Computer controlled optical tracking system

A tracking system including an acquisition sight for use by a pilot of an rcraft to acquire a target. Once the pilot acquires the target an operator uses a track handle to take control of tracking the target. The operator monitors the target utilizing narrow and wide field of view monitors. When the target is visible within the narrow field of monitor, the operator can switch tracking of the target to an automatic video tracking system which tracks the target by contrasting the target and its surroundings. A computer, which receives azimuth and elevation data from the tracking device, processes the data and provides azimuth and elevation angle signals to a gimballed mirror to steer the mirror to the target. The gimballed mirror receives image forming light from the target and then directs the light to a wide field of view camera and a zoom telescope. The wide field of view camera is connected to the wide field of view monitor to provide a wide field of view image with overlay graphics for display to the operator. The zoom telescope provides a narrow field of view image and then directs the narrow field of view image to a narrow field of view camera. The narrow field of view camera is connected to the narrow field of view monitor which provides a narrow field of view image with overlay graphics of the target for display to the operator.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates generally to tracking systems. More 
specifically, the present invention relates to an optical tracking system 
which is computer controlled and which is adapted for use on board an 
airborne platform such as aircraft, helicopter or the like. 
2. Description of the Prior Art 
In the past optical tracking systems have been extensively used for 
acquiring, locating, and tracking objects of interest from an airborne 
platform. For example, in tracking the movement of illegal drugs via an 
airborne vehicle, such as helicopter 37 of FIG. 2, or a land based vehicle 
from the air, an optical tracking system on board a helicopter can be 
extremely useful in that it continually provides updated information as to 
the movement, direction and location of the vehicle. By accurately 
identifying the movement, direction and location of the vehicle to law 
enforcement personnel on the ground an arrest can be made without undue 
endangerment to the individuals making the arrest. 
An airborne optical tracking system can also be extremely useful in 
tracking illegal aliens entering the United States across its many 
boarders which cover several hundred miles of rugged terrain and which are 
not easily accessible by land. Other uses for airborne optical tracking 
system include search and rescue missions at sea and on land where the 
terrain is very rugged. 
Generally, an optical tracking system for an airborne platform utilizing 
video cameras is referred to as an Airborne Video Tracking System (AVTS). 
These Airborne Video Tracking Systems are often manually controlled by 
either the pilot of the aircraft or a crew member. However, optical 
tracking systems which are manually controlled often lack the ability to 
quickly acquire a target. In addition, the manually controlled airborne 
optical tracking systems are generally unable to steer the optics to point 
to a specific latitude and longitude for the target in a rapid response 
time or to slave the optics of the optical tracking system with another 
tracking system and thereby follow the other tracking system. Such a 
tracking system may be an acquisition sight tracking system or an infrared 
or radar tracking system. 
It is therefore an object of the present invention to provide an airborne 
tracking system which allows for the immediate acquisition of a target of 
interest by the user of the system. 
It is another object of the present invention to provide instantaneous 
location including longitude and latitude coordinates for the target of 
interest. 
It is still another object of the present invention to provide an airborne 
optical tracking system which may be slaved with another tracking system 
so as to follow the other tracking system. 
Various other advantages and objectives of the present invention will 
become apparent to those skilled in the art by the detailed description of 
the invention and its preferred embodiments. 
SUMMARY OF THE INVENTION 
The present invention overcomes some of the disadvantages mentioned above 
in that it comprises a highly accurate and reliable airborne video 
tracking system for use in tracking a target of interest and then 
providing instantaneous location information including the longitude, 
latitude and altitude for the target. 
The airborne video tracking system comprises an acquisition sight for use 
by a pilot of an aircraft to acquire and begin tracking the target. Once 
the pilot acquires the target, an operator at an operator's console in the 
aircraft can use a track handle to manually take control of tracking the 
target from the pilot. The operator monitors the target utilizing a narrow 
field of view monitor and a wide field of view monitor located at the 
operator console. When the target is visible within the narrow field of 
view monitor the operator can switch tracking of the target from the track 
handle to an automatic video tracking system. The automatic video tracking 
system tracks the target based upon the contrast between the target and 
its surroundings. 
A computer receives azimuth and elevation positional signals from the 
tracking device being used to track the target. The tracking device may be 
the acquisition sight, the track handle, the automatic video tracking 
system or a tracking radar which is coupled to an infrared display system. 
The computer then processes the azimuth and elevation data from the 
tracking device and provides azimuth and elevation angle signals in an 
analog format to a gimballed mirror to steer the gimballed mirror to the 
target. 
The gimballed mirror receives image forming light from the target and then 
directs the image forming light via a first turning mirror to a wide field 
of view camera and a zoom telescope. The wide field of view camera is 
connected to the wide field of view monitor via an airborne video tracking 
system computer at the operator console allowing a wide field of view 
image to be displayed to the operator at the operator's console. 
The zoom telescope, which also receives image forming light from the 
gimballed mirror via a second turning mirror, provides a narrow field of 
view image ranging from about 0.1 degree to about one degree. The zoom 
telescope directs the narrow field of view image to a narrow field of view 
camera. The narrow field of view camera is connected to the narrow field 
of view monitor via the airborne video tracking system computer at the 
operator console allowing a narrow field of view image of the target to be 
displayed to the operator at the operator's console. 
The computer includes a video time inserter/video data inserter which 
overlays time and positional information of the target on the narrow field 
of view display. The video time inserter/video data inserter also overlays 
time and positional information of the aircraft as well as positional 
indicators of the gimballed mirror on the wide field of view display.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIG. 1 there is shown a simplified block diagram of the 
airborne video tracking system 20 which is adapted for use on board an 
aircraft or helicopter or the like. Airborne video tracking system 20 
includes an observer station 26 and an operator console 24. The operator 
console 24 is connected to observer station 26 which has the optical 
tracking elements of airborne video tracking system 20. The operator 
console 24 is also connected to an acquisition sight 22 which is generally 
located in the aircraft's cockpit and which is used by the aircraft's 
pilot for the initial acquisition of the target when airborne video 
tracking system 20 is being used to track a target such as the helicopter 
37 illustrated in FIG. 2. Although target 37 is depicted as a helicopter 
in FIG. 2, it should be understood that tracking system 20 is also used to 
track land based targets such as trucks and automobiles as well as the 
aforementioned airborne targets. 
