After successfully landing on the moon and exploring the sun, how is India's deep space exploration developing?

At 14:20 Beijing time on September 2, India successfully launched the Apollo-L1 solar probe from the Satish Dhawan Space Center using the PSLV-XL rocket. As the first solar probe developed and launched by India, the Apollo-L1 is the latest representative of India's ambition in deep space exploration and will become a pioneer in India's space science.

The long-awaited Helios probe

India's solar exploration program was launched very early, and was originally called "Helios", but with the passage of time, the Helios project has undergone significant changes. In 2008, the Indian Space Research Advisory Committee proposed the idea of ​​building a Helios solar probe. The "Helios" in the early plan was just a small solar probe weighing 400 kilograms and operating in a low-Earth orbit 800 kilometers above the ground. This experimental satellite was equipped with a coronagraph for observing and studying the solar corona.

India successfully launches Apollo-L1 solar probe

Although India's Apollo solar probe was demonstrated early, unfortunately, as a large developing country, purely scientific basic research has a low priority in India's aerospace industry. Not to mention compared with remote sensing satellites with great military value and communication satellites with economic value, even compared with other deep space exploration projects with political value, the solar probe can only stand aside.

In the 2012-2013 fiscal year, the Indian Space Research Organization received a large budget, paving the way for the successful launch of a Mars probe named "Mangarian" in 2013. The Mangalyaan probe was originally scheduled to be launched between 2016 and 2018, but it suddenly received a huge grant in 2012 in order to launch it during the 2013 Mars exploration window and strive to win the honor of being Asia's first Mars probe.

In comparison, the Apollo solar probe lacks publicity gimmicks. At a time when the annual budget of the Indian Space Research Organization is rising, it has been delayed several times due to insufficient project budget, which is really regrettable.

In the fiscal year 2016-2017, the Indian Space Research Organization finally allocated a pre-research experiment budget of 3 million rupees (less than 300,000 yuan) for the Apollo probe. Although the funding was belated, the project was finally implemented. With the official launch of the project and the allocation of research and development funds, the mission has changed significantly. It was changed to launch to the Sun-Earth Lagrange point L1, and the project was renamed Apollo-L1. As of July 2019, the Apollo-L1 project has been allocated a total of 3.7853 billion rupees, equivalent to about 330 million yuan, which ensures the subsequent development of the probe. Even if the launch funds of the PSLV rocket are added, compared with the deep space exploration projects in Europe, the United States and Japan, the funds for the Indian Apollo-L1 solar probe project are very small.

Solar exploration has a unique skill

India's Apollo probe is no longer the same as it used to be. It is no longer the small 400-kilogram probe. The current Apollo-L1 probe uses the I-1K satellite platform and is a 1,480-kilogram probe. The PSLV-XL rocket cannot directly launch it into a transfer orbit. After the rocket launcher and arrow separate, the probe enters a large elliptical orbit around the earth. It then performs five orbit changes and accelerations in 16 days to obtain the speed for transfer into the L1 halo orbit. After that, it flies for about 110 days and enters a halo orbit 1.5 million kilometers away, orbiting the L1 point between the sun and the earth. The probe flies in the L1 halo orbit, which can minimize the need to consume fuel to maintain the orbit, while continuously and stably conducting solar observations. In addition, this position is inside the Earth's orbit, and the spacecraft can get early warnings before the sun's high-energy particles and magnetic storms reach the Earth. It is a "feng shui treasure land" for conducting solar observation research.

The Apollo-L1 probe carries a total of seven payloads for solar observations, all developed by various laboratories in India. Its scientific objectives include studying the coronal heating and solar wind acceleration phenomena, the dynamic properties of the solar atmosphere, the anisotropy of solar wind distribution and temperature, as well as the driving factors of coronal mass ejections, solar flares and near-Earth space weather.

