Abstract:
A method and system for autonomous two-way RF communication between a launch vehicle and at least one receiving or tracking station. Detection circuitry continuously determines the identity of the optimum receiving or tracking station (ground, sea, airborne, or satellite) and selects the best launch vehicle transmission antenna to close the RF telemetry link. The method and system is designed to simultaneously transmit and receive RF signals. The antenna system includes a telemetry transmission link and an antenna selection link. Antenna selection link signals received by each antenna element on the launch vehicle are provided via RF couplers to a receiver for signal strength and modulation signal detection. The telemetry transmission link communicates with a receiving or tracking station by using a transmitter to drive one of two or more switched antennas mounted on the surface of the launch vehicle having the current higher signal strength.

Description:
FIELD OF THE INVENTION 
     This invention generally relates to a method and system for radio frequency communication, and more particularly, to a method and system for autonomous two-way radio frequency communication between at least one first station and a second station. 
     BACKGROUND OF THE INVENTION 
     In the launch vehicle industry, radio frequency (RF) telemetry signals are transmitted from the launch vehicle to one or more ground, sea, air, or space-based receiving or tracking stations to thereby indicate data on the performance, health, and status of various monitored parameters of the launch vehicle to launch personnel. In this regard, closure of the one-way RF telemetry link between the launch vehicle and the receiving or tracking station is typically accomplished by using brute-force methods. Such methods include high power transmitters and omni-directional antennas on the launch vehicle, pre-launch software coding to control the launch vehicle antenna steering and transmit antenna selection during the mission, and low telemetry data modulation rates. 
     For example, an omni-antenna provides line-of-sight coverage over a broad range of angles off of the antenna bore sight. An omni-directional design allows a combined two antenna arrangement to cover most of 360° laterally around a launch vehicle. However, the peak gain performance of omni-antennas is very low, typically around 5 db, and provides minimum coverage towards the nose and tail of a launch vehicle. In addition, the design assumes a minimum gain over 95% of the surface of the transmit antenna radiation sphere. This gain number, typically on the order of −13 db for S-Band frequencies, is then used to predict the communication link margin performance and drive the requirements of the other telemetry system components. An over-designed method such as this can drive overall cost of the system by requiring higher power transmitters and reductions in allowable data transmission rates. This lower antenna gain approach may result in earlier loss of the telemetry signal from the launch vehicle in the case of a launch anomaly or a non-nominal trajectory. 
     One major consideration in the efforts to maintain a communication link is that the pointing angle between the launch vehicle transmit antennas and the tracking station receive antennas varies continuously throughout the mission. For example, in the launch vehicle industry, most RF signals require line-of-sight geometry between the tracking station receive antenna and the launch vehicle transmit antenna to process the RF signal. However, ensuring that line-of-sight geometry is maintained throughout the mission is extremely difficult, especially during anomalous or non-predicted launch vehicle trajectories and orientations. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a method and system for autonomous two-way radio frequency communication. 
     It is another object of the present invention to provide a method and system for autonomous two-way radio frequency communication between at least one first station, such as a tracking station, and a second station, such as a launch vehicle. 
     It is a further object of the present invention to provide a method and system for autonomous two-way radio frequency communication that minimizes pre-flight analysis, pre-planning, and software coding efforts. 
     It is still another object of the present invention to provide a method and system for autonomous two-way radio frequency communication that maximizes telemetry data reception by a tracking station for the maximum time possible during a launch vehicle mission. 
     It is yet another object of the present invention to provide a method and system for autonomous two-way radio frequency communication that can transmit more telemetry data at higher transmission rates over existing systems. 
     The present invention achieves one or more of these objects by providing a method and system for autonomous two-way radio frequency communication between at least one receiving or tracking station (e.g., a first station) and a launch vehicle (e.g., a second station). Generally, in one aspect of the present invention, the two-way radio frequency communication system includes the second station which may receive unique RF signals in at least first and second antennas, or, in three, four, five, six, or any number of additional antennas (or antenna elements) that are positioned on the second station. A processor determines which of the first and second antennas, and any additional antennas, has the higher signal strength. A transmitter, located on the second station, is adapted to transmit telemetry signals over the antenna that received the unique RF signal that had the higher signal strength. 