Referring to FIGS. 1 and 2, the acquisition sight 22 used in the present 
invention is a newton ring type acquisition sight wherein the aircraft's 
pilot looks through a glass lens which includes a circle or newton ring 23 
projected to infinity. The pilot then aligns circle 23 of acquisition 
sight 22 with the target 37 such that the target 37 appears within circle 
23 of acquisition sight 22 thereby providing for the initial acquisition 
of the target 37 by airborne video tracking system 20. Acquisition sights 
22 then provides an analog signal (indicating azimuth and elevation of the 
target) to a system computer 42 (FIG. 2) located at the operator console 
24. The system computer 42 processes the analog signal and then provides 
control signals to position the optics at the observer station 26 to the 
target 37. 
Operator console 24 is also coupled to the aircraft's inertial navigation 
system 30 allowing system computer 42 to monitor the location of the 
aircraft having airborne video tracking system mounted therein. Positional 
information provided by the aircraft's inertial navigation system 30 
includes the aircraft's latitude and longitude coordinates and the 
aircraft's elevation as well as the roll, pitch and heading of the 
aircraft. The inertial navigation system 30 is, in turn, connected to a 
global positioning system 28 located on board the aircraft. The global 
positioning system 28 provides position information updates to the 
aircraft's inertial navigation system 30 to correct for drifting which 
occurs in the inertial navigation system 30 after takeoff of the aircraft. 
The operator console is connected to the aircraft's infrared display system 
34 to receive synchro/sinusoidal signals from system 34 which indicate the 
direction infrared display system 34 is pointing. Infrared display system 
34 is coupled to a tracking radar 32 which can be used to guide infrared 
display system 34. Interfacing with the aircraft's infrared display system 
34 allows an operator the ability to monitor the aircraft's tracking radar 
from operator console 24. 
Operator console 24 includes computer 42 which may be, for example, any IBM 
compatible PC computer. Connected to computer 42 is a keyboard 41 and a 
monitor 47. There is also a track handle 38 at operators console 24 which 
is connected to computer 42 through an automatic video tracker 40 and a 
control unit 36. Track handle 38 allows an operator at console 24 to 
manually track the target 37 by depressing trigger switch 39 on track 
handle 38 once the aircraft's pilot acquires the target 37 using 
acquisition sight 22. The operator monitors the target 37 at the wide 
field of view monitor 46 which is located at operator's console 24. 
By engaging a trigger switch 39 at the operator console 24, the operator 
takes control of tracking target 37 from the pilot using automatic video 
tracker 40 or track handle 38. When target 37 is within the narrow field 
of view as displayed on monitor 48, the operator at operator console 24 
can switch to automatic video tracker 40 as the means for tracking target 
37. The automatic video tracker 40 tracks the target 37 by contrasting the 
target 37 with its background. For the helicopter illustrated in FIG. 2, 
the helicopter is contrasted with the blue sky background. If the 
helicopter were camouflaged to match the trees of a forest and sufficient 
contrast were not available then automatic video tracker 40 would not be 
utilized as the tracking means for airborne video tracking system 20. 
It should be noted that acquisition sight 22 and track handle 38 are 
connected in series allowing an operator at console 24 to acquire control 
of the tracking of a target 37 from acquisition sight 22 by depressing 
trigger switch 39 on track handle 38. Automatic video tracker 40 is also 
connected in series with track handle 38 allowing the operator to use 
automatic video tracker 40 to track target 37. 
By using track handle 38 the operator at console 24 can position the target 
37 within a wide field of view monitor 46 and within a narrow field of 
view monitor 48 which is located at the operator's console 24. Displayed 
on the wide field of view monitor 46 and the narrow field of view monitor 
48 is the video from the optics at observer's station 26. As shown in FIG. 
3 positional information graphics are overlaid on the wide field of view 
display provided by monitor 46. In a like manner positional information 
graphics are displayed on the narrow field of view monitor 48. 
There is also located at operator's console 24 a pair of video tape 
recorders 50 and 52 which receive and then record the video from the 
optics at the observer's station 26. Recorder 52 records the video from 
the narrow field of view camera 80 generated by the optics at observer 
station 26, with overlaid graphics generated by computer 42, while 
recorder 50 records the video from the wide field of view camera 74 
generated by the optics at observer station 26, with overlaid graphics 
generated by computer 42. The operator can either turn on or turn off 
video tape recorders 50 and 52 by using the F4 function key on keyboard 
41. 
A gimballed mirror 56 located at observer station 26 receives image forming 
light from target 37 when mirror 56 is directed along optical path 67 to 
target 37 (which is also the line of sight to the target 37 as depicted in 
FIG. 2). Gimballed mirror 56 then reflects or directs the image forming 
light from target 37 along an optical path 62 to a pair of turning mirrors 
64 and 68 which are positioned downstream from gimballed mirror 56 along 
optical path 62. 
A portion of the image forming light from helicopter 37 is reflected by 
gimballed mirror 56 to turning mirror 64 and then redirected by turning 
mirror 64 along an optical path 65 to the lens of a wide field of camera 
74. The remainder of the image forming light from helicopter 37 is 
reflected by gimballed mirror 56 to turning mirror 68 and then redirected 
along an optical path 66 by turning mirror 68 to the lens 73 of a 
telescope 70. Image forming light from helicopter 37 which passes through 
and then exits telescope 70 via a lens 79 is directed along optical path 
78 to a flip mirror 76. As shown in FIG. 2, flip mirror 76 is positioned 
to direct the image forming light exiting telescope 70 along an optical 
path 77 to a narrow field of view camera 80. By rotating flip mirror 76 90 
degrees from the position depicted in FIG. 2, flip mirror 76 can direct 
image forming light exiting telescope 70 to a narrow field of view camera 
82. In the preferred embodiment of the present invention, narrow field of 
view camera 80 may be a black and white camera, while narrow field of view 
camera 82 may be a color camera or a low light level camera adapted for 
night missions. 
