Recently, the American Ingenuity UAV lost contact with the rover and the ground team two days after it lost contact with the surface of Mars, but due to rotor damage, it unfortunately ended its career flying on Mars. In fact, in the course of the development of human spaceflight, spacecraft will inevitably encounter thrilling moments of accidental loss of contact. With the continuous advancement of technology and the increasing complexity of space missions, the cognition and handling of accidental loss of spacecraft by scientific researchers are also keeping pace with the times. So what are some ways to save the day? And what are the tricks to prevent problems before they happen and improve the success rate and safety of space missions?
The reasons for the loss of contact are varied
In addition to "retiring after success and dying", the accidental loss of contact with spacecraft is often an "insider" complex emergency, and its reasons are varied, which can usually be summarized into three aspects: insufficient design of the spacecraft itself, complex and harsh space environment, and human factors. 
After the U.S. Ingenuity Mars drone regained contact, it was forced to retire due to rotor damage.
Spacecraft are known to face harsh environmental conditions in space, including extreme high and low temperatures, radiation, and microgravity. These factors place demanding demands on the materials and equipment performance of spacecraft, which must be carefully considered during the design and construction of spacecraft.
For example, aerospace designers may not have fully taken into account the extreme temperature differences in space—spacecraft are often exposed to high temperatures exposed to sunlight and extreme cold in the background of the universe, and materials must be selected to withstand these temperature differences and maintain stable performance. If the scientific researcher does not design the structure of the spacecraft well, or the materials selected by the spacecraft do not have good thermal conductivity properties, and cannot effectively remove heat at high temperatures, while maintaining sufficient flexibility at low temperatures, then it may lead to structural damage to the spacecraft, and accidental loss of contact is inevitable.
In addition, the use of qualified radiation-resistant materials in spacecraft, poorly designed shielding structures, or inadequate backup circuitry and redundant systems can allow cosmic ionizing radiation to cause potential damage to the spacecraft's electronic components. In the event of strong radiation interference, the spacecraft may accidentally lose contact with the team on the ground.
The microgravity environment also has a significant impact on the design of spacecraft, requiring spacecraft to overcome more complex challenges in dealing with inertial and sealing issues. If scientists do not consider how to maintain the stability of equipment and systems, and how to deal with the flow of liquids, gases and heat, the probability of spacecraft failure will also increase significantly.
However, even with a well-designed spacecraft, solar storms, cosmic rays, space debris, etc., can still have a negative impact on the normal operation of the spacecraft. The essence of a solar storm is the release of large-scale energy caused by solar activity, and the stream of high-energy particles is enough to interfere with or damage the electronic components of the spacecraft, causing equipment failure. Cosmic rays, as high-energy particles from the depths of the universe, also have the potential to penetrate the spacecraft shell and magnify the hidden danger of electronic components.
Moreover, as human space activities become more and more frequent, a large number of discarded spacecraft parts, debris and micrometeorites orbit the earth at extremely high speeds, and there is a possibility that they will further flood in a wider area such as the Earth-Moon space, and the probability of collision with spacecraft is also increasing. With the help of high-speed kinetic energy, tiny debris also has the potential to damage the spacecraft hull and even cause serious structural failure.
In addition, in the process of spacecraft launch and operation, human factors may also lead to accidental loss of contact, including ground operator errors, software errors, improper mission planning, etc., which will directly affect the safety status of the spacecraft.
Due to the relatively limited human understanding of the environment in deep space and alien planets, it is more common for spacecraft working there to accidentally lose contact. For example, the Ingenuity drone accidentally lost contact for about two months at the turn of the spring and summer of 2023, mainly because the landing site was a small hill away from the Perseverance rover, which served as a relay mission, causing the signal to be interrupted.
The rescue process is in a race against time
When a spacecraft unexpectedly loses contact with the ground team, researchers usually quickly take a series of rescue measures and do their best to reconnect with the spacecraft as soon as possible to ensure the success of the mission. 
The U.S. Voyager 1 probe has lost normal communication with the Earth team.
After the ground monitoring center found that the spacecraft was accidentally lost, it immediately activated the emergency plan and organized a professional team to analyze the failure of the spacecraft and investigate the causes. During this time, spacecraft designers and manufacturers will work closely together to develop a rescue plan.
