Everything you need to know about Gaganyaan mission:

1. Gaganyaan is India's first manned space mission. It aims to send Indian astronauts to low earth orbit on an Indian-built spacecraft for a period of 5-7 days by 2023-2024.
2. The mission was first announced by Prime Minister Narendra Modi in his 2018 Independence Day speech. The total budget is estimated to be around Rs 10,000 crores.
3. The Indian Space Research Organisation (ISRO) is responsible for developing the spacecraft, launch vehicle, habitat module, space suits, and other critical technologies needed for the mission. 
4. The astronaut training and selection process is underway. The 4 astronaut candidates will undergo rigorous training in India and Russia. The shortlisted astronauts will be pilots from the Indian Air Force.
5. For the launch, ISRO will use its Geosynchronous Satellite Launch Vehicle Mark III (GSLV MkIII) which underwent crucial tests in 2020. This will be human-rated for the first time for this mission.
6. Key mission objectives are to test India's capability to launch humans into space, develop and test technologies for crew survival in space, and conduct microgravity & scientific experiments in orbit. 
7. If successful, India will become the 4th nation after USA, Russia and China to launch a manned space mission. It will be a major step forward for India's space program.

In summary, Gaganyaan is an ambitious and prestigious mission that will demonstrate India's human spaceflight capabilities. The countdown to launch in 2023-2024 has begun.