In a test range, selection of sites for deployment of mobile telemetry stations plays a crucial role for acquiring and tracking any airborne vehicle under test. Efforts have been made to correlate the tracking performance of the auto track stations based on site selection for various test flights conducted from different launching pads. Some of the tracking methodologies discussed in this paper are single- channel amplitude comparison monopulse (SCACMP) technique and E-SCAN technique. Also, the performance of a simple telemetry data acquisition system using helical antenna is compared with these auto track stations.

1. Defence Science Journal, Vol. 53, No. 3, July 2003, pp. 233-238
© 2003, DESIDOC
SHORT COMMUNICATION
Performance Evaluation of Telemetry Stations
based on Site Selection
M. Goswami, B. Sucharita and P. Arya
Integrated Test Range, Balasore - 756 025
ABSTRACT
In a test range, selection of sites for deployment of mobile telemetry stations plays a crucial role
for acquiring and tracking any airborne vehicle under test. Efforts have been made to correlate the
tracking performance of the auto track stations based on site selection for various test flights conducted
from different launching pads. Some of the tracking methodologies discussed in this paper are single-
channel amplitude comparison monopulse (SCACMP) technique and E-SCAN technique. Also, the
performance of a simple telemetry data acquisition system using helical antenna is compared with
these auto track stations.
Keywords: Single-channel amplitude comparison monopulse technique, computer designate mode,
mobile telemetry stations, airborne vehicles, tracking-test ranges, E-SCAN technique,
tracking methodologies
1. INTRODUCTION
In a typical test range scenario, multiple
telemetry auto track stations are deployed to acquire
telemetry data not only for redundancy but also to
cater for the various diversities in space. Such
diversities may occur either due to the null depths
of the onboard antenna or to the fact that radio-
frequency waves suffer from polarisation, space
and frequency diversities at two different points
in space. Thus, the deployment of multiple auto
track stations and the associated task of site selection
becomes crucial for any test range configuration.
Normally, the choice of a site' for a particular
auto track station is done with a compromisebetween
its pedestal rates and the line-of-sight availability.
However, site selection is normally not done taking
into account the methodologies of tracking incorpo-
Revised 16 September 2002
rated in the auto track system in use. An attempt
has been made to understand the effect of site
selection on the auto track methodology incorporated
in the telemetry stations. In this paper, single-
channel amplitude comparison monopulse (SCACMP)
and E-SCAN systems have been compared for
their performance in real-time during various flight
campaigns from different launching pads.
2. TRACKING METHODOLOGIES
The conventional monopulse systems-' consist
of five crossed dipole feeds (Fig. 1) so as to
generate the azimuth error, the elevation error, and
the sum signal in the three different channels for
further processing by coherent receivers. However
in a single-channel monopulse system, the errors
are being utilised to modulate the data channel at
the feed and utilising a single channel instead of
233
Defence Science Journal, Val. 53, No. 3, July 2003, pp. 233-238
O 2003, DESIDOC
SHORT COMMUNICATION
Performance Evaluation of Telemetry Stations
based on Site Selection
M. Goswami,B. SucharitaandP.Arya
Integrated Test Range, Balasore - 756 025
ABSTRACT
In a test range, selection of sites for deployment of mobile telemetry stationsplays a crucial role
for acquiring and tracking any airborne vehicle under test. Efforts have been made to correlate the
trackingnerformanceoftheautotrackstationsbased on siteselection forvarioustest flightsconducted
fromdzerent launchingpads. Someof the trackingmethodologiesdiscussed in this piperare single-
channel amplitudecomparison monopulse (SCACMP)technique and E-SCAN technique. Also, the
performance of a simple telemetry dataacquisition system using helical antenna is compared with
these auto h.ack stations,
Keywords: Single-channel amplitude comparison monopulse technique, computer designate mode,
mobile telemetry stations, airbome vehicles, tracking-test ranges, E-SCAN technique,
tracking methodologies
1. INTRODUCTION
In a typical test range scenario, multiple
telemetry auto track stations are deployed to acquire
telemetry data not only for redundancy but also to
cater for the various diversities in space. Such
diversities may occur either due to the null depths
of the onboard antenna or to the fact that radio-
frequency waves suffer from polarisation, space
and frequency diversities at two different points
in space. Thus, the deployment of multiple auto
track stations and the associated task of site selection
becomes crucial for any test range configuration.
Normally, the choice of a site for a particular
auto track station is done with a compromise between
its pedestal rates and the line-of-sight availability.
