Microwave Remote Sensing Basics

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to Lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What does polarization primarily refer to in radar technology?

  • The frequency of the microwave radiation
  • The orientation of the electric field (correct)
  • The type of radar used
  • The angle of radar transmission

Which of the following best describes the function of passive microwave sensors?

  • They transmit signals to measure temperature.
  • They only detect energy from man-made sources.
  • They detect naturally emitted microwave energy from objects. (correct)
  • They generate microwave energy to illuminate objects.

What is a significant limitation of passive microwave sensors as compared to optical sensors?

  • They typically have low spatial resolution. (correct)
  • They operate at shorter wavelengths.
  • They provide high spatial resolution.
  • They cannot penetrate clouds.

What is an advantage of using passive microwave sensing over visible/infrared sensors?

<p>Larger field of view compared to VIS/IR sensors (D)</p> Signup and view all the answers

In what manner do passive microwave sensors typically operate?

<p>Similar to optical scanners (C)</p> Signup and view all the answers

What is the primary purpose of using synthetic aperture radar (SAR)?

<p>To enhance azimuth resolution by simulating a longer antenna (A)</p> Signup and view all the answers

Which statement correctly describes the behavior of radar beams concerning targets at different ranges?

<p>Far-range targets are illuminated longer due to the expanding beam width. (B)</p> Signup and view all the answers

What key measurement does a satellite altimeter rely on to determine sea level?

<p>The time required for a microwave pulse to travel to the sea surface and back (C)</p> Signup and view all the answers

Which of the following functions is NOT a capability of satellite altimeters?

<p>Calculating the gravitational pull of the ocean (B)</p> Signup and view all the answers

What is a typical size range for satellite radar antennas?

<p>10 to 15 meters (C)</p> Signup and view all the answers

Which instrument uses Ka-band radar for measuring ocean temperature?

<p>AltiKa (A)</p> Signup and view all the answers

What type of energy do passive microwave sensors detect?

<p>Energy that is reflected from surfaces (A)</p> Signup and view all the answers

What major obstructions hinder the thermal infrared sensors from acquiring data?

<p>Clouds, haze, and fog (D)</p> Signup and view all the answers

Which application is primarily associated with high spatial resolution in microwave remote sensing?

<p>Oil spills (B)</p> Signup and view all the answers

Which of the following sensors is included in passive microwave remote sensing?

<p>SSM/I (C)</p> Signup and view all the answers

Which aspect of microwave energy is critical for its interaction with materials?

<p>Polarization (C)</p> Signup and view all the answers

How does using two bands in water vapor correction improve sea surface temperature calculation?

<p>It differentiates between water vapor absorption and temperature drop. (B)</p> Signup and view all the answers

In the context of microwave remote sensing, what does SSH stand for?

<p>Sea surface height (B)</p> Signup and view all the answers

What is one of the benefits of using sea surface temperature (SST) images?

<p>To quantify changes in fisheries management (D)</p> Signup and view all the answers

Which of the following atmospheric corrections is simpler for infrared compared to ocean corrections?

<p>Color correction (B)</p> Signup and view all the answers

Which application is NOT typically associated with atmospheric microwave remote sensing?

<p>Soil moisture (C)</p> Signup and view all the answers

Which of the following statements about microwave remote sensing is true?

<p>It can detect low spatial resolution applications. (C)</p> Signup and view all the answers

What does the equation SST = a0 + a1Ti + a2(Ti - Tj) represent?

<p>Water vapor correction equation with two bands (B)</p> Signup and view all the answers

What type of microwave remote sensing is characterized by emitted energy?

<p>Active sensing (D)</p> Signup and view all the answers

What does the TI in the equation SST = a0 + a1Ti + a2(Ti - Tj) refer to?

<p>Infrared temperature measurement (B)</p> Signup and view all the answers

Which of the following is an application of microwave remote sensing related to oceans?

<p>Ocean wave measurements (D)</p> Signup and view all the answers

What is the term used to describe the temperature calculated assuming an object's emissivity is 1.0?

<p>Radiant temperature (D)</p> Signup and view all the answers

Which principle explains the relationship between the spectral radiance and the temperature of a black body?

<p>Planck’s law (D)</p> Signup and view all the answers

What is a significant application of passive microwave sensors?

<p>Measuring soil moisture (A)</p> Signup and view all the answers

Why might the radiant temperature (Trad) be lower than the true kinetic temperature (Tkin)?