That portion of the image forming light reflected by gimballed mirror 56 to 
turning mirror 64 which is a one inch turning mirror and then redirected 
by turning mirror 64 along an optical path 65 to the lens of a wide field 
of camera 74 comprises a one inch bundle of light. Turning mirror 64 is a 
one inch turning mirror. The view provided by camera 74 is an overall 
perspective of the scene including target 37 which the operator at 
operator console 24 observes on wide field of view monitor 46. The wide 
field of view appearing on monitor 46 is about four degrees. 
Turning mirror 68 is a four inch turning mirror reflecting a four inch 
bundle of light from gimballed mirror 56 through telescope 70 to narrow 
field of view camera 80 or narrow field of view camera 82. Narrow field of 
view cameras 80 and 82 are coupled through a switch 84 to a video time 
inserter/video data inserter 44 which is comprised of two video overlay 
circuit boards in computer 42 and which is connected to narrow field of 
view monitor 48. The view provided by narrow field of view monitor 48 is 
very narrow and may be in the order of 0.1 degrees. Telescope 70 is a zoom 
telescope which can zoom from 20 inches to about 120 inches. At 20 inches 
zoom telescope 70 provides a one degree field of view, while at 120 inches 
the field of view is about a 0.1 degree field of view. Telescope 70 is 
connected to control unit 20 which provides control signals to telescope 
36 to control the zoom function of telescope 70. 
Gimballed mirror 56 is gyro stabilized to eliminate the roll of the 
aircraft and heading changes by the aircraft when tracking the target 37. 
The gimballed mirror 56 includes a support stand 57 and a gimbal interface 
58 which is electrically connected to control unit 36. Control unit 36 
which, for example, is responsive to an operator using track handle 38 
provides analog control signals to the gimbal interface 58, which, in 
turn, orientates or steers gimballed mirror 56 to track target 37. There 
is also connected in series with track handle 38 an automatic video 
tracker 40 which when turned on by the operator locks on to video contrast 
to track target 37. 
Gimballed mirror 56 and turning mirror 68 should be flat, for example, in 
the order of lambda over ten. Turning mirror 64 is also very flat, in the 
order of lambda over four. Gimballed mirror 56 which is a four inch 
mirror, is also light weight being fabricated from beryllium. 
The light incident upon lens 73 of telescope 70 has a one inch hole or void 
in its center resulting from that portion of the image forming light which 
is reflected by turning mirror 64 to wide field of view camera 74. In 
addition, lens 73 has a one inch centrally located dark spot 72 which is 
non-transparent and which is optically aligned with mirror 64. 
When power is first turned on to airborne video tracking system 20 monitor 
47 provides the main screen menu which sets forth the function for each of 
the function keys on keyboard 41. 
##STR1## 
When the operator depresses the function F1 on keyboard 41, a Help Screen 
appears on monitor 47 at the operator console 24. The Help screen provides 
a detailed explanation for each of the function keys on keyboard 41. 
F2 Setup--Perform system calibration/boresight, set waypoints. 
F3 Toggle Color--Toggle overlay color between black and white. 
F4 Record--Start recording on both VTRs. &lt;Ctrl&gt; F4 Stop--Stop both VTRs. 
F5 Not used. 
F6 ACQ Sight--Select acquisition sight as the active pointing device. 
F7 IRDS--Select IRDS as the active pointing device. 
F8 Waypoint--Select a waypoint as the active pointing device. 
F9 Triangulate Target--Calculate position of the target from the previous 
and current designated line of sight vectors. 
F10 Mark target--Calculate position of the target being viewed. &lt;Shift&gt;ESC 
Exit program from main screen. 
Press any key to return to main screen . . . 
When the function key F2 is depressed by the operator, the operator can 
perform a system calibration or boresight and set waypoints. The function 
key F3 allows the operator to change the overlay color on wide field of 
view monitor 46 and narrow field of view monitor 48. The function key F4 
activates recorders 50 and 52, while &lt;Ctrl&gt; F4 de-activates recorders 50 
and 52. The function key F6 selects acquisition sight 22 as the means to 
track target 37. The function key F7 selects infrared display system 34 as 
the active pointing or tracking device. The function key F8 allows the 
operator to select one of five waypoints as the active pointing device. 
Selecting a waypoint results in gimballed mirror 56 pointing to the 
latitude, longitude and altitude of the selected waypoint. The function 
key F9 allows the operator to triangulate the location of the target 37 
being tracked by airborne video tracking system 20. The function key F10 
allows airborne video tracking system 20 to calculate the present latitude 
and longitude of target 37 using an estimated altitude previously supplied 
to airborne video tracking system 20 by the operator. The estimated 
altitude entered by the operator at operator console 24 is displayed in 
the marked target box in the lower portion of console display 47. The 
triangulation function can be used to accurately determine the altitude of 
target 37 after the operator enters an estimated altitude for target 37. 
An operator at operator console 24 can first estimate the altitude by 
knowing the altitude of the aircraft and then making an educated guess as 
to the difference between the aircraft altitude and the target altitude. 
The Setup Screen which appears on monitor 47 at the operator console 24 is 
set forth below. The operator accesses the Setup Screen by depressing the 
F2 key on keyboard 41 while the main menu is being displayed on monitor 
47. 
ACTIVE ACQ SIGHT 
Setup Menu 
1 Calibrate INS. 
2 Calibrate Gimbal Drive. 
3 Calibrate Gimbal Input. 
4 Calibrate Acquisition Sight. 
5 Calibrate IRDS. 
6 Adjust Tracking Box. 
7. Set Gimbal Limit Points. 
8. Edit Waypoints. 
Enter password: ******** 
Press &lt;Esc&gt; to return to main screen. 
From the setup screen, the operator can calibrate inertial navigation 
system 30 by depressing the one key on keyboard 41. The operator can also 
calibrate gimbal interface 58 from the setup screen by depressing the two 
key on keyboard 41. By selecting the three key on keyboard 41, the 
operator can calibrate input signals supplied from gimbal interface 58 
through control unit 36 to computer 42. By selecting the three key on 
keyboard 41, the operator can calibrate acquisition sight 22. 
