Abstract:
A virtual sensor mast for a ground vehicle and a method for operating a ground vehicle using a virtual sensor mast are disclosed. The virtual sensor mast includes an unmanned airborne vehicle capable of lifting itself from the ground vehicle upon deployment therefrom; a sensor suite mounted to the unmanned airborne vehicle; and a tether between the unmanned airborne vehicle and the ground vehicle over which the sensor suite is capable of communicating sensed data upon deployment. The method includes elevating a tethered unmanned airborne vehicle from the ground vehicle to a predetermined height; sensing environmental conditions surrounding the ground vehicle; and terminating the deployment.

Description:
We claim the earlier effective filing date of co-pending U.S. Provisional Application Ser. No. 60/449,271, entitled “Unmanned Ground Vehicle,” filed Feb. 21, 2003, in the name of Michael S. Beck, et al., for all common subject matter. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention pertains to remote sensing for ground vehicles and, more particularly, to a technique for achieving a higher vantage point from which the sensing occurs. 
   2. Description of the Related Art 
   One significant challenge presented by unmanned, robotic vehicles is situational awareness. Situational awareness includes detection and identification of conditions in the surrounding environment. Robotic vehicles typically carry a variety of instruments to remotely sense the surrounding environment. Commonly used instruments include technologies such as:
         acoustic;   infrared, such as short wave infrared (“SWIR”), long wavelength infrared (“LWIR”), and forward looking infrared (“FLIR”);   optical, such as laser detection and ranging (“LADAR”).
 
Typically, several different instruments are used to employ more than one of these technologies since each has advantages and disadvantages relative to the others.
       

   A common limitation for any of these technologies is the vantage point of the instrument. For instance, the height of the vantage point inherently limits the field of view for any sensor, which is particularly problematical for long-range sensors. The height of the vantage point also affects the perspective of the data collected. For instance, the perspective afforded by a higher vantage point facilitates identifying negative obstacles (e.g., ditches) and cul-de-sacs. 
   One approach to this problem is to mount at least some of the sensors relatively high on the body of the vehicle. Sensors for which this limitation is particularly problematical are sometimes mounted to a mast extending upwardly from the vehicle. However, simply positioning the sensors high on the vehicle&#39;s body or on a sensor mast may offer only marginal improvement. Mounting sensors atop a mast may complicate maneuverability for the vehicle and or have other adverse consequences, such as increasing the vehicle&#39;s profile. 
   Another approach places the sensors on an airborne vehicle that communicates wirelessly with the ground vehicle. The airborne vehicle may be, for instance, a tele-operated or robotic helicopter that senses the environment and wirelessly transfers the data to the ground vehicle. This approach can greatly enlarge the field of view, since the altitude of the airborne vehicle is independent of the ground vehicle. However, this approach also manifests several drawbacks. For instance, because the airborne vehicle is independent of the ground vehicle, it must provide its own power, which adds size, weight, and complexity to the airborne vehicle. Also, since the airborne vehicle communicates wirelessly, precautions must be taken when several are used contemporaneously in the same general area. The independence of the airborne and ground vehicles also introduces uncertainties in the data caused by uncertainties in the relative positions of the vehicles. 
   The present invention is directed to resolving, or at least reducing, one or all of the problems mentioned above. 
   SUMMARY OF THE INVENTION 
   The invention includes a virtual sensor mast for a ground vehicle and a method for operating a ground vehicle using a virtual sensor mast. The virtual sensor mast comprises an unmanned airborne vehicle capable of lifting itself from the ground vehicle upon deployment therefrom; a sensor suite mounted to the unmanned airborne vehicle; and a tether between the unmanned airborne vehicle and the ground vehicle over which the sensor suite is capable of communicating sensed data upon deployment. The method comprises elevating a tethered unmanned airborne vehicle from the ground vehicle to a predetermined height; sensing environmental conditions surrounding the ground vehicle; and terminating the deployment. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention may be understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements, and in which: 
       FIG. 1  depicts a ground vehicle employing a virtual sensor mast in accordance with the present invention; 
       FIG. 2  depicts a portion of a tether management system such as may be employed in the embodiment of  FIG. 1 ; 
     FIG.  3 A– FIG. 3B  illustrate the stowage and deployment of the unmanned airborne vehicle in the embodiment of  FIG. 1 ; 
     FIG.  4 A– FIG. 4B  illustrate the stowage and deployment of the unmanned airborne vehicle in the embodiment of  FIG. 1  in a fashion alternative to that in FIG.  3 A– FIG. 4B ; 
     FIG.  5 A– FIG. 5H  illustrate one particular embodiment of a ducted fan with which the unmanned airborne vehicle may be implemented in one particular embodiment, wherein: 
       FIG. 5A  is a view in perspective of an aerobotic single-engine ducted VTOL aircraft embodying the principles of the invention, looking slightly from above; 
       FIG. 5B  is another view in perspective, looking from a higher viewpoint, of the aircraft of  FIG. 5A ; 
       FIG. 5C  is a top plan view thereof; 
       FIG. 5D  is a view in section taken along the line  4 — 4  in  FIG. 5C , with one spoiler shown vertical and one horizontal; 
       FIG. 5E  is an enlarged fragmentary view in perspective of a portion of the aircraft of  FIG. 5A , looking from below, showing a portion of the camber vane control; 
       FIG. 5F  is a simplified fragmentary view in elevation of one duct portion, showing two non-activated camber vanes; 
       FIG. 5G  is a view similar to  FIG. 5F  with the camber vanes actuated; 
       FIG. 5H  is an enlarged fragmentary view in perspective of a portion of the aircraft of  FIG. 5A , showing a pair of spoilers and their control linkages; 
       FIG. 6  is a view in perspective of a modified form of the unmanned airborne vehicle of FIG.  5 A– FIG. 5H ; embodying the invention, having four propellers and four ducts and no spoilers; 
       FIG. 7  illustrates the acquisition of data in one particular embodiment; 
       FIG. 8  depicts the operation of an active LADAR system on the unmanned airborne vehicle of the unmanned ground vehicle in  FIG. 1  in the illustration of  FIG. 7 ; 
       FIG. 9  illustrates several options for controlling the ground vehicle of  FIG. 7 ; and 
     FIG.  10 A– FIG. 10B  depict an embodiment alternative to that illustrated in  FIG. 1 . 
   

