FAQs

1. What is a satellite?

2. What is a satellite image?

A satellite image is an image resulting from the processing of satellite-based data, by the mean of artificial satellites. The first satellite photographs of Earth were made August 14, 1959 by the US satellite Explorer 6.

3. What is remote sensing?

Remote sensing is the short or large-scale acquisition of information of an object, area or phenomenon, by the use of either recording or real-time sensing device(s) that is not in physical or intimate contact with the object (such as by way of aircraft, spacecraft, satellite, buoy, or ship).

4. What is interferometry?

Interferometry represents the design and use of optical interferometers; uses include precise measurement of wavelength, measurement of very small distances and thicknesses, study of hyperfine structure of spectral lines, precise measurement of indices of refraction and determination of separations of binary stars and diameters of very large stars.

5. What is azimuth?

Azimuth is a mathematical concept defined as the angle, usually measured in degrees (°), between a reference plane and a point. This concept is used in many practical applications including navigation, astronomy, mapping and artillery.

6. What is the bite error rate (BER)?

BER is the ratio of the number of bits, elements, characters, or blocks incorrectly received to the total number of bits, elements, characters, or blocks sent during a specified time interval.

7. What is Synthetic Aperture?

Synthetic Aperture is a technique used in radio astronomy to obtain the resolution of a radio telescope with a very large effective aperture from observations made using a group of smaller antennas.

8. What is Synthetic Aperture Radar (SAR)?

Synthetic aperture radar is a form of radar in which sophisticated post-processing of radar data is used to produce a very narrow effective beam. In SAR imaging, microwave pulses are transmitted by an antenna towards the earth surface. The microwave energy scattered back to the spacecraft is measured. The SAR makes use of the radar principle to form an image by employing the time delay of the backscattered.

9. Can SAR capture images on all kind of weather?

Due to the cloud penetrating property of microwave, SAR is able to acquire "cloud-free" images in all weather. Being an active remote sensing device, it is also capable of nighttime operation.

10. What type of waves SAR uses?

Synthetic Aperture Radar operates in the microwave portion of the electromagnetic spectrum.

11. What are microwaves?

Microwaves are electromagnetic waves with wavelengths shorter than one meter and longer than one millimeter, or frequencies between 300 megahertz and 300 gigahertz.

12. What is real aperture radar?

Real aperture radar is a system that uses electromagnetic waves to identify the altitude, range, direction or speed of moving and fixed objects. A transmitter emits radio waves, which are reflected by the target and detected by a receiver, typically in the same location as the transmitter.

In real aperture radar imaging, the ground resolution is limited by the size of the microwave beam sent out from the antenna. Finer details on the ground can be resolved by using a narrower beam. The beam width is inversely proportional to the size of the antenna, i.e. the longer the antenna, the narrower the beam.

A moving ship (or any other object moving at or near the water surface) generates a kind of trace on the water surface that is called a wake. Around and directly behind the ship, the wake is rather complex, with so-called bow and stern waves, eddies and currents, and foam. Ship waves are viewed in satellite images because they generate and modify surface waves.

15. What information can satellite images provide?

Using archive data of past catastrophic events and data of more recent events (e.g., the 2004 hurricane season) CSTARS could document and provide a current assessment of landscape/seascape damage by catastrophic events, including major hurricanes, landslides, sink holes, flooding, seismic activity and volcanic eruption.

16. What SARs currently orbiting in space are accessible to CSTARS?

Currently existing SARs orbiting in space and accessible to CSTARS are the Canadian Space Agency’s (CSA) RadarSat-1, the European Space Agency’s (ESA) ERS-2 and ENVISAT ASAR.

17. What is Global Positioning System (GPS)?

GPS is a system consisting of 25 satellites in six orbital planes at 20,000-km altitude with 12-hr periods, used to provide highly precise position, velocity and time information to users anywhere on Earth.

18. What is Ingest Archive System (IAS)?

This component of the CSTARS ground station consists of the real-time collection and archiving systems. The IAS uses multiple computers to acquire the serial data, which streams from the antennas. Once the data is received, it is processed by a large server computer into a format that ultimately will be archived for long-term storage. Finally, this data is written to a large disk drive array as well as to a tape library, and an Oracle database is updated with information about where the archived data resides and how to retrieve it for processing.

This component steps in when an image product is requestor by a user of CSTARS data. A production request is submitted through a user interface, and the relevant data is retrieved from the archive and placed into a large server computer. There it is processed to the user's specifications, then made available for retrieval either through being written to media (CD/DVD/Tape) or placed on an FTP server.

20. What is Data Exploitation System (DES)?

CSTARS also has some powerful workstations that are available for use by visiting research personnel. These computers allow visualization and interpretation (i.e. exploitation) of the imagery, which would have been previously ordered via the PGS system.

S band is a frequency range from 2 to 4 GHz, part of the microwave band of the electromagnetic spectrum. The S band is used by weather radar, some communications satellites and for optical communications. The 10-cm radar short-band ranges roughly from 1.55 to 5.2 GHz.

Very high frequency (VHF) is the radio frequency range from 30 MHz to 300 MHz. Regular uses for VHF are FM radio broadcast, television broadcast, Amateur Radio, marine communications, air traffic control communications and terrestrial navigation systems. VHF propagation characteristics are ideal for short-distance terrestrial communication.