The Indian Remote Sensing (IRS) satellite series, starting with IRS-1A (1988), is primarily placed in which type of orbit?
- AGeostationary transfer orbit
- BLow Earth polar sun-synchronous orbitCorrect
- CMedium Earth orbit
- DElliptical Molniya orbit
Solution
Concept
Indian Remote Sensing (IRS) satellite orbit classification
Formula
h approx 800 - 900 km, i approx 98 deg - 99 deg
Step-by-step solution
1. The IRS constellation (IRS-1A/1B, IRS-1C/1D, Resourcesat, Cartosat) comprises dedicated civilian earth observation satellites. 2. These satellites are launched by PSLV into polar sun-synchronous Low Earth Orbits (LEO) at ~817 km altitude. 3. This orbital class enables repetitive multispectral imaging under identical daylight illumination conditions. Answer: B
Explanation
The Indian Remote Sensing (IRS) satellite series, initiated with IRS-1A in 1988, is deployed in near-circular, near-polar sun-synchronous low Earth orbits at altitudes between 800 and 900 km. This configuration guarantees consistent solar illumination for national resource surveying and agricultural inventory across repetitive passes. Therefore, option B is correct.
Why the other options are wrong
A) Geostationary transfer orbits are intermediate paths for placing communication satellites into geostationary slot. C) Medium Earth orbits are primarily used by GNSS constellations (GPS, GLONASS). D) Molniya orbits are Russian high-inclination elliptical orbits for polar communications.
Shortcut
IRS & Cartosat = Polar Sun-Synchronous LEO; INSAT = Geostationary.
Common mistake
Confusing IRS earth observation satellites with INSAT communication/weather satellites placed in geostationary orbit.
Correct answer: B) Low Earth polar sun-synchronous orbit