Space Missions — Maharashtra (SSC) Class 10 Science Solutions (Free)

A satellite is an object that orbits around a planet under gravitational force. Natural satellites are celestial bodies like Earth's Moon and Mars's Phobos. Artificial satellites are human-made devices: communication satellites (INSAT), weather satellites (Kalpana), GPS satellites (IRS). They orbit at specific altitudes determined by Kepler's laws and serve various scientific and commercial purposes.

Orbital velocity is the minimum speed required for an object to stay in circular orbit: v = √(GM/r). For Earth orbit at 200 km altitude, it is ~7.8 km/s. Escape velocity is the speed needed to break free from gravitational pull: v = √(2GM/r) = √2 × orbital velocity ≈ 11.2 km/s for Earth. Satellites use orbital velocity; rockets need escape velocity to reach space.

Chandrayaan-1 (2008): lunar orbiter discovering water on the Moon. Chandrayaan-3 (2023): successfully landed on lunar south pole. Mangalyaan (2013): Mars Orbiter Mission, first interplanetary mission, still orbiting Mars. Gaganyaan: planned crewed spaceflight program to send Indian astronauts to space. These missions establish India's leadership in space exploration with low-cost, indigenous technology.

Geosynchronous orbit: orbital period equals Earth's rotation (24 hours), satellite appears stationary over fixed ground location. Geostationary orbit is a special case at the equator (altitude 36,000 km) where satellite remains directly above one point. Used for communication satellites (INSAT), weather monitoring, and broadcasting. One geostationary satellite covers 1/3 of Earth's surface.

PSLV (Polar Satellite Launch Vehicle): workhorse for polar orbits, capacity 1600 kg, launched Chandrayaan, Mangalyaan. Four stages, all-solid first and third, liquid second and fourth. GSLV (Geosynchronous Satellite Launch Vehicle): heavier lift, 2000+ kg to GEO, indigenous cryogenic engine, carries INSAT satellites. Both are cost-effective, reliable systems developed entirely by ISRO.