Abstract:
A method is described that involves determining a higher altitude wind. The method further includes determining a wind model with the higher altitude wind. The wind model includes a linear or logarithmic increase in wind magnitude with increasing altitude beneath the higher altitude. The method further includes determining locations of a flight path for a parafoil based on calculations that use the wind model. The calculations are performed by an electronic control unit that is transported by the parafoil. The method also includes controlling the parafoil&#39;s flight path consistently with the determined locations. The controlling is performed by the control unit.

Description:
CLAIM TO PRIORITY 
       [0001]    The application claims the benefit of U.S. Provisional Application No. 61/324,222 entitled, “Method and System For Optimized Terminal Guidance Of Autonomous Aerial Delivery Systems”, filed on Apr. 14, 2010 and U.S. Provisional Application No. 61/324,551 entitled, “Method and System for Improving Touchdown Accuracy Of Aerial Payload Delivery Using Ground Weather Station Uplink”, filed on Apr. 15, 2010, and U.S. Provisional Application No. 61/323,792 entitled, “Method and System For Control Of Autonomous Aerial System via GSM Cellular Network”, filed on Apr. 13, 2010 and U.S. Provisional Application No. 61/323,750 entitled, “Method and System For Establishing A Short-term Network Mesh Using Miniature Autonomously Guided Parafoils”, filed on Apr. 13, 2010 and U.S. Provisional Application No. 61/323,675 entitled, “Method and System For Vertical Replenishment Of Naval Vessels Via Precision Guided Airdrop”, filed on Apr. 13, 2010 all of which are also hereby incorporated by reference. 
     
    
     FIELD OF INVENTION 
       [0002]    The field of invention pertains to guided aerial vehicles and more specifically to method and apparatus for parafoil guidance that accounts for ground winds. 
       BACKGROUND 
       [0003]      FIG. 1   a  shows a parafoil  101 . A parafoil is a wing shaped parachute capable of steerable, controlled descent. Essentially, the parachute aspect of the parafoil causes the parafoil to exhibit a gradual descent, while, the wing aspect of the parafoil permits the parafoil to have a guided flight path. The flight path of a parafoil can be controlled by tugging/releasing lines coupled to the left and right trailing edges of the parafoil. Specifically, as observed in  FIG. 1   b , a parafoil can be made to turn to the left if the left trailing edge line  102  is tugged/pulled. Likewise, referring to  FIG. 1   c , a parafoil can be made to turn to the right if the right trailing edge line  103  is tugged/pulled. A parafoil can even be made to momentarily rise, or at least change its pitch upward if both the left and right trailing edge lines  102 ,  103  are tugged/pulled. 
         [0004]    Parafoils have been used for guided drops as a consequence of the ability to control their flight path. In order to successfully land a parafoil at or near some target, however, an individual or person is needed to control the trailing edge lines  102 ,  103  so as to guide the parafoil with the requisite accuracy. Said another way, the intelligence and sensory abilities of the human brain are needed to manipulate the trailing edge lines  102 ,  103  of the parafoil in view of the location of the target, the height of the parafoil, the forward and transverse speeds of the parafoil, the roll, yaw and pitch of the parafoil and the presence of winds. 
         [0005]    Various applications can be envisioned, however, for automatically guided parafoil drops. For instance, consider a situation where a team of catastrophe surveyors/workers/soldiers are in a remote area and in need of certain supplies. Having the ability to simply attach the needed supplies to the parafoil with some computerized intelligence to control the parafoil&#39;s trailing edge lines so as to automatically guide the parafoil and its payload in the vicinity of the surveyors/worker/soldiers would obviate the need for keeping skilled parachutists at the ready in case such a need for supplies arises. Moreover, even if skilled parachutists are available and at the ready, a parachutist would be delivered along with the payload. Without the same skills as the surveyors/workers/soldiers, the parachutist is apt to become a burden for the surveyors/workers/soldiers after the payload has been successfully delivered. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    A better understanding of the present invention can be obtained from the following detailed description in conjunction with the following drawings, in which: 
           [0007]      FIGS. 1   a,b,c  depict a parafoil; 
           [0008]      FIG. 2  shows an embodiment of a parafoil  201  and payload assembly  204 ; 
           [0009]      FIG. 3  shows an embodiment of the sensors, motors and control unit within a payload assembly; 
           [0010]      FIG. 4  shows a control system  400  implemented by the control unit&#39;s computer system; 
           [0011]      FIG. 5  shows an embodiment of a trajectory plan; 
           [0012]      FIG. 6  shows an embodiment of a methodology executed by a trajectory planning unit during a loitering phase; 
           [0013]      FIG. 7  diagrams an approach for measuring forward speed and wind magnitude; 
           [0014]      FIG. 8  shows an embodiment of a methodology executed by a trajectory planning unit during a downwind phase; 
           [0015]      FIGS. 9   a , 9   b , 9   c  pertain to an embodiment of a methodology executed by a trajectory planning unit during a turn phase; 
           [0016]      FIG. 10  pertains to a second embodiment of a methodology executed by a trajectory planning unit during a turn phase; 
           [0017]      FIG. 11  shows a linear wind model and a logarithmic and linear wind model; 
           [0018]      FIG. 12  shows an embodiment of a methodology executed by a trajectory planning unit to calculated a wind model; 
           [0019]      FIGS. 13   a  and  13   b  pertain to an attempt to land a parafoil on a moving target; 
           [0020]      FIGS. 14   a  and  14   b  pertain to a trajectory planning unit that utilizes the model of a vehicle; 
           [0021]      FIG. 15  shows an embodiment of a networked IS that involves a descending parafoil; 
           [0022]      FIG. 16  shows a wireless network established by parafoils; 
           [0023]      FIG. 17  shows a computing system. 
       
    
    