   While the invention is susceptible to various modifications and alternative forms, the drawings illustrate specific embodiments herein described in detail by way of example. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. 
   DETAILED DESCRIPTION OF THE INVENTION 
   Illustrative embodiments of the invention are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers&#39;specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort, even if complex and time-consuming, would be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure. 
     FIG. 1  illustrates an unmanned ground vehicle (“UGV”)  100  employing a virtual sensor mast  110  in accordance with the present invention. The virtual sensor mast  110  comprises an unmanned airborne vehicle (“UAV”)  120  communicating with the ground vehicle over a tether  130 . The UAV  120  includes a suite of sensors (not shown) discussed more fully below. The UAV  120  is shown deployed, i.e., elevated from the ground vehicle  100 , and may be stowed in a fashion discussed more fully below. The UAV  120  is a vertical takeoff and landing (“VTOL”) vehicle, and is electrically powered over the tether  130  in the illustrated embodiment. A tether management system  200 , partially shown in  FIG. 2 , is housed in the chassis  140  of the UGV  100  and manages the tether  130  as the UAV  120  is deployed and retrieved in a manner described more fully below. The tether management system  200  includes an electric motor and winch  205  and a drum  210  used to control the tension/spooling of the tether  130 . Variable stops can be achieved through freezing the drum  210  at the desired locations using sensory feedback (drum encoder, string potentiometer or infrared/ultrasonic sensor, none shown). Note that some embodiments may employ rollers or bearings around the lip  215  of the opening  220  through which the tether  130  is deployed and retracted. 
   Referring again to FIG.  1 ,the UGV  100 , in the illustrated embodiment, is a six-wheeled vehicle including six wheel assemblies  150  (only one indicated) that comprise a suspension system for the UGV  100 . Each wheel assembly  150  includes an airless wheel  152  fabricated from a composite material and mounted to an independently articulated suspension arm  154 . Note that alternative embodiments may employ a commercial-off-the-shelf (“COTS”), all terrain vehicle (“ATV”) tire, e.g., the Dunlop KT401C. The articulated suspension arms  154  are capable of rotation facilitating extreme mobility and obstacle negotiation as well as inverted operability. A rotary magnetorheological (“MR”) damper  156 , facilitated by substantially real time damping control, is mounted coaxially with the arm pivot  158 . Each suspension arm  154  has a compliant rotary suspension with controllable damper  156  to absorb impacts and provide for sensor stability. Air springs (not shown) and double wishbone suspension (also not shown) at each wheel  152  provide a lightweight, robust and fail-soft suspension. 
   Each suspension arm  154  has a high torque rotation actuator (not shown) that enables the UGV  100  to perform maneuvers not ordinarily possible in manned vehicles. The wheel assemblies  150  enable the UGV  100  to: 
   “walk” over large obstacles; 
   vary height/ground clearance; 
   adapt steering and suspension dynamics on the fly; and 
   safely accommodate high impact velocities. 
   Individual articulation of the wheel assemblies  150  further enhances skid steering through footprint variation. Survivability and stability are enhanced by squatting the UGV  100  to reduce presented area and lower center of gravity (“CG”), enhance mobility in soft terrain and improve sensor visibility via front elevation. 
   Each wheel  152  includes a two-speed transmission (not shown) embedded in the hub to allow for high and low speed operation with hub drive motors (not shown). Each suspension arm  154  is driven by an independent, dedicated drive. The assembly of wheel, drive motor, switching hub, etc., eliminates (or at least reduces) the need for mechanical brakes. Each wheel  120  contains a hub drive motor (not shown) and integrated gear set (not shown) that allow wheel-to-wheel speed variations and enhanced skid steering. Each articulated suspension arm  125  houses a hub motor controller (not shown). This improves reliability through the reduction of slip rings (not shown) required in the shoulder joint, or arm pivot,  158  between the suspension arm  154  and the chassis  140  and provides redundancy. Each suspension arm  152  becomes an independent power system providing tractive effort from a common electrical, direct current (“DC”)-link. A failure in a motor controller or motor therefore may not disable the UGV  100 . 
   The chassis  140  provides the structure for vehicle integration with desirable stiffness, payload protection and thermal management. Important design considerations include: structural strength; stiffness; survivability; weight; stiffness-to-weight ratio; damage tolerance; reparability; corrosion resistance; modularity; and optimized component packaging and integration. In the illustrated embodiment, the chassis  140  comprises a shell (not indicated), or frame, with integral bulkheads (not shown) covered by a plurality of panels (also not indicated). The shell of the chassis  140  is comprised of graphite/epoxy sheets (not shown) sandwiching an aluminum honeycombed core (not shown). The panels are reinforced by KEVLAR™ to improve puncture and abrasion resistance. All points of attachment where significant loads are transferred are reinforced with glass fiber/epoxy inserts (not shown) and high-density foam (not shown). 
   The chassis  140  also houses charge-coupled device (“CCD”) and acoustic sensors (not shown) located around the periphery of the chassis  105  for situational awareness. The illustrated embodiment employs four Emkay WP-3502 acoustic sensors, four Nevada Systems NSI-5000c CCD cameras, eight near field MASSA M-5000/220 ultrasonic sensors, and eight far field MASSA E-220B/26 ultrasonic sensors. Data generated from these sensors may be used to augment or may be used in conjunction with data generated from sensors aboard the virtual sensor mast  110 . However, this is not necessary to the practice of the invention and these sensors may be omitted in some alternative embodiments. 
   The chassis  140  houses a power plant (not shown) that provides power and charges batteries (also not shown) used in powering various drives and other electrically powered components, including powering and/or recharging the UAV  120 . More particularly, the illustrated embodiment employs a series hybrid power plant comprising a commercial, off-the-shelf-based single cylinder air-cooled Direct Injection (“DI”) diesel engine (not shown) and a Variable Reluctance Motor (“VRM”) used in conjunction with two parallel strings of lithium-ion batteries (not shown). More particularly, this power plant consists of a four-stroke, direct injection compression ignition (diesel) engine power plant, a motor/generator, a power distribution management system, an energy storage system, and in-hub variable reluctance motors. The VRM is efficient at high torques and low speeds, the exact operating envelope of the UGV  100  during silent motion. 
   A power management system (not shown) enhances battery life by efficiently managing the energy distribution throughout the vehicle. The energy from the batteries is converted to the appropriate DC level using bi-directional converters. The DC-link supports system efficiency by level-ranging from module voltage to 400 VDC depending on the speed of the vehicle. During engine start, the bi-directional inverter (generator controller) provides energy to start the diesel engine. Thereafter, the diesel engine is used to support the system and drive loads. The bi-directional converters reverse the energy flow from the DC-link to the battery packs and system loads. If the demand for the loads exceeds the engine generator capability, the bi-directional inverters provide the additional energy required from the batteries. Another function of the bi-directional inverter is to convert land power (i.e., 115, 208, and 240 VAC) to charge the batteries between missions or power the system for training, and maintenance. 
