Question

Which is/are the CORRECT option(s) that indicate(s) a multispectral sensor?

• A. A sensor with 10 non-contiguous spectral bands having a bandwidth of about 0.04 μm
• B. A sensor with 256 contiguous spectral bands with each having a bandwidth of 5 nm
• C. A sensor with a single spectral band having a bandwidth of 0.4 μm
• D. A sensor with 1000 contiguous spectral bands with each having a bandwidth of 1 nm

Hint:

A multispectral sensor has a small number of non-contiguous, moderately wide bands, unlike a hyperspectral sensor, which has hundreds of narrow contiguous bands, or a panchromatic sensor, which has just one band.

Answer 1

The Correct Option is A

Step 1: Recall the defining features of a multispectral sensor.
A multispectral sensor records reflected or emitted energy in a relatively small number, typically fewer than about 20, of discrete, non-contiguous spectral bands. Each band is deliberately placed over a chosen part of the spectrum and separated from its neighbors by gaps, and each band is fairly broad, with a bandwidth commonly in the range of a few tens of nanometers up to roughly 0.1 to 0.3 micrometers. Well known examples are Landsat and Sentinel-2, which carry on the order of 8 to 13 such bands.

Step 2: Recall the defining features of a hyperspectral sensor for contrast.
A hyperspectral sensor, by contrast, records in hundreds of very narrow, contiguous bands, typically with bandwidths of only a few nanometers to about 10 nanometers, placed side by side across the spectrum with no gaps, so that the sensor effectively reconstructs an almost continuous spectral reflectance curve for every pixel. A panchromatic sensor, at the other extreme, uses just a single very broad band covering a wide range of wavelengths to record a black and white, high spatial resolution image.

Step 3: Test each option against these definitions.
Option (A) describes 10 non-contiguous bands with a bandwidth of about 0.04 micrometers, that is 40 nanometers, this matches the multispectral pattern exactly: a small number of bands, spectrally separated, moderately broad. Option (B) describes 256 contiguous bands of 5 nanometers each, a large number of narrow, gap-free bands, this is the signature of a hyperspectral sensor, not multispectral. Option (C) describes a single band of 0.4 micrometers, a sensor with only one band is a panchromatic sensor by definition, since "multispectral" requires multiple discrete bands. Option (D) describes 1000 contiguous bands of 1 nanometer each, an even larger, narrower, gap-free set of bands than option (B), which is an ultra-fine hyperspectral (sometimes called ultraspectral) sensor, again not multispectral.

Step 4: Conclusion.
Only option (A) has the combination of a small number of bands, non-contiguous placement, and moderate bandwidth that defines a multispectral sensor, so it is the only correct choice.

\[ \boxed{\text{Option (A) only}} \]