     DETAILED DESCRIPTION 
     1.0 Parafoil, Payload Assembly and Control Unit 
       [0024]      FIG. 2  shows an embodiment of a parafoil  201  and payload assembly  204  sufficiently capable of self guidance in a number of situations. The payload assembly  204  includes: i) the payload to be delivered  205  (e.g., supplies to be delivered to workers/soldiers on the ground); ii) sensors  206  to detect, for example, the parafoil&#39;s speed and orientation,; iii) motors (e.g., actuators)  207   a,b  to “rein in” and “rein out” the left and right trailing lines  202 ,  203  in accordance with the parafoil&#39;s currently desired direction and orientation; and, iv) a control unit  208  having electronic circuitry to apply the appropriate control signals to the electronic motors  207   a,b  in response to signals received by the control unit  208  from the sensors  206 . Here, payload assembly  204  may be any mechanical package that physically integrates the payload  205 , sensors  206 , motors  207   a,b  and control unit  208  as a cohesive whole. 
         [0025]      FIG. 3  shows an embodiment of the sensors  306 , motors  307  and control unit  308 . In the embodiment of  FIG. 3   a , the sensors  306  include an internal navigation system (INS) sensor set  312  including: i) three accelerometers  309   a,b,c  to measure linear acceleration in three different, respective directions (x, y, z); ii) three rate gyroscopes  310   a,b,c  to measure angular velocity (dθ/dt, dφ/dt, dψ/dt) along three different axis; and, iii) three magnetometers  311   a,b,c  to sense a three dimensional vector v that defines the parafoil&#39;s present pointing. The sensors  306  also include the Global Positioning System (GPS) receiver  312  (to measure the parafoil&#39;s location) and barometric altimeter  313  to measure the parafoil&#39;s altitude. As is known in the art, an accelerometer output can be integrated once over time to produce a measurement of velocity traveled in the same direction that the acceleration was measured. Likewise, the velocity can be integrated over the same time to determine the distance traveled in the same direction. Similarly, angular velocity as provided by the rate gyroscopes can be integrated over time to determine the number of degrees that have been rotated about the respective axis over the same time period. 
         [0026]    The motors  307 , in an embodiment, include a set of actuators  314   a,b  for the left and right trailing edge lines  302 ,  303 . A third actuator  315  is used to release a canopy of the payload assembly after it is dropped from an aircraft so that the parafoil can deploy. The embodiment of  FIG. 3  also depicts the control unit  308  as including wireless communication circuitry  316 . Specifically, the control unit  308  includes circuitry  317  to communicate with a local carrier&#39;s network (such as GSM circuitry  317  to communicate with a local carrier&#39;s GSM network). The wireless communication circuitry  316  may also include wireless circuitry  320  to communicate with a proprietary wireless network or link (e.g., established by the operators of the parafoil). 
         [0027]    As observed, the control unit  306  represents a computer system having a processing core  318  (e.g., microprocessor) and with the sensors  306 , motors  307  and wireless communication circuitry  316  acting as some form of the computing system&#39;s I/O. As shown, the sensors  306 , motors  307  and wireless communication circuitry  316  have their own dedicated interfaces (e.g., busses) to the processing core  318  but conceivably communications between the processing core  318  and the different units  306 ,  307 ,  316  may be shared over a same interface in various combinations. The processing core  318  is coupled to a volatile memory  319  (e.g., DRAM or SRAM) and flash memory  321 . The software executed by the processing core  318  is stored in flash memory  321  and loaded into volatile memory  319  when the control unit is first powered on (in an embodiment, well before the unit is dropped from an airplane). Thereafter the processing core  318  executes the software from volatile memory  319 . 
       2.0 Control System 
       [0028]      FIG. 4  shows a control system  400  implemented by the control unit&#39;s computer system to automatically guide the parafoil&#39;s flight. The control system of  FIG. 4  includes a trajectory planning unit  401 , a difference unit  402 , a path following unit  404 , the sensors  406  and the motors  407 . The trajectory planning unit  401  is responsible for determining the overall flight path of the parafoil. The flight path essentially defines the parafoil&#39;s desired location and orientation at a moment of time. The sensors  406  measure the parafoil&#39;s actual location and orientation at the moment of time. The difference unit  402  determines an error signal  403  defined as the difference between the desired and actual location/orientation of the parafoil. 
         [0029]    When there is no difference between the desired and actual location of the parafoil, the parafoil is “on track” and therefore no error signal exists. In this case, the parafoil&#39;s trailing edge lines do not need to be adjusted. By contrast, when a difference exists between the desired and actual location/orientation of the parafoil, the difference unit  402  produces a substantive error signal  403  that the path following unit  404  reproduces into one or more control signals  405  that are presented to either or both of the motors  407  to adjust the trailing edge lines in a manner that brings the parafoil closer to the desired location/orientation. In various embodiments the trajectory planning unit  401 , difference unit  402  and path following unit  404  are implemented with software program code that is executed by the parafoil&#39;s processing core. Other implementations may impose various functions performed by these units in hardware either entirely or partially. 
         [0030]    In an embodiment a model predictive control (MPC) approach is utilized based on a Single-Input Single Output (SISO) discrete system of the form: 
         [0000]        s   k+1   =As   k   +Bu   k   Eqn. 1 a  
 