Referring to FIGS. 1, 2 and 3, from the setup screen, the operator can 
calibrate infrared display system 34 by depressing the five key on 
keyboard 41. Depressing the six key on keyboard 41 allows the operator to 
change the size of tracking box 90 (FIG. 3) which is displayed on wide 
field of view monitor 46. The size (including width, height and position 
on monitor 46) of the tracking box 90 is changed whenever there is a 
change in the zoom function on telescope 70. It should be noted that the 
telescope zoom function is not changed during the flight of the aircraft. 
Tracking box 90 represents the narrow field of view within wide field of 
view monitor 46. 
Depressing the seven key on keyboard 41 allows the operator to set gimbal 
limit points for gimballed mirror 56 to prevent damage to gimballed mirror 
56. Depressing the eight key on keyboard 41 allows the operator to edit 
waypoints which are fixed locations at a fixed altitude above sea level. 
It should be noted that the Setup Screen as well as other screens display 
the active pointing device in the upper right hand corner. The active 
pointing devices are the acquisition sight, the infrared display system 
and selected waypoints. The setup screen also requires a password which 
the operator must provide to allow the operate to calibrate any of the 
devices identified in the setup screen. 
The Calibrate Inertial Navigation Screen which appears on monitor 47 at the 
operator console 24 is set forth below. The operator accesses the 
Calibrate Inertial Navigation Screen by depressing the 1 key on keyboard 
41 while in the Setup Screen. 
ACTIVE ACQ SIGHT 
Calibrate INS 
Turn aircraft to a known heading. 
Modify corrected heading (in degrees): 
+ or UP Increment heading 
- or DOWN Decrement heading 
Displayed INS heading (in degree):60.00 
Corrected INS heading (in degree): 60.00 
Press &lt;Esc&gt; to return to main screen . . . 
The+key or the up arrow key on keyboard 41 is used to increment the 
inertial navigation system heading, while the -key or the down arrow key 
are used to decrement the inertial navigation system heading. The aircraft 
is first placed in a known heading or position and then the inertial 
navigation system heading is adjusted to compensate for any error which 
may occur in its heading. 
The Calibrate Gimbal Drive Screen which appears on monitor 47 at the 
operator console 24 is set forth below. The operator accesses the 
Calibrate Gimbal Drive Screen by depressing the 2 key on keyboard 41 while 
in the Setup Screen. 
ACTIVE ACQ SIGHT 
Gimbal Drive Calibration 
Azimuth scale factor: 1.71 
Azimuth offset (volts): 2.72 
Elevation Scale factor: 0.87 
Elevation offset (volts): 0.13 
Press &lt;Tab&gt; or &lt;Up&gt; or &lt;Down&gt;to use new value. 
Press &lt;Enter&gt; to save changes. 
Press &lt;Esc&gt; to return to main screen . . . 
The Azimuth scale factor, Azimuth offset (volts), Elevation Scale factor 
and Elevation offset (volts) for the gimbal drive calibration values are 
edited and then accepted using the Tab or Up arrow or Down arrow keys on 
keyboard 41. These gimbal drive calibration values are adjusted to allow 
for accurate and concise steering of gimballed mirror 56 by computer 42 
via control unit 36. 
The Calibrate Gimbal Input Screen which appears on monitor 47 at the 
operator console 24 is set forth below. The operator accesses the 
Calibrate Gimbal Input Screen by depressing the 3 key on keyboard 41 while 
in the Setup Screen. 
ACTIVE ACQ SIGHT 
Gimbal Input Calibration 
Azimuth scale factor: 1.04 
Azimuth offset (volts): -0.54 
Elevation scale factor: 1.27 
Elevation offset (volts): 0.23 
Press &lt;Tab&gt; or &lt;Up&gt; or &lt;Down&gt; to use new value. 
Press &lt;Enter&gt; to save changes. 
Press &lt;Esc&gt; to return to main screen . . . 
The Azimuth scale factor, Azimuth offset (volts), Elevation Scale factor 
and Elevation offset (volts) for the gimbal input calibration values are 
edited and then accepted using the Tab or Up arrow or Down arrow keys on 
keyboard 41. These calibration values provide accurate calibration for the 
gimbal position indicators 95, 96, 97 and 98 on the wide field of view 
screen 46 shown in FIG. 3. When computer 42 is used to control gimballed 
mirror 56, the gimbal position indicators 95 and 96 align respectively 
with the acquisition pointing angle indicators 93 and 92. When computer 42 
is providing an active waypoint and an operator is using the track handle 
38 to steer the gimballed mirror 56 the gimbal position indicators 97 and 
98 may differ significantly from the acquisition pointing angle indicators 
93 and 92 as shown in FIG. 3. 
The Calibrate Acquisition Sight Screen which appears on monitor 47 at the 
operator console 24 is set forth below. The operator accesses the 
Calibrate Acquisition Sight Screen by depressing the 4 key on keyboard 41 
while in the Setup Screen. 
ACTIVE ACQ SIGHT 
Acquisition Sight Calibration 
Azimuth scale factor: 1:15 
Azimuth offset (volts): 1:36 
Elevation scale factor: 1:10 
Elevation offset (volts): 0.11 
Press &lt;Tab&gt; or &lt;Up&gt; or &lt;Down&gt; to use new value. 
Press &lt;Enter&gt; to save changes. 
Press &lt;Esc&gt; to return to main screen . . . 
The Azimuth scale factor, Azimuth offset (volts), Elevation Scale factor 
and Elevation offset (volts) for the acquisition sight calibration values 
are edited and then accepted using the Tab or Up arrow or Down arrow keys 
on keyboard 41. 
The Calibrate Infrared Display System Screen which appears on monitor 47 at 
the operator console 24 is set forth below. The operator accesses the 
Infrared Display System Screen by depressing the 5 key on keyboard 41 
while in the Setup Screen. 
ACTIVE IRDS 
IRDS Calibration 
Azimuth scale factor: 1.00 
Azimuth offset (volts): 2.56 
Elevation Scale factor: 1.00 
Elevation offset (volts): 0.50 
Press &lt;Tab&gt; or &lt;Up&gt; or &lt;Down&gt; to use new value. 
Press &lt;Enter&gt; to save changes. 
Press &lt;Esc&gt; to return to main screen . . . 
The Azimuth scale factor, Azimuth offset (volts), Elevation Scale factor 
and Elevation offset (volts) for the infrared display system calibration 
values are edited and then accepted using the Tab or Up arrow or Down 
arrow keys on keyboard 41. 
