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					AIAA Tactical Missile Symposium                                  January 15, Huntsville, AL


               AIAA Tactical Missile Design Symposium Transcription

                         January 16, 2004, Huntsville Alabama

                                       Title: Seekers

                         Author: Tim Carroll/Melissa Stumpe

                            Email: Put Speaker Email Here




                                   Transcription Team

       Jennifer Whitton, timandjennywhitton@yahoo.com, 4.5 hours on the project

           Karen Potter, karen.potter@amd.army.mil, 4.5 hours on the project

                               Summary of Team Method:

 Our team was small so we advertised on the bulletin board for new members but didn’t
get any responses. We had two lectures so each of us took on. The first one finished was
     to forward their information to the last to be put together, posted and sent to Dr.
                                        Frederick.


 Chart01-Seeker/Sensor Technology Assessment
for ECAP
Hi, my name is Jim Carroll I’m going to present the technology assessment for the secret
sensor section for the ECAP program. Next slide.

Chart 02- Seeker/Sensor Technology Assessment
A brief outline of what of I’m going to talk about basic definitions, background
information, the different seeker types, radar seekers, electrical optical seekers, and laser
seekers. Next slide please.

Chart 03- Definition of Seeker

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AIAA Tactical Missile Symposium                                  January 15, Huntsville, AL


What is a seeker? Basically the seeker is eye of the missile who’s job is to acquire and
attract the target until the missile impact the target the seeker provide bore-site error
signals and as the position of the target relative to the missile center axis to the guidance
algorithm. Typical seekers use electromagnetic energy however there are other examples
of where different forms of energy are used to trap target acoustics being one of them
there used quite a bit in underwater torpedo’s and there is actually one army program that
used acoustic to located moving vehicles. A basic function block diagram of what a
seeker looks like is shown at the bottom of the slide. There is an aperture which receives
the energy or transmits energy of an active seeker there’s a gimbals platform there’s a
receiver detector, electrical processing. Electrical processing is divided into two parts:
signal processing, and also tracker algorithms. Next slide please.

Chart 04- Seeker Field-of-View and Field of Regard
A couple of definitions there something called a field of view. And that’s the angular area
in space in which the seeker can observe at any given time the field of view for radar
seeker is referred to as ‘Beam Width’. For seekers that are gimbal and mounted on a two-
axis gimbal platform they can be slewed the area that they can cover with the field of
view is called a field of regard. Next slide please.

Chart 05- Seeker/Sensor Discipline Interaction
Here is an overview chart of the seeker sensor discipline interactions. There is a list of the
predominate factors that go into any seeker design operation engagement requirements
which include the engagement guidelines, the coverage area of the system, the
engagement ranges, that will also feed into the guide schemes depending on which
guidance scheme is chosen for a particle system has a large impact on the seeker sensor
design. Obviously size constraints target type will have a part in playing and what type of
wavelength and the power requirements required for a seeker cost constraints and
logistics considerations is also a factor in what a seeker sensor design will impact is the
aerodynamics. Obviously the output of a seeker sensor needed to go into the simulation
so points can be accessed the mechanical design and layout and the electrical system
requirements. Next slide please.

Chart 06- Electromagnetic Waves
Like I mentioned earlier most seekers today use electromagnetic energy. Electromagnetic
energy you learned about in physics is a electromagnetic disturbance that is composed of
time variant creating and electromagnetic fields and it can transport energy through space
even if no matter is present in that space they call it the propagation electromechanical
wave. EM wave propagate at the speed of light EM wave has an electric and magnetic
part there 90 degrees apart from each other and both of those are 90 degrees apart from
the direction of propagation. EM waves travel in straight lines so that you have to have
line of sight and one other important factor is that all object above absolute zero emit EM
waves in the infrared spectrum. Next slide.


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AIAA Tactical Missile Symposium                                January 15, Huntsville, AL


Chart 07- EM Wavelengths and Frequencies
Here is a chart showing the overview of the electromagnetic wavelengths and
frequencies. It ranges from very large waves like AM radio all the way down to very very
small waves X-rays and gamma rays. Typically, missiles use the frequencies between
microwaves, which are about a centimeter in length to very very small infrared
wavelengths that are in the order of micrometers. Frequency and wavelength are coupled
through the equation shown at the bottom wavelength is equal to the speed of light
divided by frequency. Next slide.

Chart 08- EM Atmospheric Attenuation
EM wave are continuated as they travel through the atmosphere typical particles size in
the atmosphere has a large influence as that is related to the wavelength the larger the
wavelength the less the atmospheric attenuasic. As you can see here, microwaves
electromagnetic wave aren’t even on the chart they have very very little continuation in
the atmosphere the smaller the wavelength the more the continuation. Next slide.