However, site selection is normally not done taking
into account the methodologies of tracking incorpo-
rated in the auto track system in use. An attempt
has been made to understand the effect of site
selection on the auto track methodology incorporated
in the telemetry stations. In this paper, single-
channel amplitude comparison monopulse (SCACMP)
and E-SCAN systems have been compared for
their performance in real-time during various flight
campaigns from different launching pads.
2. TRACKING METHODOLOGIES
The conventional monopulse systems1,*consist
of five crossed dipole feeds (Fig. 1) so as to
generate the azimuth error, the elevation error, and
the sum signal in the three different channels for
further processing by coherent receivers. However
in a single-channel monopulse system, the errors
are being utilised to modulate the data channel at
the feed and utilising a single channel instead of
Revised 16September 2002

2. DEF SCI J, VOL. 53, NO. 3, JULY 2003
element always being active and an electronic switching
taking place between the dipoles of elevation and
the azimuth planes. Here, superposition of two
beams instead of three beams occurs in space as
of SCACMP system. Thus, tracking is achieved by
a shift in the phase centre of the beam patterns.
Such a system with a high G{f value of 16 dB/°K
was used.
Figure 1. Conventional monopulse systems
the three channels, thus, avoiding complexities
at the receiver level. Such an SCACMP telemetry
auto track station with the G{f value of 3 dB/ "K
was used for the study.
Another system having E-SCAN technique of
auto track was also utilised. Such a systenr'" also
consists of five crossed dipole feeds with the central
180
3. SYSTEM LOOP PERFORMANCE
A comparative study of the system loop
performance of both the systems was taken up
using the antenna image (angle data and antenna
controller status) during real-time as logged by a
central computer of both the systems for various
flight campaigns. The SCACMP system on some
occasions was placed very near to the launching
pad (typical distance of 2 km to 3 km) and on some
occasions, at an appreciable distance from the launch-
ing pad (typical distance of 40 km to 50 km). The
whole process was repeated for the E-SCAN system.
"(a)
MANUAL TRACKING
AUTO TRACKING
bO
170
3
160
:,:
f..;
::,
150::.
-
?N
<
140
130
20
?
..
"
::e.
? 10
?
>
::l
0"'
0 500 1000 1500 2000
SAMPLES
(b)
2500 3000 3500 4000
Figure 2. System loop performance of a SCACMP system when placed very near to the launching pad
DEF SCI 1, VOL. 53, NO. 3, JULY 2003
element alwaysbeing activeandanelectronicswitching
taking place between the dipoles of elevation and
the azimuth planes. Here, superposition of two
beams instead of three beams occurs in space as
of SCACMP system. Thus, tracking is achieved by
a shift in the phase centre of the beam patterns.
Such a system with a high G/T value of 16 dBIoK
was used.
3. SYSTEM LOOP PERFORMANCE
A comparative study of the system loop
performance of both the systems was taken up
Figure 1. Conventional monopulse systems
using the antenna image (angle data and antenna
the three channels, thus, avoiding complexities contr011er status) during real-time as logged by a
at the receiver level. Such an SCACMP telemetry central computer of both the systems for various
auto track station with the G/T value of 3 dB/ "K flight campaigns. The SCACMP System on Some
was used for the study. occasions was placed very near to the launching
pad (typical distance of 2 km to 3 km) and on some
Another system having E-SCAN technique of occasions, at an appreciable distance from the launcb-
auto track was also utilised. Such a s y ~ t e r n ~ - ~also ing pad (typical distance of 40 km to 50 km). The
consists of five crossed dipole feeds with the central whole process was repeated for the E-SCAN system.
- MANUAL TRACKING
- AUTO TRACKING
F
150
SAMPLES
(b)
Figure 2. System loop performance of a SCACMP system when placed very near to the launching pad

3. GOSWAMI, et al.: PERFORMANCE EVALUATION OF TELEMETRY STATIONS BAS1'U VN ,u? ,u---··-··
2500 3000 3500 4000
143.0
142.8
00
'"
'.2,
142.6
:,:
f-<
? 142.4
f:l
«:
142.2
142.0
30
?
..
20'"
""
?
?
?
lO
?
;>
"'
..J
"' 0
.JO
0 500 !000 1500 2000
{a)
MANUAL TRACKING
AUTO TRACKING
4500 5000
SAMPLES
(b)
Figure 3. System loop performance of a SCACMP system when placed very far to the launching pad
When the monopulse system is placed very
near (Fig. 2), it represents a typical situation where
the system repeatedly goes to side-lobe tracking
while initiating auto track after lift-off. The operator
is forced to initiate auto track after an appreciable
time, while the vehicle has an appreciable height.
