The Operational Land Imager (OLI) is a remote sensing instrument aboard Landsat 8, built by Ball Aerospace & Technologies. Landsat 8 is the successor to Landsat 7 and was launched on February 11, 2013. [1]
OLI is a push broom scanner that uses a four-mirror telescope with fixed mirrors.
OLI operates alongside TIRS (Thermal Infrared Sensor) on board the LDCM. [2] The build and design of OLI differs from previous generations of instruments, while still maintaining data continuity with archived Landsat data from the last 40 years by keeping the same spectral and spatial resolutions of previous instruments.
OLI aids the Landsat-8 mission in the imaging of Earth's surface and the collection of moderate resolution data that is used to monitor changing trends on the surface and evaluate how land usage changes over time. The images and data that OLI has helped collect have practical applications today in agriculture, mapping, and monitoring changes in snow, ice, and water. [3]
OLI is a pushbroom sensor that operates in the visible (VIS) and short wave infrared (SWIR) spectral regions. [4] It has a swath width of 185-kilometer (115 mi), which means it can image the entire Earth over a repeating cycle of 16 days. [5] The OLI has nine spectral bands, including a panchromatic band:
| Spectral Band | Description | Wavelength | Resolution |
|---|---|---|---|
| Band 1 | Coastal Aerosol | 0.43 - 0.45 μm | 30 m |
| Band 2 | Blue | 0.450 - 0.51 μm | 30 m |
| Band 3 | Green | 0.53 - 0.59 μm | 30 m |
| Band 4 | Red | 0.64 - 0.67 μm | 30 m |
| Band 5 | Near-Infrared | 0.85 - 0.88 μm | 30 m |
| Band 6 | SWIR 1 | 1.57 - 1.65 μm | 30 m |
| Band 7 | SWIR 2 | 2.11 - 2.29 μm | 30 m |
| Band 8 | Panchromatic (PAN) | 0.50 - 0.68 μm | 15 m |
| Band 9 | Cirrus | 1.36 - 1.38 μm | 30 m |
While the spectral and spatial resolution of OLI's channels were kept the same as prior instruments in order to maintain data continuity with the entire Landsat archive, two spectral bands (the first a blue visible channel and the second an infrared channel) were added. [3] These bands were designated as band 1 and band 9, and serve as an enhancement from previous instruments, which lacked these channels. Band 1 was created to locate and determine water resources and investigate coastal areas, and band 9 serves a unique purpose of detecting cirrus clouds. [2]
OLI has several different applications due to the many different bands. Band 1 is helpful in imaging shallow water resources and tracking aerosols. Bands 2, 3, and 4 are in the visible spectrum and are helpful in creating true color composite images. Band 5 is helpful for ecology purposes and can help determine vegetation index or NDVI. Bands 6 and 7 are useful in geology and can help in distinguishing different saturated and unsaturated rocks and soils. Band 8 is helpful in creating images with very high resolution and precision. Band 9 is used for detecting different types of clouds. [7]
Remote sensing is the acquisition of information about an object or phenomenon without making physical contact with the object, in contrast to in situ or on-site observation. The term is applied especially to acquiring information about Earth and other planets. Remote sensing is used in numerous fields, including geophysics, geography, land surveying and most Earth science disciplines. It also has military, intelligence, commercial, economic, planning, and humanitarian applications, among others.
The Landsat program is the longest-running enterprise for acquisition of satellite imagery of Earth. It is a joint NASA / USGS program. On 23 July 1972, the Earth Resources Technology Satellite was launched. This was eventually renamed to Landsat 1 in 1975. The most recent, Landsat 9, was launched on 27 September 2021.
The multi-angle imaging spectroradiometer (MISR) is a scientific instrument on the Terra satellite launched by NASA on 18 December 1999. This device is designed to measure the intensity of solar radiation reflected by the Earth system in various directions and spectral bands; it became operational in February 2000. Data generated by this sensor have been proven useful in a variety of applications including atmospheric sciences, climatology and monitoring terrestrial processes.
Satellite images are images of Earth collected by imaging satellites operated by governments and businesses around the world. Satellite imaging companies sell images by licensing them to governments and businesses such as Apple Maps and Google Maps.
