Recently, the US Spirit probe completed a deep space laser communication test with ground facilities 16 million kilometers away, setting a new space optical communication distance record. So what are the advantages of laser communication? Based on technical principles and mission requirements, what difficulties does it need to overcome? What is the prospect of its application in the field of deep space exploration in the future?

Technological breakthroughs, not afraid of challenges
Deep space exploration is an extremely challenging task in the course of space researchers exploring the universe. Probes need to cross distant interstellar space, overcome extreme environments and harsh conditions, acquire and transmit valuable data, and communication technology plays a vital role.

Schematic diagram of deep space laser communication experiment between the Spirit satellite probe and the ground observatory

On October 13, the Spirit probe launched, beginning a journey of exploration that will last at least eight years. At the beginning of the mission, it worked with the Hale telescope at the Palomar Observatory in the United States to test deep-space laser communication technology, using near-infrared laser coding to communicate data with teams on Earth. To this end, the detector and its laser communication equipment need to overcome at least four types of difficulties. Respectively, the distant distance, signal attenuation and interference, bandwidth limitation and delay, energy limitation and heat dissipation problems deserve attention. Researchers have long anticipated and prepared for these difficulties, and have broken through a series of key technologies, laying a good foundation for the Spirit probe to carry out deep space laser communication experiments.
First of all, the Spirit detector uses high-speed data transmission technology, selected laser beam as the transmission medium, equipped with a high-power laser transmitter, using the advantages of laser transmission rate and high stability, trying to establish laser communication links in the deep space environment.
Secondly, in order to improve the reliability and stability of communication, the Spirit detector adopts efficient coding technology, which can achieve higher data transmission rate within the limited bandwidth by optimizing the data coding. At the same time, it can reduce the bit error rate and improve the accuracy of data transmission by using the technology of forward error correction coding.
Thirdly, with the help of intelligent scheduling and control technology, the probe realizes the optimal utilization of communication resources. The technology can automatically adjust communication protocols and transmission rates according to changes in task requirements and communication environment, thus ensuring the best communication results under limited energy conditions.
Finally, in order to enhance the signal reception capability, the Spirit probe uses multi-beam reception technology. This technology uses multiple receiving antennas to form an array, which can enhance the receiving sensitivity and stability of the signal, and then maintain a stable communication connection in the complex deep space environment.

The advantages are obvious, hidden in the secret
The outside world is not difficult to find that the laser is the core element of the deep space communication test of the Spirit probe, so what specific advantages does the laser have to help the significant progress of deep space communication? What's the mystery?
On the one hand, the growing demand for massive data, high-resolution images and videos for deep space exploration missions is bound to require higher data transmission rates for deep space communications. In the face of the communication transmission distance that is often "starting" with tens of millions of kilometers, radio waves are gradually "powerless."
While laser communication encodes information on photons, compared with radio waves, near-infrared light waves have a narrower wavelength and higher frequency, making it possible to build a spatial data "highway" with more efficient and smooth information transmission. This point has been preliminarily verified in the early low-Earth orbit space experiments. After taking relevant adaptive measures and overcoming atmospheric interference, the data transmission rate of the laser communication system was once nearly 100 times higher than that of the previous communication means.