Chart 09- Classification of Seekers/Sensors
Spectral Band
Here is a classification of seeker sensors based upon spectral band that there have
observed. There is about five major areas there is microwaves, millimeter waves, the
electro-optical which is broken into two areas visual and IR and then lasers and there is
three pretty common lasers listed there and their in the micrometer bandwidth.
Microwave seeker go to the L band to the KA band Millimeter wave their frequencies is
above 30 GHz usually if magnitude applies millimeter length and size and visible in IR
wavelengths are very very small high frequency waves. Next slide.

Chart 10- Classification of Seekers/Sensors
Active/Passive/Semi-Active
Seekers are also categorized as the way they operate and they are active seekers, passive
seekers, and semi-active seekers. Active seekers actually transmit the energy out of their
antenna it bounces off the target and they listen for the return or observe the return
through the same antenna. Microwave radar or millimeter radars are examples of this and
also something new called LADAR uses this same principle. Passive seeker look for
natural occurring electromagnetic radiation typical your passive sensors are infrared and
visual. Visual your looking for the reflected light, infrared is the nature emitting
wavelengths that we discussed early. Then there another one called a semi-active seeker
and they operate in one of two modes. The first one is that you will have a laminating
asset somewhere other than the seeker it could be the platform the missile fired from or
some other asset and it sends some energy out. All the missile has to do is operate in a


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AIAA Tactical Missile Symposium                                   January 15, Huntsville, AL


passive mode and observe the energy that’s being bounced off. There is another one to
that also called semi-active that where a missile flies out and it’s updated from the
platform to where to fly to and when it get to a certain range it turns on its radar or sensor
and becomes active they call this ‘Terminal Active’. Next slide please.

Chart 11- Classification of Seekers/Sensors
Stabilization Mechanization
And there’s finally one more categorization of seekers and that’s there stabilization
mechanism there’s two kinds there’s stabilized seeker and non-stabilized seeker. They
call the non-stabilized seeker a strap-down seeker. The seeker head is in a stabilized
situation it’s isolated from the motion of the missile we put rate sensors on there and a
control system and it keeps the seeker pointed no matter what the missiles doing until
drive it past giblets we should try to avoid the down side of the stabilized seeker its
expensive its complex and increases the size and weight. A strap-down seeker is a rigidly
mounted missile body is seeks the same motion as the missile does they’re typical
cheaper but, however, they have a low quality of image signal that sent back to the
processing algorithm because the motion not isolated so you can get blurring and things
like that and I also have another problem because you can’t slew the seek you have
limited engagement geometry because you field of view is your field of regard and you
can’t look very far distances to the side the motion the missiles O.K. next slide.

Chart 12- Microwave Radar Seekers/Sensors
I’m going to go into the five different slides here that discuss each different type of radar
categorized by wavelength primarily, microwave radars they have some advantages,
weather does not affect them, they provide range and range rate information to the
guidance algorithms, they have long operating ranges that part because they do
continuate in the atmosphere they have low degradation due to battlefield obscurant
smoke, dust and things like that. They can use Doppler detection for moving targets.
There’s not a requirement to have a certain shape nose on the missile to some degree so
you can actually send the microwave energy through the radar and they can be made
more aerodynamic. The disadvantages is that you need a large component for the aperture
the reason you have to do that is because the wave length is a microwave radar or larger
that limits you to the diameter of the missile diameter missile you can’t fit radar in there
and have any kind of a descent detection range. They usually have to operate in the active
or semi-active mode. They have large angular resolution that also a function of the
wavelength that means you can’t and very small angular resolution to where to target is
inside of the beam and they’re expensive. States of the arts for microwave radars are
phase relay radars they set up a lot of antenna and play which the phase difference
between them and they can make the beam move around Doppler beam sharping
synthetic aperture radars. This radiometric that’s something that relatively new and it ‘s a
passive radar and there actually looking at naturally occurring radiation in certain bands
there is nothing out there that uses that but, that’s on the horizon. And I put down there
on the bottom and you will see this in all of them multi sensor that’s something that really


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AIAA Tactical Missile Symposium                                  January 15, Huntsville, AL


new with missile that putting multiple seekers or sensors on there that for different bands
because they all have advantages and disadvantages and the fusion for those seekers
make for very sophisticated and complex missiles are very hard to counter make and they
have very good performance. O.K. Next slide.