First of all, the professional team will analyze the data records of the spacecraft and strive to determine the accidental loss of contact and potential causes of failure as soon as possible. At about the same time, the ground operator's operating records are scrutinized to determine if there is a human factor that caused the error. Next, if a software bug is found, the scientist will try to fix the problem through a software update or fix. If a spacecraft is unexpectedly lost due to mission misplanning, they reassess the mission plan and make adjustments.
After the activation of the emergency plan, the operator will attempt to "wake up" and restore the functionality of the spacecraft. The most common method is to send instructions and search for signals, including checking the operation of key components such as the spacecraft's power system, navigation system, and communication system, reconfiguring the spacecraft's mission mode, and possibly adjusting the spacecraft's attitude.
If it is confirmed that the spacecraft communication system is failing, the ground control team will activate backup communications equipment to increase the chance of success in rebuilding communications. These devices will utilize lasers, millimeter waves, etc., and will theoretically be able to achieve higher communication rates and longer communication distances.
In order to seize the opportunity to rescue, the ground control team will also use multi-party cooperation and resource deployment to use other spacecraft to assist in the search for "accidental missing persons". For example, satellites in orbit and Mars rovers can provide support such as navigation and positioning, remote sensing monitoring, etc., to help ground control teams determine the location of target spacecraft as soon as possible, at least to help narrow down the search area, and provide critical information. For example, the Perseverance rover climbed to the top of a mountain, expanded the communication range, narrowed the signal blind spots, and re-established communication with the Ingenuity drone.
The precautionary measures are rigorous and comprehensive
Although it is not possible to completely avoid the accidental loss of contact with spacecraft, by taking a series of preventive measures, researchers can reduce such accidents and improve the safety of spacecraft and the success rate of missions. 
Spacecraft that accidentally lose contact often have abnormal operating attitudes.
There is no doubt that spacecraft manufacturing and quality control are key to preventing accidental loss of contact. Spacecraft design and manufacturing staff should strictly implement quality control and management processes, including mandatory testing and verification procedures, to ensure excellent reliability and stability of the spacecraft before leaving the factory, reduce failure rates, and extend the uptime and working life of the spacecraft.
In addition, manufacturers should pay close attention to the maintenance and overhaul status of the spacecraft, and repair and replace parts that may have hidden dangers in a timely manner to minimize the risk of the spacecraft accidentally losing contact due to its own shortcomings.
In fact, redundant design is one of the important means to improve the reliability and fault tolerance of spacecraft. By using a dual power supply system, multiple communication links, backup software, etc., the spacecraft can automatically switch to backup work and operate normally when it encounters a component or system failure. In this way, the spacecraft's ability to respond to failures in a timely manner is greatly increased, significantly increasing the likelihood of mission success. Of course, backup devices are also rigorously tested and validated during the manufacturing process.
With the advancement of artificial intelligence and other technologies, strengthening the autonomous monitoring and diagnosis capabilities of spacecraft will also be an effective means to avoid accidental loss of contact. At that time, the spacecraft will be able to detect signs of abnormal operation in time, issue fault alarms, autonomously analyze the cause of failure, and automatically initiate repair procedures or switch to standby equipment operation. Autonomous navigation systems can also help spacecraft maintain normal operation in the event of poor signals and inaccurate positioning. The introduction of these advanced technologies and functions will significantly improve the autonomy and safety of spacecraft, making accidental loss of contact no longer so "scary".
In addition, by optimizing spacecraft mission planning and orbit design, researchers can also control the influence of space environmental factors as much as possible and improve the success rate of the mission. For example, when choosing the orbit and flight path of a spacecraft, it is necessary for researchers to consider factors such as the timing of solar storms and space debris dense areas to reduce the risk of damage to spacecraft. This requires researchers to grasp enough signs and laws of space environment changes, comprehensively weigh the space environment change trends, space weather**, spacecraft mission feasibility, etc., and finally formulate the best mission planning and orbit design strategies.
In short, the unexpected loss of contact with the spacecraft is an emergency situation at a critical juncture, which requires the ground control team to have the ability to respond quickly, make accurate judgments and execute efficiently. At the same time, by strengthening the prevention and response measures of spacecraft, scientists are expected to minimize such incidents and improve the success rate of space missions. In the future, with the continuous progress of aerospace technology and the improvement of space mission planning, it is believed that spacecraft rescue measures and accident prevention plans will provide new "surprises" and promote the safety and reliability of spacecraft to a new high.
This article was originally published in China Aerospace News Flying Science Weekly
Text: Ma Jie, editor, Gao Chen, review, Yang Jian, Yang Lei, producer, Suo Adi