     The telemetry signals contain data on monitored parameters of the launch vehicle. Once transmitted by the transmitter via the connected antenna, the telemetry signals may be received in the one or more first stations that transmitted the unique RF signals to the second station. Throughout the launch vehicle mission the transmitter output signal is repeatedly switched to the particular antenna that currently is receiving the unique RF signal having the higher signal strength, which is at that moment the best RF communication link between the first station and the second station. Thus, the peak gain of that particular launch vehicle antenna at that moment is more aligned with the peak gain of the first station receiving antenna. Selecting the antenna with the higher signal strength as the transmit antenna helps ensure that the telemetry signals transmitted are more likely to be received in the first station for evaluation by launch personnel. 
     In another aspect of the two-way radio frequency communication system, the system includes the second station which may receive unique RF signals in at least a first receive antenna, or, in two, three, four, five, six, or any number of additional receive antennas that are positioned on the second station. The receive antennas in this embodiment are adapted to scan for and receive the unique RF signals transmitted from the one or more first stations. A phased array antenna would be an example of such an antenna. 
     A processor determines which of the receive phased array antennas has the best quality signal vector, which is an indication of the best RF communication link between the first station and the second station. A transmitter located on the second station is adapted to radiate telemetry signals over at least a first transmit antenna to the first station along a path parallel to the best quality signal vector. Such a first transmit antenna may also be a phased array antenna. There may be two, three, four, or any number of transmit phased array antennas located on the second station. Transmitting telemetry data along a path parallel to the best quality signal vector helps ensure that the telemetry signals transmitted by the transmitter via the connected transmit phased array antenna are more likely to be received in the first station for evaluation by launch personnel. 
     Generally, in one aspect of the two-way radio frequency communication method of the present invention, the method includes the steps of transmitting a unique RF signal from a first station, receiving the unique RF signal with at least first and second antennas on the second station, determining a first signal strength for the unique RF signal received in the first antenna, determining a second signal strength for the unique RF signal received in the second antenna, determining which of the first and second signal strengths is higher, connecting a transmitter on the second station to whichever first or second antenna received the unique RF signal with the higher signal strength, and transmitting with the transmitter a first telemetry signal containing monitored parameters of the second station over the connected first or second antenna. 
     For purposes of facilitating communication, and otherwise avoiding loss of the RF telemetry link, in one embodiment of the method of the present invention, the radio frequency signals are transmitted from at least one ground station and at least one non-ground station. Telemetry signals transmitted from the launch vehicle may be received in either or both of the at least one ground station or the at least one non-ground station. Thus, as the second station moves along its mission path in relationship to the at least one ground station and the at least one non-ground station, the method of the present invention continually selects the antenna on the second station for transmitting telemetry data that has the best RF communication link to one or the other of the at least one ground station or the at least one non-ground station. 
     In another embodiment of the method of the present invention, the step of connecting the transmitter to the first or second antenna includes an optimizing step of applying a smoothing algorithm, which is executed within a processor. The smoothing algorithm inhibits switching between the first and second antennas if the change in the higher signal strength between the first and second antennas is less than a selected absolute change amount. This inhibits rapid and unnecessary switching between antennas. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a notional diagram of the two-way transmission links between a launch vehicle having a two-omni-antenna-element transmit coverage pattern and various receiving or tracking stations of the system of the present invention. 
     FIG. 2 shows a notional diagram of a launch vehicle cycling through a six-antenna-element narrow-beam transmit coverage pattern of the method and system of the present invention. 
     FIG. 3 shows a block diagram of the system for autonomous two-way radio frequency communication of the present invention for the launch vehicle of FIG.  2 . 