This is because ·of the fact that at close proximity
of the launching pad along with the signal from the
boresight, the reflected signals from nearby locations
also become predominant. Under these conditions,
the SCACMP system has a probability to lockon
to the false target, which later gives confusing
results. When placed very far (Fig. 3), the same
system can perform better because false targets
due to reflection becomes ineffective compared to
the actual boresight at such distances.
The E-SCAN system seems to have no such
problems at either close locations (Fig. 4) or at
far-off distance from the launching pad (Fig. 5).
The superior performance of the B-SCAN
system can be explained mainly on the basis of
difference in philosophy of achieving auto track.
Unlike the SCACMP system where all the elements
are active continuously, here, respective elements
in the azimuth and elevation planes are active,
thus always incorporating an additional spatial
shift while tracking. This additional shift in space
further differentiates the reflections from the
actual boresight, giving a better resolution of
the radio-frequency source. Moreover, the fact
that in the B-SCAN system, the elements of
both the planes are not active simultaneously
provides a better crosstalk performance compared
to SCACMP system. Thus, auto track with E-
SCAN system seems to be more stable and
jerk-free compared to SCACMP system. The
only disadvantage of B-SCAN system seems to
be the theoretical prediction of being blind to
235
GOSWAMI, el nl.: PERFORMANCE EVALUATION OF TELEMETRY STATIONS BASEU un o l ~ rulll-..-..
- MANUAL TRACKING
- AUTO TRACKING
SAMPLES
(b)
Figure 3. System loop performance of a SCACMP system when placed very far to the launching pad
When the monopulse system is placed very
near (Fig. 2), it represents a typical situation where
the system repeatedly goes to side-lobe tracking
while initiating auto track after lift-off. The operator
is forced to initiate auto track after an appreciable
time, while the vehicle has an appreciable height.
This is because of the fact that at close proximity
of the launching pad along with the signal from the
boresight, the reflected signals from nearby locations
also become predominant. Under these conditions,
the SCACMP system has a probability to lockon
to the false target, which later gives confusing
results. When placed very far (Fig. 3), the same
system can perform better because false targets
due to reflection becomes ineffective compared to
the actual boresight at such distances.
The E-SCAN system seems to have no such
problems at either close locations (Fig. 4) or at
far-off distance from the launching pad (Fig. 5).
The superior performance of the E-SCAN
system can be explained mainly on the basis of
difference in philosophy of achieving auto track.
Unlike the SCACMP system where all the elements
are active continuously, here, respective elements
in the azimuth and elevation planes are active,
thus always incorporating an additional spatial
shift while tracking. This additional shift in space
further differentiates the reflections from the
actual boresight, giving a better resolution of
the radio-frequency source. Moreover, the fact
that in the E-SCAN system, the elements of
both the planes are not active simultaneously
provides a better crosstalk performance compared
to SCACMP system. Thus, auto track with E-
SCAN system seems to be more stable and
jerk-free compared to SCACMP system. The
only disadvantage of E-SCAN system seems to
be the theoretical prediction of being blind to

4. DEF SCI J, VOL. 53, NO. 3, JULY 2003
140001200010000
MANUAL TRACKING
AUTO TRACKING
8000
(a)
600040002000
180
? 160
=
E-, 140
::,
:.
-
N
120-e
100
60
oil
3 40
z
0
20-
!;;:
? 0
-20
0
SAMPLES
(b)
Figure 4. System loop performance of E-SCAN system when placed very near to the launching pad
150
oil
u
?
100
=
E-,
::,
:.
50-
N
<
0
(a)
30
oil
-
MANUAL TRACKING
u 20 --
AUTO TRACKING
?
z
0 10
?
>
? 0
?
-10-1-----?----?----?----?--?-?
0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000
SAMPLES
(b)
Figure 5. System loop performance of E-SCAN system when placed very far to the launching pad
DEF SCI J, VOL. 53, NO. 3, JULY 2003
-20 1 I I I I I I I
0 2000 4000 6000 8000 10000 12000 14000
SAMPLES
(b)
Figure 4. System loop performance of E-SCAN system when placed very near to the launching pad
1802
-M
4 160-
-31
S 140-
z2 120-
100 I I I I I I I
(a)
3 0 J
(a)
- -
F 20- -MANUAL TRACKING
'p
AUTO TRACKING
10-
53 O -
W
-10 I I
0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000
60'
-00
3 40-
g 20-
s 0-
SAMPLES
(b)
Figure 5. sysiem loop performance of E-SCAN system when placed very far to the launching pad
- MANUAL TRACKING
- AUTO TRACKING

5. GOSWAMI, et al., PERFORMANCE EVALUATION OF TELEMETRY STATIONS BASED ON SITE SELECTION
r-,HELICAL
ANTENNA
t>
RECEIVER '--
RHC
.
