Remote Sensing - Vocabulary Flashcards

Vocabulary flashcards covering key Remote Sensing concepts, satellites, instruments, atmospheric and climate topics, image interpretation, and fundamental physics relevant to the subject.

Remote Sensing

The science of acquiring data about an area or object without being in physical contact, often using satellites or aircraft to observe Earth systems.

Active Sensing

Remote sensing that emits energy (e.g., radar, lidar) and measures the backscatter or reflection from targets.

Passive Sensing

Remote sensing that measures naturally occurring radiation (e.g., sunlight reflected from surfaces) without emitting its own energy.

RADAR

Radio Detection and Ranging; an active sensing system using microwaves to locate objects and measure elevation.

LIDAR

Light Detection and Ranging; uses laser pulses to measure distances and create high-resolution 3D surface maps.

TM (Thematic Mapper)

Landsat sensor with seven spectral bands used for Earth observation and land mapping.

ETM+ (Enhanced Thematic Mapper Plus)

Landsat 7 sensor, an eight-band upgrade to TM with improved performance.

MSS (Multispectral Scanner)

An earlier Landsat sensor that collected data in multiple spectral bands.

ALI (Advanced Land Imager)

A Landsat-era instrument designed for high-resolution multispectral imagery.

MODIS

Moderate-resolution Imaging Spectroradiometer; on Terra and Aqua; measures clouds, land, oceans, and atmospheric properties.

CERES

Clouds and the Earth's Radiant Energy System; measures broadband radiative energy flux on Terra and Aqua.

SeaWiFS

Sea-viewing Wide Field-of-View Sensor; monitors ocean color and radiative energy flux.

AVHRR

Advanced Very High Resolution Radiometer; NOAA sensor for earth observation across multiple spectral bands.

AVIRIS

Airborne Visible/Infrared Imaging Spectrometer; airborne hyperspectral instrument.

CZCS

Coastal Zone Color Scanner; early satellite sensor for ocean color and chlorophyll.

MISR

Multi-angle Imaging Spectro Radiometer; measures Earth's surface and atmosphere from multiple viewing angles.

MSR

Microwave Scanning Radiometer; measures microwave emissions from Earth's surface.

RAR

Real Aperture Radar; type of radar system used for imaging.

Landsat (Landsat 7, 8, 9)

Series of Landsat satellites; currently Landsat 7, 8, and 9 in operation with multiple spectral bands.

Terra

EOS satellite part of the Earth Observing System; focuses on atmosphere, land, and water.

Aqua

EOS satellite focused on the Earth's water cycle (precipitation, evaporation, etc.).

Aura

EOS satellite studying ozone, air quality, and climate.

OCO-2

Orbiting Carbon Observatory 2; studies atmospheric carbon dioxide.

GCOM-W1 (SHIZUKU)

JAXA satellite studying the water cycle.

PARASOL

Radiative and microphysical properties of clouds and aerosols; moved to a lower orbit and deactivated in 2013.

CloudSat

Radar satellite studying clouds and their properties.

CALIPSO

Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation; studies clouds and aerosols.

EOS Morning Constellation (EOS-AM)

Second EOS constellation named for its 10:30 AM equatorial crossing; includes EO-1.

EOS-A-Train

A train of satellites in Sun-synchronous orbit; seven satellites planned/operating for coordinated observations.

OCO (Orbiting Carbon Observatory)

Failed to achieve orbit; intended to study atmospheric CO2.

Glory

NASA mission that failed to reach orbit while studying aerosols and climate.

LEO

Low Earth Orbit; ~200–2,000 km altitude; high-resolution Earth observation, but limited ground coverage per pass.

MEO

Medium Earth Orbit; ~2,000–35,786 km; larger coverage, moderate latency (e.g., GPS).

GEO

Geostationary Orbit; ~35,786 km; instruments appear stationary relative to Earth, ideal for weather and communications.

Geosynchronous Orbit

Orbit with a 24-hour period; may be non-equatorial; appears to trace a figure-eight path from the ground.

Polar Orbit

Orbit that passes over the poles; enables global coverage and sun-synchronous imaging.

Non-Polar Orbit

Inclined or equatorial orbit offering regional coverage with potential polar gaps.

Milankovitch Cycles

Variations in Earth’s orbital parameters—eccentricity, obliquity, and precession—that influence glacial/interglacial cycles.