The Adjust Tracking Box Screen which appears on monitor 47 at the operator 
console 24 is set forth below. The operator accesses the Adjust Tracking 
Box by depressing the 6 key on keyboard 41 while in the Setup Screen. 
ACTIVE IRDS 
Adjust Tracking Box 
Use cursor keys to move tracking box. 
Use following keys to size tracking box: 
T Taller 
S Shorter 
W Wider 
N Narrower 
Press &lt;Enter&gt; to save changes . . . 
Press &lt;Esc&gt; to return to main screen . . . 
The cursor keys on keyboard 41 are utilized to move tracking box 90 left, 
right, up or down on wide field of view monitor 46. Tracking box 90 is 
sized using the keys T, S, W and N on keyboard 41. Tracking box 90 
illustrates the boundary of the narrow field of view overlaid on wide 
field of view monitor 46. 
The Set Gimbal Limit Points Screen which appears on monitor 47 at the 
operator console 24 is set forth below. The operator accesses the Set 
Gimbal Limit Points Screen by depressing the 7 key on keyboard 41 while in 
the Setup Screen. 
ACTIVE IRDS 
Gimbal Limits (degrees) 
Forward warning point: 35 
Aft warning point: -5 
Up warning point: 35 
Down warning point: -35 
Forward stop point: 45 
Aft stop point: -15 
Up stop point: -45 
Down stop point: -45 
Press &lt;Tab&gt; or &lt;Up&gt; or &lt;Down&gt; to use new value. 
Press &lt;Enter&gt; to save changes. 
Press &lt;Esc&gt; to return to main screen . . . 
The gimbal limits are set to prevent damage to gimballed mirror 56. Warning 
indicators, such as warning indicator 94 shown in FIG. 3 are also set via 
the set gimbal limits point screen. Warning indicators are provided at 
each end of the azimuth and elevation axis depicted in FIG. 3. When a 
position indicator such as position indictor 97 passes the warning 
indictor, the warning indicator 94 is displayed as shown in FIG. 3. This 
indicator tells the operator at operator console 24 that gimballed mirror 
56 is approaching its azimuth and elevation limits for safe operation of 
gimballed mirror 56. The forward stop point, aft stop point, the up stop 
point and the down stop point for gimballed mirror 56 are edited from the 
set gimbal limits point screen and limit the drive signals supplied by 
control unit 36 to gimbal interface 58 to prevent damage to mirror 56. 
The Edit Waypoints Screen which appears on monitor 47 at the operator 
console 24 is set forth below. The operator accesses the Edit Waypoints 
Screen by depressing the 8 key on keyboard 41 while in the Setup Screen. 
______________________________________ 
ACTIVE WAYPOINT 
Edit Waypoints. Laguna Peak 
______________________________________ 
1 N 34 06.43 
1413 ft. Dome 
W 119 04.00 
2 N 34 07.37 
550 ft. Lone Tree 
W 119 04.13 
3 N 34 06.67 
259 ft. Water Tower 
W 119 05.00 
4 N 34 06.50 
1476 ft. Laguna Peak 
W 119 03.88 
5 N 34 06.08 
1080 ft. ET Sign 
W 119 04.00 
______________________________________ 
Press &lt;Tab&gt; or &lt;Up&gt; or &lt;Down&gt; to use new value. 
Press &lt;Enter&gt; to save changes. 
Press &lt;Esc&gt; to return to main screen . . . 
By accessing the Edit Waypoints Screen, the operator can edit the waypoint 
latitude, longitude, altitude and description fields for each waypoint 
shown on the screen. 
The Select Waypoint Screen which appears on monitor 47 at the operator 
console 24 is set forth below. The operator accesses the Select Waypoints 
Screen by depressing the F8 key on keyboard 41. 
______________________________________ 
ACTIVE WAYPOINT 
Select Waypoint Laguna Peak 
______________________________________ 
1 N 34 06.43 
1413 ft. Dome 
W 119 04.00 
2 N 34 07.37 
550 ft. Lone Tree 
W 119 04.13 
3 N 34 06.67 
259 ft. Water Tower 
W 119 05.00 
4 N 34 06.50 
1476 ft. Laguna Peak 
W 119 03.88 
5 N 34 06.08 
1080 ft. ET Sign 
W 119 04.00 
______________________________________ 
Choose the number of the desired waypoint. 
Press &lt;Esc&gt; to return to main screen . . . 
By accessing the Select Waypoint Screen the operator can select one of five 
waypoints as the active pointing waypoint for airborne video tracking 
system 20. For example if the operator at operator console 24 depresses 
key 4 on keyboard 41, the active pointing waypoint for tracking system 20 
will be Laguna Peak. 
The narrow field of view monitor 48 provides the following display for an 
operator to view. 
Marked Target 
166:16:25:05 
N 34 06.60 
W 119 06.60 
Altitude =0 
166:16:29:17 
The program listing for the computer software used by computer 42 is set 
forth in Appendix A and is written in well known computer software 
language C. Upon power up of system 20, the software enters the main 
program which is in the AVTSC.C module. This module initializes and 
updates all airborne video tracking system computer functions. This module 
also includes an abort function which exits to dos (program steps 104 and 
106). If, for example, an operator attempts to uses the software on an 
authorized computer the software will exit to dos. 
Referring to FIGS. 1, 2 and 4, after system initialization (program step 
102) and an indication not to abort, the software retrieves and then 
updates data from inertial navigation system 30 (program step 108). During 
program step 110 the software retrieves the acqsight angles from 
acquisition sight 22. During program step 112 the software retrieves the 
irds angles from infrared display system 34. During program step 114 the 
software retrieves the gimbal angles for gimballed mirror 56 from gimbal 
interface 58 through analog output signals from interface 58. 
When tracking is by waypoint, the software determines the required gimbal 
orientation angles for the waypoint and then provides them in the form of 
analog output signals which are supplied to gimbal interface 58. Gimbal 
interface 58 then orientates gimballed mirror 56 to the waypoint allowing 
airborne video tracking system 20 to begin tracking (program steps 118 and 
120). When tracking is not by waypoint, the analog output signals for 
controlling the orientation of gimballed mirror 56 are determined by 
computer 42 from the acqsight and irds angular inputs and then supplied 
via control unit 36 to gimbal interface 58 (program step 120). During 
program step 122 the software again retrieves the gimbal angles for 
gimballed mirror 56 from gimbal interface 58 through analog output signals 
from interface 58. 
