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A positive radial velocity indicates the distance between the objects is or was increasing; a negative radial velocity indicates the distance between the source and observer is or was decreasing. William Huggins ventured in 1868 to estimate the radial velocity of Sirius with respect to the Sun, based on observed redshift of the star's light. [6]
Frequency ambiguity resolution is required to obtain the true radial velocity when the measurements is made using a system where the following inequality is true. R a d i a l V e l o c i t y > 0.5 ( P R F × C T r a n s m i t F r e q u e n c y ) {\displaystyle Radial\ Velocity>0.5\left({\frac {PRF\times C}{Transmit\ Frequency}}\right)}
This is an issue only with a particular type of system; the pulse-Doppler radar, which uses the Doppler effect to resolve velocity from the apparent change in frequency caused by targets that have net radial velocities compared to the radar device. Examination of the spectrum generated by a pulsed transmitter, shown above, reveals that each of ...
Radar is a system that uses radio waves to determine the distance , direction (azimuth and elevation angles), and radial velocity of objects relative to the site. It is a radiodetermination method [ 1 ] used to detect and track aircraft , ships , spacecraft , guided missiles , motor vehicles , map weather formations , and terrain .
The unambiguous zone is in the lower left corner. All of the other blocks have ambiguous range or ambiguous radial velocity. Pulse Doppler radar relies on medium pulse repetition frequency (PRF) from about 3 kHz to 30 kHz. Each transmit pulse is separated by between 5 km and 50 km of distance.
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Radial velocity is the speed along the line of sight of toward the radar and away from the radar. This kind of motion degrades cross section performance due to the following phenomenon. Scalloping; Doppler ambiguity function; Moving target indication blind velocities
To capture most of this traffic, even when it is moving almost tangentially through the radar (i.e., perpendicular to the radar-target line), a system must have the ability to detect very slow radial velocities. As the radial component of a target's velocity approaches zero, the target will fall into the clutter or blind zone.