PC-BASED
DAPS BIT SYNC
DIVERSITY
COMBINER
1
MAGNETIC
TAPE
RECORDER
?HELICAL
ANTENNA
.
RECEIVER '-
LHC
v
Figure 6. Dual polarised helical antenna-based data acquisition station for telemetry data acquisition
rotating target, which has not been investigated
in the present study. However, the authors suggest
that scanning the elements with two different polarities
can be a better approach to deal with rotating
targets.
The plots shown here are typical cases. However,
similar results are observed during most of the
flight campaigns, and thus can be generalised to
a greater extent.
4. HELICAL ANTENNA-BASED
RECEIVING STATION
The test range has also configured a helical
antenna-based telemetry acquisition system2 which
is extensively used during various flight campaigns.
Figure 6 represents the dual polarised helical
antenna (nine-and-a-half turn, 30° beamwidth
and 15 dB gain)-based data acquisition station
which can be used as a full-fledged station for
telemetry data acquisition using manual tracking
for short-range flights. Low gain, dual polarisation
reception and the available beam width can easily
cater for the requirement of data acquisition
from close proximity of the launching pad at
acceptable signal-to-noise ratio by simple manual
tracking or by remote-steering at computer designate
mode for any short-range flights. Such a station
can also be useful to acquire data at the initial
phase of any long-range flight where SCACMP
system faces difficulties.
5. CONCLUSIONS
The performance of different auto track stations
during real-time on the basis of site selection was
investigated. It has been found that the SCACMP
system suffers from problems of side-lobe tracking
due to lockon to false targets when placed very
close to the vehicle under test. The same system
performs much better when placed at a far-off
distance. The E-SCAN system seems to have a
better resolution of the target and a superior auto
track performance in both the cases. Thus, it is
recommended that SCACMP system should not be
placed very near to launching pad even if pedestal
rates can cater for it. It has also been suggested
to deploy the helical antenna-based acquisition
system at close proximity of the launching pad
while configuring the range with SCACMP system.
GOSWAMI. e l a / . : PERFORMANCE EVALUATION OF TELEMETRY STATIONS BASED ON SITE SELECTION
HELICAL
ANTENNA RECEIVER
RHC
PC-BASED
DIVERSITY
BIT SYNC COMBINER
RECORDER
HELICAL
ANTENNA RECEIVER
LHC
Figure 6. Dual polarised helical antenna-based data acquisition station for telemetry data acquisition
rotating target, which has not been investigated
in the present study. However, the authors suggest
that scanning the elementswith two different polarities
can be a better approach to deal with rotating
targets.
The plots shown here are typical cases. However,
similar results are observed during most of the
flight campaigns, and thus can be generalised to
a greater extent.
4. HELICAL ANTENNA-BASED
RECEIVING STATION
The test range has also configured a helical
antenna-based telemetry acquisition systemZwhich
is extensively used during various flight campaigns.
Figure 6 represents the dual polarised helical
antenna (nine-and-a-half turn, 30" beamwidth
and 15 dB gain)-based data aqquisition station
which can he used as a full-fledged station for
telemetry data acquisition using manual tracking
for short-range flights. Low gain, dual polarisation
reception and the available beamwidth can easily
cater for the requirement of data acquisition
from close proximity of the launching pad at
acceptable signal-to-noise ratio by simple manual
tracking or by remote-steering at computer designate
mode for any short-range flights. Such a station
can also be useful to acquire data at the initial
phase of any long-range flight where SCACMP
system faces difficulties.
5. CONCLUSIONS
The performance of different auto track stations
during real-time on the basis of site selection was
investigated. It has been found that the SCACMP
system suffers from problems of side-lobe tracking
due to lockon to false targets when placed very
close to the vehicle under test. The same system
performs much better when placed at a far-off
distance. The E-SCAN system seems to have a
better resolution of the target and a superior auto
track performance in both the cases. Thus, it is
recommended that SCACMP system should not be
placed very near to launching pad even if pedestal
rates can cater for it. It has also been suggested
to deploy the helical antenna-based acquisition
system at close proximity of the launching pad
while configuring the range with SCACMP system.

