Differentiate between IRS and INSAT series of satellites.
The IRS series satellites are remote sensing satellites placed in a near-polar sun synchronous orbit at an altitude of 700–900 km. These satellites record the energy received from the Earth's surface for remote sensing purposes.
In contrast, the INSAT series satellites are weather monitoring and telecommunication satellites placed in a Geostationary position at an altitude of nearly 36,000 km. These satellites remain positioned over their orbit, synchronizing with the direction of Earth's rotation.
Thus, the key differences lie in their purpose (remote sensing vs. weather monitoring/telecommunication), orbit type (sun synchronous vs. geostationary), and altitude (700–900 km vs. 36,000 km).
Explanation
The textbook clearly distinguishes between IRS and INSAT series in the section discussing detection of reflected/emitted energy by sensors. IRS satellites are explicitly mentioned as remote sensing satellites in sun synchronous orbit at 700-900 km altitude, while INSAT satellites are described as weather monitoring and telecommunication satellites in geostationary orbit at 36,000 km altitude. The comparison is also referenced in Box 6.1.