve the efficiency of restoring contact between the earth and the sky, thereby helping the mission to proceed smoothly and achieve greater space exploration achievements. (Author: Ma Jie Image source: NASA gatekeeper expert: Jiang Fan, deputy director of the Science and Technology Committee of China Aerospace Science and Technology Corporation)