   Some embodiments include a mast base enclosure (not shown) housing a majority of the payload (also not shown) and centered in the front of the UGV  100 . The mast base is pivoted in the center of the UGV  100  and has a total rotational travel of 180 degrees to allow it to be deployed vertically from the top or bottom of the UGV  100 . In these embodiments, the portion of the chassis  140  on either side of the mast base enclosure is referred to as the “sponson.” Much of the volume of each sponson is available for payload. There are three areas in the chassis  140  allocated for fuel and battery storage. One area is in the center of the UGV  100  and the other two are in the sponsons. The majority of the vehicle control and power electronics are located above the center fuel tank or in the areas on either side of the mast pivot in these embodiments. 
   Note that the UGV  100  of the illustrated embodiment is but one particular implementation. The present invention may be employed in virtually any suitably modified and/or equipped ground vehicle, whether manned or unmanned and regardless of whether it is robotic. For instance, the invention may be employed with wheeled vehicles whose suspension is not independently articulable, e.g., the HUMVEE. The invention may be employed on tracked vehicles, e.g., the Bradley fighting vehicle. The invention may also be employed on vehicles that are both wheeled and tracked, e.g., the now retired M-16 and M-3 half-tracks of World War II vintage. Furthermore, the invention is not limited to deployment on military vehicles, and may find applicability in civilian contexts. 
   The UAV  120  of the illustrated embodiment is a VTOL aircraft including one or more ducted fans. The particular embodiment of  FIG. 1  actually employs four ducted fans  162   a – 162   d , but the number of ducted fans is not material to the practice of the invention. The UAV  120  may be deployed and stowed, as is best shown in FIG.  3 A– FIG. 3B , in a recess  300  in the surface  305  of the chassis  140  of the UGV  100 . When stowed, as shown in  FIG. 3B , a plurality of clamps  310  secure the UAV  120  in the recess  300 . To deploy the UAV  120 , the clamps  310  can be released and the ducted fans  162   a – 162   d  activated until the UAV  120  elevates itself from the UGV  100 , as indicated by the arrow  320 . As the UAV  120  elevates, the electric motor and winch  205  of the tether management system  200 , shown in  FIG. 2 , release the drum  210  so that the tether  130  plays out. 
   The UAV  120  elevates to some desired altitude to remotely sense the environment in which the UGV  100  is situated. Typically, the UGV  100  will not be moving during the deployment, or will move only very little. Also, the deployment will typically be of relatively short duration. Once the remote sensing is completed, the UAV  120  is retracted back into the recess  300 , as indicated by the arrow  322 . Note that the recess  300  may be oversized, as shown, and that the positions of the clamps  315  may be so dimensioned as to facilitate the retraction. To terminate the deployment, the electric motor and winch  205  can spool the drum  210  with force sufficient to overcome the lift exerted by the ducted fans  162   a – 162   d . The ducted fans  162   a – 162   d  may be powered down some to facilitate retraction. The tether  130  is attached to the UAV  120  in a position selected, in part, to facilitate the retraction, as well. As the UAV  120  retracts into the recess  300 , the clamps  310  engage the UAV  120  to secure it in the recess  300  until the next deployment. Note that the clamps  310  may be omitted in some embodiments where the recess  300  is deep enough. 
   The UAV  120  may be stowed and deployed from the UGV  100  in any number of ways, some of which will depend on the implementation of the UAV  120 . FIG.  4 A– FIG. 4B  illustrate a technique for stowing and deploying the UAV  120  alternative to that shown in FIG.  3 A– FIG. 3B . In this implementation, the UAV  120  is stored in and deployed from a “basket”  400 . The deployment and retraction are otherwise the same. 
   FIG.  5 A– FIG. 5H  illustrate a ducted fan UAV  500 , that can be modified from that disclosed and claimed in United States Letters Patent No. 4,795,111, issued Jan. 3, 1989, to Moller International, Inc., as assignee of the inventor Paul S. Moller (“the &#39;111 patent”). The particular ducted fan of the &#39;111 patent can, as will be discussed further below, be readily modified to implement the present invention. Note that this particular UAV includes only a single ducted fan, rather than the four of the UAV  120  in  FIG. 1 . The limited number of ducted fans in the illustrated embodiment will improve the clarity and coherence of the discussion. However, an embodiment employing four such ducted fans will be discussed further below. 
   More particularly, FIG.  5 A– FIG. 5H  show a single-engine ducted fan VTOL vehicle  500  with a propeller  511  and a duct  512 . The propeller  511  is mounted horizontally on a shaft  513  and is powered by a single engine  514  below it. The illustrated propeller  511  has two blades  515  and  516  and a nose  517 . The circular duct  512  has a curved flange  518  at its upper end and has a planar lower edge  519 . As shown in FIG.  5 A– FIG. 5B  the duct  512  may have a support member  520  with a hollow bottom or base ring  521  and four support columns  522 . The ring  521  also serves as a muffler and is connected by a pair of vertical exhaust tubes  523  to the exhausts from the engine  514 , there being two such exhaust tubes for a two-cylinder engine  514 . The exhaust gas goes down the tubes  523  into the ring  521  and passes out from the ring  521  at exhaust openings  524 , spaced around the ring  521  at distances beginning about 90° away from the tubes  523  and extending downwardly at about 45°. 
   Mounted on the exterior face of the duct  512  is a series of control devices and other instrumentation, each a type of electronic device, including a detector and receiver  526 , and various programmed control initiators  527 , which control the engine or motor  514  and the various lever systems described below. In the illustrated embodiment, the motor  514  is an electrical motor powered by the UGV  100  over the tether  130  in a manner described more fully below. 
   In the duct  512  are twelve fixed vanes  531 ,  532 ,  533 ,  534 ,  535 ,  536 ,  537 ,  538 ,  541 ,  542 ,  543 , and  544 . The eight identical vanes  531 ,  532 ,  533 ,  534 ,  535 ,  536 ,  537 , and  538  are disposed along two mutually perpendicular axes. That is, there are four vanes  531 ,  532 ,  533 ,  534  arranged as two diametrically opposite pairs  531 ,  532  and  533 ,  534  parallel to one diametral line  539 , shown in  FIG. 5C . There are two other diametrically opposite pairs of vanes  535 ,  536  and  537 ,  538  parallel to a diametral line  541  perpendicular to the line  539 . Each pair of vanes forms a generally rectangularly shaped duct segment and adjacent pairs form generally quadrant shaped duct segments. These eight vanes  531 – 538  are preferably not simply vertical planes but are preferably shaped as shown in FIG.  5 F– FIG. 5G , and they each have a variable-camber flap  545  or  546  attached to their lower or trailing edge. 
   For yaw control, or control about the vertical axis, the flaps  545  and  546  of all eight of these vanes  531  through  538  move together in the same rotational direction, resulting in torque about the vertical axis. For translational control, the flaps  545  and  546  of two diametral pairs move together, shown in  FIG. 5G , while the flaps  545  and  546  of the other diametral pairs either do not move or move in a direction or directions. As a result, a force is generated for accelerating the vehicle  500  horizontally at a speed up to a point where its aerodynamic drag equals its ventable translational force 
   Preferably, each camber flap  545 – 546  is equal in area to its respective vane  531 – 538 . As a result the center of pressure of the vane-flap combination occurs at the three-quarter chord position C back from the leading edge L, i.e., near the center of the camber flap  545  or  546 , and this is where the center of pressure of the vanes occurs. This center of pressure is kept as close as possible to the position along the vertical-axis occupied by the center of gravity of the vehicle  500  and is preferably within the limits of the vertical extremities of the flaps  545 – 546 . 
