Sensors and Platforms Questions and Answers

Q: What is 'SAR' in remote sensing, a technology for producing fine-resolution images from a resolution limited radar system?

SAR stands for Synthetic Aperture Radar.A radar's resolution depends on the size of its antenna (aperture). SAR uses the motion of the aircraft or satellite to combine echoes received along the flight path, synthesising the effect of a very long antenna and so producing fine-resolution images, day or night and through cloud.The other expansions change 'aperture', the key word that explains the technique, and are not used terms.

Q: Which one of the following is not a sensor of Indian remote sensing (IRS) satellite ?

The sensor that is not on IRS satellites is TM.TM, the Thematic Mapper, is the multispectral sensor of the American Landsat 4 and 5 satellites, operated by NASA and the USGS.The other three are Indian sensors: LISS-III (Linear Imaging Self-Scanning sensor) flew on IRS-1C, 1D and Resourcesat; PAN, the panchromatic camera, also flew on IRS-1C and 1D; and WiFS, the Wide Field Sensor, gave wide-swath coverage on the same satellites.

Q: Which of the following is Active sensor ?

The active sensor is RADAR.An active sensor supplies its own energy: RADAR transmits microwave pulses and records the echoes returned from the surface, so it works day or night and through cloud. Synthetic aperture radar on satellites such as RISAT and Sentinel-1 is the main example in remote sensing; LiDAR, using laser pulses, is another.The other three are passive sensors that record reflected sunlight or emitted heat. LISS (Linear Imaging Self-Scanning sensor) flies on India's IRS satellites, AVHRR (Advanced Very High Resolution Radiometer) on NOAA satellites, and MSS (Multispectral Scanner) on the early Landsats.

Q: An orbit is the course of motion taken by the satellite in space and the ground trace of the orbit is called :

The ground trace of a satellite's orbit is called its path.As a satellite orbits, the point directly beneath it traces a line on the Earth's surface, the ground track. In the Worldwide Reference System used for Landsat and similar satellites, each ground track is numbered as a path, and positions along it, at regular intervals of latitude, are numbered as rows; a scene is identified by its path and row.So the row is a position along the path, not the trace itself. 'Column' is not used in this system. Apogee is the point of an orbit farthest from the Earth, not a ground trace.

What is 'SAR' in remote sensing, a technology for producing fine-resolution images from a resolution limited radar system?

A.Synthetic Array Radar
B.Synthetic Aperture Radar
C.Synthetic Apron Radar
D.Systematic Array Radar

Exam Year(s)

RSMSSB JE - 2025, RSMSSB JE Agriculture - 2025, RSMSSB - 2025,

Answer: B

SAR stands for Synthetic Aperture Radar.

A radar's resolution depends on the size of its antenna (aperture). SAR uses the motion of the aircraft or satellite to combine echoes received along the flight path, synthesising the effect of a very long antenna and so producing fine-resolution images, day or night and through cloud.

The other expansions change 'aperture', the key word that explains the technique, and are not used terms.

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Which one of the following is not a sensor of Indian remote sensing (IRS) satellite ?

A.LISS - III
B.PAN
C.WiFS
D.TM

Exam Year(s)

MH SET - 2018, SET Exam - 2018,

Answer: D

The sensor that is not on IRS satellites is TM.

TM, the Thematic Mapper, is the multispectral sensor of the American Landsat 4 and 5 satellites, operated by NASA and the USGS.

The other three are Indian sensors: LISS-III (Linear Imaging Self-Scanning sensor) flew on IRS-1C, 1D and Resourcesat; PAN, the panchromatic camera, also flew on IRS-1C and 1D; and WiFS, the Wide Field Sensor, gave wide-swath coverage on the same satellites.

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Which of the following is Active sensor ?

A.LISS
B.AVHRR
C.RADAR
D.MSS

Exam Year(s)

MH SET - 2025, SET Exam - 2025,

Answer: C

The active sensor is RADAR.

An active sensor supplies its own energy: RADAR transmits microwave pulses and records the echoes returned from the surface, so it works day or night and through cloud. Synthetic aperture radar on satellites such as RISAT and Sentinel-1 is the main example in remote sensing; LiDAR, using laser pulses, is another.

The other three are passive sensors that record reflected sunlight or emitted heat. LISS (Linear Imaging Self-Scanning sensor) flies on India's IRS satellites, AVHRR (Advanced Very High Resolution Radiometer) on NOAA satellites, and MSS (Multispectral Scanner) on the early Landsats.

Discuss in Forum

An orbit is the course of motion taken by the satellite in space and the ground trace of the orbit is called :

A.Path
B.Row
C.Column
D.Apogee

Exam Year(s)

MH SET - 2025, SET Exam - 2025,

Answer: A

The ground trace of a satellite's orbit is called its path.

As a satellite orbits, the point directly beneath it traces a line on the Earth's surface, the ground track. In the Worldwide Reference System used for Landsat and similar satellites, each ground track is numbered as a path, and positions along it, at regular intervals of latitude, are numbered as rows; a scene is identified by its path and row.

So the row is a position along the path, not the trace itself. 'Column' is not used in this system. Apogee is the point of an orbit farthest from the Earth, not a ground trace.

Discuss in Forum

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