<p>Emissivity is generally less than 1.0 (D)</p> Signup and view all the answers

What type of satellite provides global coverage and high stability for environmental measurements?

<p>Polar orbiting satellites (B)</p> Signup and view all the answers

Which physical constant is essential in the Rayleigh–Jeans law for calculating spectral radiance?

<p>Boltzmann Constant (C)</p> Signup and view all the answers

What method is often used to calculate true ground temperature from radiant temperature?

<p>Estimation of emissivity (C)</p> Signup and view all the answers

What does the relationship between spectral radiance, temperature, and wavelength involve?

<p>Speed of light dependency (B)</p> Signup and view all the answers

What is the primary use of scatterometers in satellite remote sensing?

<p>Determining wind velocity and direction over water (C)</p> Signup and view all the answers

Which scatterometer operates with a 50 km spatial resolution?

<p>METOP-C (C)</p> Signup and view all the answers

What is a common application of satellite scatterometers?

<p>Weather forecasting (C)</p> Signup and view all the answers

Which formula is used for calculating daytime MCSST using AVHRR?

<p>c1 + (c2<em>T4) + (c3</em>(T4-T5)) + (c4*(sec(Ó©)-1)*(T4-T5)) (A)</p> Signup and view all the answers

Which characteristic is NOT shared by the scatterometers listed?

<p>Ku band operation (B)</p> Signup and view all the answers

What is the operational frequency characteristic of the HY-2B scatterometer?

<p>Ku band (C)</p> Signup and view all the answers

Which of the following terms is a component in the MCSST formulas for both AVHRR and MODIS?

<p>T4 (B)</p> Signup and view all the answers

What does the 'sec(Ó©)' term in the MCSST formulas represent?

<p>The angle of observation (B)</p> Signup and view all the answers

Flashcards

Microwave Remote Sensing

A technique using microwaves to sense the Earth's surface and atmosphere.

Active Microwave Sensing

Sensors that emit microwaves and measure the reflected energy.

Passive Microwave Sensing

Sensors that detect naturally emitted microwaves from the environment.

Microwave Wavelengths

Specific wavelengths of radiation used for different sensing applications.

Signup and view all the flashcards

Radar

A type of active microwave sensing.

Signup and view all the flashcards

Spatial Resolution

The level of detail in a microwave image.

Signup and view all the flashcards

Polarization

The direction of the electric field in the electromagnetic wave.

Signup and view all the flashcards

Imaging in Microwave Remote Sensing

Collecting images of the environment using microwaves.

Signup and view all the flashcards

Microwave Polarization

The orientation of the electric field in microwave radiation.

Signup and view all the flashcards

Radar Polarization

Radars transmit and receive horizontally (H) or vertically (V) polarized microwave radiation.

Signup and view all the flashcards

Passive Microwave Sensor Advantages

Advantages include penetration through clouds and large field of view compared to other sensors.

Signup and view all the flashcards

Passive Microwave Sensor Disadvantages

Passive microwave sensors generally have lower spatial resolution due to the low energy compared to optical wavelengths and variable emissivity.

Signup and view all the flashcards

What is Synthetic Aperture Radar (SAR)?

A technique that uses the platform's forward motion to simulate a very long antenna, resulting in high azimuth resolution.

Signup and view all the flashcards

How does SAR achieve constant resolution?

Adjusting the radar beam width and illumination time compensates for varying distances, ensuring consistent resolution across the entire swath.

Signup and view all the flashcards

What are satellite altimeters used for?

Measuring the ocean's surface height to understand its topography, circulation, and variability.

Signup and view all the flashcards

Altimeter measurement?

The time it takes for a microwave pulse to travel from the satellite to the ocean surface and back.

Signup and view all the flashcards

What can satellite altimeters measure?

Changes in ocean volume, seasonal heating/cooling, tides.

Signup and view all the flashcards

Passive Microwave Applications

Passive microwave sensors measure various Earth surface properties, including soil moisture, snow water equivalent, sea/lake ice characteristics, sea surface temperature, atmospheric water vapor (over oceans), surface wind speed, and cloud liquid water.

Signup and view all the flashcards

Radiant Temperature (Trad)

The temperature calculated from emitted radiation; often lower than the true, kinetic temperature (Tkin).

Signup and view all the flashcards

Kinetic Temperature (Tkin)

The true temperature of an object, measurable with a contact thermometer.

Signup and view all the flashcards

Emissivity

A measure of how well an object radiates relative to a perfect blackbody.

