Small target detection from the Next Generation SCANTER ... - terma

Small target detection from the Next Generation SCANTER 5000
and 6000 Series of radars from Terma A/S
By Jens Chr. Pedersen, Director, Product Portfolio & Innovation, Radar Systems, Terma A/S
The SCANTER 5000 series comprises a new generation of Fully Coherent, Frequency
Diversity and Time Diversity, Solid State Radars with Software Defined Functionality for
professional applications such as VTS, Coastal Surveillance and Airport Surface Movement
Radars (SMR). Similar technology is employed in the SCANTER 6000 series of
radars for Ship-borne applications.
Several tests with targets of opportunity as well as controlled tests were made during the
development. This was complemented with a repeated series of trials made during release
for operational use of the SCANTER 5102 transceiver in June 2010.
Furthermore, the performance was compared to a SCANTER 2001 FD transceiver installed
next to the SCANTER 5102, utilising the same 21’HP-F-38 antenna. Both transceivers
were configured for stationary surface surveillance applications. The SCANTER
2001 includes two 25 KW magnetron amplifiers. The SCANTER 5102 is fitted with a 50
W Solid State Power amplifier.
The tests were made at the Terma HQ test range, and with targets sailing in the bay of
Aarhus.
Figure 1: Radar image from the SCANTER 5102 at the Terma test site
A 5.2 meter zodiac with outboard motor was used for verification test of the performance.
The Radar Cross section was measured to 1.4 square meters and the estimated
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center of gravidity for the RCS is 0.5 m ASL, with the boat driver sitting up. Speed during
the tests was varying between 0 and 30 knots, without significant influence on the results.
A floating, calibrated reference reflector was placed in the test area at a distance
of approximately 4 nautical miles.
Figure 2 Target used for controlled tests.
Figure 3 2 m 2 reference reflector used for measurement of target Radar Cross
Section during the tests.
The CARPET program from TNO was used to calculate expected range performance,
taking actual weather into consideration. Very different weather situations appeared.
On 07/06/2010 it was very dense rainfall; approximately 50 millimeters of rainfall
were recorded during daytime on nearby meteorological stations. The rainfall
during the test was estimated to 5 mm/hour, fairly uniform over the entire area.
On 10/06/2010 it was less dense rainfall; approximately 20-25 millimeters of rainfall
were recorded during daytime on nearby meteorological stations. The rainfall
during the test was estimated to 2 mm/hour, not as uniform as on the first day
and with cells of dense shower like rain.
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On 16/06/2010 it was clear sunny weather with a mild breeze.
The rain during the first 2 days was completely removed by processing resulting in an as
clear image as on the day with clear weather.
Most of the range between the radar and the test area is over land. Evaporation ducting
will in such case only have marginal effect on the propagation and standard atmospheric
conditions.
Antenna height at the Terma test site is approximately 50 meters ASL and the
waveguide length between the antenna and the transceivers is 22 meters
Calculation and test results are summarized in Table 1.
Table 1 Calculation and test results.
Date of test
Conditions
Calculated detection range with
used Radar setup, 99% Pd
SCANTER
2001 FD
SCANTER
5102
SCANTER
5202
Measured detection range @ first
loss of detection
SCANTER
2001 FD
SCANTER
5102
SCANTER
5202
07/06/2010
10/06/2010
Aproximately 5
mm/h rain, Sea
state 1-2
Aproximately 2
mm/h rain, Sea
state 1-2
3.7 nmi 4.0 nmi 4.2 nmi 4 nmi 5.7 nmi
4.2 nmi 4.4 nmi 4.7 nmi 5.6 nmi 6.5 nmi
Not
included
in test
16/06/2010
Clear, light breeze,
Sea state 2
6.0 nmi 5.6 nmi 6.2 nmi 6.5 nmi 7.8 nmi
The difference between calculated and measured results for the SCANTER 2001 is in
accordance with typical experience, the CARPET calculations are a bit pessimistic.
We have by now observed that the Next Generation radar technology is performing substantially
better than expected. The main reason for that is most likely that the empiric
models behind the CARPET tools are insufficient in respect to modeling of the new series
of SCANTER radars. Looking at the radar screen, target fluctuations are much reduced
with the new technology and this does explain most of the excess performance.
Furthermore, the differences seem to appear in all weather conditions. However, tests
with high sea clutter conditions are yet to be completed. In the meantime, evidence is
sufficient to allow use of CARPET with SCANTER 2001 FD parameters to determine
performance for the 50 W versions, SCANTER 5102 and 5502, of the Next Generation
radars in respect to surface target detection.
In respect to the 200W versions, SCANTER 5202, 5602 and 6002, it is OK to calculate
with 5% increased range (20% increased volume) when compared to SCANTER 2001.
However, BE CAREFULL, the horizon (lowest lobe) may be the limiting factor, in which
cases the range performance is identical. This counts especially for low antenna elevations
and in clear weather without ducting.
It is in any case better to use the new Terma performance evaluation Tool, ASPECT, it
does include better modeling of the new radars and it is being further refined as experience
with the new products is gained.
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Figure 4 Test target at 6.1 and 7.4 Nautical Miles respectively
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