The keyboard functions entered by the operator at operator console 24 are 
processed during program step 124. The console display appearing on 
monitor 47, the wide field of view display appearing on monitor 46 and the 
narrow field of view display appearing on monitor 48 are updated during 
program step 126. 
During program step 128 the mode of operation is checked. If the mode is 
changed to exit by the operator at operators console 24 the software exits 
to dos (program step 106) and returns the displays of airborne video 
tracking system 20 to their default mode. 
Referring to FIGS. 1, 2 and 5 the module INIT.C is the software module 
which initializes all Airborne Video Tracking System Computer interfaces, 
initializes waypoints, initializes Analog to Digital and Digital to Analog 
boards in system 20. 
During program step 130 certain global variables within the INIT.C module 
are set. Tracking is set to use acquisition sight 22 as the means for 
acquiring target 37. When waypoint tracking is being used by airborne 
video tracking system 20 the waypoint is preset to waypoint one which for 
the waypoint screen illustrated above is the Dome at an altitude of 1413 
feet. The estimated altitude is initially set to zero. A 
"designated.sub.-- point.alt" is undefined. The "designated.sub.-- 
point.alt" is used with the triangulation calculation for determining the 
location of a target. The serial number is set for the particular computer 
which is to be used to run the software of Appendix A. 
When the serial number of the computer does not match the serial number in 
the software the program is aborted (program steps 132 and 146). When the 
serial number of the computer does matches the serial number in the 
software the program loads data from the file setup.cal which is the 
calibration file for all devices connected to computer 42. During program 
step 136 the displays including monitor 47, wide field of view monitor 46 
and narrow field of view monitor 48 are initialized. During program step 
138 the video tape recorder ports are initialized allowing for 
communication with wide field of view recorder 50 and narrow field of view 
recorder 52. During program step 140 an analog input/output board is 
initialized allowing analog data from track handle 38, automatic video 
tracker 40 or acquisition sight 22 to be read by computer 42. The analog 
signal from gimbal interface 58 is also read through this input/output 
board. 
During program step 142 the inertial navigation system board which couples 
inertial navigation system 30 to computer 42 is initialized. It should be 
noted that the the inertial navigation system board is an "ARINC 429" 
interface board within computer 42. The signals from inertial navigation 
system 30 are signals having a digital format. 
During program step 144 the infrared display system board which couples 
infrared display system 34 to computer 42 is initialized. It should be 
noted that the the infrared display system board is a "Synchro" interface 
board within computer 42 which converts synchro data to digital data. As 
shown in FIG. 2 terminal 43 is the input terminal for synchro data from 
infrared display system 34, while terminal 45 is the input terminal for 
ARINC 429 data from inertial navigation system 30. 
Referring to FIGS. 1, 2, 6a and 6b, the module INS.C in the software of 
Appendix A is utilized to input the aircraft location and orientation from 
inertial navigation system 30 including the aircraft latitude, longitude 
and altitude and the aircraft roll, pitch and heading. During program step 
140 updated latitude data for the aircraft is obtained from inertial 
navigation system 30 and the latitude is then extracted from the latitude 
data. During program step 142 updated longitude data for the aircraft is 
obtained from inertial navigation system 30 and the longitude is then 
extracted from the longitude data. During program step 144 updated 
altitude data for the aircraft is obtained from inertial navigation system 
30 and the altitude is then extracted from the altitude data. For the wide 
field of view illustrated in FIG. 3 the aircraft latitude is North 34 
degrees 6.40 minutes, the aircraft longitude is West 119 degrees 6.50 
minutes and the aircraft altitude is ten feet. 
During program steps 146, 148, 150 and 152 aircraft roll, pitch, heading 
and ground speed data is obtained from the inertial navigation system 30. 
The monitor 47 at operator console 24 displays the aircraft roll, pitch 
and heading in degrees. The wide field of view monitor 46 displays the 
aircraft heading in degrees and the aircraft speed in miles per hour. For 
the wide field of view illustrated in FIG. 3 the aircraft heading is 280 
degrees and the aircraft speed is 385 miles per hour. 
During program steps 154 the latest time, data and day is obtained from 
computer 42. If communication between computer 42 and inertial navigation 
system 30 is established, then time is obtained from inertial navigation 
system 30 (program step 160). However, when communication between computer 
42 and inertial navigation system 30 is not established, then time is 
obtained from computer 42. During program step 163 the computer clock is 
updated to the time provided by inertial navigation system 30. 
During program step 166, 168, 170 and 172 the heading is corrected to 
provide for a positive angle between 0 degrees and 360 degrees. When the 
heading provided by inertial navigation system 30 is greater than 360 
degrees then 360 degrees is subtracted from the heading to provide a 
corrected heading (program steps 166 and 168). When the heading provided 
by inertial navigation system 30 is less than 0 degrees, 360 degrees are 
added to the heading to provide a corrected heading (program steps 170 and 
172). 
Referring to FIGS. 1, 2 and 7, the module ACQSIGHT.C in the software of 
Appendix A is utilized to input the acquisition sight angles (azimuth and 
elevation) for acquisition sight 22 as well as track handle 38 and 
automatic video tracker 40. The tracking mode is examined during program 
step 174. If tracking is performed by waypoint or the infrared display 
system 34 then the software returns to the main program. When, however, 
acquisition sight 22 is being used to track target 37 position data is 
obtained from the analog voltages provided by acquisition sight 22 to 
computer 42. 
During program step 176 there is a set up of conversion scale factors to 
convert volts to degrees for both azimuth and elevation. During program 
step 178 the conversion scale factors of program step 176 are modified or 
adjusted to convert azimuth volts to radians. During program step 180 the 
azimuth analog data is retrieved from an A/D board within computer 42 and 
then converted to a voltage value. This azimuth analog data is a count 
representative of the azimuth analog voltage signal from acquisition sight 
22. During program step 182, the azimuth analog data with adjustments is 
converted to an angle in radians. During program step 184, the value 
acqsight. AZ is established as the azimuth angle in radians for use by 
gimballed mirror 56 and other functions of airborne video tracking system 
20. 