   Each pair of flaps  545  and  546  is joined together by a tie rod  547  having a clevis clip  548  at each end pivoted to it by a pin  549 , controlled, as shown in  FIG. 5E , by a servomotor  550 . The servomotor  550  is actuated by a potentiometer  551 , and both are in a foam-rubber fitted housing  552 . The servomotor  550  acts on the tie rod  547  through the vane control arm  553 , having a sleeve  554  held on a servomotor shaft  555  by a recessed Allen-head screw  556 . The arm  553  may act through a ball-and-socket joint  557  on a drag linkage  558 , which operates on the tie rod  547  through another ball-and-socket joint  559 . 
   The other four vanes  541 ,  542 ,  543 , and  544 , shown in  FIG. 5B , are rigid and extend in from the wall of the duct  512  to bisect the right angles made by the mutually perpendicular vanes  532 ,  537  and  538 ,  534  and  533 ,  536  and  537 ,  531 , shown in  FIG. 5C . In other words the vanes  541 ,  542 ,  543 , and  544  lie at an angle of 45° to the eight diametral vanes  532 ,  537  and  538 ,  534  and  533 ,  536  and  535 ,  531 . Preferably, these four vanes  541 ,  542 ,  543 , and  544  are not simply vertical planes but are shaped like the rigid upper portions of the vanes shown in FIG.  5 F– FIG. 5G  (but without the attachment of variable-camber vanes). 
   Between the vanes  531  and  532  is a generally rectangular duct segment or passage  561 ; between the vanes  533  and  534  is a diametrically opposite rectangular passage  563 . At right angles to these openings are a rectangular passage  564  between the vanes  535  and  536  and a rectangular passage  562  between the vanes  537  and  538 . Thus, between the vanes  532  and  537  is a quadrant divided into two equal passages  565  and  566  by the vane  541 ; between the vanes  538  and  534  is a quadrant shaped duct segment divided into two equal passages  567  and  568  by the vane  542 ; between the vanes  533  and  536  is a quadrant shaped segment bisected into two passages  569  and  570  by the vane  543 ; and between the vanes  535  and  531  is a quadrant shaped segment bisected into two passages  571  and  572  by the vane  544 . 
   Each vane  541 ,  542 ,  543 , and  544  preferably supports a pair of spoilers  575 ,  576  or  577 ,  578  or  579 ,  580  or  581 ,  582 , one for each passage  565 ,  566 ,  567 ,  568 ,  569 ,  570 ,  571  and  572 . The spoilers  575 – 582  each have a circular-arc outer rim  583  concentric with the duct  512  and are otherwise generally trapezoidal in shape to fill most of the outer portion of their respective passages  565 – 572  when in the fully closed or horizontal position, as depicted in FIG.  5 B– FIG. 5C . When rotated down to their fully open or vertical position, they lie generally parallel to their respective vanes  541 – 544 , as shown at  581  in  FIG. 5D , and take up very little room in the passages  565 – 572 . 
   The spoilers  575 – 582  are each supported by their associated vanes  541 – 544  through a tension bracket  584  and are operated, as shown in  FIG. 5H , via a remotely activated system embodying a potentiometer  585  supported with a servomotor  586  inside a housing  587 . The servomotor  586  operates, like the servomotor  550 , through a linkage arm  588  and a drag linkage  589  having a ball-and-socket joint at each end, and a lever arm  590  that rotates on shaft  591 . 
   In each quadrant, a single servomotor  586  operates the pair of spoilers  575 ,  576 , etc.; so that in each quadrant the spoilers are paired. Moreover, the pivot axis of each spoiler lies along and coincides with the position where the torque on its spoilers is minimized as a function of its angular position; thereby the torque required to deploy that pair of spoilers is reduced, and the size of the servomotors  586  is kept small. Since each spoiler  575 – 582  has its surface concentrated near the duct wall, the resulting control moment is maximized. Each spoiler may be made from lightweight wood, to minimize its inertia and provide rapid response to its servomotor  586 . 
   The functional mixing of yaw and translation forces is preferably done electronically by the control circuits  527 , with the vehicle  500  employing eight separate servomotors  550  and  586  for control. Thus, there are four servomotors  550  for yaw or translational controls and four servomotors  586  for pitch-and-roll controls. One servomotor controls one parallel set of yaw vanes or one pair of spoilers. 
   This system for controlling the flight of the vehicle  500  has the additional capability of being able to trim the vehicle  500  into a non-vertical position and holding that position through the use of translational control power. This may be desirable when a rigidly attached TV camera is used and is directed in the plane of vision by, for instance, gimballing the vehicle rather than gimballing the camera. 
   The principles of the UAV  500  can be extrapolated, as shown in  FIG. 6 , for use with multiple ducted fans in a single UAV, as in the case of the UAV  120  in  FIG. 6 . If the UAV employs a plurality of ducts, as in the case of the vehicle  600  shown in  FIG. 6 , then the spoiler approach can be augmented or even replaced by a system that alters the thrust in the individual ducts, either by individual fan pitch control or individual throttle engine control. 
   The illustrated UAV, whether utilizing a single-engine ducted fan (e.g., FIG.  5 A– FIG. 5H ) or utilizing a plurality of such ducted fans (e.g.,  FIG. 6 ), provides pitch-and-roll control seperate from translational control. The spoiler system is automatically driven by an on-board inertial reference system (not shown), and the spoilers are deployed only for the purpose of keeping the vehicle lift axis parallel to or coincident with the gravitational axis. The moment of inertia about the pitch-and-roll axis and the response time of the spoilers are both minimized, so that only very low forces are required from the spoilers  575 – 576 ,  577 – 578 ,  579 – 580 ,  581 – 582 . The result is that there is little loss of lift; hence, there is little coupling between the pitch-and-roll control and the heave or vertical movement. The vehicle  500  may be trimmed to level, but trimming is not used for controlling maneuvers about the pitch-and-roll axis. 
   The spoilers  575 – 576 ,  577 – 578 ,  579 – 580 ,  581 – 582  are paired in each quadrant. This ensures that little or no torque or force is generated which might rotate the vehicle  500  about the vertical or yaw axis when the spoilers  575 – 576 ,  577 – 578 ,  579 – 580 ,  581 – 582  are employed. The pivot axis of each spoiler vane coincides with the position where the torque on the spoiler is minimized as a function of its angular position. This positioning reduces the amount of torque required to deploy the pair of spoilers and hence reduces the size of the servomotors required. Most of the spoiler surface is concentrated near the maximum duct diameter, in order to maximize the resulting control moment. Preferably, the spoilers  575 – 576 ,  577 – 578 ,  579 – 580 ,  581 – 582  are made of extremely light material in order to reduce their inertia and to obtain rapid spoiler response with reduced servomotor power. 
   Translational control is obtained by use of a flexible vane instead of a pivoted rigid vane. In a deflection vane system, it is desirable to recognize that a rigid vane generates two major problems when used to deflect a slip stream:
         (1) The forces generated by swinging a rigid vane are highly nonlinear relative to the changing angle of the vane, and particularly when the aircraft is near the stall condition.   (2) The stall condition is reached by rigid vanes at fairly low angles of vane deflection, generally less than 15°. However, for significant translational forces, such as those which are required to move a vehicle of this type at a velocity greater than one-third of the slip stream velocity, the slip stream deflection required becomes significant and is greater than 15°.
 
