The story behind the development of Shanghai's "intelligent manufacturing" Mars rover payload

The National Space Administration has released the first batch of scientific images taken by the Zhurong Mars rover, marking the complete success of my country's first Mars exploration mission. The rover carries a scientific payload developed by the Shanghai Institute of Technical Physics of the Chinese Academy of Sciences (hereinafter referred to as Shanghai Institute of Technical Physics) - the Mars Surface Composition Detector.

On the 11th, the National Space Administration released the first batch of scientific images of the Tianwen-1 probe landing on Mars, and announced the panoramic view of the landing site, the Martian topography, the "Chinese footprints" and the "landing and patrolling group photo" taken by the Zhurong Mars rover, marking the complete success of my country's first Mars exploration mission. Reporters learned from the Shanghai Institute of Technical Physics of the Chinese Academy of Sciences that the "Shanghai Eyes" for Mars exploration developed by the institute - the Mars mineral spectrometer carried on the orbiter and the Mars surface composition detector on the Zhurong Mars rover have been successfully started and successfully transmitted detection data. While the Mars payload development team of the Shanghai Institute of Technical Physics is excited about obtaining the first batch of scientific data, it is also considering how to improve payload performance and enhance scientific exploration capabilities.

After Tianwen-1 entered the orbit around Mars, the Mars Mineral Spectrometer was turned on for the first time on February 28, and has been turned on several times since then to obtain scientific data from the landing area. It is expected that after July, the Tianwen-1 orbiter will enter the scientific exploration orbit, and the Mars Mineral Spectrometer will officially enter the working state. It has internationally advanced spectral detection capabilities, with a spectral detection range that can extend from 0.378 microns to 3.425 microns, and up to 576 detection spectrum bands.

The Mars Surface Composition Detector, which landed on the surface of Mars with the Zhurong rover, was not turned on until June 4, and the first batch of data was sent back to Earth on June 5. Shu Rong, deputy director of the Shanghai Institute of Technical Physics and commander of the lunar and deep space exploration series payload, introduced that this payload combines two technologies: active laser-induced breakdown spectroscopy detection and passive short infrared spectroscopy detection. "The equipment is very sensitive, and it uses two calibration plates from China and France at the same time. Our data can be mutually verified with existing international data." Shu Rong said that this will strongly prove my country's scientific research strength in planetary exploration.

The highest temperature on the surface of Mars is 20 to 30 degrees Celsius, while at night it is only several dozen degrees below zero. The payload is most afraid of the "low temperature challenge", and it was designed based on the standard of -100 degrees Celsius during development. Now, Mars is entering summer, the weather is relatively stable, and the temperature is gradually rising, which is a good time for patrolling and detecting Mars.

Because the Mars Surface Composition Detector's calibration rods and lasers are exposed outside the Zhurong rover and difficult to keep warm, the detector's operating period is chosen to be around 2 p.m. on the Martian day, so that the instrument can heat up naturally and save energy for the rover.

The infrared focal plane detector in the Mars mineral spectrometer on the orbiter also has to experience low-temperature operation and room-temperature storage. For this reason, researchers have adopted various temperature control methods to ensure the performance and reliability of the payload.

In a test laboratory of the Shanghai Institute of Technology Physics, the first batch of devices that came off the production line in 2017 have undergone 2,000 "ice and fire" temperature cycle tests. Zhou Songmin, an associate researcher at the Materials and Devices Center of the Shanghai Institute of Technology Physics, explained that this is three times more than the requirements of the Mars mission.

In addition to the Mars surface composition detector, the Shanghai Institute of Technical Physics is also responsible for the development of the Mars mineral spectrometer on the Mars orbiter, making the institute the only scientific research institution responsible for the development of two payloads.

Shu Rong, deputy director of the Shanghai Institute of Technical Physics and payload commander of the lunar and deep space exploration series, said that the Mars Surface Composition Detector will conduct high-precision scientific detection of elements, minerals and rocks on the Martian surface in the landing area. "It was turned on on June 4 and successfully downloaded the first set of data on June 5." The Mars Mineral Spectrometer was turned on on February 28 and conducted multiple detections of the pre-selected landing area.