         [0000]      p k =CS k   Eqn. 1b
 
         [0000]    where: 1) k is the present state of the parafoil and payload assembly (hereinafter, “parafoil”); 2) k+1 is the next state of the parafoil; 3) A, B and C are matrices that describe the parafoil dynamics; 4) s k  is a vector that describes the present state of the parafoil mechanical system in terms of its roll, change in roll with respect to time, yaw and change in yaw with respect to time; 5) u k  describes the control signals being applied to the parafoil&#39;s motors in the present state; and, 6) y k  is the parafoil&#39;s trajectory in the present state (that is, the path along which the parafoil is currently headed). 
         [0031]    As provided in Appendix A of the instant application, the above system can be solved for u k  as a function of the parafoil&#39;s currently desired trajectory w k . Thus, for a present parafoil state k, appropriate control u k  to be applied to the parafoil&#39;s trailing line motors can be determined to keep the parafoil&#39;s path along its desired path w k . 
         [0032]    Generally, the ability to calculate proper control signals for a desired trajectory is well known in the art. That is, given a desired flight path and an actual deviation from the desired flight path, it is well known (or can be readily determined) how to adjust a parafoil&#39;s trailing edge lines to bring the parafoil closer to the flight path. What has heretofore not been known is a generic algorithm or set of algorithms, executable by the parafoil as it is descending, for determining the parafoil&#39;s desired flight path to a specific target area where the algorithm takes into account various factors such as the precise location of the target relative to the parafoil when the parafoil is dropped, the altitude at which the parafoil is dropped and the applicable winds. In this respect, the ensuing discussion will focus primarily on algorithms executed by the trajectory planning unit  401 . 
         [0033]    As described in more detail further below, various embodiments exist as to the manner in which the algorithms executed by the trajectory planning unit account for the presence of winds. According to one perspective, the parafoil is purposely landed into the wind (for the sake of a “soft” landing). As a consequence, the strategy of the parafoil&#39;s flight plan is based on establishing a reference inertial trajectory with the major axis being aligned with the direction of prevailing/anticipated/known ground winds. The aloft winds component in this direction dictates the flight plan&#39;s logistics, while the crosswind component (measured or unmeasured) is considered as a disturbance. According to one embodiment, the prevailing wind component, estimated at current altitude is assumed to have constant magnitude through the entirety of the parafoil&#39;s descent. According to another embodiment the wind is assumed to linearly weaken in terms of magnitude over the course of the parafoil&#39;s descent. According to a third embodiment, the wind is assumed to weaken logarithmically over the course of the parafoil&#39;s descent. For simplicity, the first embodiment (in which the wind is assumed to have constant magnitude over the course of the parafoil&#39;s descent) will be described to provide an overall view of the flight path determination strategy. Subsequently, modifications will be introduced to this basic approach to account for more sophisticated wind modeling. 
         [0034]    As observed in  FIG. 4 , the trajectory planning unit  401  receives input information in the form of the target&#39;s position  408  (e.g., x, y, z coordinates of the target&#39;s position or just x, y if the z position of the target is assumed to be zero) and information concerning the applicable winds  409  and the amount of time (T app ) the parafoil is to spend on its “final approach”  410 . As will be discussed further below, the parafoil&#39;s flight path as determined by the trajectory planning unit  401  has a plurality of different legs, where, the final approach is the last leg. Here, the final approach time input  410  corresponds to a user input that is set before the parafoil is dropped. In an embodiment where the target is fixed (i.e., is not moving), the target position  408  is also a static input that can be entered before the parafoil is dropped. 
         [0035]    The set of inputs received by the trajectory planning unit  401  also include a dynamic component in the form of a feedback path  411  that exists from the sensors  406  to the trajectory planning unit  401 . In an embodiment, the sensor information that is fed back to the trajectory planning unit  401  at least includes the x, y, z spatial position of the parafoil and its horizontal pointing direction or “yaw” (ψ) (although not all of these parameters are necessarily used at all times during all flight path phases). Here, the flight path determined by the trajectory planning unit  401  need not be static. That is, once a first flight path is determined, the trajectory planning unit  401  is free to change or adjust the flight path as circumstances warrant. 
         [0036]    Referring to  FIG. 5 , in an embodiment, the control unit is turned on and operational before the payload assembly with packed parafoil is dropped from an airplane, helicopter or other airborne vehicle at drop point DP. The parafoil is purposely dropped upwind from the target (i.e., so that the wind will initially move the parafoil closer to the target). From the drop point DP, the payload assembly freefalls  500  for a set period of time. During the freefall  500  phase, the flight path control system of  FIG. 4  is essentially not activated. Rather, after a first preset time (e.g., 3 seconds) to allow the falling payload assembly to gain some distance from the airborne vehicle it was dropped from, the payload assembly&#39;s canopy is opened  501  to release the parafoil. After another preset time period (e.g., 4 seconds) of additional free fall the parafoil is presumed to be fully deployed and its trailing lines untangled  502 . 
         [0037]    At this point, the flight path control system of  FIG. 4  becomes operational and in control of the parafoil&#39;s flight path for the remainder of the parafoil&#39;s descent. As observed in  FIG. 5 , the flight path as determined by the trajectory unit  401  includes four major phases  503 _ 1  (“loiter”),  503 _ 2  (“downwind leg”),  503 _ 3  (“turn”), and  503 _ 4  (“final approach”). The flight path is essentially a high level strategy that is believed to be workable across a range of situations and environments. According to one perspective of the strategy, the parafoil is deliberately landed into the wind on the final approach leg  503 _ 4 . That is, when the parafoil is on the final approach  503 _ 4  part of its flight path, the parafoil&#39;s flight path direction is opposite that of the wind&#39;s direction  520 . 
         [0038]    A rationale for this approach is that when heading into the wind, the responsiveness of the parafoil to control input on its trailing edge lines is enhanced (as compared when the parafoil is heading with the wind) and it provides for a slower landing of the parafoil on the ground so as to protect the payload from the shock of landing. After exiting the initial loitering phase  503 _ 1   b , the parafoil sails with the wind along the downwind leg  503 _ 2  to a point “D_switch”  506  along the x axis, at which point, the parafoil enters the turn phase  5033  to turn the parafoil onto its final approach path  503 _ 4 . 
       2.1 Loitering Phase 
       [0039]    Upon entering the loitering phase  503 _ 1 , the trajectory planning unit maps out a helical descent pattern  504 . In an embodiment the helical descent pattern  504  is defined by points A, B, C and D in x,y space in the proximity of the location where the parafoil is dropped. Each time the parafoil reaches a point sufficiently proximate to one of points A, B, C and D in xy space, the parafoil turns to effect the helical descent. In a further embodiment, points ABCD define a rectangle or square in xy space where two of the rectangle&#39;s/square&#39;s sides are arranged to be parallel with the wind direction  520 . In various embodiments. The wind direction  520  is entered into the flight control system either before the payload assembly is dropped from the airborne vehicle, or, communicated to the flight control system (e.g., via the control unit&#39;s wireless network interface(s)) during its free fall or early loitering state). Points A, B, C, D may also be similarly entered into the flight control system (based on anticipated parafoil dynamics and/or tactical conditions). 
         [0040]    During the helical descent  504  the parafoil accomplishes a number of tasks including: 1) gaining an initial understanding of the parafoil&#39;s positioning relative to the target; 2) estimating its currect (weight-specific) performance of the payload system, specifically its forward speed V h ; 3) measuring the wind at its altitude; and, 4) calculating the altitude A_switch  503 _ 1   b  at which the loitering phase  503 _ 1  ends and the downwind leg phase  503 _ 2  begins. 
         [0041]      FIG. 6  shows an embodiment of the algorithm executed by the trajectory planning unit  401  while in the loitering phase in more detail. As observed in  FIG. 6 , based on the estimate of V h  the trajectory planning unit calculates the time T turn  spent in the turn phase  503 _ 3  and A_switch  507 . Specifically, in an embodiment, first a value of T turn  is calculated  601 , then, a value for A_switch is calculated  602 . While these calculations are ensuing, the actual output of the trajectory planning unit  401  corresponds to the ABCD helical descent pattern  504 , so that the trailing edge lines of the parafoil are adjusted as appropriate to keep the parafoil on the ABCD helical descent track. 
         [0042]    As the parafoil descends in the ABCD helical pattern the control unit measures the parafoil&#39;s ground speed  603  and, based on these ground speed measurements, estimates the parafoil&#39;s air or forward speed (V h )  604  and the magnitude of the wind (W) at its present altitude  605 . The descent rate (V u ) is also calculated  606 . As observed in  FIG. 6 , each of these determinations  604 ,  605 ,  606  as well as the target location, the preconfigured time of the parafoil&#39;s final approach (T app ) and the radius (R) of the turn in the turn phase  503 _ 3  can be used to calculate T turn  and A_switch  507 . Before discussing these calculations, however, embodiments for making each of the forward speed  604 , wind  605  and descent rate  606  calculations will be discussed first. 
         [0043]      FIG. 7  pertains to the trajectory planning unit&#39;s ground speed  603  and wind  604  measurements. In various embodiments, the direction of the prevailing/expected ground wind is entered into or communicated to the parafoil&#39;s control unit (e.g., prior to the payload assembly being dropped from the airborne vehicle or through one of the control unit&#39;s wireless interfaces after it is dropped). While loitering, the parafoil&#39;s control unit determines the prevailing winds along the downwind direction and can also determine the crosswind (much smaller) wind component, which maybe useful during the final turn. 
         [0044]    With the direction of the ground wind (desired landing direction)  520  being known, the trajectory planning unit is able to establish: 1) the direction of the final approach  503 _ 4 ; 2) the direction of the downwind leg  503 _ 2  and turn  503 _ 3 ; and, 3) the orientation of the “legs” of the loitering phase&#39;s ABCD helical descent. As such, when the loitering phase  503 _ 1  first begins, the trajectory planning unit  401  defines the ABCD helical pattern with straight “out” and “back” legs  701 ,  702  that run parallel to the direction  720  of the wind. 
         [0045]    During its descent in the loitering phase, the parafoil will run through one or more straight “out” and “back” legs  701 ,  702  of the helical descent. During the run of the parafoil along one of these legs, over time, the trajectory planning unit presents values that correspond to x, y positions along the leg so the parafoil follows the planned leg path. When the parafoil reaches the end of a leg, the trajectory planning unit presents an output that corresponds to a turn so the parafoil can begin to approach its next leg in the pattern. During each pass through a downwind or upwind leg  701 ,  702 , the trajectory planning unit measures its ground speed  603  in the direction of the leg. Here, the ground speed of the parafoil in the downwind legs  702  should be faster than the ground speed of the parafoil along the upwind legs  701 . 
         [0046]    The parafoil&#39;s air speed (V h ) and the magnitude of the wind (W) can be determined from the opposing measured ground speeds. Specifically, 
         [0000]      ( W+V   h )= V 1=ground speed measured in the downwind (+ x ) direction  Eqn. 2a
 
         [0000]      ( V   h   −W )= V 2=ground speed measured in the upwind (− x ) direction  Eqn. 2b
 
         [0000]      such that 
         [0000]        V   h =( V 1 +V 2)/2  Eqn. 3
 
         [0000]        W=V 1/2 −V 2/2  Eqn. 4.
 
         [0000]    Multiple wind measurements can be taken through multiple loops of the helical descent (e.g., and averaging them) or only a single wind measurement can be taken through a single loop. Similarly, the crosswind component of the current winds can be estimated while the parafoil travels along two other legs (leg CD and led AB in  FIG. 7 ). This may be important if the landing is scheduled differently than into the wind. This latter case may be applicable to landing onto a moving target (platform) or delivering payload from a specified direction, not necessarily aligned with a ground wind. 
         [0047]    Referring back to  FIG. 6 , the descent rate  606  (V v ) can also be calculated by measuring the parafoil&#39;s change in altitude over a period of time. Here, the barometric altimeter readings of INS and/or GPS readings can be used to determine altitude. 
         [0048]    With the estimate provided by Eqn.3, the time T turn  expected to be spent in the turn phase  503 _ 3  can be estimated  601  as 
         [0000]        T   turn   =πR/V   h   Eqn. 5
 
         [0000]    where R is an estimated radius of the turn which, in an embodiment, is a parameter that is entered by a user into the control unit. In another embodiment, the control unit sets an initial value of R=ΔY/2 where ΔY is the lateral distance along the y axis  511  between the target and the approximate position of the parafoil while loitering. Here, Eqn. 5 essentially corresponds to the time spent in a 180 degree turn with radius R and air speed V h  with a constant turn rate. 
         [0049]    With numerical values being assigned to each of T turn , V h , V v  and T app , the parafoil can determine  602  the altitude A_switch at which it exits the loitering phase  503 _ 1  and enters the downwind phase  503 _ 2  as: 
         [0000]    
       
         
           
             
               
                 
                   
                     A 
                     switch 
                   
                   = 
                   
                     
                       V 
                       v 
                       * 
                     
                      
                     
                       
                         L 
                         + 
                         
                           
                             V 
                             h 
                             * 
                           
                            
                           
                             ( 
                             
                               
                                 T 
                                 turn 
                               
                               + 
                               
                                 2 
                                  
                                 
                                   T 
                                   app 
                                   des 
                                 
                               
                             
                             ) 
                           
                         
                       
                       
                         W 
                         - 
                         
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                   Eqn 
                   . 
                   