6. DEF SCI J, VOL. 53, NO. 3, JULY 2003
ACKNOWLEDGEMENTS
The authors thank Shri S.C. Narang, Director,
Integrated Test Range, Balasore, for the support,
encouragement, and the facilities provided.
Thanks are also due to Shri K.G.K. Sarma, Jt
Director, for his valuable suggestions and also their
colleagues for their support.
REFERENCES
I. Serman, Samuel H. Monopulse principles and
techniques. Artech House, 1984.
2. Goswami, M.; Alli, S.M. & Pradhan, A.K.
Performance evaluation of ·telemetry tracking
systems applied to short and long range missiles-
a case study. In International Conference on
Contributors
Communication, Computers and Devices, December
14-16, 2000, IIT Kharagpur. pp. 775- 78.
3. Technical manuals-8 foot reflector and two
band feed tracking antenna. Scientific-Atlanta
Inc, 1987 and technical manual for tracking
and acquition feeds of GRS#l system. Orbit
Advanced Technologies Ltd, 1997.
4. Pedroza, Moises. Antenna pattern evaluation
for link analysis. In Proceedings of International
Telemetry Conference, SanDiego, CA, USA,
1996. pp. 111-18.
5. Dunn, Daniel S. & Augustin, Eugene P. A single-
channel monopulse antenna with low effective
sidelobes. In Proceedings of the International
Telemetry Conference, SanDiego, CA, USA,
1992. pp. 661- 70.
Mr M Goswami received his MSc (Physics) in Electronics and Radio Physics from
Burdwan University in 1998. He has been working as Scientist at the Integrated Test
Range (ITR), Balasore, since 1998. Presently, he is working on radio frequency front-
end areas of telemetry ground receiving stations.
Ms B Sucharita received her BTech from the Jadavpur University in 1986. Presently,
she is working as scientist at the !TR, Balasore. Her area of research includes radio
frequency of telemetry system.
Mr P Arya received his BSc (Engg) in Electronics from the Ranchi University in 1999.
He has been working as Scientist at the !TR, Balasore, since 1999. Presently, he is
working on radio frequency front-end and base-band areas of telemetry ground receiving
stations.
DEF SCI J, VOL. 53, NO. 3, JULY 2003
ACKNOWLEDGEMENTS Communication,Computersand Devices,December
14-16, 2000, IIT ~ h a r a ~ ~ u r .pp. 775-78.
The authors thank Shri S.C. Narang, Director,-
Integrated Test Range, Balasore, for the support,
3. Technical manuals-8 foot reflector and two
encouragement, and the facilities provided.
band feed tracking antenna. Scientific-Atlanta
Thanks are also due to Shri K.G.K. Sarma, Jt
Inc, 1987 and technical manual for tracking
Director, for his valuable suggestions and also their
and acquition feeds of GRS#l system. Orbit
colleagues for their support.
Advanced Technologies Ltd, 1997.
REFERENCES 4. Pedroza, Moises. Antenna pattern evaluation
for link analysis. In Proceedings of International
1. Serman, Samuel H. Monopulse principles and Telemetry Conference, SanDiego, CA, USA,
techniques. Artech House,1984. 1996. pp. 111-18.
2. Goswami, M.; Alli, S.M.& Pradhan, A.K. 5. Dunn, Daniel S. &Augustin, Eugene P. A single-
Performance evaluation of.telemetry tracking channel monopulse antenna with low effective
systems applied to short and long range missiles- sidelobes. In Proceedings of the International
a case study. In International Conference on Telemetry Conference, SanDiego, CA, USA,
1992. pp. 661-70.
Contributors
Mr M Goswami received his MSc (Physics) in Electronics and Radio Physics from
Burdwan University in 1998. He has been working as Scientist at the Integrated Test
Range (ITR), Balasore, since 1998. Presently,he is working on radio frequency front-
end areas of telemetry ground receiving stations.
Ms B Sueharita received her BTech from the Jadavpur University in 1986. Presently,
she is working as scientist at the ITR, Balasore. Her area of research includes radio
frequency of telemetry system.
Mr PArya received his BSc (Engg) in Electronicsfrom the Ranchi University in 1999.
He has been working as Scientist at the ITR, Balasore, since 1999. Presently, he is
working on radio frequency front-end and base-band areasof telemetryground receiving
stations.