     FIGS. 4A and 4B show a flow chart of an embodiment of the method for autonomous two-way radio frequency communication of the present invention for the launch vehicle of FIG. 2 that utilizes modulated RF signals. 
     FIGS. 5A and 5B show a flow chart of another embodiment of the method for autonomous two-way radio frequency communication of the present invention for the launch vehicle of FIG. 2 that utilizes modulated RF signals. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 shows a notional diagram of the two-way transmission links between a launch vehicle having a two-omni-antenna-element transmit coverage pattern and various receiving or tracking stations of the system of the present invention. One skilled in the art will recognize that the launch vehicle could have more than two antenna elements, and the antenna elements may also be narrow-beam. Narrow-beam antennas are designed to operate over a particular beam width such as a ±30° cone as shown in FIG.  2 . Over this beam width the antenna is designed to radiate RF with a minimum gain of −10 db. The beam width of the antenna is inversely proportional to the antenna gain, i.e., the wider the beam width, the lower the peak gain of the antenna beam. In order for the RF communication system to operate with the highest efficiency, the peak gain region of the transmit narrow-beam antenna element should be line-of-sight with the receive antenna peak gain. 
     Referring now to FIG. 1, launch vehicle  100  is shown in three phases of flight: launch phase  102 , ascent phase  104 , and orbit phase  106  in relation to ground stations  108  and  110  and non-ground stations  112  and  114 . Ground stations  108  and  110  may be stationary within a building or other fixed structure, or movable on a truck, on a rail car, or a ship at sea. Non-ground stations  112  and  114  may be satellites moving in relation to the ground or in geosynchronous orbit. Non-ground stations  112  and  114  may also be airborne stations housed in airplanes in flight. In FIG. 1, ground stations  108  and  110  are stationary within buildings, and non-ground stations  112  and  114  are satellites in geosynchronous orbit. One skilled in the art will recognize that more ground and non-ground stations may be utilized, but only ground stations  108  and  110 , and non-ground stations  112  and  114 , are shown in FIG. 1 for simplicity. 
     Arrows  116  represent the high gain signal from the 0 db part of the omni-antenna-element transmit coverage pattern. Arrows  118  represent the medium gain signal from the −10 db part of the omni-antenna-element transmit coverage pattern. Arrows  116  represent the low gain signal from the −20 db part of the omni-antenna-element transmit coverage pattern. 
     The present invention employs two-way radio frequency communication between launch vehicle  100  and ground stations  108  and  110  and non-ground stations  112  and  114 . The system may be tuned for any frequency but operation is assumed to be at typical telemetry range frequencies from 2.2-2.3 GHz. Whenever launch vehicle  100  is in a position to transmit to any of non-ground stations  112  and  114  and/or ground stations  108  and  110 , it is able to receive a signal from any of non-ground stations  112  and  114  and/or ground stations  108  and  110  as well. Part of the two-way radio frequency communication system is used as a verification link. Non-ground stations  112  and  114  and/or ground stations  108  and  110  are tasked with transmitting a unique RF signal that is identified in launch vehicle  100 . 
     In launch phase  102 , two-way communication is represented by arrow pairs  122 ,  124 , and  126 . Non-ground stations  112  and  114  and ground stations  108  and  110  transmit the unique RF signal to be identified in launch vehicle  100 . Launch vehicle  100  transmits telemetry data to be received by non-ground stations  112  and/or  114 , and/or ground stations  108  and/or  110 . 
     Arrow pair  122  shows two-way communication between launch vehicle  100  and non-ground station  114 . Arrow pair  124  shows two-way communication between launch vehicle  100  and ground station  110 . Arrow pair  126  shows two-way communication between launch vehicle  100  and ground station  108 . No operative RF communication link is possible between launch vehicle  100  and non-ground station  112  due to their orientation in relation to each other in launch phase  102 . 