Eccentricity

Shape of Earth's orbit around the Sun; variations influence seasonal contrast over long timescales.

Obliquity

Axial tilt of the Earth; affects insolation distribution and seasons.

Precession

Wobble of Earth's axis; shifts the timing of seasons relative to eccentricity and obliquity.

Keeling Curve

Long-term record of atmospheric CO2 concentrations from Mauna Loa, showing rising levels and seasonal cycles.

Global Warming

Increase in Earth's near-surface air and ocean temperatures due to enhanced greenhouse gas concentrations.

Greenhouse Gases

Atmospheric gases (e.g., H2O, CO2, CH4, O3) that trap heat and warm the planet.

Radiative Forcing

Measure of the influence of a factor (e.g., greenhouse gases) on the energy balance of the climate system.

Global Dimming

Reduction in solar radiation reaching Earth's surface due to atmospheric aerosols and other factors.

Carbon Cycle

Cycle of carbon among atmosphere, biosphere, oceans, and soils, including sources and sinks.

Hydrological Cycle

Water cycle: evaporation, condensation, precipitation, infiltration, runoff, and storage processes.

Ozone Layer

Stratospheric layer rich in ozone that absorbs harmful UV radiation.

Ozone Depletion

Reduction of ozone concentration due to chemical pollutants, notably CFCs, via catalytic reactions.

Montreal Protocol

International agreement (1989) to phase out ozone-depleting substances like CFCs.

CCN

Cloud Condensation Nuclei; particles on which water vapor condenses to form clouds.

Twomey Effect

Increase in cloud reflectivity (albedo) with higher aerosol concentrations, enhancing cooling.

NDVI

Normalized Difference Vegetation Index; NDVI = (NIR − Red) / (NIR + Red); indicates vegetation density/health.

EVI

Enhanced Vegetation Index; improves NDVI by reducing canopy background noise; uses NIR, Red, Blue with coefficients.

Albedo

Fraction of incoming solar radiation reflected by a surface; higher for bright surfaces.

Emissivity

Efficiency with which a real surface emits thermal radiation relative to a blackbody.

Blackbody vs Graybody

Blackbody: ideal absorber/emitter; Graybody: emits less than a perfect blackbody (emissivity < 1).

Planck Function

Equation describing spectral radiance of a blackbody as a function of wavelength and temperature.

Stefan-Boltzmann Law

Total radiant exitance of a blackbody is proportional to the fourth power of its temperature.

Wein’s Law

Relates peak wavelength of emitted radiation to the object's temperature; shorter wavelength for hotter objects.

Peak vs Dominant Wavelength

Peak wavelength: wavelength with maximum emission; Dominant wavelength: wavelength corresponding to perceived color.

Atmospheric Windows

Wavelength ranges where Earth's atmosphere is relatively transparent to EM radiation.

Atmospheric Scattering (Rayleigh, Mie)

Scattering of light by particles in the atmosphere; Rayleigh (small particles), Mie (larger particles).

True Color Image

An image where DN values are mapped to colors representing real-world visible colors.

False Color Composite (FCC)

An image where colors are assigned to spectral bands that do not correspond to natural colors to highlight features.

Contrast

Difference in brightness between an object and its surroundings; higher contrast aids detection.

Resolution (Spatial, Spectral, Radiometric, Temporal)

Spatial: smallest discernible detail; Spectral: ability to distinguish wavelengths; Radiometric: sensitivity to energy differences; Temporal: frequency of data capture.

Pixel

The smallest element of a digital image representing a sample of the scene’s energy.

DN (Digital Number)

Digital value assigned to a pixel representing detected radiance before scaling.

Scale

Ratio of image measurements to real-world measurements; affects area/length calculations.

NDVI Equation (Channel reference)

NDVI = (NIR − Red) / (NIR + Red); used to assess vegetation health.

Surface Area Estimation (Finding Area)

Technique to estimate irregular areas by dividing into simple shapes and summing their areas.

NDVI vs EVI Usage

NDVI is common for vegetation; EVI improves performance in dense canopies and atmospheric corrections.

Ocean Acidification

Decrease in ocean pH due to CO2 dissolving and forming carbonic acid, affecting marine life.

Coral Bleaching

Discoloration and loss of coral symbiotic algae due to stress (e.g., warming water).