Among them, the visible light emission line coronagraph is responsible for studying the dynamic characteristics of the corona and coronal mass ejections; the Solar Ultraviolet Imaging Telescope will take images of the solar photosphere and chromosphere in the near-ultraviolet spectrum and measure changes in solar radiation; the Solar Low Energy X-ray Spectrometer and the High Energy L1 Orbit X-ray Spectrometer are responsible for measuring solar flares in the X-ray range; the Helios Solar Wind Particle Experiment and the Helios Plasma Analyzer are responsible for studying the solar wind, high-energy ions and their energy distribution; the magnetometer is used to measure the interplanetary magnetic field in the Sun-Earth L1 orbit.

Although the Apollo-L1 probe is small and is the "vanguard" of India's solar observation, it still strives to achieve some "unique skills": it is the first probe to observe the sun in the near-ultraviolet region, and it is also the first to observe coronal mass ejections near the solar disk (1.05 times the radius of the sun), and it is said to be able to conduct multi-directional observations of the direction and energy anisotropy of the solar wind. In general, although it is a small step for human solar research, it is a big step for India's solar exploration.

India's Rise in Deep Space Exploration

The Apollo-L1 probe has been successfully launched and is on its way to the Sun-Earth L1 point. Not long ago, on August 23, India's Chandrayaan-3 probe successfully landed near the South Pole of the Moon. The Pragyan rover it carried went into hibernation on September 2 after traveling more than 100 meters. India, which has long been questioned, has given people a new impression in the field of deep space exploration.

India's success in deep space exploration is not accidental. Although the overall level of India's aerospace is not high due to the country's overall industrial strength and development level, the Indian Space Development Organization has been working hard to develop aerospace since its founding, and its achievements are second only to China among third world countries.

India is also actively promoting future deep space exploration projects, including the lunar exploration plan, which includes the Indo-Japanese cooperation on lunar polar exploration missions. India is actively developing the Chandrayaan-4 probe, a large lander with a launch mass of about 6 tons and a 350-kilogram-class large lunar rover. Compared with the "landing on the South Pole" concept of "Chandrayaan-3", "Chandrayaan-4" will actually land near the South Pole of the Moon, and search for polar water ice and other resources through in-situ drilling of the lander and roaming inspections of the large lunar rover. "Chandrayaan-4" will be launched using Japan's H-3 rocket, and the lunar rover is also developed by the Japan Aerospace Exploration Agency.

In addition to cooperation, India also plans to develop its own similar project, using a domestically produced large launch vehicle to launch a large lander and transport a large lunar rover for exploration. India also plans to carry out a lunar sample return exploration project in the more distant future, but this will definitely be after 2030.

India is also promoting Mars and Venus exploration projects. Mangalyaan 2/Mars Orbiter 2 has not yet been officially launched. It is reported that this is due to the lack of relevant Mars exploration payloads, but outside speculation is more likely due to lack of budget. Early reports said that the Mangalyaan 2 mission included a lander, and even said that it would be completed in one orbit, but in 2021, the chairman of the Indian Space Research Organization said in an interview that the mission will only include an orbiter, but it will use aerodynamic braking to slow down, and carry hyperspectral cameras, radars and ultra-high-resolution cameras to conduct observations and research on the Martian topography and crust.

India has also turned its deep space exploration target to Venus. It is reported that India is developing a Venus orbiter, which may be named "Venus Ship". This 2.5-ton Venus probe will be launched using the LVM3 large rocket and will eventually enter an elliptical orbit with a perigee of 500 kilometers and an apogee of 60,000 kilometers. It carries a variety of payloads weighing 100 kilograms, mainly used to study the structural composition and dynamic characteristics of Venus' atmosphere, as well as the stratigraphy and resurfacing process of the surface and underground of Venus.

In order to conduct in-depth research on the atmosphere of Venus, it will also release balloons to conduct exploration work. If the Venus probe can be launched as scheduled at the end of 2024, India is expected to take the lead in observing and studying the atmosphere of Venus, especially the problem of methane, and even make unique scientific discoveries. (Author: Zhang Xuesong Image source: ISRO Check expert: Jiang Fan, deputy director of the Science and Technology Committee of China Aerospace Science and Technology Corporation)