     In ascent phase  104 , two-way communication is represented by arrow pairs  128 ,  130 ,  132 , and  134 . Arrow pair  128  shows two-way communication between launch vehicle  100  and non-ground station  112 . Arrow pair  130  shows two-way communication between launch vehicle  100  and non-ground station  114 . Arrow pair  132  shows two-way communication between launch vehicle  100  and ground station  110 . Arrow pair  134  shows two-way communication between launch vehicle  100  and ground station  108 . 
     In orbit phase  106 , two-way communication is represented by arrow pairs  136 ,  138 , and  140 . Arrow pair  136  shows two-way communication between launch vehicle  100  and non-ground station  114 . Arrow pair  138  shows two-way communication between launch vehicle  100  and ground station  108 . Arrow pair  140  shows two-way communication between launch vehicle  100  and ground station  110 . No operative RF communication link is possible between launch vehicle  100  and non-ground station  112  due to their orientation in relation to each other in orbit phase  106 . 
     FIG. 2 shows a notional diagram of a launch vehicle cycling through a six-antenna-element narrow-beam transmit coverage pattern of the method and system of the present invention. Referring now to FIG. 2, at any given point in time during the mission, launch vehicle  200  may be receiving unique RF signals from one or more ground stations and/or one or more non-ground stations. During a launch and orbit operation, each telemetry receiving or tracking station, ground or non-ground, is configured to transmit a unique verification RF signal. Various techniques may be employed to transmit the unique RF signal, such as frequency hopping, or modulating the RF signal with a specific handshake bit stream. One skilled in the art will recognize that many other suitable techniques could also be employed to transmit the unique RF signal. 
     In this embodiment, launch vehicle  200  has a six-antenna-element narrow-beam transmit coverage pattern represented by transmit coverage patterns  202 ,  204 ,  206 ,  208 ,  210 , and  212 . The method and system for autonomous two-way radio frequency communication of the present invention constantly determines which of the six antenna elements is receiving the strongest RF signal. This continuous monitoring of received signal strength from all antenna elements combined with identifying the unique RF signal is used to identify the optimal antenna element to transmit telemetry signals back to the receiving ground or non-ground station. 
     For example, at any particular discrete period of time during the mission, launch vehicle  200  may be receiving modulated RF signals having the correct handshake bit stream over antenna elements associated with transmit coverage patterns  204 ,  206 , and  208 . If the modulated RF signal received by the antenna element associated with transmit coverage pattern  206  over the discrete period of time is the strongest, then this antenna element will be selected by the method and system of the present invention to transmit the telemetry data from launch vehicle  200 . At a next particular discrete period of time during the mission, launch vehicle  200  may be receiving modulated RF signals having the correct handshake bit stream over antenna elements associated with transmit coverage patterns  206 ,  208 , and  210 . If the modulated RF signal received by the antenna element associated with transmit coverage pattern  208  over the discrete period of time is the strongest, then this antenna element will be selected by the method and system of the present invention to transmit the telemetry data from launch vehicle  200 . 
     FIG. 3 shows a block diagram of the system for autonomous two-way radio frequency communication of the present invention for the launch vehicle of FIG.  2 . One skilled in the art will recognize that the present invention requires at least two antenna elements located on the launch vehicle. More than two antenna elements may provide enhanced performance. Six antenna elements are shown in FIG. 3 as one embodiment of the invention. Referring now to FIG. 3, antenna system  300  is contained within launch vehicle  200  of FIG.  2 . Antenna elements  302 ,  304 ,  306 ,  308 ,  310 , and  312  are adapted such that when properly placed on launch vehicle  200  they yield the corresponding transmit coverage patterns  202 ,  204 ,  206 ,  208 ,  210 , and  212  shown in FIG.  2 . RF couplers  316  located on the cables  314  of antenna elements  302 ,  304 ,  306 ,  308 ,  310 , and  312  couple the signals received by each of the antenna elements and route the signals over cables  318  through receiver switch  320  to receiver  322 . Receiver switch  320  may be an electro-mechanical switch that has a throw that moves to physically connect one of antenna elements  302 ,  304 ,  306 ,  308 ,  310 , and  312  at a time to receiver  322 , or any other suitable type of switching device capable of routing the individual signals received by the antenna elements  302 ,  304 ,  306 ,  308 ,  310 , and  312  to receiver  322 . 
