Our Universe - Artificial Satellites and Space exploration

Artificial Satellites are man-made objects launched into space to orbit the Earth or other celestial bodies. Unlike the Moon, which is a natural satellite, these are designed for specific tasks.

For a satellite to stay in orbit and not fall back to Earth, it must travel at a very high speed, typically around $8 \text{ km/s}$ for Low Earth Orbit (LEO).

Communication Satellites (like the $INSAT$ series) are used for television broadcasting, telephone connections, and internet services. They often reside in Geostationary Orbit at an altitude of approximately $36,000 \text{ km}$.

Weather Satellites monitor atmospheric conditions, helping scientists predict storms, cyclones, and temperature changes.

Remote Sensing Satellites (like $IRS$) take high-resolution pictures of the Earth's surface to help in mapping, agriculture, and identifying natural resources.

Space Exploration involves using rockets to overcome Earth's gravity. To leave Earth's atmosphere entirely, a rocket must reach the Escape Velocity, which is approximately $11.2 \text{ km/s}$.

Historical Milestones: $Sputnik\ 1$ was the first artificial satellite (1957). $Aryabhata$ was India's first satellite (1975). $Yuri\ Gagarin$ was the first human in space, and $Neil\ Armstrong$ was the first human to walk on the Moon during the $Apollo\ 11$ mission.