Indian Satellites — Interactive LMS
Explore ISRO Earth observation (EOS), communications (GSAT) and regional navigation (IRNSS / NavIC).
INDIAN SPACE TECHNOLOGY · ORBIT LAB
Aim & Learning Outcomes
Aim: Understand the architecture, mission objectives, payloads and orbital choices of Indian EOS, GSAT and IRNSS/NavIC satellites through an interactive orbit lab.
After completing this LMS, students can
- Differentiate Earth observation, communications and navigation missions.
- Explain the operating principles of SAR imaging, communication transponders and navigation ranging signals.
- Compare low Earth, geostationary and inclined geosynchronous orbits.
- Identify examples EOS-04, GSAT-30 and IRNSS-1I.
- Connect orbital design to coverage and mission requirements.
Explore three Indian satellite families
EOS: observing Earth. GSAT: relaying communication signals. IRNSS/NavIC: regional positioning, navigation and timing.
Activities
Select satellites, animate schematic orbital motion, compare mission properties, solve the satellite classification puzzle and answer 12 viva questions.
Indian Satellites — Theory & Mission Architecture
Core concept: A satellite’s orbit, payload and ground segment are selected to match the mission: Earth observation, communications or navigation. Different satellites within the same family may have different specifications.
Mission families and orbital science
EOS — Earth Observation Satellites: EOS is an Indian naming series for Earth-observation missions. Sensors differ by spacecraft: optical imaging, radar imaging and other Earth-monitoring instruments. Example: EOS-04 uses C-band SAR and can image through cloud cover and at night.
GSAT — Communication Satellites: GSAT spacecraft support satellite communications, broadcasting and related services. Many operate in geostationary orbit; individual GSAT spacecraft vary in mission and payload. Example: GSAT-30 carries C- and Ku-band transponders.
IRNSS / NavIC — Navigation: The Indian Regional Navigation Satellite System (IRNSS), operationally known as NavIC, is India’s regional satellite navigation system. Its constellation uses geostationary and inclined geosynchronous orbits to provide positioning, navigation and timing services.
LEO and Sun-synchronous orbit: Low Earth orbit typically lies a few hundred to around 2,000 km above Earth. Sun-synchronous orbits are near-polar orbits designed for approximately consistent local solar time at repeated observations.
Geostationary orbit (GEO): A circular equatorial orbit with a sidereal-day period makes a satellite appear fixed over one longitude. Altitude is approximately 35,786 km above mean sea level.
Inclined geosynchronous orbit (IGSO): A geosynchronous satellite has a period matching Earth’s sidereal rotation; with inclination it traces a figure-eight ground track instead of remaining fixed in the sky.
Spacecraft systems and applications
SAR versus optical imagingSynthetic-aperture radar is an active microwave sensor and can collect imagery at night and through many clouds; optical sensors measure reflected sunlight or emitted radiation, depending on sensor type.
Navigation versus communicationNavigation satellites transmit precisely timed signals for ranging and location determination; communications satellites relay user data, broadcasting and connectivity.
Ground segmentGround stations support tracking, telemetry, control, orbit maintenance, payload operations and user services.
Coverage and trade-offsLEO Earth-observation satellites pass over regions as Earth rotates; GEO communication satellites offer persistent regional visibility. NavIC uses a regional GEO/IGSO configuration.
Satellite busA spacecraft bus provides structure, power, attitude determination/control, propulsion when needed, onboard computing, and thermal management.
Educational model limitationsOrbital tracks, spacecraft drawings, periods and motion are schematic. This is not a real-time ephemeris, positioning receiver or mission telemetry display.
Representative satellites
| EOS-04 | C-band SAR; LEO sun-synchronous orbit |
| GSAT-30 | C/Ku-band communications; GEO |
| IRNSS-1I | NavIC regional navigation; inclined geosynchronous orbit |
Sources:ISRO and ISRO Satellite Navigation Services. Mission parameters are approximate educational references.
ISRO Satellite Simulator — EOS · GSAT · IRNSS