In order to better complete this Mars exploration mission, the Shanghai Institute of Technical Physics has created a series of "firsts".

The anticipation and tension of the moment of "real combat"

Before the Mars Surface Composition Detector was turned on, Shu Rong's team was worried about whether it would be intact and "obedient" after following the "Zhurong" Mars rover through a "long journey"... Before successfully transmitting data, they were also worried about whether the data transmission process would be smooth...

In fact, Shu Rong's team had conducted countless simulation experiments in the early stages, but when it came to the "real combat", they could not hide their inner nervousness and anticipation.

In fact, the moment when the Zhurong rover landed was the most tense moment for them. According to statistics, the success rate of a rover landing on the surface of Mars is only 50%. Even if the rover lands successfully, how will the Mars surface composition detector be after the thermal shock of landing on Mars? Can the detector, which is attached to the outside of the rover and accounts for more than 1/2 of the rover's load, withstand the test of the large temperature difference between day and night on Mars?

The answer was revealed on June 4. On that day, the Mars Surface Composition Detector started up normally and successfully downloaded the first set of data the next day. Shu Rong's team members were extremely excited.

"After being turned on, the detector calibrated the titanium sample plate and detected the Martian rocks near the Zhurong rover." Shu Rong said that the detector's telemetry data is currently normal and its working status is stable.

2.5 to 3.4 micron hyperspectral spectrum has the ability to detect water molecules

Tianwen-1's analysis of the pre-selected landing area requires the help of payloads such as the Mars Mineral Spectrometer. "Before landing, the scientific data obtained by the Mars Mineral Spectrometer will help determine the mineral composition and distribution of the landing area," said He Zhiping, a researcher at the Shanghai Institute of Technical Physics and chief designer of the Mars Mineral Spectrometer. The analyzer was turned on for the first time on February 28, after Tianwen-1 entered the orbit around Mars.

Subsequently, the Mars mineral spectrometer was turned on several times and successfully obtained scientific data, contributing to leaving a "Chinese mark" on Mars.

This payload has the world's most advanced spectral detection capability, with a spectral detection range of 0.378 microns to 3.425 microns and up to 576 detection spectrum bands. "Especially in the 2.5 micron to 3.4 micron high-spectral detection, it is the first time that my country has verified and applied it in space." In Ho Zhiping's view, this spectrum band is of great value and has the ability to detect water molecules.

He further explained that in past space-based earth exploration missions, the above-mentioned spectrum band had never been used for earth remote sensing observations because it was absorbed by the earth's atmosphere.

In the detection of the 1 micron to 3.4 micron spectrum of the Mars Mineral Spectrometer, the mercury cadmium telluride detector needs to withstand the test of a temperature difference of 200 degrees Celsius. "It's like throwing the instrument into a stove, then into an ice cube, and repeating the cycle," said Zhou Songmin, associate researcher at the Shanghai Institute of Technical Physics and chief designer of the infrared array detector of the Mars Mineral Spectrometer.

According to design requirements, researchers needed to carry out 500 cycle life tests, but in order to make it better adapt to the "ice and fire" Martian environment, they conducted as many as 2,000 tests on the ground.

However, the Mars Mineral Spectrometer has not yet officially started its scientific exploration mission. "Later, after the Mars rover entered the scientific exploration orbit, the analyzer officially started working," Ho said. They also expect the analyzer to make more discoveries.

Foreign research institutions specialize in analyzing their technical solutions

The working process of the Mars Surface Composition Detector is to first use an ultra-high-definition camera to "navigate". After the researchers find the target of interest, they will give instructions to the detector by comprehensively considering factors such as the solar altitude angle and temperature, and it can then work within the specified time.

However, unlike lunar exploration, the research team combined active laser-induced breakdown spectroscopy detection technology and passive short-wave infrared spectroscopy detection technology. The former is the first time that my country has used it in space.

Shu Rong introduced that active laser induced breakdown spectroscopy detection is to shoot a beam of laser from the payload, using the instantaneous temperature of up to thousands of degrees Celsius to excite plasma from the material on the surface of Mars. By detecting the spectral composition and gas composition of the spark, the elemental composition of the surface of Mars can be analyzed with high precision. "Most of the elements in the periodic table can be analyzed."