my country's first Mercury-dropping star was successfully launched! What is a Mercury-dropping star and why is it so important?

On April 16 this year, my country's first dedicated precipitation measurement satellite, Fengyun-3 precipitation satellite, was successfully launched. This is the 20th satellite in the Fengyun series of meteorological satellites, Feng-20. For the first time, the global precipitation satellite family has a "made in China". This is the first precipitation satellite in our country and the third in the world. The first two were jointly developed by the United States and Japan, which shows how difficult it is.

To understand why Mercury is so important, we must first understand what precipitation is.

Precipitation is an important process of the earth's energy and water cycle. It has a great impact on agriculture and people's daily travel. Understanding the precipitation situation can help people better arrange production and life. In order to understand precipitation, ancient people developed bone armor, ruler measurement, rain reporting system, etc. Nowadays, countries around the world still cannot do without observation of precipitation. We often complain that weather forecasts are not accurate enough. One of the reasons is that the meteorological observation capabilities need to be strengthened. Only with accurate observations can accurate forecasts be possible. In order to solve this problem, "Precipitation Star" has gradually stepped onto the stage of meteorological observation. The full name of "Precipitation Star" is precipitation measurement satellite, but don't misunderstand it as a satellite that can precipitate from space. With it, it's like having a "clairvoyant" in the sky, which can monitor precipitation on a large scale in space. However, the development of this star is very difficult from satellite platforms to remote sensing instruments. Since 2006, our country has begun the technical research and development of Precipitation Star, and it will be successfully launched in 2023. It can be said to be "seventeen years of sharpening a sword."

So what new capabilities does the launch of Mercury bring us?

Before launching the Mercury Satellite, we mainly observed precipitation through radars, rain gauges and other instruments placed on the ground. These devices are limited in coverage due to the influence of terrain, and it is difficult to cover vast seas, mountains, deserts and other areas; satellites have unique advantages in monitoring these areas. So is it necessary to move powerful instruments and equipment to satellites to achieve a strong combination of satellites and the ground? The purpose of developing the Mercury Satellite is to achieve this. The Mercury Satellite is like a CT scanner that can monitor atmospheric precipitation, and realize three-dimensional detection of atmospheric precipitation from space to the ground. This is our country’s first precipitation satellite. It is the first time that the three-dimensional structure of the precipitation system has been measured on a satellite through the combined means of active and passive microwaves, and the first time that the imaging and detection integrated design of the passive microwave radiometer on the satellite has been realized. The Mercury Satellite embodies many breakthroughs and many firsts.

So how does Mercury achieve more accurate precipitation observations?

In order to achieve the best observation purpose, the precipitation satellite carries several instruments, including active microwave instruments, passive microwave instruments, optical imaging instruments, etc., each with its own unique skills, working together and complementing each other. The mainstay of the precipitation satellite, the precipitation radar, has superb layered observation capabilities, and obtains fine three-dimensional structural information of precipitation from top to bottom, just like doing a CT scan of atmospheric precipitation. This instrument is the first time that our country has tackled key problems and developed it, and its overall technical indicators have reached the international advanced level. By designing two radar working frequency bands, which are equivalent to two precise rain gauges with different scales, it can accurately measure heavy rain and light rain, and further distinguish the specific state of precipitation, such as liquid water droplets or solid ice crystals. Through active precipitation detection, passive microwave precipitation remote sensing and infrared instrument precipitation estimation, we can help meteorologists accurately monitor precipitation and make more accurate weather forecasts for future precipitation. This is of great significance for my country's heavy precipitation monitoring, forecasting and warning, precipitation mechanism research and support for artificial weather modification business.

Currently, the precipitation satellite is in the stage of in-orbit testing. After the test, data products will be released to the public to help users understand the three-dimensional structure and mechanism of the precipitation system more deeply. It will also further leverage the advantages of low-orbit meteorological satellite network observation and contribute Chinese wisdom and Fengyun solutions to the world in the field of meteorological disaster monitoring.

This article is a work supported by Science Popularization China Starry Sky Project

Author: Shang Jian

Reviewer: Wang Bo, Deputy Secretary-General of China Satellite Navigation and Positioning Association

Produced by: China Association for Science and Technology Department of Science Popularization

Producer: China Science and Technology Press Co., Ltd., Beijing Zhongke Xinghe Culture Media Co., Ltd.