Signup and view all the flashcards

Rayleigh-Jeans Law

An approximation that describes the spectral radiance of blackbody radiation at longer wavelengths.

Signup and view all the flashcards

Spectral Radiance

The power emitted per unit emitting area per steradian per unit wavelength.

Signup and view all the flashcards

Polar Orbiting Satellites

Satellites used for remote sensing, providing high stability, global coverage, and discontinuous temporal coverage over low latitudes.

Signup and view all the flashcards

TIRS Technology

A technology that uses quantum physics to measure land surface temperatures and calculate "spectral radiance" at specific wavelengths.

Signup and view all the flashcards

Sea Surface Temperature (SST)

The temperature of the ocean's surface, typically measured using satellite remote sensing.

Signup and view all the flashcards

Passive Microwave Remote Sensing

A technique that measures naturally emitted microwave radiation from the Earth's surface, like the ocean.

Signup and view all the flashcards

What are the benefits of SST measurements?

SST images provide valuable information for fisheries management, climate monitoring, validating atmospheric models, evaluating coral bleaching, studying ocean heat storage and currents, and understanding temperature-sensitive biological activity.

Signup and view all the flashcards

What are some instruments for SST measurement?

Satellite instruments used for SST measurement include the Advanced Very High Resolution Radiometer (AVHRR), Moderate Resolution Imaging Spectroradiometer (MODIS), and Visible Infrared Imaging Radiometer Suite (VIIRS).

Signup and view all the flashcards

Water Vapor (WV) Correction

Adjusting SST data to account for the absorption of infrared radiation by water vapor in the atmosphere.

Signup and view all the flashcards

How to Correct for WV?

Two bands are used to correct for water vapor absorption: one band is more sensitive to WV than the other. The difference in radiance between these bands provides a measure of WV, which is then used to correct the SST.

Signup and view all the flashcards

Thermal Bands of AVHRR and MODIS

Specific infrared wavelengths used by AVHRR and MODIS to measure the thermal radiation emitted by the ocean's surface.

Signup and view all the flashcards

Atmospheric Corrections

Adjusting infrared measurements for the effects of the atmosphere, such as water vapor and scattering.

Signup and view all the flashcards

What is MCSST?

MCSST stands for Multi-channel Sea Surface Temperature. It is a technique used to derive sea surface temperature (SST) from satellite data. It involves combining measurements from multiple infrared channels to compensate for atmospheric effects.

Signup and view all the flashcards

How does MCSST work?

MCSST uses a specific mathematical equation incorporating measurements from multiple infrared channels, including the brightness temperature in those channels. This equation accounts for atmospheric effects and other factors that can influence the temperature reading, resulting in a more accurate SST measurement.

Signup and view all the flashcards

What are the applications of Scatterometers?

Scatterometers are satellite sensors used to measure wind speed and direction over water. They have various applications, including weather forecasting, marine safety, fishing, and long-term climate studies.

Signup and view all the flashcards

What is the unique advantage of Scatterometers?

Scatterometers are unique among satellite remote sensors as they are the only ones capable of determining wind velocity and direction over water.

Signup and view all the flashcards

How does a Scatterometer work?

Scatterometers emit pulses of microwave radiation towards the ocean surface. The backscattered signal is then measured and used to determine the wind speed and direction.

Signup and view all the flashcards

What is the 'scan characteristics' of a Scatterometer?

The 'scan characteristics' refer to how a Scatterometer collects data. It can use a conical scan or a double swath scan, impacting the coverage and resolution of the data.

Signup and view all the flashcards

What is the 'background period of service' for a Scatterometer?

The background period of service' refers to the timeframe during which a specific Scatterometer was operational, providing data about the wind conditions.

Signup and view all the flashcards

What are the different 'operational frequencies' of Scatterometers?

Scatterometers operate at different frequencies, either C-band or Ku-band, which impacts their data quality and applications. C-band is better for stronger winds while Ku-band is better for calmer conditions.

Signup and view all the flashcards

Study Notes

Microwave Remote Sensing Basics

  • Microwave remote sensing utilizes electromagnetic radiation in the microwave region of the electromagnetic spectrum.
  • The entire range of electromagnetic radiation constitutes the electromagnetic spectrum.
  • Microwave sensors detect electromagnetic waves.

Remote Sensing Fundamentals

  • The entire range of electromagnetic radiation constitutes the electromagnetic spectrum.
  • Microwave remote sensing detects EM radiation in the microwave region.
  • Visible spectrum wavelengths range from .400 to .700 micrometers

Radar Wavelengths

  • Radar uses various frequency bands (Ka, Ku, X, C, S, L, P).
  • Each band has a specific range of wavelengths and corresponding frequencies.
  • Water vapor and oxygen absorption bands influence microwave transmission.