     Receiver  322  continuously monitors the signals received by each antenna element  302 ,  304 ,  306 ,  308 ,  310 , and  312  through receiver switch  320 . In one embodiment, receiver  322  is adapted to collect a single frequency signal that is modulated with a handshake bit stream. The frequency may be connector selectable to keep from interfering with other transmission activity in the area. Receiver  322  provides received signal strength output via path  326  to processor  332 , and demodulation outputs via path  324  to demodulator  328 . Processor  332  may also be a logic circuit or other suitable logic device adapted to process inputs from receiver  322 . 
     In one embodiment of the invention, receiver switch  320  connects a first antenna element, such as antenna element  302 , to receiver  322  for a selected period of time, typically a few microseconds. When successful demodulation of the RF signal occurs, and the correct handshake bit stream is detected, the demodulated signal is passed via path  330  to processor  332 . The signal strength for the signal received on antenna element  302  is sent from receiver  322  via path  326  and stored in processor  332 , or some other memory device (not shown in FIG.  3 ). If the correct handshake bit stream is not detected, the signal is ignored. The handshake bit stream length is selected short enough to allow for this rapid querying of each antenna element during the few microseconds each antenna element is connected to receiver  322 . Receiver switch  320  then connects a next antenna element, such as antenna element  304 , to receiver  322  for the selected period of time. This process is repeated until all antenna elements have been connected to receiver  322 , and all signal strengths have been stored in processor  332 , thus completing a first monitoring cycle. This monitoring cycle is repeated throughout the launch vehicle mission. In the case where no unique RF signal is detected for too long a period of time, a nominal antenna element or antenna element combination selected by the method and system of the present invention is used to provide a fallback or default transmission route for the telemetry data. 
     After each monitoring cycle, processor  332  is adapted to compare the signal strengths stored for the current monitoring cycle, and identify the antenna element with the higher received signal strength for the current monitoring cycle. This signal strength may be higher or lower than the previously determined higher signal strength from the previous monitoring cycle. Processor  332  then sends a command via path  334  to transmitter switch  336  to connect the antenna element with the higher signal strength for the current monitoring cycle to transmitter  338 . After the next monitoring cycle, if the antenna element currently connected to transmitter  338  has a signal strength higher than a desired threshold compared to the current antenna element, processor  332  sends a command via path  334  to transmitter switch  336  to switch from the currently connected antenna element to the antenna element identified in the latest monitoring cycle with the higher signal strength. If the current antenna element is the same antenna element currently connected to transmitter  338 , processor  332  does not send a command to transmitter switch  336  to make a switch. This antenna element selection process operates continuously throughout the duration of the launch vehicle mission. 
     In another embodiment of the system of the present invention, it is not necessary to store the signal strengths. Instead, after initially selecting one of the antenna elements to connect to transmitter  338 , the signal strength for the next antenna element is compared to the signal strength of the antenna element currently connected to transmitter  332 . If the new signal-strength is higher than a desired threshold, then processor  332  sends a command via path  334  to transmitter switch  336  to switch from the currently connected antenna element to the antenna element newly identified as having the higher signal strength. If the new signal strength is lower than a desired threshold, then processor  332  does not send a command to switch and the currently connected antenna element remains connected to transmitter  338 . 
     In another embodiment of the system of the present invention there is no receiver switch. Instead, the output from each antenna element receiving the unique RF signal charges up a capacitor (not shown in FIG.  3 ). The stronger the signal that is being received, the larger the charge build up on the capacitor. Processor  332  monitors the charges on the capacitors, and sends a command via path  334  to transmitter switch  336  to switch to the antenna element having the higher capacitor charge. As the capacitor charges rise and fall with the rise and fall of received signal strength, processor  332  sends commands to transmitter switch  336  to switch to the antenna element having the current higher capacitor charge. 