                       
                   
                    
                   6 
                 
               
             
           
         
       
     
         [0000]    where, in Eqn. 6, L is the distance separating the parafoil and the target along the x axis. Said another way, L is the x axis intercept of the parafoil&#39;current position. As drawn in  FIG. 5 , L is shown approximately as of the moment the parafoil exits the loitering phase. The distance of L “shortens” however as the parafoil draws nearer the target along the x axis in the downwind phase  503 _ 2 . A theoretical discussion and derivation of Eqn. 6 above is provided in Appendix B. 
       2.2 Downwind Leg Phase 
       [0050]    In an embodiment, once the trajectory planning unit recognizes that the parafoil has descended to an altitude of z=A_switch, the trajectory planning unit switches phases from the loitering phase  503 _ 1  to the downwind leg phase  503 _ 2 . In so doing, the trajectory planning unit changes the desired path of the parafoil from the helical ABCD descent with a line that runs along the x axis positioned at the y axis location of +2R (notably, in situations where the parafoil is to make a right turn in the turn phase  503 _ 3  rather than a left turn, the line is positioned at the y axis location of −2R). As such, while in the downwind leg phase  503 _ 2 , the parafoil simply tracks to the correct y axis location and then, keeping the y axis location fixed as best as practicable, follows the +x axis while descending. 
         [0051]    During its descent along the x axis (during the downwind leg phase  503 _ 2 ), the trajectory planning unit continually updates the current winds calculates the position D_switch at which the parafoil should exit the downwind phase  503 _ 2  and enter the turn phase  503 _ 3 . Here, D_switch is the distance along the x axis between the parafoil and the target at which the parafoil should begin the turn phase. D_switch can be expressed as 
         [0000]    
       
         
           
             
               
                 
                   
                     D 
                     switch 
                   
                   = 
                   
                     - 
                     
                       
                         
                           
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                             ^ 
                           
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                                 ^ 
                               
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                         + 
                         
                           
                             
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                               ^ 
                             
                             h 
                             * 
                           
                            
                           
                             
                               V 
                               ^ 
                             
                             v 
                             * 
                           
                            
                           
                             
                               T 
                               turn 
                             
                             ( 
                             
                               
                                 
                                   V 
                                   ^ 
                                 
                                 h 
                                 * 
                               
                               - 
                               
                                 W 
                                 ^ 
                               
                             
                             ) 
                           
                         
                         + 
                         
                           
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                             ^ 
                           
                            
                           
                             
                               
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                         2 
                          
                         
                           
                             V 
                             ^ 
                           
                           h 
                           * 
                         
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                           * 
                         
                       
                     
                   
                 
               
               
                 
                   Eqn 
                   . 
                   
                       
                   
                    
                   7 
                 
               
             
           
         
       
     
         [0000]    Notably, the above expression for D_switch is a function of: 1) z, the parafoil&#39;s “current” altitude; and 2) x, the parafoil&#39;s “current” position along the x axis. 
         [0052]    Recalling the above definitions of D_switch and L, note that the parafoil should begin the turn phase when, substitution of the x and z parameters describing its current position into Eqn. 7 yields D_switch=L=parafoil&#39;s current x axis position. As such, as observed in  FIG. 8 , during the parafoil&#39;s descent along the downwind leg  503 _ 2 , the trajectory planning unit repeatedly calculates  801 ,  802  a value for D_switch as a function of its current position. The trajectory planning unit continues to estimate wind W (assuming constant V h  determined via Eqn.3) during the downwind phase and continuously substitutes updated values for them into Eqn. 7 along with the parafoil&#39;s positional information. Based on the known V h  (Eqn.3) and measured ground speed V, the current wind is determined as 
         [0000]        W=V−V   h   Eqn. 8
 
         [0053]    When the latest calculated value for D_switch is recognized as being sufficiently the same as its present distance (L) along the x axis from the target, the trajectory planning unit exits the downwind leg phase  503 _ 2  and enters the turn phase  503 _ 3 . Notably, the calculated value of D_switch can be negative indicating that the parafoil is to begin its turn before reaching the target&#39;s x axis location on the downwind leg. Appendix B also provides a derivation of Eqn. 7. 
       2.3 Turn Phase 
       [0054]    As discussed above, the decisions made by the trajectory planning unit are based on various measurements (such as forward speed V h  and wind magnitude W) and assumptions (such as a small magnitude for the crosswind component of the wind). Ideally there is no error in such measurements/assumptions, and, when the parafoil reaches the D_switch position and begins its turning phase, not only is the parafoil precisely where the trajectory planning algorithm “hoped” it would be, but also, the winds do not drastically change thereafter. Realistically, however, either or both of these conditions may not materialize. That is, for instance, when the trajectory planning unit decides to enter the turning phase, the parafoil may be “somewhere” in the xy plane other than its targeted location for the specific turn radius R and turn rate over time T turn  that the parafoil&#39;s trajectory was planned around. Moreover, the winds are constantly changing, which cannot possibly be accounted for during the turn itself. Finally, sudden updrafts and downdrafts may change the descent rate (relative to the ground) and therefore ruin a major estimate of how long the system has to stay in the air. 
         [0055]      FIG. 9   a  shows an example of the former problem (entering turn phase in other than ideal x,y position). Here, representative actual paths  901 - 905  of the parafoil in the xy plane are different than the ideal planned path  900 . These deviations from the ideal path  900  can result in unwanted error between the target location  910  and the corresponding actual landings  911 - 915 .  FIG. 9   b  shows an example of the later problem (sudden change in wind magnitude W). In this case, the wind has suddenly increased which effectively blows the parafoil short of its target in representative actual paths  921 - 925 . In each of the representative actual paths  901 - 905  and  921 - 925  of  FIGS. 9   a  and  9   b , the trajectory planning unit maps out a simplistic a 180 degree turn over radius R with constant angular rate over T turn . 
         [0056]      FIG. 9   c  shows an improved approach in which the trajectory planning unit calculates an optimum turn based on its current position  950  in the turn relative to the exit point  951  of the turn phase. Here, a two point boundary-value problem is solved by minimizing the “cost” of an arc  952  that spans from the parafoil&#39;s current x,y,ψ position  950  (where ψ is the parafoil&#39;s yaw angle=the angle at which the parafoil is headed or pointing along the x,y plane) to the x,y,ψ position  951  where the final approach is supposed to start. The “cost” of an arc is determined by N points  953  spaced along the arc in a certain manner and: i) determining the time spent by the parafoil traveling between the points, summing these times to represent the total time spent traversing the arc, and, taking a difference between this total time and T turn ; and, ii) determining the yaw rate (angular change of the pointing of the parafoil in the xy plane) beyond a maximum desired yaw rate from each point needed to steer the parafoil to its next point. 
         [0057]    Here, i) above penalizes deviation of the parafoil&#39;s total turn time from T turn ; and, ii) above penalizes an excessive yaw rate (“sharp turn”) needed to accomplish the turn. By formulating the cost as an optimization problem to minimize the cost, the respective positions for a set of N points along an arc between the parafoil&#39;s current position and the point where the final approach is to begin will be determined that correspond to an arc whose travel time is closest to T turn  and that does not exhibit excessive yaw rate. 
         [0058]    As such, as observed in  FIG. 9   c , the trajectory planning unit determines the position at which the final approach phase is to begin  951  (e.g., in terms of x,y,ψ), and determines its current position  952  (e.g., again in terms of x,y,ψ). With these input parameters, the trajectory planning unit then solves an optimization problem  954  to determine (e.g., x,y) positions of a set of N points  953  that define an arc  902  between the parafoil&#39;s current position  952  and the position  951  at which it is to end the turn phase. In one embodiment, the algorithm only optimizes a few parameters pertaining to the initial and final points of the turn. The optimal trajectory is determined analytically. This accelerates trajectory optimization so as to perform optimization about 100 times faster than in real time. This analytically defined inertial reference trajectory is passed to the control unit assuring that the parafoil actually follows the determined arc in flight. 
         [0059]    Notably, the trajectory planning unit is free to repeatedly calculate a new trajectory (and therefore a new set of N points) throughout the turn phase. For example, as observed in  FIG. 10 , upon entering the turn phase, the parafoil&#39;s trajectory planning unit calculates a first arc/set of N points  1000  that is used to define a first trajectory for the parafoil in the turn phase. Sometime later, for instance, because it is recognized that the parafoil&#39;s actual flight path  1002  has substantially deviated from the initial trajectory  1000 , the trajectory planning unit recalculates a second arc/set of N points  1003  that are used to define a second trajectory for the parafoil in the turn phase. In various alternative embodiment, the parafoil automatically (e.g., periodically) recalculates its trajectory in the turn phase (e.g., without reference to its deviation from an earlier trajectory), or, only calculates a new trajectory if the parafoil&#39;s flight path breaches its intended trajectory beyond some threshold. When calculating a new trajectory in the midst of the turn phase some modification is made to the optimization problem to address the fact that the parafoil is not at the beginning of the turn phase (e.g., by comparing the total time in a proposed arc against T turn −T spent , where T spent  corresponds to the time spent in the turn phase since the turn phase was initiated). 
         [0060]    While optimizing the final turn trajectory, the parafoil&#39;s current x,y,ψ position  950  can be determined from the control unit&#39;s sensors (e.g., GPS or INS). The (x,y,ψ) position  951  at which the parafoil is to exit the turn phase and enter final approach is defined as: 
         [0000]        FA =(( V   h   −W ) T   app ,0,−π)  Eqn. 9
 
