Question 1

Because it uses the GSLV rocket and the I-3K bus, NISAR is a heavy communication satellite.

Accepted Answer

NISAR is strictly an Earth observation and scientific satellite. The I-3K bus, traditionally used for communication satellites, was selected because the massive radar payload requires immense power (6.5 kW) and structural support.

Question 2

NASA and ISRO contributed equally to the $1.5 billion funding of the mission.

Accepted Answer

NASA bore the vast majority of the mission's cost (approximately $1.1-$1.2 billion), while ISRO's contribution was roughly $96 million (around ₹788 crore).

Question 3

NISAR is placed into a Geosynchronous orbit because it was launched by the GSLV.

Accepted Answer

NISAR was injected into a 747 km near-polar, Sun-synchronous Low Earth Orbit (LEO).

Question 4

Consider the following statements regarding the NASA-ISRO Synthetic Aperture Radar (NISAR) mission:
1. It was injected into a Geosynchronous Transfer Orbit (GTO) by the GSLV Mk II launch vehicle.
2. NASA's L-band radar payload has a longer wavelength than ISRO's S-band payload, allowing it to penetrate dense forest canopies.
3. Data from the mission is kept restricted under the strategic defense protocols of India and the United States.
How many of the above statements are correct?

Accepted Answer

(a) Only one — Statement 1 is incorrect: Despite being launched by the GSLV, NISAR operates in a 747 km Sun-synchronous Low Earth Orbit (LEO). Statement 2 is correct: NASA's L-band has a 24-cm wavelength which penetrates vegetation to measure ground layers, whereas ISRO's S-band (12-cm) captures finer surface details. Statement 3 is incorrect: A core pillar of the NISAR mission is its completely free and open data policy for global public use. Therefore, only statement 2 is correct.

Question 5

Match the components/features of the NISAR mission (List I) with their respective providers or properties (List II):

List I
A. S-band SAR payload
B. L-band SAR payload
C. Orbit Type
D. Antenna Reflector Size

List II
1. Sun-synchronous (near-polar)
2. ISRO
3. 12 meters
4. NASA

Select the correct code:

Accepted Answer

(b) A-2, B-4, C-1, D-3 — ISRO is responsible for the S-band SAR (A-2). NASA JPL provided the L-band SAR (B-4). The satellite operates in a 747 km Sun-synchronous orbit (C-1), and it utilizes a massive 12-meter unfurlable mesh antenna reflector (D-3) provided by NASA.

Question 6

Assertion (A): The NISAR satellite combines both L-band and S-band microwave radar frequencies on a single platform.
Reason (R): Optical imaging satellites face severe limitations in providing continuous global data due to heavy cloud cover and the absence of solar illumination at night.
Select the correct answer:

Accepted Answer

(a) Both A and R are correct, and R is the correct explanation of A — Assertion (A) is true, as NISAR is the first mission to feature a dual-frequency SAR. Reason (R) is also true and provides the justification for A: to achieve a continuous 12-day global mapping cycle required to track natural disasters and biomass effectively, scientists cannot rely on optical sensors that are hindered by weather and darkness. Synthetic Aperture Radar (SAR) is an active sensor that penetrates clouds and operates 24/7, overcoming optical limitations.

ISRO Launches NASA-ISRO Synthetic Aperture Radar (NISAR)

Launch of PANKHUDI Digital Portal