     In another embodiment of the system of the present invention, a smoothing algorithm (not shown in FIG. 3) is executed within processor  332 . The smoothing algorithm inhibits switching between antenna elements  302 ,  304 ,  306 ,  308 ,  310 , and  312  if the change in the higher signal strength between the previously selected antenna element and the currently determined antenna element with the higher signal strength is less than a selected absolute change amount. For example, suppose antenna element  302  had been selected by processor  332  to transmit telemetry data because it had the previously determined higher signal strength. In the next evaluation, the signal strength of antenna element  302  may rise or fall based on changing conditions, or remain the same in the absence of changing conditions. If in the next evaluation processor  332  determines that antenna element  304  has the higher signal strength, and the absolute value of change in signal strength between antenna element  302  and antenna element  304  is 2 db or less, processor  332  does not issue a new selection command and antenna element  302  remains selected for transmitting telemetry data. In other words, if the signal strength of antenna element  302  fell compared to its previous strength, and antenna element  304  has the current higher signal strength but is 2 db or less greater than the signal strength for antenna element  302 , antenna element  302  remains selected for transmitting telemetry data. Or, if the signal strength of antenna element  302  rose compared to its previous strength, and antenna element  304  has the current higher signal strength but is 2 db or less greater than the signal strength for antenna element  302 , antenna element  302  remains selected for transmitting telemetry data. 
     Master data unit  342  gathers the telemetry data generated by the various sensors located on the launch vehicle and sends the telemetry data via path  340  to transmitter  338 . Transmitter  338  then transmits the telemetry data over the antenna element currently connected by transmitter switch  336  to transmitter  338 . 
     There may be times when no receiving or tracking station antennas are within enough of a line-of-sight orientation with any of antenna elements  302 ,  304 ,  306 ,  308 ,  310 , and  312 , resulting in signal strengths too low to maintain an RF communication link. Telemetry data would be lost if transmitted during these times. To compensate for this problem, in another embodiment of the invention, the detection of the handshake bit stream in the received RF signal is time-tagged in order to identify which telemetry data would be lost if transmitted when no RF communication link exists or is likely to exist based on the measured signal strength. At such times, the telemetry data is temporarily stored for transmission at a later time after an RF communication link is re-established. For example, if the current higher signal strength is below a certain minimum value, processor  332  can note the time and send that information via path  344  to master data unit  342  to direct the telemetry data to temporary data storage  348  via path  346  instead of to transmitter  338 . Temporary data storage  348  may be sized to handle the full telemetry data stream, or a subset of the most critical measurements. When the RF communication link recovers, the telemetry data in temporary data storage  348  may now be transmitted in one of several ways. Temporary data storage  348  may be a separate storage device, a memory buffer in processor  332 , or any other suitable storage medium. 
     For example, the telemetry data in temporary data storage  348  may be sent via path  350  to data interleave program  352 , which interleaves the telemetry data via path  354  with realtime telemetry data in master data unit  342  to allow transmission to the receiving or tracking stations. Data interleave program  352  may be executable on a separate device, or executable in processor  332 . Alternatively, the telemetry data in temporary data storage  348  may be transmitted on a separate RF communication link. 
     Performance of the method and system for autonomous two-way radio frequency communication of the present invention can be optimized for a particular mission to select the best position, number, and shape of the antenna element transmit coverage patterns. In the simplest case, the antenna system can toggle between two antenna elements on the launch vehicle. One skilled in the are will recognize that this antenna system and method can be used with any number of antenna elements of two or more. 
