Ongoing research: The following is the approximate outline for ongoing studies on Synthetic aperture radar data retrieval and visualization. The ouline likely contains factual, spelling, and gramatical errors that are not reflected in final deliverables.
Research collected on synthetic aperture radar for reference. Record the research process and develop a comprehensive summary of SAR remote sensing for use in the future.
info draft:
"Remote sensing is the process of detecting and monitoring the physical characteristics of an area by measuring its reflected and emitted radiation at a distance (typically from satellite or aircraft).1"
Optical remote sensing is done by passively2 capturing only the radiation with a wavelength that falls within the visible spectrum. Optical satellite imagery offers numerous benefits in regards to image resolution3, and is relied on by a wide variety of applications requiring geological observation. This process, however, requires certain strict environmental conditions to be met to yield usable data. Environmental conditions such as cloud cover, atmospheric debris, or lack of reflected radiation (A.K.A. any observations made at nighttime) would all present impassable scenarios preventing the capture of usable imagery. Images from optical remote sensors tend to be more easily recognizable than other forms of remote sensing due to their familiar format. But unfortunate environmental constraints limit the potential uses of optical sensors to provide up-to-date imagery at a moment's notice.
Radio remote sensing is conducted through capture of energy with wavelengths that fall, very surprisingly, within the Radio spectrum. The conditional requirements for this mode of data collection are much less environmentally dependent. However, this form of remote sensing dictates by nature that the resolution of any radio data collected is largely dependent on the size of the aperature used in its collection. Meaning that radio wave data collected from any source cannot be resolved without the presence of an astronomically large collection aperature. (Such as the one synthesized to collect images of the accretion disk surrounding the event horizon of the black hole at the center of the Milky Way (26,000 light-years away from earth) , Sagittarius A)
Synthetic Aperture Radar is defined by NASA as "a type of active data collection where a sensor produces its own energy and then records the amount of that energy reflected back [to the sensor] after interacting with the Earth."(Herndon)4 Synthetic Aperature Radar data is gathered with the use of onboard microwave emitters and recievers. These remote sensors collect data from the target by emitting radio waves towards an area. The radio waves reflect off the user-defined area and are collected by the satelite. The reciever records multiple attributes of the microwaves reflected from the the target surface. It is these attributes that are manipulated in the image processing stage to reveal information about the target surface that typical optical imagery cannot gather.
Radar remote sensing advantages:
- All-weather Capability
- Day or Night Capability
- Penetration through vegitation
- Penetration through soil
- Minimal atmospheric effects
- sensitivity to dielectric properties (liquid vs frozen water)
- Sensitivity to structure
Radar remote sensing disadvantages:
- Information content in radar data is different than optical data
- Speckle effects (graininess in image)
- effects of topography
The length of a wave defines the interaction of the signal with the medium in the target area.
Pause for interesting rabit hole.
The same process used to collect and visualize data of Sagittarius A was first conducted on Messier 87, another black hole at the center of the Virgo Cluster. An image of the visualizations is included below. The ring around the perimeter and the centrally placed dot within the image of Sgr. A represent a rough approximation of Mercury's orbit and the Sun's diameter respectively. The small ring and white dot in the image of M87 however, represents the the entire approximated ellipsal orbit of pluto, and the distance covered by Voyager 1 over the entirety of its journey to interstellar space since it's launch on September 5th, 1977.
USGS. (n.d.). What is remote sensing and what is it used for? What is remote sensing and what is it used for? | U.S. Geological Survey. Retrieved August 28, 2022, from https://www.usgs.gov/faqs/what-remote-sensing-and-what-it-used#:~:text=Remote%20sensing%20is%20the%20process,sense%22%20things%20about%20the%20Earth.
Passive remote sensing collects radiation produced by other objects that is reflected from the target area. Active remote sensing emits its own energy and collects the energy reflected from the target area.
For this application, resolution can be defined as the finest amount of detail that still enables the user to distinguish between two distant objects. This is measured in meters. (ex: image y has a resolution of 10 meters, two different objects sitting in close proximity to one another with measurements of 10m x 10m can be differentiated) Follow this link for an excellent presentation with content on spacial resolution.
Herndon, K., Meyer, F., Flores, A., Cherrington, E., & Kucera, L. (n.d.). What is Synthetic Aperture Radar? Earthdata. Retrieved August 21, 2022, from https://www.earthdata.nasa.gov/learn/backgrounders/what-is-sar
Capella Space Synthetic Aperture Radar (SAR) Open Dataset was accessed on 8/14/2022 from https://registry.opendata.aws/capella_opendata.
"Capella Space specializes in the delivery of up-to-date information at the moment it is needed most. Access to live satelite imagery regardless of environmental factors is vital to make decison that save human life."
Information is collected by a constellation of 6 active satellites that can provide geological imagery scans updated by the hour.
Begin by first collecting data from open s3 bucket and visualize using OSGeo
Outline deployed tech and gather credentials.
- Amazon AWS CLI
- Amazon S3
- OSGeo
- SNAP
- Copernicus Open Access Hub
Use credentials to download data from Capella Space's s3 bucket
Open data in GEO.tif format
Later explored the Sentinel 1, 2, & 3 open data through SNAP interface
Visualize remotely sensed imagery