Landsat 3 is the third satellite of the Landsat program. It was launched on March 5, 1978, with the primary goal of providing a global archive of satellite imagery. Unlike later Landsat satellites, Landsat 3 was managed solely by NASA. Landsat 3 decommissioned on September 7, 1983, beyond its design life of one year. The data collected during Landsat 3's lifetime was used by 31 countries. Countries that cannot afford their own satellite are able to use the data for ecological preservation efforts and to determine the location of natural resources.
Multispectral imaging captures image data within specific wavelength ranges across the electromagnetic spectrum. The wavelengths may be separated by filters or detected with the use of instruments that are sensitive to particular wavelengths, including light from frequencies beyond the visible light range, i.e. infrared and ultra-violet. It can allow extraction of additional information the human eye fails to capture with its visible receptors for red, green and blue. It was originally developed for military target identification and reconnaissance. Early space-based imaging platforms incorporated multispectral imaging technology to map details of the Earth related to coastal boundaries, vegetation, and landforms. Multispectral imaging has also found use in document and painting analysis.
The normalized difference vegetation index (NDVI) is a widely-used metric for quantifying the health and density of vegetation using sensor data. It is calculated from spectrometric data at two specific bands: red and near-infrared. The spectrometric data is usually sourced from remote sensors, such as satellites.
The Advanced Very-High-Resolution Radiometer (AVHRR) instrument is a space-borne sensor that measures the reflectance of the Earth in five spectral bands that are relatively wide by today's standards. AVHRR instruments are or have been carried by the National Oceanic and Atmospheric Administration (NOAA) family of polar orbiting platforms (POES) and European MetOp satellites. The instrument scans several channels; two are centered on the red (0.6 micrometres) and near-infrared (0.9 micrometres) regions, a third one is located around 3.5 micrometres, and another two the thermal radiation emitted by the planet, around 11 and 12 micrometres.
Landsat 2 is the second satellite of the Landsat program. The spacecraft originally carried a designation of ERTS-B but was renamed "Landsat 2" prior to its launch on January 22, 1975. The objective of the satellite was to acquire global, seasonal data in medium resolution from a near-polar, Sun-synchronous orbit. The satellite, built by General Electric, acquired data with the Return Beam Vidicon (RBV) and the Multispectral Scanner (MSS). Despite having a design life of one year, Landsat 2 operated for over seven years, finally ceasing operations on February 25, 1982.
Landsat 8 is an American Earth observation satellite launched on 11 February 2013. It is the eighth satellite in the Landsat program; the seventh to reach orbit successfully. Originally called the Landsat Data Continuity Mission (LDCM), it is a collaboration between NASA and the United States Geological Survey (USGS). NASA Goddard Space Flight Center in Greenbelt, Maryland, provided development, mission systems engineering, and acquisition of the launch vehicle while the USGS provided for development of the ground systems and will conduct on-going mission operations. It comprises the camera of the Operational Land Imager (OLI) and the Thermal Infrared Sensor (TIRS), which can be used to study Earth surface temperature and is used to study global warming.
Sentinel-2 is an Earth observation mission from the Copernicus Programme that acquires optical imagery at high spatial resolution over land and coastal waters. The mission's Sentinel-2A and Sentinel-2B satellites are to be joined in orbit in 2024 by a third, Sentinel-2C.
Sentinel-3 is an Earth observation heavy satellite series developed by the European Space Agency as part of the Copernicus Programme. As of 2024, it consists of 2 satellites: Sentinel-3A and Sentinel-3B. After initial commissioning, each satellite was handed over to EUMETSAT for the routine operations phase of the mission. Two recurrent satellites, Sentinel-3C and Sentinel-3D, will follow in approximately 2025 and 2028 respectively to ensure continuity of the Sentinel-3 mission.
Multispectral remote sensing is the collection and analysis of reflected, emitted, or back-scattered energy from an object or an area of interest in multiple bands of regions of the electromagnetic spectrum. Subcategories of multispectral remote sensing include hyperspectral, in which hundreds of bands are collected and analyzed, and ultraspectral remote sensing where many hundreds of bands are used. The main purpose of multispectral imaging is the potential to classify the image using multispectral classification. This is a much faster method of image analysis than is possible by human interpretation.