         [0000]    The final turn maneuver is a pertinent part of the guidance algorithm. The parafoil may exit loitering earlier and it can be corrected by delaying the start of the final turn. However, once the final turn maneuver has started, varying the turn rate is the only way to make final corrections to intersect the top of the final approach slope. Varying the turn rate causes the parafoil to do either a steep or shallow turn, but precisely at the top of the final approach, i.e. at the point defined by Eqn.9 in exactly T turn  after entering the turn. Only at this final phase can three-dimentional wind disturbances be accounted for by constant reoptimization of the maneuver, i.e. by adjusting T turn  and producing a new yaw rate profile. 
         [0061]    Mathematically, the optimization problem can be expressed as 
         [0000]    
       
         
           
             
               
                 
                   J 
                   = 
                   
                     
                       
                         ( 
                         
                           
                             
                               ∑ 
                               
                                 j 
                                 = 
                                 1 
                               
                               
                                 N 
                                 - 
                                 1 
                               
                             
                              
                             
                                 
                             
                              
                             
                               Δ 
                                
                               
                                   
                               
                                
                               
                                 t 
                                 j 
                               
                             
                           
                           - 
                           
                             T 
                             turn 
                           
                         
                         ) 
                       
                       2 
                     
                     + 
                     
                       
                         k 
                         
                           Ψ 
                           . 
                         
                       
                        
                       Δ 
                     
                   
                 
               
               
                 
                   
                     Eqn 
                     . 
                     
                         
                     
                      
                     10 
                   
                    
                   a 
                 
               
             
             
               
                 
                   Δ 
                   = 
                   
                     
                       max 
                       j 
                     
                      
                     
                       
                         ( 
                         
                           0 
                           ; 
                           
                             
                                
                               
                                 
                                   Ψ 
                                   . 
                                 
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                             - 
                             
                               
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                                 . 
                               
                               max 
                             
                           
                         
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                       2 
                     
                   
                 
               
               
                 
                   
                     Eqn 
                     . 
                     
                         
                     
                      
                     10 
                   
                    
                   b 
                 
               
             
           
         
       
     
         [0000]    where: 1) Δt j  is the time spent by the parafoil traveling from the jth point to the jth+1 point among the arc&#39;s N points; 2) k ψ  is a scaling factor; 3) ψ j  is the change in yaw rate at a jth point among the arc&#39;s N points; and, 4) ψ max  is a desired maximum change in yaw rate. The analytical representation of a trajectory itself is given by 
         [0000]      τ f   P′   η (  τ )= a   1   η +2 a   2   η   τ +3 a   3   η   τ   2   +πb   1   η cos(π  τ )+2 πb   2   η cos(2π  τ )
 
         [0000]      τ f   P′   η (  τ )=2 a   2   η +6 a   3   η   τ −π 2   b   1   η sin(π  τ )−(2π) 2   b   2   η sin(2π  τ )  Eqn. 11
 
         [0000]    where  τ =τ/τ f ε[0;1] is a scaled abstract argument, a i   η  and b i   η  (η=1,2) are coefficients defined by the boundary conditions up to the second-order derivative at τ=0 and τ=τ f  (  τ =1), and τ f  is a varied parameter. Derivations for Eqns. 10a, 10b, 11 Δt j , ψ j , and ψ max  can be found in Appendix C. Appendix D provides additional information on the final arc optimization in the case where the wind profile is not constant including a major crosswind component of the wind. 
       2.4 Final Approach Phase 
       [0062]    Upon the parafoil deciding that it has reached the end of the turn phase (e.g., by recognizing T turn  has lapsed since the beginning of the turn phase), the trajectory planning unit produces an output that causes the parafoil to head in the −x direction and maintain that direction until the parafoil lands. 
       3.0 Improved Wind Models 
       [0063]    The above discussion assumed computation of D switch  (Eqn.7), and the final approach point (Eqn.9) based on a constant wind in the x-direction for the entirety of the parafoil&#39;s descent. The basic optimization algorithm presented in Appendix C was also based on this assumption, specifically, in one of two kinematic equations describing the horizontal position of the parafoil 
         [0000]        dx/dt=V   h  cos(ψ t )+ W   Eqn. 12
 
         [0000]    A more general optimization algorithm presented in Appendix D, however, removes these assumptions and deals with an arbitrary wind profile based on wind models discussed immediately below. 
         [0064]    Three possible improvements resulting in better assumptions about the wind&#39;s behavior from the current altitude all the way down to the ground can be made. A first improvement is based on the assumption that we have multiple parafoils deployed one after another to the same area. Then, a wind profile can be measured by the first system and transmitted to all following systems. A second improvement can be made if we have a ground station that constantly measures ground winds (in the x-direction) and transmits them to all descending parafoils (or a single parafoil) using an RF link or wireless network as described in Section 5. In this case, rather than assuming a constant wind, we can model the wind as varying linearly with altitude as shown in  FIG. 11  (improvement  1101 ). Finally, a third improvement  1102  can be used if no information about the ground winds is available at all. In this case, rather than using a constant wind speed profile, we will model wind magnitude as varying logarithmically with altitude. In any case a new wind profile will be used: i) during the downwind leg to constantly update D switch , i.e. an altitude to start the final turn maneuver (Eqn.7); ii) determine the final approach point given by Eqn.8; iii) determine the turn time T turn  of Eqn.5; and iv) determine the turn rate profile during the final turn to be at the final approach point at the prescribed time. 
         [0065]    In the case of the first improvement a three-dimensional altitude-dependent wind profile can be available 
         [0000]        W ( h )={ W   x ( h ), W   y ( h ), W   z ( h ))  Eqn. 13
 