     FIGS. 4A and 4B show a flow chart of an embodiment of the method for autonomous two-way radio frequency communication of the present invention for the launch vehicle of FIG. 2 that utilizes modulated RF signals. Referring now to FIGS. 4A and 4B, in step  400  the autonomous two-way radio frequency communication of the present invention starts when one or more antenna elements located on a launch vehicle receive modulated RF signals continuously transmitted from one or more receiving and tracking stations. In step  402  the modulated RF signals received are continuously routed to a receiver through a receiver switch that cycles between the antenna elements. The first modulated RF signal received by the receiver from a first antenna element is demodulated in step  404 , and a check is made for a correct handshake bit stream. In step  406  a determination is made if a correct handshake bit stream was detected in the demodulated RF signal. If a correct handshake bit stream is not detected in step  406 , in step  410  that signal is disregarded and control returns to step  404  where the modulated RF signal received in a next antenna element connected by the receiver switch is demodulated. If a correct handshake bit stream is detected in step  406 , then in step  408  the signal strength for that particular antenna element is determined. 
     In step  412  the signal strength for the current selected antenna element is compared to the signal strength for the previously selected antenna element to determine which has the higher signal strength. In step  414  transmitter  338  is connected to the antenna element having the higher signal strength identified in step  412  through a transmitter switch. 
     In step  416  a transmitter transmits telemetry data received from a master data unit through the antenna element having the higher signal strength identified in step  412  to be received in one or more ground stations and/or non-ground stations. In step  418  a determination is made if there is more telemetry data to be transmitted from the launch vehicle. If yes, then control returns to step  404  for demodulation of the modulated RF signal received in the next antenna element connected by the receiver switch. If there is no more telemetry data to be transmitted as determined in step  418 , then the autonomous two-way radio frequency communication of the present invention ends. 
     FIGS. 5A and 5B show a flow chart of another embodiment of the method for autonomous two-way radio frequency communication of the present invention for the launch vehicle of FIG. 2 that utilizes modulated RF signals. Referring now to FIGS. 5A and 5B, in step  500  the autonomous two-way radio frequency communications of the present invention starts when one or more antenna elements located on a launch vehicle receive modulated RF signals that have been transmitted from one or more ground stations and/or non-ground stations. In step  502  the modulated RF signals received are continuously routed to a receiver through a receiver switch that cycles between the antenna elements. The first modulated RF signal received by the receiver from a first antenna element is demodulated in step  504 , and a check is made for a correct handshake bit stream. In step  506  a determination is made if a correct handshake bit stream was detected in the demodulated RF signal received. If a correct handshake bit stream is not detected in step  506 , in step  510  that signal is disregarded and control returns to step  504  where the modulated RF signal received in a next antenna element connected by the receiver switch is demodulated. If a correct handshake bit stream is detected in step  506 , then in step  508  the signal strength for that particular antenna element is determined and stored. 
     In step  512  it is determined if the first monitoring cycle of each antenna element is complete. If the determination in step  512  is that the cycle is not complete, then control returns to step  504  where the modulated RF signal received in the next antenna element and switched by the receiver switch to the receiver is demodulated, and a check is made for a correct handshake bit stream. If the determination in step  512  is that the monitoring cycle is complete, then in step  514  the antenna element in the monitoring cycle that had the higher signal strength is determined. In step  516  a transmitter is connected via a transmitter switch to the antenna element having the higher signal strength as identified in step  514 . 
     In step  518  telemetry data received from a master data unit is transmitted through the antenna element having the higher signal strength as identified in step  514 . The telemetry data may be received in one or more ground stations and/or non-ground stations. In step  520  a determination is made if there is more telemetry data to be transmitted from the launch vehicle. If yes, then control returns to step  504  for the next monitoring cycle. If there is no more telemetry data to be transmitted as determined in step  520 , then the autonomous two-way radio frequency communication of the present invention ends. 
     Having described a presently preferred embodiment of the present invention, it will be understood by those skilled in the art that many changes in construction and circuitry and widely differing embodiments and applications of the invention will suggest themselves without departing from the scope of the present invention, as defined in the claims. The disclosures and the description herein are intended to be illustrative and are not in any sense limiting of the invention, defined in scope by the following claims.