IRS-1A, Indian Remote Sensing satellite-1A, the first of the series of indigenous state-of-art remote sensing satellites, was successfully launched into a polar Sun-synchronous orbit on 17 March 1988 from the Soviet Cosmodrome at Baikonur. IRS-1A carries two sensors, LISS-1 and LISS-2, with resolutions of 72 m (236 ft) and 36 m (118 ft) respectively with a swath width of about 140 km (87 mi) during each pass over the country. Undertaken by the Indian Space Research Organisation (ISRO). It was a part-operational, part-experimental mission to develop Indian expertise in satellite imagery.
The Visible Infrared Imaging Radiometer Suite (VIIRS) is a sensor designed and manufactured by the Raytheon Company on board the polar-orbiting Suomi National Polar-orbiting Partnership, NOAA-20, and NOAA-21 weather satellites. VIIRS is one of five key instruments onboard Suomi NPP, launched on October 28, 2011. VIIRS is a whiskbroom scanner radiometer that collects imagery and radiometric measurements of the land, atmosphere, cryosphere, and oceans in the visible and infrared bands of the electromagnetic spectrum.
Landsat 9 is an Earth observation satellite launched on 27 September 2021 from Space Launch Complex-3E at Vandenberg Space Force Base on an Atlas V 401 launch vehicle. NASA is in charge of building, launching, and testing the satellite, while the United States Geological Survey (USGS) operates the satellite, and manages and distributes the data archive. It is the ninth satellite in the Landsat program, but Landsat 6 failed to reach orbit. The Critical Design Review (CDR) was completed by NASA in April 2018, and Northrop Grumman Innovation Systems (NGIS) was given the go-ahead to manufacture the satellite.
Gaofen is a series of Chinese high-resolution Earth imaging satellites launched as part of the China High-resolution Earth Observation System (CHEOS) program. CHEOS is a state-sponsored, civilian Earth-observation program used for agricultural, disaster, resource, and environmental monitoring. Proposed in 2006 and approved in 2010, the CHEOS program consists of the Gaofen series of space-based satellites, near-space and airborne systems such as airships and UAVs, ground systems that conduct data receipt, processing, calibration, and taskings, and a system of applications that fuse observation data with other sources to produce usable information and knowledge.
Remote sensing is used in the geological sciences as a data acquisition method complementary to field observation, because it allows mapping of geological characteristics of regions without physical contact with the areas being explored. About one-fourth of the Earth's total surface area is exposed land where information is ready to be extracted from detailed earth observation via remote sensing. Remote sensing is conducted via detection of electromagnetic radiation by sensors. The radiation can be naturally sourced, or produced by machines and reflected off of the Earth surface. The electromagnetic radiation acts as an information carrier for two main variables. First, the intensities of reflectance at different wavelengths are detected, and plotted on a spectral reflectance curve. This spectral fingerprint is governed by the physio-chemical properties of the surface of the target object and therefore helps mineral identification and hence geological mapping, for example by hyperspectral imaging. Second, the two-way travel time of radiation from and back to the sensor can calculate the distance in active remote sensing systems, for example, Interferometric synthetic-aperture radar. This helps geomorphological studies of ground motion, and thus can illuminate deformations associated with landslides, earthquakes, etc.
Remote sensing in oceanography is a widely used observational technique which enables researchers to acquire data of a location without physically measuring at that location. Remote sensing in oceanography mostly refers to measuring properties of the ocean surface with sensors on satellites or planes, which compose an image of captured electromagnetic radiation. A remote sensing instrument can either receive radiation from the Earth’s surface (passive), whether reflected from the Sun or emitted, or send out radiation to the surface and catch the reflection (active). All remote sensing instruments carry a sensor to capture the intensity of the radiation at specific wavelength windows, to retrieve a spectral signature for every location. The physical and chemical state of the surface determines the emissivity and reflectance for all bands in the electromagnetic spectrum, linking the measurements to physical properties of the surface. Unlike passive instruments, active remote sensing instruments also measure the two-way travel time of the signal; which is used to calculate the distance between the sensor and the imaged surface. Remote sensing satellites often carry other instruments which keep track of their location and measure atmospheric conditions.
Thermal remote sensing is a branch of remote sensing in the thermal infrared region of the electromagnetic spectrum. Thermal radiation from ground objects is measured using a thermal band in satellite sensors.
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