Therefore, the illustrated UAV employs a variable-camber vane or flap, which is attached to the trailing edge of fixed anti-torque vanes that serve to remove the swirl introduced by the fan.
       

   The UAV thus obtains translational control by redirecting the slip stream with vanes  575 – 576 ,  577 – 578 ,  579 – 580 ,  581 – 582  that are provided with flexible camber portions or flaps extending downwardly from an upper fixed rigid portion, and the vanes are mounted so that the center of lift or force providing the transverse force is at or as close as possible to the center of gravity of the vehicle. This mounting ensures that deflection of the variable-camber vane or flap does not generate significant moments about the center of gravity; such moments, if generated, would have to be overcome by the spoiler system. Small coupling moments are automatically dealt with by the spoiler system and result only from forces produced about the pitch-and-roll axis, due to translational control. 
   If the flexible portion of the vane is equal in size to the rigid upstream portion, then the transverse force (or center of pressure) of the rigid-flexible deflector vane occurs at approximately the three-quarter chord position back from the leading edge. Put another way, the center of pressure or lift appears to occur near the center of the flexible portion of the vane. In fact, this position is a function of the amount of vane deflection. For greater deflections this position is probably correct. For small deflections this center of pressure will be farther forward. Preferably, the center of left on the vane is at the center of gravity of the vehicle, on the vertical axis. 
   The variable-camber vanes act like a flap (or aileron) on a wing. Such a flap may involve comparatively small forces and be small in size relative to the forces it can generate. Thus, when a variable-camber vane system employs two or more vanes in parallel, a cascade vane effect is created. This cascade effect continues to deflect the slip stream up to 90°, if that should be necessary. However, it is unlikely that deflection greater than 30° will ever be required. 
   More succinctly summarized, there is least one ducted fan, comprising power means, a horizontally mounted fan connected to and driven by the power means for causing a vertically and downwardly directed airstream, and a cylindrical duct that extends around and beneath the fan, for confining the airstream. In the duct is a vane system comprising two mutually perpendicular pairs of diametrically opposite generally rectangularly shaped duct segments, each defined and bounded by a pair of generally vertical stationary walls extending across the duct parallel to a diametral line thereacross. Each pair of these walls also defines one boundary of a quadrant shaped duct segment located between adjacent wall pairs. Each duct segment forming a wall includes an upper, rigid portion having a variable-camber flap portion affixed to its lower extremity. A first set of remotely controlled servo motors is employed for varying the camber of each of the flaps. In each pair of variable vanes, the flap camber is at all times the same in amount and direction for both flaps. 
   The UAV disclosed in the &#39;111 patent can be readily modified to accommodate and take advantage of the present invention. The UAV of the &#39;111 patent includes an antenna for radio communication, which is unnecessary in the present invention. Thus, the antenna and the transmitter/receiver associated with radio communication are eliminated from the implementation of the UAV  120 . A connection for the tether  130  will similarly need to be added. Furthermore, the UAV  120  will typically fly at lower altitudes than the UAV of the &#39;111 patent, and can receive power from the UGV  100  over the tether  130 . Thus, the internal combustion engine (and gas tank) for the UAV of the &#39;111 patent are replaced by a lighter electric motor. The invention admits wide variation in the sensing capabilities that may be implemented on the UAV  120 . Further modification may be desirable to accommodate different sensing capabilities, as will be discussed further below. 
   Note that, in the illustrated embodiment, the UAV  120  is intended to hover above the UGV  100  while the UGV  100  is stopped. The UAV  120  consequently need only provide vertical lift, and need not provide horizontal propulsion. Thus, the weight and complexity of the UAV  120  can be reduced relative to conventional UAVs. Note also that in the illustrated embodiment, power is provided to the propulsion systems and sensor packages aboard the UAV  120  over the tether  130  from the UGV  100 . This results in further savings in weight and complexity since the UAV  120  need not provide its own power. The UAV  120  and/or its sensor suite can also be recharged from the UGV  100  over the tether  130  and/or recharged and/or refueled from the UGV  100  when not deployed. 
   Returning to  FIG. 1 , the tether  130  may be any suitable transmission medium known to the art. For instance, in the illustrated embodiment, the tether  130  is comprised of one or more optical fibers cabled together. Alternative embodiments may employ coaxial cables or twisted wire pairs. The present invention is not limited by the implementation of this aspect. However, the characteristics of various media may affect the design of some implementations in ways well known to the art. For example, some media do not spool as well or as tightly as do other media, and the dimensions of the drum  210 , shown in  FIG. 2 , will be sized accordingly. In some embodiments, the UAV  120  may receive power from the UGV  100  over the tether  130 . The tether  130  in such embodiments then includes a power lead over which the UAV  120  receives power and the tether becomes an umbilical. 
   Returning once again to  FIG. 1 , the UAV  120 , when deployed, remotely senses the environment in which the UGV  100  is situated. As was mentioned above, the UAV  500  illustrated in FIG.  5 A– FIG. 5H  is equipped with a suite of sensors including a detector and receiver  526 . The type and number of sensors will be implementation specific, and may employ almost any type of remote sensing technology. In one proposed implementation, illustrated in  FIG. 7 , the remote sensing technologies includes an active LADAR system and a passive infrared system. Note, however, that the number and type of sensors in the sensor suite will be implementation specific. For instance, in some embodiments, the sensor suite may comprise a single, passive IR sensor. One particular embodiment is described immediately below. 
