Image source, Getty Images

As the countdown for India's Moon probe begins, SpaceX and Tesla boss Elon Musk's post on X, formerly Twitter, is drawing attention.

Responding to a post about how the mission's cost is lower than the budget of Hollywood film Interstellar, Musk wrote: "Good for India!"

The mission, which could be the first to land on the Moon’s south pole, costs 6.1bn rupees ($75m; £58m). This is less than half the cost of Russia’s craft Luna-25 which had crashed on Sunday. The Russian craft cost $200m.

Image source, Reuters

South Africa’s President Cyril Ramaphosa has congratulated Indian Prime Minister Narendra Modi ahead of his country's attempt to land on the Moon.

The two leaders are currently at a summit of the Brics countries - Brazil, Russia, India, China and South Africa - in Johannesburg.

"This for us, as the Brics family, is a momentous occasion and we rejoice with you," Ramaphosa said.

Our colleagues in London are covering the Brics summit in detail. Follow along here.

The stage is set for India's Chandrayaan-3 to land on the Moon's south pole. A successful soft landing will make India the only country to land on the lunar south pole, and would join an exclusive group of four states to have successfully landed a spacecraft on the Moon.

The BBC's Samira Hussain reports from Isro headquarters in Bengaluru.

The excitement around India is palpable as the moment of Chandrayaan-3's landing draws nearer.

Image source, Reuters

Image source, Reuters

Image source, EPA

Ali Abbas Ahmadi

Image source, EPA

A soft landing is the controlled descent of a spacecraft, resulting in a safe and gradual touchdown - in this case, on the Moon’s surface. A soft landing is used when the craft is expected to take scientific measurements after landing, or when there is a crew on board.

The mountainous terrain of the Moon’s south pole, and the absence of light, make this landing extremely challenging.

No craft has landed this near the Moon’s south pole before – so Chandrayaan-3 is in uncharted territory.

As we've been reporting, there's great excitement in India where people are closely following the progress of Chandrayaan-3.

These schoolchildren in Mumbai made posters to show their support for the spacecraft - with some expert colouring in on display!

Hopefully they'll be able to follow along with landing attempt today.

Image source, Getty Images

Image source, Getty Images

Geeta Pandey
BBC News, Delhi

Image source, Getty Images

The whole of India’s Moon mission, from lift-off to entry into lunar orbit, along with the separation of the propulsion module which carried the lander and rover close to the Moon and the preparations for the landing, are being controlled by scientists through precise complex manoeuvres.

For today's landing, Isro’s Nilesh M Desai told news agency ANI that the plan had been worked out in great detail. Once the lander starts descending towards the Moon’s surface, its speed will be gradually reduced - from 1.68km per second at its present height of 25km to almost zero by the time it reaches 800 metres.

A call will be taken on landing once Vikram is down to 150 metres and if the area is found unsuitable, the lander would travel a little towards its left or right to find a better spot. If it gets worse - there’s “a salvage mode” which will help the lander choose a spot for an emergency landing.

• Chandrayaan-3's lander is scheduled to start its descent at 17:45 India time on Wednesday (13:15 BST)
• The lander will attempt touchdown at 18:04 local time (13:34 BST)
• You'll be able to watch live at the top of this page, and we'll bring you updates on all the action
• The Indian Space Research Organisation (Isro) will be starting its live telecast at 1720 India time (about five minutes from now)
• You'll be able to watch it on their website, external, as well as YouTube, external and Facebook, external - it's also being broadcast on India's DD National TV station

Geeta Pandey
BBC News, Delhi

India is less than an hour away from attempting the first landing near Moon's south pole. Excitement is building up as scientists are taking their place at the Isro’s command centre in Bengaluru from where they will be guiding the lander in its descent towards the Moon’s surface.

Chandrayaan-3 lifted off on 14 July and has since travelled 360,000km in space to reach the Moon. The spacecraft’s every move has been keenly tracked as it circled the Earth several times before entering into the lunar orbit.

Excitement built up further when last week the lander separated from the propulsion module which had carried it close to the Moon.

On Wednesday, as the lander-rover nears the finishing line, a billion people across the country are praying in temples, mosques and churches for a successful touchdown near the lunar south pole – an area that still remains unexplored.

It's been nearly six weeks since Chandrayaan-3 took off from Isro’s spaceport in the southern Indian state of Andhra Pradesh as crowds cheered.

Watch the moment of launch here:

Image source, .

As you can see from this graphic, the Chandrayaan-3 mission has already travelled a long way since it blasted off on 14 July.

It performed several orbits of the Earth, increasing in size, until it entered lunar orbit on 5 August.

It then travelled around the Moon, with orbits decreasing in size. On 17 August the lander module separated from the propulsion module.

In the past few days, the Vikram lander's camera has been extensively mapping the lunar surface, attempting to locate a safe landing spot.

The lander is scheduled to start its descent at 17:45 India time on Wednesday (13:15 BST) and to attempt touchdown at 18:04 local time.

An Isro scientist has told Indian media that the lander's speed will be reduced during its descent, to almost zero by the time it reaches 800m above the Moon's surface.