Radar Wavelengths (Detailed)

  • A table showing the relationship between frequency bands, wavelengths (in cm), and corresponding frequencies (in GHz) for different radar bands is presented
  • The formula f (in Hertz) = C/λ where C is the speed of light and λ is the wavelength is given.

Microwave Remote Sensing

  • Active microwave sensors emit their own energy.
  • Passive microwave sensors detect naturally emitted energy.
  • Passive sensors are typically radiometers or scanners.
  • They typically have low spatial resolution.
  • Low spatial resolution is a characteristic of passive microwave sensors.
  • Resolution and application types are interlinked
  • Land, Ocean, and atmospheric applications
  • Examples include soil moisture, glacier studies, SST, wind speed, cloud liquid water, and rainfall rate.

Passive Microwave Sensing from Space

  • Microwave sensors can penetrate non-precipitating clouds.
  • Radiance is linearly related to temperature.
  • Sensors have a consistent calibration.
  • Global coverage and wide swaths are possible.
  • Disadvantages include larger field of view compared to visible or infrared sensors and variable emissivity across land surfaces.

Passive Microwave Applications

  • Applications include measuring snow water equivalent, sea/lake ice extent, and atmospheric water vapor.
  • Measurement of sea surface temperature, surface wind speed, cloud liquid water, and rainfall rate are also possible.

Brightness Temperature and Emissivity

  • Microwave radiometers measure brightness temperature.
  • It's related to the kinetic temperature of the surface.
  • Rayleigh-Jeans approximation provides a linear relationship with emissivity.
  • Emissivity is a dimensionless material property.
  • It's a ratio of energy radiated by a material to energy radiated by a black body at the same temperature.
  • A table lists emissivity values for water and sand, and highly polished silver.

Active Microwave Remote Sensing

  • Active sensors emit their own microwave radiation.
  • Categorized into imaging and non-imaging types.
  • RADAR is a common imaging technique.
  • RADAR measures backscattered signal strength.
  • Radar range (R) is calculated from transmission time (t) and speed of light (c).

Viewing Geometry and Spatial Resolution

  • Radar systems often use side-looking and oblique geometry.
  • Imaging geometry differs from optical systems.
  • Range refers to the perpendicular distance, while azimuth is parallel to the flight direction.
  • The illumination width (swath) can be affected by the radar beam's width and distance from the sensor.

Synthetic Aperture Radar (SAR)

  • SAR increases azimuth resolutions of radar.
  • Simulates a larger antenna through signal processing and platform movement is a core function.
  • SAR viewing geometry depends on the positioning and movement of the platform and the target position.

Satellite Altimeters

  • Satellite altimeters measure sea-level topography and variability of currents
  • Measurement accuracy is high.
  • Altimeters measure the time it takes for the pulse to travel to the surface and back to the satellite.

Various Parameters Using Microwave

  • Sea surface temperature (SST) measured via passive sensing of emitted thermal radiation.
  • Examples of sensors used for active microwave include AVHRR, MODIS, VIIRS, SMMR, SSM/I, TRMM-TMI, and AMSR-E.
  • SST images help with fisheries management, climate monitoring, forecasts, atmospheric model validation, and identifying coral bleaching.

Radar Backscatter Coefficient, Roughness, and Wavelength Dependence

  • Radar backscatter coefficient quantifies how efficiently a surface reflects radar signals.
  • It is inversely proportional to the area and surface roughness of a target.
  • Backscattering varies with surface roughness and wavelength.
  • Rayleigh criterion describes when a surface is considered smooth with respect to wavelengths.
  • A smoother surface has smaller height variations.
  • The diagram illustrates how radar backscattering is dependent on surface roughness and incidence angle.
  • The backscattering coefficient drops as the wavelength lengthens.

Summary of Microwave Applications

  • Various phenomena including water vapor, ocean currents, rainfall, and surface temperature can be detected using microwave sensors.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Quiz Team

Related Documents

Microwave Remote Sensing PDF

More Like This

Radars and Microwave Sensors for Remote Sensing
5 questions
Remote Sensing Radar System Properties
10 questions
Microwave Remote Sensing Overview
47 questions
Passive Microwave Remote Sensing Quiz
45 questions
Use Quizgecko on...
Browser
Browser