   In the proposed embodiment of  FIG. 7 , the UAV  120  includes a laser  710  that produces a laser signal  715 , a detector subsystem  720 , a processor  725 , and an electronic storage  730  communicating via a bus system  740 . The processor  725  may any kind of processor, such as, but not limited to, a controller, a digital signal processor (“DSP”), or a multi-purpose microprocessor. The electronic storage  730  will probably be magnetic (e.g., some type of random access memory, or “RAM”, device), but may also be optical, in whole or in part, in some embodiments. The storage  730  may also include removable storage (not shown), such as a floppy magnetic disk, a zip magnetic disk, or an optical disk. The bus system  740  may employ any suitable protocol known to the art to transmit signals. Note that the bus system  740 , in this particular embodiment, transmits over the tether  130 . Particular implementations of the laser  710 , laser signal  715 , and detector subsystem  720  are discussed further below. 
   The processor  725  controls the laser  710  over the bus system  725  and processes data collected by the detector subsystem  720  from an exemplary scene  750 . The scene  750  includes trees  755  and  760 , a military tank  765 , a building  770 , and a truck  775 . The tree  755 , tank  765 , and building  770  are located at varying distances from the system  700 . Note, however, that the scene  750  may have any composition. One application of the remote sensing system  700 , as shown in  FIG. 7 , may be to detect the presence of the tank  765  within the scene  750 . A second application may be to detect objects such as the trees  755 ,  760 , or negative obstacles (not shown). The processor  725  operates under the direction of the operating system  745  and application  750  to fire the laser  710  and process data collected by the detector subsystem  720  and stored in the data storage  755  in a manner more fully described below. 
   The operation of the LADAR system aboard the UAV  120  is conceptually illustrated in  FIG. 8 . The LADAR system includes the laser  710  of  FIG. 7  as well as some portions of the detector subassembly  720 . The LADAR system collects three-dimensional data from a field of view  825 , shown in  FIG. 8 , within the scene  750 , shown in  FIG. 7 . The laser signal  715  is transmitted by the laser  710  on the UAV  120  to scan a geographical area called a scan pattern  820 , shown in  FIG. 8 . Each scan pattern  820  is generated by scanning elevationally, or vertically, several times while scanning azimuthally, or horizontally, once within the field of view  825  for the UAV  120  within the scene  750 , shown in  FIG. 7 . The scan patterns are sometimes, and will be hereafter herein, referred to as “footprints.”  FIG. 8  illustrates a single elevational scan  830  during the azimuthal scan  840  for one of the footprints  820 . Thus, each footprint  820  is defined by a plurality of elevational scans  850  such as the elevational scan  830  and the azimuthal scan  840 . The velocity and depression angle of the sensor with respect to the horizon, and total azimuth scan angle of the LADAR system, determine the footprint  820  on the ground. 
   The laser signal  715  is typically a pulsed signal and may be either a single beam or a split beam. Because of many inherent performance advantages, split beam laser signals are typically employed by most LADAR systems. A single beam may be split into several beamlets spaced apart from one another by an amount determined by the optics package (not shown) aboard the UAV  120  transmitting the laser signal  715 . Each pulse of the single beam is split, and so the laser signal  715  transmitted during the elevational scan  850  in  FIG. 8  is actually, in the illustrated embodiment, a series of grouped beamlets. The optics package aboard the UAV  120  transmits the laser signal  715  while scanning elevationally  850  and azimuthally  840 . The laser signal  715  is continuously reflected back to the UAV  120 , which receives the reflected laser signal through the detector subsystem  820 . 
   While the LADAR system is operating, the detector subsystem  820  is also passively detecting infrared (“IR”) radiation from the scene  850 . The IR detection is “passive” because the detected radiation does not result from energy introduced to the scene  850  by the sensors. The IR detection comprises a passive IR imaging of the scene  750  by a portion of the detector subsystem  720 . This produces a two-dimension passive image data set with each pixel (picture element) having passive intensity information corresponding to the magnitude of the passive IR energy collected for that pixel. In some embodiments, the same detector may be used for both the active LADAR and passive infrared detection, e.g., U.S. Pat. No. 6,323,941, entitled “Sensor Assembly for Imaging Passive Infrared and Active LADAR and Method for Same,” issued Nov. 27, 2001, to Lockheed Martin Corp. as the assignee of the inventors Evans, et al. 
   Remote sensing techniques combining laser and infrared technologies are known to the art. See, e.g.:
         U.S. Pat. No. 6,359,681, entitled “Combined Laser/FLIR Optics System,” issued Mar. 19, 2002, to Lockheed Martin Corp. as the assignee of the inventors Housand, et al.;   U.S. Pat. No. 6,323,941, entitled “Sensor Assembly for Imaging Passive Infrared and Active LADAR and Method for Same,” issued Nov. 27, 2001, to Lockheed Martin Corp. as the assignee of the inventors Evans, et al.;   U.S. Pat. No. 5,345,304, entitled “Integrated LADAR/FLIR Sensor,” issued Sep. 6, 1994, to Texas Instruments Incorporated, as the assignee of the inventor John E. Allen; and   U.S. Pat. No. 4,771,437, entitled “Integrated Laser/FLIR Rangefinder,” issued Sep. 13, 1988, to Texas Instruments Incorporated, as the assignee of the inventors Powell, et al.
 