With just 150m to go, the lander may move sideways a little if the landing area is found to be unsuitable, he said.

Once it lands, if all goes to plan, the six-wheeled rover will crawl out of the lander's belly, and begin gathering data and images.

Soutik Biswas
India Correspondent

India's Chandrayaan-3 is just a couple of hours away from hopefully making a soft landing on the lunar surface later today.

But other countries are also interested in exploring the Moon's mysteries. As we've been reporting, earlier this week Russia's unmanned Luna-25 spacecraft crashed into the Moon after spinning out of control.

It was Moscow's first mission to the Moon in almost 50 years.

Later this year, US entrepreneur Elon Musk’s SpaceX plans to take Japanese billionaire Yusaku Maezawa and eight other passengers on the dearMoon project to orbit the Moon.

And Nasa, the US space agency, plans to launch its next Moon mission - Artemis II - in 2024.

In a joint mission scheduled for 2026, Japan and India also plan to embark on a lunar polar exploration to investigate the shadowy "dark side" of the Moon.

Prayers have been held in temples, mosques and churches across India ahead of the attempted landing, now just a couple of hours away.

Geeta Pandey
BBC News, Delhi

Image source, Getty Images

All previous successful missions to the Moon have touched down near the equator, including India’s Chandrayaan-1.

Scientists say landing near the south pole can be tricky as the surface is “very uneven” and “full of craters and boulders”. The crash of Russia’s Luna-25 last weekend has once again put the spotlight on how difficult it is to land in the region.

India’s second lunar mission, which also attempted to soft land near the south pole, was unsuccessful - with its lander and rover destroyed.

Isro chief Sreedhara Panicker Somanath says they have carefully studied data from the crash and carried out simulation exercises to fix the glitches in Chandrayaan-3.

“We have more scientific interest in this spot because the equatorial region, which is safe for landing, has already been reached and a lot of data is available for that," Mr Somanath said.

“If we want to make a significant scientific discovery, we have to go to a new area such as the south pole, but it has higher risks of landing."

Image source, EPA

The Moon landing attempt might be a big moment for India, but its prime minister, Narendra Modi, is far away in Johannesburg, South Africa, attending a summit of the Brics bloc of nations.

But space is clearly on his mind.

Addressing the summit, he called for Brazil, Russia, India, China and South Africa to think about creating a "Brics space exploration consortium".

Under it, we can work on areas such as space research and weather monitoring for global good, he said.

He said work was already under way on a Brics satellite constellation.

Soutik Biswas
India Correspondent

The Moon's south pole, according to Nasa, is full of "mystery, science and intrigue".

It sits on the rim of a massive impact crater with a diameter of 2,500km (1,600 miles) and reaches depths of up to 8km (five miles).

The crater is one of the most ancient features in the solar system.

"By landing on the pole you can begin to understand what is going on with this large crater," Noah Petro, a project scientist at Nasa, told the BBC. But a major reason why scientists have zeroed-in on the south pole is the prospect of finding water.

Image source, ISRO

Scientists believe that frozen water, untainted by the Sun's radiation, might have accumulated in cold polar regions over millions of years and can provide a unique sample for scientists to analyse and understand the history of water in our solar system.

Space entrepreneurs also see "lunar ice as an opportunity to supply astronauts with locally sourced water", said Prof Simeon Barber, a planetary scientist at the UK's Open University, who also works with the European Space Agency.

Water molecules can be broken into hydrogen and oxygen atoms which can be used as propellants for rockets. But first scientists need to know how much ice is there on the Moon, in what form, and whether it can be extracted efficiently and purified to make it safe to drink.

Read more here on why the south pole is emerging as a compelling scientific destination

Samira Hussain
BBC News, Isro

We are at the media centre at Isro's headquarters in Bengaluru (formerly Bangalore), where journalists have gathered to watch the live telecast of the landing.

The centre we are in is some distance away from the control centre, but there’s a buzz and palpable excitement here as everyone waits for the crucial final moments of this mission to play out over the next few hours.

It's been a long journey to this point. Here we explain the key moments in the mission so far.

Geeta Pandey
BBC News, Delhi

As the name suggests, Chandrayaan-3 is the third in India's lunar exploration programme and the Indian space agency says it is expected to build on the success of its earlier Moon missions.

It comes 15 years after the country's first Moon mission in 2008, which discovered the presence of water molecules on the parched lunar surface and established that the Moon has an atmosphere during daytime.

Chandrayaan-2 - which also comprised an orbiter, lander and rover - was launched in July 2019 but was only partially successful.

Its orbiter continues to circle and study the Moon today, but the lander-rover failed to make a soft landing and crashed during touchdown.

Image source, Isro

Samira Hussain
BBC News, Isro

As the countdown begins for the Vikram lander's attempt to touchdown on the Moon, hundreds of journalists have gathered outside Indian Space Research Organisation's (Isro) headquarters in Bengaluru (formerly Bangalore), eagerly waiting to get inside.

The mood is jubilant but there's also a sense of nervousness about whether India will be able to successfully land the spacecraft on the Moon.

There is also a huddle of curious onlookers who are taking photos and wondering what is happening out here.