spaceborne remote sensing Flashcards
What is a sensor in remote sensing?
A sensor is an instrument that determines the quantity of light that hits it, measuring specific types of light.
hat are the two types of energy sources for sensors?
Passive systems rely on solar energy, while active systems provide their own energy source
How does the atmosphere affect remote sensing?
The atmosphere absorbs, scatters, and transmits energy, influencing the sensor’s ability to measure reflected energy.
What is spatial resolution in remote sensing?
The ability of a sensor to distinguish fine spatial details, such as in high-resolution aerial photographs.
What is radiometric resolution
The number of discrete brightness levels a sensor can distinguish, e.g., 8-bit allows 256 levels.
What is spectral resolution?
The ability of a sensor to distinguish between different wavelengths or spectral bands.
Define the principle of operation for most remote sensing sensors.
Sensors measure photons, and their detectors emit electrons proportional to light intensity.
What are the two broad classes of sensors?
Passive sensors and active sensors.
What is a whiskbroom scanner?
A scanner using a rotating or oscillating mirror to sweep a scene line by line
What is a pushbroom scanner?
A scanner with a linear array of detectors capturing an entire line at once as the platform moves.
What is the role of a detector in a sensor?
It converts electromagnetic radiation into electrons, producing a measurable electrical signal.
What is the IFOV in a whiskbroom scanner?
Instantaneous Field of View, describing the spatial resolution of the sensor.
How does a pushbroom scanner differ geometrically from a whiskbroom scanner?
A pushbroom scanner records one line at a time without using mirrors, unlike the whiskbroom
What is off-track viewing in pushbroom scanners?
The ability to point the scanner toward areas left, right, forward, or backward of the orbit.
Name a disadvantage of CCDs in pushbroom scanners.
CCDs are limited to visible and near-IR wavelengths.
What is the dynamic range of a detector?
The range of input radiance a detector can handle, typically converted into digital formats (e.g., 8-bit, 12-bit).
What is a radiometer?
An instrument that quantitatively measures electromagnetic radiation in a specific spectrum
What is a spectroradiometer?
A sensor measuring radiation in bands rather than discrete wavelengths.
What are the two types of scanning systems?
Optical-mechanical (e.g., moving mirrors) and optical-electronic (e.g., direct to detectors).
What is a panchromatic sensor?
A sensor capturing a broad range of wavelengths without spectral separation.
Define a multispectral system.
A system with filters or devices to separate radiation into multiple spectral bands.
What are absorption filters?
Filters that pass a specific wavelength range while absorbing others.
What is an interference filter?
A filter reflecting unwanted wavelengths while transmitting a specific range.
What is a dichroic filter?
A filter made of thin refractive index layers selectively transmitting specific wavelengths.
What is the main advantage of solid-state detectors?
igh spectral sensitivity and the ability to measure specific energy ranges.
What materials are common in visible light detectors?
Silicon metal and PbO.
What is the purpose of cooling detectors to near absolute zero?
To optimize the efficiency of electron release in infrared detectors.
What is a CCD (Charge-Coupled Device
A light-sensitive microdetector array used in pushbroom scanners.
What determines the spatial resolution of CCDs?
The size of the CCD and the height of the observing platform.
What is the main limitation of current CCD systems?
Their sensitivity is limited to visible and near-IR wavelengths.
What are the three main options for transmitting satellite data to Earth?
Direct transmission to a ground station, onboard recording for later transmission, and relaying via geosynchronous satellites.
What is NEΔP?
Noise Equivalent Power, a measure of a sensor’s sensitivity for reflectances.
What is NEΔT?
Noise Equivalent Temperature, a sensitivity measure for thermal emission detectors.
What is a framing system in remote sensing?
A system capturing the entire scene at once, like a photo camera or TV vidicon.
How is the FOV (Field of View) defined in framing systems?
The size of the scene captured, determined by the system’s optics.
What is quantization in digital imaging?
The conversion of energy levels into discrete digital values (DN values).
What is the role of prisms in multispectral systems?
To break radiation into spectral intervals for detection.
What is the spectral sensitivity of a detector?
A characteristic curve showing the range and efficiency of wavelengths detected.
Why is off-track viewing advantageous?
It enables stereo-imaging and avoids cloud-covered areas.
What is S/N ratio in sensor performance?
Signal-to-noise ratio, indicating data quality relative to noise.