         [0000]    Here h is the altitude above the ground while W x , W y  and W z  are the x-, y- and z-components of the wind. Depending on how this profile was measured it may lack some of the components, i.e. W z  component. Generally speaking, to compute D switch , final approach point and final turn rate profile only x component is needed. Therefore, the only change in Eqns. 7 and 8 will be to substitute the constant wind W with the x-component of so-called ballistic wind W B , which basically represents the average of winds from a specific altitude all way down to the ground, as explained in Appendix E. 
         [0066]    the case of the second (linear) wind model improvement  1101 , upon exiting the loitering phase the wind profile below the current altitude will be estimated as 
         [0000]        W ( h )= W   0 +( m   W ) h   Eqn. 14
 
         [0000]    where W 0  is the ground wind as measured at/near the ground (h=0) in the vicinity of the target and m W  is the rate at which the wind magnitude varies with altitude. In an embodiment, as observed in  FIG. 12 , the ground wind term W 0  is provided 1205 to the parafoil (e.g., by being manually or electronically communicated to the parafoil before it is dropped, or, in mid flight after it is dropped such as during the loitering phase). The parafoil&#39;s control unit also measures (updates) the wind magnitude  1206  at any altitude W h     —     high  as described above. In order to determine the current altitude, the parafoil&#39;s control unit receives a barometric pressure reading from the target  1201  and receives a reading from its own on board barometric altimeter  1202 . With these readings and an altitude reading from the on board GPS system  1203 , the control unit estimates its altitude  1204 . During the downwind leg (if the ground station is available) the value of W 0  may be constantly updated as well as an estimate of W h     —     high . The parafoil&#39;s control unit then calculates  1207  m W =(W h     —     high −W 0 )/(h_high) where h_high is the altitude at which the wind was measured to be W h     —     high . Once again, the ballistic wind value W B  (Appendix E) will be used in lieu of W in Eqns. 8 and 9. Other than these modifications, the flight path of the parafoil may be controlled as described in Section 2.0. 
         [0067]    In the case of the third (logarithmic) wind model improvement  1102 , starting from the downwind leg the wind is modeled as 
         [0000]        W ( h )=( m   W )ln( h/h   0 ), when h≧h 0 ( W ( h )=0, when 0 &lt;h&lt;h   0 )  Eqn. 15
 
         [0000]    Here, m W  is a coefficient that is defined by the onboard control unit based on the current wind measurements taken at several consequent altitudes using standard regression analysis. Parameter h 0 , a small number below 1 meter, is called the “aerodynamic roughness length” and defines the type of terrain around the landing zone and is set before flight. This model needs no prior knowledge of the ground winds. The value of m W  is constantly updated during the downwind leg to come up with more accurate estimates of D switch  and the final approach point. Again, the ballistic wind value W B  (Appendix E) is used in lieu of W in Eqns. 8 and 9. Other than these modifications, the flight path of the parafoil may be controlled as described in Section 2.0. Derivations of the coefficient m W  in Eqn. 15 along with analytical dependences for Eqn.8 (which may be used even without computing the ballistic wind) is provided in Appendix F. 
       4.0 Moving Target 
       [0068]    The discussions above have been directed to an environment where the target is assumed to be a fixed location on the ground. Other applications are envisioned where it may be desirable to land the parafoil on a moving target such as a ship at sea.  FIGS. 13   a  and  13   b  pertain to an embodiment where the target is moving in the −x direction (against the wind) and the parafoil is dropped upwind of the moving target at point DP. The target can therefore be stated in two ways which are equated. The first way to define the target is by the difference in its position along the x axis from the moment the parafoil leaves the loitering phase to the moment the parafoil lands. 
         [0069]    This value can be expressed as x T −V T ((A_switch)/V V ) where V T  is the velocity of the target and A_switch)/V V  is the amount of time expended from the moment the loitering phase is ended to the moment the parafoil lands. Another way to define the target is simply from its earlier definition L as the distance from the parafoil to the target along the x axis. Equating the two expressions, which essentially states that the upon the parafoil exiting the loitering phase the parafoil must move a net distance L along the x axis to land on a moving target that will be at position x T −V T ((A_switch)/V V ) from its location x T  when the loitering phase was exited yields: 
         [0000]    
       
         
           
             
               
                 
                   L 
                   = 
                   
                     
                       x 
                       T 
                     
                     - 
                     
                       
                         
                           V 
                           T 
                         
                         
                           V 
                           V 
                         
                       
                        
                       
                         A 
                         switch 
                       
                     
                   
                 
               
               
                 
                   Eqn 
                   . 
                   
                       
                   
                    
                   16 
                 
               
             
           
         
       
     
         [0000]    The above Eqn for L can be substituted into Eqn. 6 above and solved for A_switch as 
         [0000]    
       
         
           
             
               
                 
                   
                     A 
                     switch 
                   
                   = 
                   
                     
                       V 
                       v 
                     
                      
                     
                       
                         
                           x 
                           T 
                         
                         + 
                         
                           
                             V 
                             h 
                           
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                             ( 
                             
                               
                                 T 
                                 turn 
                               
                               + 
                               
                                 2 
                                  
                                 
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                                   app 
                                   des 
                                 
                               
                             
                             ) 
                           
                         
                       
                       
                         W 
                         - 
                         
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                           h 
                         
                         + 
                         
                           V 
                           T 
                         
                       
                     
                   
                 
               
               
                 
                   Eqn 
                   . 
                   
                       
                   
                    
                   17 
                 
               
             
           
         
       
     