It should be noted that computer 42 reads an azimuth analog value from 
track handle 38, acquisition sight 22 or automatic video tracker 40 and 
then converts this azimuth analog value to an azimuth angle in radians 
which is supplied as a voltage to gimballed mirror 56 to point mirror 56 
to target 37. It should also be noted that the identical procedure is used 
to provide the elevation angle in radians to gimballed mirror 56 (program 
steps 186-192). 
Referring to FIGS. 1, 2, 8a and 8b, the module IRDS.C in the software of 
Appendix A inputs the Infrared Display System angles (azimuth and 
elevation) from system 34. Infrared display system 34 provides azimuth and 
elevation data in a synchro or sinusoidal format via a pair of channels 
through a synchro board in computer 42. Each channel can be in a tracking 
mode, a stabilizing mode or a non-tracking mode. During program step 202 
the elevation channel is sampled to determine if the channel is tracking 
or stabilizing. If the elevation channel is not tracking or stabilizing 
then computer 42 can not read the elevation data and the software proceeds 
to program step 216 to sample the azimuth channel. If the elevation 
channel is tracking (program step 202) then the software of the IRDS.C 
module freezes the elevation channel data (program step 204). During 
program step 206 a test is made to determine if the data is stable. If the 
elevation channel data is not stable then the software of the IRDS.C 
module proceeds to program step 216. 
When the elevation channel data is stabilized the tracking flag is set to 
no indicating that the data is stabilized. The elevation channel is 
retrieved and the elevation channel is next set to a tracking mode to 
obtain another sample of elevation data. During program step 210, the 
elevation data is then converted directly to an angle in radians. The 
elevation angle is kept in radians between +180 degrees and -180 degrees 
(program step 212). The calculated value for the elevation angle is set to 
irds. EL during program step 214 and is available to other functions 
within the software of Appendix A. The azimuth channel data from infrared 
display system 34 is processed in exactly the same manner as the elevation 
channel data during program steps 216-228. 
Referring to FIGS. 1, 2 and 9, the module GIMBAL.C in the software of 
Appendix A is utilized to input the Line of Sight of the gimballed mirror 
56 (azimuth and elevation). 
During program step 230 there is a set up of conversion scale factors to 
convert volts to degrees for both azimuth and elevation gimbal angles. 
During program step 232 the conversion scale factors of program step 230 
are modified or adjusted to convert azimuth volts to radians. During 
program step 234 the azimuth analog data is retrieved from the A/D board 
within computer 42 and then converted to a voltage value. This azimuth 
analog data is a count representative of the azimuth analog voltage signal 
from gimballed mirror 56. During program step 236, the azimuth analog data 
for gimballed mirror 56 with adjustments is converted to an angle in 
radians. The azimuth angle is set equal to the gimbal.sub.-- input. Az 
variable which is available to other functions within the computer 
software of Appendix A. The gimballed mirror analog elevation data is 
processed in exactly the same manner as the gimballed mirror analog 
azimuth data (program steps 240-246). Once the azimuth and elevation 
angles for gimballed mirror 56 are converted to radians, the location of 
gimbal position indicator 95 and 96 are set on wide field of view monitor 
46. 
Referring to FIGS. 1, 2 and 10, when tracking is by waypoint or the fixed 
position of an object on the ground, the azimuth and elevation angles for 
pointing gimballed mirror 56 at the waypoint are determined in the 
pointing.c module of the software of Appendix A. During program step 248 
the aircraft's geographic location (latitude, longitude and altitude) is 
converted into a geocentric XYZ coordinate location with the earth's 
center being the origin for the X, Y and Z axis. During program step 252 
the object or waypoint's geographic location is converted into a 
geocentric XYZ coordinate location. The waypoints coordinates are rotated 
to account for longitudinal distance from the aircraft to the waypoint. 
The aircraft is now located at Y equal to zero. 
The aircraft coordinates are set to 0,0,0 to establish a new coordinate 
system to describe the waypoint with respect to the aircraft (program step 
254). The coordinate system is then rotated to align the aircraft with the 
surface of the earth (program step 256). During program step 258 the 
coordinate system is next rotated to account for the roll, pitch and 
heading of the aircraft. The azimuth and elevation angles for gimballed 
mirror 56 are calculated to point the gimballed mirror 56 to the target 37 
during program step 260. 
Referring to FIGS. 1, 2 and 11, the gimbal.c module of Appendix A is used 
to control the orientation of the gimballed mirror 56. A selection is made 
as to which input angles to output to the gimballed mirror 56 (program 
step 262). The infrared display system angles are irds.az and irds.el; the 
acquisition sight angles are acq.sub.-- sight.az and acq.sub.-- sight.el 
and the waypoint angles are pointing.az and pointing.el. During program 
step 264 there is a limit placed on gimbal travel to within the gimbal 
stops. During program step 266 conversion scale factors are set up for 
both azimuth and elevation to convert degrees to volts. During program 
step 268 adjustment parameters to convert azimuth angular data to volts 
are retrieved. During program step 270 the azimuth angle in radians with 
adjustments is converted to volts. During program step 272 adjustment 
parameters to convert elevation angular data to volts are retrieved. 
During program step 274 the elevation angle in radians with adjustments is 
converted to volts. During program step 276 the gimbal azimuth and gimbal 
elevation angles in an analog signal format are output to gimbal interface 
58. Gimballed interface unit 58 then steers gimballed mirror 56 to the 
target 37. 
Referring to FIGS. 1, 2, 12a and 12b, the keyboard.c module of Appendix A 
is utilized to process keyboard input from the operator at operator 
console 24. During program step 280 a determination is made as to whether 
the mode for airborne video tracking system 20 is the startup mode. If the 
mode is the startup mode then monitor 47 is selected and the main screen 
menu is displayed during program step 282. However if the mode is not the 
startup mode then the software proceeds to program step 284 to sample the 
input from keyboard 41. If the operator has not used a key on the keyboard 
41 to select a particular console display, then the program returns to the 
main program function. 