Any suitable approach known to the art may be used to implement this aspect of the present invention. The LADAR system produces a LADAR image of the scene  750  by detecting the reflected laser energy to produce a three-dimensional image data set in which each pixel of the image has both z (range) and intensity data as well as x (horizontal) and y (vertical) coordinates. The IR system generates an IR image comprised of two-dimensional data.
       

   Different embodiments may, however, employ different sensing capabilities depending on intended mission profiles. As those in the art having the benefit of this disclosure will appreciate, many engineering considerations go into the design of any given implementation. Weight and size of the sensors, for instance, should be considered in light of the lift capacity of the UAV  120 . Common types of remote sensors include a day camera, a FLIR sensor, a laser rangefinder, and a Global Positioning System (“GPS”) sensor. Table 1, below, lists several sensors that might be employed in various embodiments according to a purpose for which their data may be employed. Note, however, that other sensors, sensor suites, and assemblies may be employed in alternative embodiments. For instance, some embodiments may employ TV cameras (day or night, i.e., low light cameras) and nuclear, biological and chemical (“NBC”) sensors. 
   
     
       
             
           
             
             
           
         
             
               TABLE 1 
             
           
           
             
                 
             
             
               Sensor Payloads 
             
           
        
         
             
               Purpose 
               Sensor 
             
             
                 
             
             
               Targeting 
               SWIR, Indigo Merlin NIR w/50 MM Fixed 
             
             
                 
               FLIR - Long Lens, Indigo Alpha 
             
             
                 
               Target Designator, Litton - LLDR 
             
             
               Perception 
               Daylight Cameras - Watec 902S (Stereo) 
             
             
                 
               FLIR - Short Lens and Long Lens (Same as Above) 
             
             
                 
               LADAR, SRI 
             
             
               Other Sensors and 
               PC-104/CPU w/VGA (Real-time Devices) 
             
             
               Electronics 
               Sony EX470 Video w/18× Zoom 
             
             
                 
               Pan and Tilt (Directed Perception, PTU-46-17.5) 
             
             
                 
             
           
        
       
     
   
   The data generated by the sensors aboard the UAV  120  is then transmitted over the tether  130  and the bus system  740 . The data is captured in the data storage  755  and processed by the processor  725  under the control of the application  750 . The data may be processed in any suitable manner known to the art, depending on the nature of the data collected and the reason for which it is collected. For instance, the data may be processed to identify obstacles for navigating the scene  750 . See, e.g.:
         Hebert, et al., “Evaluation and Comparison of Terrain Classification Techniques from LADAR Data for Autonomous Navigation,” 23d Army Science Conference (December 2002), available over the Internet;   Bellutta, et al, “Terrain Perception for DEMO III,” Proceedings of the 2000 Intelligent Vehicles Conference, (2000);       

   Macedo, et al., “Ladar-based Discrimination of Grass from Obstacles for Autonomous Navigation,” ISER 2000 (2000); and 
   Matthies, et al., “Obstacle Detection for Unmanned Ground Vehicles: A Progress Report,” Robotics Research: Proceedings for the 7 th  International Symposium (1996). 
   However, in some embodiments, the data may be processed for reasons other than navigation. For instance, in military environments, the data might be processed through an automatic target recognition (“ATR”) system to determine whether some obstacle is a vehicle and, if so, whether a friend or a foe. See, e.g.:
         U.S. Pat. No. 5,867,118, entitled “Apparatus for and Method of Classifying Patterns,” issued Feb. 2, 1999, to Lockheed Martin Corp. as the assignee of the inventors McCoy, et al.;   U.S. Pat. 5,893,085, entitled “Dynamic Fuzzy Logic Process for Identifying Objects in Three-Dimensional Data,” issued Apr. 6, 1999, to Lockheed Martin Corp. as the assignee of the inventors Phillips, et al.;   U.S. Pat. 5,852,492, entitled “Fused Lasar Range/Intensity Image Display for a Human Interpretation of Lasar Data,” issued Dec. 22, 1998, to Lockheed Martin Corp. as the assignee of the inventors Nimblett, et al.;
 
These examples are illustrative only, and the list is not exhaustive. Other embodiments may process the data in still other ways for still other purposes.
       

   The use of the tether  130  in the virtual sensor mast  110  imparts numerous advantages over conventional practice. The data may be more simply formatted since there is no danger of receipt by the wrong UGV  100 . The data is generally more free of noise because it is not broadcast wirelessly and because fewer instruments (i.e., no transmitter, no receiver) are needed. Consequently, the data is generally easier to process relative to data collected by conventional, untethered UAVs. At the same time, the data can be acquired at an aspect angle greater that that available from mast mounted sensor packages. Thus, it is relatively easier to identify negative obstacles (e.g., ditches) and cul-de-sacs relative to mast-mounted sensors. Deployment of the UAV  120  also permits the UGV  100  to hide the chassis  105  while peering over defilade positions, buildings and water. The additional height afforded by deploying the UAV  120  with the tether  130  also reduces multi-path error, which improves data quality and eases data processing. 
   In the illustrated embodiment, the UGV  100  can be operated in several control modes including:
         tele-operation, characterized by passive suspension compliance and manually commanded articulation;   tele-managed, characterized by active suspension compliance, active self-articulation; and   semi-autonomous, characterized by active suspension compliance, active self-articulation.
 
Capabilities associated with the various control modes in the illustrated embodiment are listed in Table 2.
       