         [0000]    which expresses the altitude that the parafoil can exit its loitering phase at its location along the x axis within the loitering phase. With the new value of A_switch, the operation of the parafoil may be controlled as described above in Section 2.0. Introduction of improved wind models such as those discussed above with respect to Section 3.0 will yield further changes to the A_switch calculation. 
         [0070]    Another enhancement that may be necessary to accurately land a parafoil on a moving target is the specific location of the landing area on the target itself. For example, referring to  FIG. 14   a , if the target is a moving ship  1400  and its reported position is presumed to be some location  1401  in the middle of the ship at sea level, some pre-processing may be necessary to more accurately define the actual landing area on the ship. In the example of  FIG. 14   a , the appropriate landing area for the parafoil is a rear deck  1404  that is above sea level at the ship&#39;s stern  1405 . As such, the “true” landing area target  1406  needs to be offset from the position of the ship  1401  as it is reported to the parafoil&#39;s guidance system. Moreover, different ships may have different landing areas as a function of the ship&#39;s design. For example, a first type of ship may have its appropriate landing on a read deck as observed in  FIG. 14   a  whereas other ships may have its appropriate landing area on a forward deck (toward the bow of the ship) or on a deck in the middle of the ship but more toward the port or starboard sides. 
         [0071]    A possible benefit of the guidance algorithm described in Section 2.0 is that it establishes the reference trajectory in the inertial reference frame. In the case of the moving target (ship, submarine, etc.) this trajectory is tied to the moving target. Therefore, while planning the trajectory it is possible to construct the trajectory so that the parafoil avoids, e.g., a superstructure on the ship&#39;s deck. No other known guidance algorithm has this feature. 
         [0072]    In an embodiment, as shown in  FIG. 14   b , the parafoil&#39;s control unit includes a data store that models the different kinds of ships that the parafoil may be asked to land on, where, each ship&#39;s model effects the necessary modification to the actual target based on the type of ship and also affects the calculations accordingly. In operation, a ship&#39;s position, velocity and type are entered or communicated to the parafoil (e.g., before or after it is dropped). The parafoil&#39;s trajectory planning unit not only uses the ship&#39;s position and velocity to calculate the target but also modifies the equations appropriately in view of the ships&#39; type to more accurately define the target in a manner that is customized to the particular ship. 
         [0073]    In the case of  FIG. 14   a , for example, the fact that the rear deck is raised means that the parafoil will have to exit the loitering phase sooner to keep the guidance calculations consistent. As such, Eqn. 17 would be modified by the trajectory planning unit to be A_switch=[ . . . ]+z ship     —     x  where z ship     —     x  corresponds to the vertical offset between the precise location where the ship&#39;s recognized position x T  at loiter exit is and the height of the rear deck relative to that position. Similarly, Eqn. 16 would be modified by the trajectory planning unit as L=(x T −x ship )−V T ((A_switch)/V V ) to adjust for the fact that the rear deck is behind the ship&#39;s recognized position. Lateral changes along the y axis could either affect the loitering position of the parafoil or the radius of the turn R. 
         [0074]    The guidance algorithm features the optimized final turn which allows adjusting the actual landing time. In this case the heave motion of the ship can also be taken into account. This motion can be estimated by the parafoil&#39;s control unit based on the altitude above the sea data at the intended touchdown point. Such data can be uplinked to the parafoil using the ground weather station or a GPS unit using network connectivity as described in Section 5. 
       5.0 Applications of Wireless Network Connectivity to Parafoil Control Unit 
       [0075]    Recall from the discussion of  FIG. 3   a  that the control unit may include various wireless interface circuitry, such as first wireless network interface circuitry  317  that is capable of communicating (including transmission and/or reception) over a local carrier&#39;s network and/or second wireless network interface circuitry  320  that is capable of communicating over a proprietary network. In various embodiments, the wireless interface circuitry  317 ,  320  is used to communicate pertinent information to the parafoil&#39;s control unit after the parafoil has been dropped from the airborne vehicle. Examples include, for instance, uploading the ground wind magnitude or the entire winds profile versus altitude along with the ground barometric pressure (to build a wind model as described in Section 3.0), uploading constantly changing target position (such as in the case of a moving ship), including its vertical elevation (to account for a ship&#39;s heave motion as described in Section 4.0), a change in a new stationary target location or the new desired landing direction, not necessarily aligned with the ground winds. 
         [0076]      FIG. 15  shows an exemplary information systems (IS) infrastructure for transferring such information to the parafoil. As observed in  FIG. 15  an airborne parafoil  1501  is within range of a local carrier&#39;s wireless network  1502  such as a tactical cellular GSM network. The local carrier&#39;s wireless network  1502  includes a gateway to a wide area network (WAN)  1503  such as the Internet. A voice recognition server  1504  and a situational awareness (SA) server  1505  are each coupled to the WAN  1503  (notably the recognition server  1504  and situational awareness server  1505  may be integrated into a single endpoint). 
         [0077]    According to one embodiment, a command to be given to the airborne parafoil  1501  is verbally spoken, for instance, by an individual on the ground in the vicinity of the parafoil&#39;s target  1506  into a handheld and/or portable device  1507  such as a cell phone or smartphone. The verbal command may be any of (but not necessarily limited to) a command to change the target and/or a command to update the ground wind information (e.g., a command to enter a ground wind profile, a command to enter a change in ground wind magnitude and/or ground wind direction, or, a command to change the target to a new location). The verbal command is communicated via a network connection  1508  between the device  1507  and the voice recognition server  1504 . 
         [0078]    The voice recognition server  1504  (e.g., by way of voice recognition software and/or hardware) processes the verbal command and converts the verbal command information into a digital format that is understandable to a computing system. For example if the verbal command was to update the ground wind speed and/or direction, the voice recognition server might create an XML based message or other body of information  1508  in some kind of syntax that is understandable to a computing system. The information  1508  is then sent by way of a network connection  1509  from the voice recognition server  1504  to the situational awareness server  1505 . The situational awareness server  1505  then translates the digitally formatted command  1508  into a packet  1510  that is sent  1550  to the airborne parafoil  1501  over the local carrier&#39;s wireless network  1502 . 
         [0079]    In an alternate embodiment, rather than a verbal command being spoken into the device  1507 , the command is instead entered by way of a keyboard or other user interface of the portable device  1507  and sent  1511  by way of a packet to the situational awareness server  1505  or the parafoil directly  1512 . In the former case  1511  where the packet is sent to the situation awareness server first, the situational server sends a packet  1510  having the entered command to the airborne parafoil. In an embodiment, the portable device  1507  may be specialized equipment. For example, the portable device  1507  may be a portable weather station or wind measurement equipment (such as the kind made by Kestrel, Inc. of Sylvan Lake, Mich.) having its own wireless network interface (and/or integrated cell phone and/or smartphone circuitry). In this case, with the same portable device  1507 , wind information can be measured, packetized and sent  1511  to either the situational awareness server  1505  (for subsequent delivery to the airborne parafoil  1501 ) or to the airborne parafoil directly  1512 . 
         [0080]    In even further alternate embodiments, a verbal or entered command is made from a command center or other computing system  1551  that is remote from the parafoil&#39;s drop zone. For instance, a command  1514  to change the parafoil&#39;s target may be made, while the parafoil is in flight, from a computing system  1515  that is coupled to the WAN  1503  many miles away from the parafoil&#39;s drop zone. The WAN may be commercial, proprietary, public or some combination thereof and may even have global reach capability. The command may be sent to the parafoil directly  1514 , or, to a situational awareness server beforehand. 
         [0081]    The parafoil may further be configured to transmit into the wireless network  1502  any/all of its measurement information, such as the wind&#39;s magnitude at higher altitudes, its ground speed measurements and/or its positional measurements for analysis and/or observation at some endpoint. For instance, according to one embodiment, a plurality of parafoil&#39;s are dropped simultaneously over a common area, and, as the parafoils descend (e.g., in a loitering phase), they transmit their locations (and/or ABCD loitering parameters) to a remote command center  1515  that tracks all of the parafoils in flight in real time. An individual or application software then decides, while the parafoils are descending, what their respective targets are. Respective packets are then sent to each of the airborne parafoils informing them of their specific target. 
         [0082]    In another application of a parafoil&#39;s ability to transmit measured information into a wireless network, according to one approach a first parafoil is dropped prior to one or more subsequent parafoils. The purpose of the first parafoil is to make wind measurements during its descent and send the measurement results (and/or a wind profile) “up” to the second set of one or more subsequently dropped parafoils. Here, the parafoil can transmit the wind information in the form of one or more packets into the local carrier&#39;s network  1502  which redirects (or multicasts or broadcasts) the packet(s) back to each subsequent parafoil. Alternatively, a private wireless link or network can be established between the descending parafoils and the wind information transmitted up to them through the proprietary wireless link. 
         [0083]    To further that point although much of the previous examples discussed the transmission of wireless information to/from an airborne parafoil through a local carrier&#39;s wireless network, the same core schemes may be implemented with a proprietary wireless network or link. For example, the portable device  1507  in the vicinity of the target may transmit ground wind information up to a descending parafoil through a proprietary wireless link that is established between the device  1507  and the descending parafoil. Likewise, any packets that are sent to an airborne parafoil may traverse only a proprietary network without any public traffic (up to an including the wireless network) or some combination of proprietary and public traffic networks may be utilized. 