Chart 13- Millimeter Wave Seekers/Sensors
Millimeter sensors there all weather they have some degradation with rain, and that
because the rain drops are hitting on the size of the wavelength of the energy small
components they have small angular resolution that again depends on the wavelength
they also can use Doppler detection for moving targets and they have the same advantage
as low drag shaft. Some disadvantages you need to have active mode or semi-active
mode someone’s broadcasting and can be expensive and have relative short operating
ranges around the microwave state of the art making very small millimeter wave antenna
again you see some of the same thing microwave Doppler beam sharping radio metrics
listed and multi-sensors listed also. Also they are starting to use some missiles with the
strap-down configuration for millimeter wave and that’s relatively new. You can make
you beam wet and increase you beam width so that you can have a significant surf area
strap down with the millimeter. Next slide.

Chart 14- IR Seekers/Sensors
Infrared seekers they also can have small components of relatively small apertures they
have very good angular resolution, they are passive, you can achieve very small miss
distances and provide a point vise capability and what that means it you can take a tracker
and identify features on a target and based upon those features you can write you tracking
software selectively pick at any point and you can very highly validate with an infrared
seeker. Some of the disadvantages: There is some weather degradation, there is some
battle field obscurant degradation, you don’t get any range or range rate information out
of a passive system, they can be expensive, and you have to have a hemispheric nose on
there and that true with all the electro-optical sensors. And that will impure a prang
penalty. State of the art focal plane array IR detectors are state of the art and that where
instead of having a few detectors that scan and the field of view you have an entire array
of detectors that have are constantly starring at the field of view. Now they are starting to
use this thing called biosensors in the past they had to use cool biosensors and that’s so
you can have sensors and good detects sensitivity and now they are getting the materials
such that you don’t need to cool them before they have good sensitivities again you see
strap-down configurations and multi-sensor fusion is another state of the art. The strap-
down one you can get into some problems here with an infrared seeker because there is
an integration time on it and if you get a lot of motion on the missile you will get blurring
of the target. Next slide.

Chart 15- Visual Seekers/Sensors


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AIAA Tactical Missile Symposium                                  January 15, Huntsville, AL


Visual seeker and sensors these have a lot of the same problems that an infrared sensor
does except this one has one glaring problem they depend upon reflected light, visual
light that means you can’t operate these at night and that’s a sever limitation. They have
used this is a picture of a maverick missile the first one’s use visuals and since they
created versions that use infrared you don’t see many missiles now with visual seekers on
them anymore because the no-night capability and of course weather obscurant and
battlefield obscurant can degrade high and you can’t see through dust and cloud and
things like that. O.K. next slide.

Chart 16- Laser Seekers/Sensors
Laser seekers and sensors these again use and is consider electro-optical so you have to
have a hemispherical dome on the front of the missile for them to see. Typically you see
the laser seeker sensor as a semi-active mode you have a designated asset that put target
on an object that looks for that frequency of energy and guides on it they can have small
components and small apertures. I put range and rating information on here for one
reason and that is because of a state of the art thing called a LADAR. You can get very
good range and rate information from a radar you can achieve small miss missiles
distances and you can achieve point vise capability with this type of sensor. They can be
d by weather and by battlefield obscurant another disadvantage is the dependency on
other asset and resonator for a semi-active mode high cost. I put high cost on there
because it is very expensive to have a powerful laser that can shine its beam at any
significant distance. You won’t have and fire and forget capability with a semi-active
mode and also a problem with the radar site has a small search area because of speed so it
has to be able to scan very rapidly if you want to cover a large search area state of the art
for a laser is a LADAR they have something too for a beam configuration the side
looking and it can tell how far it is off a beam by looking sideways and also put multi-
sensors fusion on here incase you want to couple a laser with a infrared or millimeter
wave. O.K. next slide

Chart 17- Sample Calculations
On my last chart I provide and little brief here on the sample calculations. I have the radar
range equation here. A snapshot I have from a utility and you can do some calculations.
For microwave and millimeter wave and you will see that it is R to the fourth and that
because the radar wave equation works and is typical and is by R squared come back and
it is squared again and if the transmitter and receiver is in a platform it is R to the fourth
on a semi-active mode your two R’s would be separate your one R going out to the target
and then you have the one that actually goes back to the sensor missile that’s detecting
that radiation for infrared and electro-optical the ranged term is squared instead of to the
fourth there will be in this spread sheet calculations for millimeter waves, microwave and
infrared laser so you can come up with performance parameter which can be feed into
simulations and that conclusions my presentation.




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