   
     
       
             
           
             
             
             
           
         
             
               TABLE 2 
             
           
           
             
                 
             
             
               Capabilities Matrix 
             
           
        
         
             
                 
               Control Class 
               Obstacle Capability 
             
             
                 
                 
             
             
                 
               Tele-Operation 
               obstacle course, includes each of the 
             
             
                 
                 
               following- 
             
             
                 
                 
               articulation over 0.5–0.75 m step 
             
             
                 
                 
               0.5–0.75 m step drive off 
             
             
                 
                 
               flat, benign terrain at 20 kph 
             
             
                 
                 
               side slope stability 
             
             
                 
                 
               max up-slope and down-slope climb 
             
             
                 
                 
               high center recovery w/mast 
             
             
                 
                 
               inverted operation 
             
             
                 
               Tele-Managed 
               40 kph in tall grass 
             
             
                 
                 
               flip-over recovery 
             
             
                 
                 
               moderate terrain at 20 kph 
             
             
                 
                 
               high wall stand-up &amp; peek over 
             
             
                 
                 
               GPS waypoint navigation (for total 
             
             
                 
                 
               endurance testing on closed circuit courses 
             
             
                 
               Semi-Autonomous 
               very rough terrain at 10 kph 
             
             
                 
                 
               silent operations in very rough terrain 
             
             
                 
                 
               at 6 kph 
             
             
                 
                 
               canonical trench crossing (quasi- 
             
             
                 
                 
               static) 
             
             
                 
                 
               canonical wall crossing (quasi-static) 
             
             
                 
                 
               1 meter step climb (quasi-static) 
             
             
                 
                 
               active ground pressure control 
             
             
                 
                 
               walking in very rough terrain 
             
             
                 
                 
               transition to and from water 
             
             
                 
                 
               Semi-Autonomous, Performance 
             
             
                 
                 
               Envelop Expansion: 
             
             
                 
                 
               Collaborative (using test mule as 
             
             
                 
                 
               surrogate) obstacle crossing assistance 
             
             
                 
                 
               Chimney-climb demo 
             
             
                 
                 
             
           
        
       
     
   
   In the illustrated embodiment, tele-operation and tele-management are performed through an Operator Control Unit (“OCU”, not shown). The OCU is an extremely lightweight, man portable, hand-held and wearable unit remote from the UGV  100  (and out of harm&#39;s way), connected via military RF command link. It includes tele-operational capability as well as data display, storage and dissemination. A secondary fiber optic link can be used when RF signals are undesirable. The general microprocessor-based system has easily expandable I/O capabilities and substantial memory/processing power, providing much more flexibility and extensibility in the design. Exemplary OCUs with which this aspect of the invention can be implemented include, but are not limited to, FBI-Bot, AST, RATLER, DIXIE, SARGE, and TMSS. 
   The OCU of the illustrated embodiment also encompasses standard interfaces for versatility and future expandability; conforms with military specifications regarding temperature, humidity, shock, and vibration; allows operator to independently tele-operate single or multiple UGVs; uses standard military symbology to display location, movement, and status of friendly, hostile, and unknown units; represents terrain maps and nuclear, biological and chemical (“NBC”) assessments using military grid reference system; and can provide auditory feedback for system status or relaying information from acoustic sensors onboard. The OCU provides real-time vehicle control capabilities as well as situational awareness displays for the forward element. The display can be wrist-mounted, head-mounted, or integral to the computing unit. 
   More particularly, in the illustrated embodiment, a map display (not shown) is updated in real-time with data from one or more UGVs  100 . Standard military symbology, such as is detailed in MIL-STD-2525B, displays the location, movement and status of friendly, hostile and unknown units. Vehicle status is displayed continually beside the unit icons and optionally with popup display of more detailed status information. Sensory data from the NBC detector and other sensory payloads are overlaid on the map display. Laser range finder and optical sensor gaze direction are represented on the display as a line radiating from the UGV icon. The terrain maps and NBC assessments are represented using the military grid reference system. Auditory feedback can be provided for system status or relaying information from acoustic sensors onboard the UGV. 
   Tele-operation of a single UGV  100  can be done with a first-person perspective view through use of real-time video and pointing device to control vehicle course and speed. Tele-management of single or multiple UGVs  100  can be accomplished via manipulating the corresponding UGV icons on the map to set destination objectives and paths. The real time video display can optionally be zoomed to fill the display with overlaid vehicle status appearing in a head-up display. The real-time video display also can be used during reconnaissance to show the live video view from the UGV  100  as if through binoculars. Multiple UGVs  100  can be controlled via mission orders issued by manipulating the UGV fleet icons on the map display or by issuing high-level commands, such as to surround a particular objective or to avoid a particular area while moving autonomously. 
   Note, however, that tele-operation and tele-management of the invention is not so limited. Various alternatives for remote operation and management of the UGV  100  are illustrated in  FIG. 9 . For instance, control in these embodiments may be exercise from aboard an airborne command center  905 , at a forward observation post  910 , at a rear-echelon command and control center  920 , or at a central processing facility  930  over communications links  935   a – 935   d . The forward observation post  910 , rear-echelon command and control center  920 , and the central processing facility  930  may be airborne, ground-based (as shown) or marine. The communications links  935   a – 935   d  may be direct, line of sight communications or relayed by satellite (not shown). 
   The invention admits wide variation. Consider the embodiment of FIG.  10 A– FIG. 10B . In FIG.  10 A– FIG. 10B , a UAV  1000  is implemented with a lighter-than-air vehicle, e.g., a balloon  1005  fitted with a sensor platform  1010 . The UAV  1000  can be stowed, as shown in  FIG. 10B , in the same manner as the UAV  120  in  FIG. 3B . The balloon  1005  is filled from a source of pressurized gas (not shown), and the latches  310  released. As the balloon  1005  rises, indicated by the arrow  1015  in  FIG. 10A , the UAV  1000  lifts from the recess  300 , thereby lifting the sensor platform  1010 . Once the sensing is complete, the UAV  1000  can be winched back to the recess  300  by the tether management system  200 , shown in  FIG. 2 , and secured by the latches  310 . The balloon  1005  can then be deflated and the UAV  1000  stowed away. Alternatively, the tether  130  the deployment can terminating by severing or releasing the tether  130 , and the UAV  1000  permitted to float away. Note that, in this latter variation, the sensors aboard the sensing platform  1010  will preferably be inexpensive, as they may not be recoverable. It may also be desirable provide for the tether  130  to be detachable from the UGV  100  and/or the UAV  1000  and/or to be readily replaceable. Alternatively, the UAV  1000  can be retrieved, the sensor platform  1010  (or just the sensors mounted thereon) retained, the balloon  1005  (or the rest of the UAV  1000 ) severed and allowed to float away. 
   Thus, the particular embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the invention. Accordingly, the protection sought herein is as set forth in the claims below.