         [0084]    For any of the embodiments discussed above, note that a parafoil may wirelessly transmit its location, altitude and/or high altitude wind information into the network and ultimately to a computing system which executes the trajectory planning unit algorithms (e.g., with other accumulated information such as ground winds, velocity of moving target, etc.). The computing system then sends an updated trajectory plan through the network and wirelessly to the descending parafoil which implements the newly received trajectory plan. 
         [0085]      FIG. 16  shows another approach in which a group of parafoils  1601  are simultaneously descending to establish a temporary wireless network  1602 , for example, between the access point  1603  of an established network  1604  and another remote location  1605  which has no connection to the established network  1604 . For example, if a group of workers or soldiers are at a remote location  1605  (e.g., separated by a mountain range) and a need arises to communicate to them over the established network  1604 , the parafoils  1601  are dropped so as to descend (e.g., in a permanent loitering phase) along an imaginary line  1606  that connects the access point  1603  to the remote location  1605 . 
         [0086]    Apart from wireless network interface circuitry, each of the parafoils  1601  further includes wireless network routing and/or switching software/hardware to route packets. As such, an airborne wireless network is created with each of the parafoils acting as a node of the network. A packet sent from the access point  1603  to the remote location  1605  is relayed by way of nodal hops from parafoil to parafoil until it reaches the remote location  1605 . Likewise, a packet sent from the remote location  1605  is relayed by way of nodal hops from parafoil to parafoil in the reverse direction until it reaches the access point  1603 . The parafoils  1601  may include nearest neighbor or other awareness technology that permit them to periodically update configure (e.g., by way of periodic updates) their routing tables mid flight (e.g., forming a so-called mesh network), or, the nodal configuration and routing tables may be predetermined ahead of time. The drop pattern and/or guidance systems may be used to orient each of the parafoils in its proper nodal position. 
         [0087]    Whether the individuals at the remote location  1605  are aware of the establishment of the temporary network in their direction may depend on the circumstances. For instance, if a verbal communication needs to take place between individuals at some command center  1607  coupled to the established network  1604  and the individuals at the remote location  1605 , the parafoils  1601  may be equipped with transmission circuitry that transmits a signal to equipment held by the personnel at the remote location  1605  that triggers some kind of alarm that an imminent verbal communication is being arranged. By contrast, if only an electronic message is to be delivered to the remote personnel, such as an email, no alarm need be triggered ahead of time. 
         [0088]    The above discussion spoke of the network established by the parafoils as being temporary in the sense that the network is torn down or otherwise made unworkable prior to or approximately at the time of the landing of the parafoils. A temporary network is useful where, for instance, the safety or security of the remote team  1605  is comprised by the presence of the network. For example, continued transmissions by the parafoil/nodes might lead to the unwanted discovery of the network and the remote individuals. Other circumstances may arise where a permanent network is desired. In this case, the parafoil/nodes can continue to operate to implement a wireless network long after the parafoils have landed. 
         [0089]    Lastly, that  FIG. 16  is simplistic in that only a single line  1606  is drawn to connect to a single access node  1603  to a single emote location  1605 . In actuality the “line” may take any shape suitable to connect an access point to a remote location (e.g., curved, triangular, etc.). Moreover, the parafoil implemented network may reach more than one access point and/or more than one remote location by arranging multiple lines/branches as appropriate. Conceivably, a cental core of parafoils may form a short-term network backbone and branches of parafoils extended along lines stemming from the backbone/core may reach out to various established network access points and/or remote locations. 
         [0090]      FIG. 17  shows an embodiment of a computing system (e.g., a computer). The exemplary computing system of  FIG. 17  includes: 1) one or more processing cores  1701  that may be designed to include two and three register scalar integer and vector instruction execution; 2) a memory control hub (MCH)  1702 ; 3) a system memory  1703  (of which different types exist such as DDR RAM, EDO RAM, etc.); 4) a cache  1704 ; 5) an I/O control hub (ICH)  1705 ; 6) a graphics processor  1706 ; 7) a display/screen  1707  (of which different types exist such as Cathode Ray Tube (CRT), flat panel, Thin Film Transistor (TFT), Liquid Crystal Display (LCD), DPL, etc.) one or more I/O devices  1708 . 
         [0091]    The one or more processing cores  1701  execute instructions in order to perform whatever software routines the computing system implements. The instructions frequently involve some sort of operation performed upon data. Both data and instructions are stored in system memory  1703  and cache  1704 . Cache  1704  is typically designed to have shorter latency times than system memory  1703 . For example, cache  1704  might be integrated onto the same silicon chip(s) as the processor(s) and/or constructed with faster SRAM cells whilst system memory  1703  might be constructed with slower DRAM cells. By tending to store more frequently used instructions and data in the cache  1704  as opposed to the system memory  1703 , the overall performance efficiency of the computing system improves. 
         [0092]    System memory  1703  is deliberately made available to other components within the computing system. For example, the data received from various interfaces to the computing system (e.g., keyboard and mouse, printer port, LAN port, modem port, etc.) or retrieved from an internal storage element of the computing system (e.g., hard disk drive) are often temporarily queued into system memory  1703  prior to their being operated upon by the one or more processor(s)  1701  in the implementation of a software program. Similarly, data that a software program determines should be sent from the computing system to an outside entity through one of the computing system interfaces, or stored into an internal storage element, is often temporarily queued in system memory  1703  prior to its being transmitted or stored. 
         [0093]    The ICH  1705  is responsible for ensuring that such data is properly passed between the system memory  1703  and its appropriate corresponding computing system interface (and internal storage device if the computing system is so designed). The MCH  1702  is responsible for managing the various contending requests for system memory  1703  access amongst the processor(s)  1701 , interfaces and internal storage elements that may proximately arise in time with respect to one another. 
         [0094]    One or more I/O devices  1708  are also implemented in a typical computing system. I/O devices generally are responsible for transferring data to and/or from the computing system (e.g., a networking adapter); or, for large scale non-volatile storage within the computing system (e.g., hard disk drive or semiconductor non volatile storage device that is the main store for the system&#39;s program code when the system is powered off). ICH  1705  has bi-directional point-to-point links between itself and the observed I/O devices  1708 . 
         [0095]    Processes taught by the discussion above may be performed with program code such as machine-executable instructions that cause a machine that executes these instructions to perform certain functions. In this context, a “machine” may be a machine that converts intermediate form (or “abstract”) instructions into processor specific instructions (e.g., an abstract execution environment such as a “virtual machine” (e.g., a Java Virtual Machine), an interpreter, a Common Language Runtime, a high-level language virtual machine, etc.)), and/or, electronic circuitry disposed on a semiconductor chip (e.g., “logic circuitry” implemented with transistors) designed to execute instructions such as a general-purpose processor and/or a special-purpose processor. Processes taught by the discussion above may also be performed by (in the alternative to a machine or in combination with a machine) electronic circuitry designed to perform the processes (or a portion thereof) without the execution of program code. 
         [0096]    It is believed that processes taught by the discussion above may also be described in source level program code in various object-orientated or non-object-orientated computer programming languages (e.g., Java, C#, VB, Python, C, C++, J#, APL, Cobol, Fortran, Pascal, Perl, etc.) supported by various software development frameworks (e.g., Microsoft Corporation&#39;s .NET, Mono, Java, Oracle Corporation&#39;s Fusion, etc.). The source level program code may be converted into an intermediate form of program code (such as Java byte code, Microsoft Intermediate Language, etc.) that is understandable to an abstract execution environment (e.g., a Java Virtual Machine, a Common Language Runtime, a high-level language virtual machine, an interpreter, etc.) or may be compiled directly into object code. 
         [0097]    According to various approaches the abstract execution environment may convert the intermediate form program code into processor specific code by, 1) compiling the intermediate form program code (e.g., at run-time (e.g., a JIT compiler)), 2) interpreting the intermediate form program code, or 3) a combination of compiling the intermediate form program code at run-time and interpreting the intermediate form program code. Abstract execution environments may run on various operating systems (such as UNIX, LINUX, Microsoft operating systems including the Windows family, Apple Computers operating systems including MacOS X, Sun/Solaris, OS/2, Novell, etc.).\ 
         [0098]    An article of manufacture may be used to store program code. An article of manufacture that stores program code may be embodied as, but is not limited to, one or more memories (e.g., one or more flash memories, random access memories (static, dynamic or other)), optical disks, CD-ROMs, DVD ROMs, EPROMs, EEPROMs, magnetic or optical cards or other type of machine-readable media suitable for storing electronic instructions. Program code may also be downloaded from a remote computer (e.g., a server) to a requesting computer (e.g., a client) by way of data signals embodied in a propagation medium (e.g., via a communication link (e.g., a network connection)). 
         [0099]    In the foregoing specification, the invention has been described with reference to specific exemplary embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention as set forth in the appended claims. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.