During program step 286 the key input is retrieved and the corresponding 
console screen is displayed. The various modes are entered by the operator 
via the function and numeral keys on keyboard 41. For example, if the 
operator at operator console 24 enters the F2 function key the setup 
screen will be appear on monitor 47 (program step 300). When the operator 
at operator console 24 enters the F8 function key the select waypoint 
screen will be appear on monitor 47 (program step 338). When the operator 
at operator console 24 enters the "8" key from the setup screen the edit 
waypoint screen will appear on monitor 47 (program step 334). When the 
operator at operator console 24 enters the "6" key from the setup screen 
the adjust tracking box screen will appear on monitor 47 (program step 
326). 
Referring to FIGS. 1, 2 and 13, the displays.c module in the software of 
Appendix A controls the displays in airborne video tracking system 20. If 
the mode is main screen the console display provided by monitor 47 is 
updated (program step 352). This update includes the aircraft latitude, 
longitude, altitude, speed, heading, roll and pitch. 
The displays for the wide field of view monitor 46 (FIG. 3) and the narrow 
field of view monitor 48 are updated during program step 354. The overlay1 
display in the software of Appendix A is the wide field of display, while 
the overlay2 display in the software of Appendix A is the narrow field of 
display. The current time is read from computer 42 during program step 
356. During program step 358 a display location flag is checked. If the 
flag is "yes", a location is displayed on the monitors of airborne video 
tracking system 20. For example, in the marked target box appearing on 
monitor 47 the current latitude and longitude of target 37 is displayed. 
In addition, the current latitude and longitude of target 37 is displayed 
on narrow field of view monitor 48. The F10 key on the keyboard sets the 
location flag to "yes". 
The designation time is set equal to the current time. The designated time 
is the time that target was designated for display. In the marked target 
box and the narrow field of view display the designated time is 
166:16:25:05. The real time shown in the narrow field of view display is 
166:16:29:17. If the software is in the main screen mode then monitor 47 
displays the target location in the marked target box during program step 
364. Target 37 position information including latitude, longitude, 
altitude and designated target time is displayed on the narrow field of 
view monitor 52 during program step 366. 
During program step 368 the display location flag is set equal to IS.sub.-- 
DISPLAYED to indicate that target position information is being displayed. 
The time location displayed is set equal to the current time. 
If the display location flag is set to IS.sub.-- DISPLAYED, then the 
display time (designated target time) is tested. If the display time is 
greater than ten seconds the display location flag is set to IS NOT 
DISPLAYED (program step 372). The marked target display is then cleared 
from narrow field of view monitor 48 with only the current time being 
overlaid on the monitor. 
Referring to FIGS. 1, 2 and 14, the estimate location function for the 
target is within the POINTING.C module. When the operator depresses the 
F10 function key on keyboard 41, computer 42 determines or calculates the 
latitude and longitude of target 37 from the pointing angles (azimuth and 
elevation angles) from gimballed mirror 56 and the estimated altitude of 
target 37 provided by the operator at operator console 24. During program 
step 382, the pointing angles are converted to angles for a platform with 
a roll, pitch and heading of zero. During program step 384 the geocentric 
coordinates of the aircraft are determined, that is the coordinate system 
for the aircraft is now an XYZ coordinate system. 
During program step 386 the geocentric coordinates of the target 37 are 
determined, that is the coordinate system for the target is now an XYZ 
coordinate system. This determination is a mathematical determination. 
Target 37 is assumed to reside on the surface of an ellipsoid. The surface 
of the ellipsoid resides at the estimated altitude above the surface of 
the earth. The intersection of the line of sight vector with the surface 
of the ellipsoid establishes the geocentric coordinates of the target 37 
or the object. The geocentric coordinates of the object are next converted 
to a geographic location in program step 388 (latitude and longitude of 
target 37). 
The pointing.c module also includes a triangulation function which is 
accessed by depressing the F9 function key on keyboard 41. To utilize the 
triangulation function the operator must designate one location point for 
the target meaning that the operator must provide an estimated altitude 
and then utilize the F10 key on keyboard 41 to allow computer 42 to 
calculate an estimated latitude and longitude for target 37. This 
establishes a reference vector for target 37. During program step 394 a 
determination is made as to whether one location point for the target 37 
has been designated. If one location point has been designated the 
software proceeds to program step 396 to perform the triangulation 
function. 
At this time it should be noted that all function keys except F1 or F8 may 
be utilized from any screen appearing on monitor 47. Thus, for example, 
the operator may depress the function key F9 or the function key F10 on 
keyboard 41 while the setup screen is displayed on monitor 47. 
Once the operator at operator console 24 estimates the altitude of target 
37 by entering the altitude via keyboard 41, the operator can then use the 
F9 or F10 key to provide an initial designation for the location of target 
37, which is used to establish the reference vector for the target. 
Computer 42 also uses the aircraft location (latitude, longitude and 
altitude) and orientation (roll, pitch and heading), and the azimuth and 
elevation angles of gimballed mirror 56 to calculate the reference vector. 
The altitude entered by the operator may be positive which is above sea 
level or negative which is below sea level. 
The operator then utilizes the F9 key to obtain a second line of sight 
vector for target 37 which is calculated from the aircraft's current 
location (latitude, longitude and altitude) and orientation (roll, pitch 
and heading), and the azimuth and elevation angles of gimballed mirror 56. 
The two line of sight vectors are then used to calculate the current 
latitude, longitude and altitude of target 37. By continuing to use the F9 
key and thereby continuing to use the triangulation function of the 
pointing.c module, the operator can accurately determine the latitude, 
longitude and altitude of target 37. 
For all subsequent triangulation functions computer 42 uses the previous 
location of target 37 and the current location and orientation of the 
platform or aircraft and the gimballed angles. 
It should be noted that whenever an operator attempts to triangulate 
without sufficient change in the line of sight to allow for triangulation 
a warning message is provided to the operator and computer 42 does not 
process the triangulation function. 
From the foregoing, it may readily be seen that the present invention 
comprises a new, unique and exceedingly useful airborne video tracking 
system which constitutes a considerable improvement over the known prior 
art. Obviously, many modifications and variations of the present invention 
are possible in light of the above teachings. It is therefore to be 
understood that within the scope of the appended claims the invention may 
be practiced otherwise than as specifically described. 
##SPC1##