All about Satellites

A satellite is any object that orbits another, larger object in space.

What is an Orbit?

An orbit is the curved path that an object in space takes around another object due to gravity.

This happens in a way that is similar to throwing a ball out of the window of a tall tower – to get the ball going, you need to first give it a ‘push’ by throwing it, making the ball fall towards the ground on a curved path. Whilst it is your throw that gives the ball its initial speed, it is gravity alone that keeps the ball moving towards the ground once you let go.

But what if we say, no object in space orbits around an object?

It's about something called the Barycenter. Learn more from the folks at NASA: Barycenter

With the definition in mind, can you think of every object that goes around a larger object in Space?

Lets get to the next section for examples of what can be termed satellites.

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"Artificial Satellites are man-made devices that are launched into space and orbit the Earth or another celestial body. They come in many shapes and sizes and are designed for various purposes."

Pioneers of artificial satellite

The idea and realization of the artificial satellite were collaborative achievements of visionary thinkers and dedicated scientists. Konstantin Tsiolkovsky, often termed the "father of astronautics," introduced the concept of space stations orbiting Earth in the early 20th century. Though Tsiolkovsky laid down theoretical foundations, it was Sergei Korolev, known as the chief architect of the Soviet space program, who brought this vision to life.

Under Korolev's leadership, the USSR successfully launched the world's first artificial satellite, Sputnik 1, on October 4, 1957. This monumental achievement wasn't the result of one individual's effort but a collective endeavor by a team of scientists, engineers, and technicians.

What are parts of an artificial satellite?

It's about something called the Barycenter. Learn more from the folks at NASA: Barycenter

Can you think of what applications can we derive from an object orbiting a bigger object? We will explore them next..

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"Satellites specifically designed to observe Earth from orbit, typically for environmental, meteorological, and strategic purposes."

Orbits

• Low Earth Orbit (LEO): Provides high-resolution imagery due to proximity to Earth.
• Sun-Synchronous Orbit (SSO): Ensures consistent daylight illumination for the areas being observed, aiding in capturing images at regular intervals with consistent lighting conditions.

Instruments

• Optical (visible and infrared)
• Thermal
• Multi-spectral and hyper-spectral imagers

Applications

• Weather Forecasting: Monitor atmospheric conditions to predict weather patterns.
• Environmental Monitoring: Track climate change impacts, such as glacier retreat and sea-level rise. Monitor and assess deforestation, desertification, and urban growth.
• Agriculture: Monitor soil moisture levels and assess irrigation needs.
• Disaster Management: Real-time observation for natural disasters like cyclones, wildfires, and floods.
• Resource Management: Track land usage and manage urban development.
• Oceanography: Study ocean currents, wave heights, and sea surface temperatures. Monitor marine life and detect oil spills.
• Mapping & Geospatial Analysis: Aid in cartography, urban planning, and land surveys.

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"Satellites designed to facilitate various forms of communication, including voice, data, and television broadcasting, by relaying signals between transmitters and receivers on Earth."

Orbits

• Geostationary Orbit (GEO): Positioned at 35,786 km above the Earth, these satellites remain over the same point on Earth's surface, providing consistent coverage to a large geographical area.
• Medium Earth Orbit (MEO): These are positioned at altitudes ranging from 2,000 km to 35,786 km and are sometimes used for regional communication needs.
• Low Earth Orbit (LEO): Positioned below 2,000 km, these are becoming increasingly popular for satellite internet constellations due to their reduced latency.

Key Features

• Transponders: These are series of interconnected units onboard the satellite that receive, amplify, and re-transmit signals back to Earth.
• Footprint: The area on the ground that can receive signals from the satellite. A single satellite in GEO can cover one-third of the Earth.

Applications

• Television Broadcasting: Direct-to-home (DTH) broadcasting of television content and live transmission of international events globally.
• Internet Connectivity: Provide broadband internet, especially in areas with limited terrestrial infrastructure. Emerging satellite constellations in LEO aim to provide global high-speed internet coverage.
• Voice Communication: Long-distance telephony and mobile satellite services.
• Data Transmission: Secure governmental communications and corporate network communications.
• Navigation and Global Positioning: Some communication satellites can also facilitate navigational aids.
• Disaster Recovery: Providing essential communication services in disaster-affected areas.
• Military & Defense Communications: Secure channels for defense purposes.

Indian Communication Satellite Examples

• INSAT Series: Multipurpose geostationary satellites. Examples: INSAT-3A, INSAT-4B.
• GSAT Series: Dedicated communication satellites. Examples: GSAT-6A, GSAT-7A, GSAT-15.
• EDUSAT: India's first satellite for educational services.
• GSAT-9 or South Asia Satellite: Offers services to India's neighboring countries.

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"Satellites designed for Global Navigation Satellite Systems (GNSS) services, enabling precise positioning, navigation, and timing."

Orbits

• Medium Earth Orbit (MEO): Most navigation satellites operate in this orbit, approximately 20,000 km above Earth. This positioning allows them to cover vast areas while ensuring precision.

Key Components

• Atomic Clocks: Essential components of navigation satellites, they generate accurate timing signals, pivotal for determining position.
• Coverage: Minimum of four satellites is required for precise positioning. More satellites improve accuracy and reliability.

Applications

• Location-Based Services: Turn-by-turn navigation for vehicles, location tracking for mobile devices.
• Aviation: Assisting aircraft in precise route navigation and supporting airport operations.
• Maritime: Aiding ships in open sea navigation and assisting with port operations.
• Agriculture: Precision farming and land measurement.
• Military & Defense: Precise navigation, secure communication, and data relay.
• Surveying & Geospatial Applications: Land surveying and GIS applications.
• Disaster Management: Tracking relief forces and locating affected regions.
• Railway & Road Transport: Monitoring transportation fleets and ensuring safety.

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"Satellites designed for scientific research about Earth's environment, outer space, or celestial bodies."

Orbits & Destinations

• Low Earth Orbit (LEO): For Earth-centric scientific investigations.
• Highly Elliptical Orbits (HEO): To study phenomena like auroras.
• Lagrange Points: For solar or deep space observations.
• Interplanetary & Beyond: Missions to planets, moons, asteroids, or beyond our solar system.

Instrumentation

• Packed with instruments like spectrometers, cameras, and particle detectors tailored to each mission.

Applications

• Astronomical Observations: Study of stars, galaxies, black holes, and the universe's structure.
• Planetary Exploration: Studying atmospheres, surfaces, and potential life on other planets and moons.
• Space Physics: Investigating solar flares, cosmic rays, and black holes.
• Earth Science & Climate Studies: Detailed study of Earth's systems to understand climate change, geology, and other processes.
• Cosmology: Investigating the origins and fate of the universe.
• Biology & Medicine: Studying microgravity effects on organisms, including humans.

Indian Satellite Examples

• Astrosat: India's first dedicated space observatory observing the universe in multiple wavelengths.
• Chandrayaan Series: Moon missions that studied the presence of water and the lunar surface.
• Mars Orbiter Mission (Mangalyaan): India's first mission to Mars.
• Aditya-L1: A mission aiming to study the Sun, especially its corona.

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