Chapter 3 discusses the overall facility development for remote operation of simulated weapon systems. For this trial there were three main functioning programs that fa- cilitated the experiment. These were; the Remote Operator Terminal software, the Network Protocol Code for Re-tasking messages, and the GBU weapon simulation.
5.3.1 Remote Operator Terminal
The Remote Operator Terminal, is a map display which represents key information to the user (shown later in Figures 5.1 & 5.2). This information is pulled from the data available from VMF type messages received from the weapon and from remote targeting systems such as an aircraft mounted targeting pod or a FAC CAS 9-Line Brief. These messages must be processed by the remote operator terminal system before being displayed to the user. The main functions within the Remote Operator Terminal software are:
• Map Function - loads the background map based on the current world position being interrogated by the user. The function loads relevant map tiles from open source mapping databases in either satellite, map or hybrid views.
• Objects Function - loads objects onto the map view to represent assets, targets and other information about objects within the battle-space.
• Status Function - displays the current weapon status to inform users of the state of the weapon that they are controlling.
• Key-press Function - records the human interaction with the keyboard control device and carries out the appropriate command. In this interface the potential keyboard commands are minimised to; ‘R’ re-task weapon, ‘O’ keep the original target, and ‘Return’ proceed to next scenario.
• Decision Aid Function - displays one of two variations in display type used to aid decision making by the user.
• Network Function - reads data from the network protocol used to send and receive information between the user interface PC and the NEW simulation PC.
The Remote Operator Terminal developed is similar to those developed for the B-1B weapon operator interface [34, 35]. The B-1B weapon operator interface displays circu- lar shapes on a digital map along with the expected flight path of the aircraft. These circles represent the LAR for the weapons to be launched against pre-configured tar- gets. When the aircraft is within these LARs the weapon operator can release the weapons onto their targets. However, the interface does not produce RS – areas on the
ground that can be hit from the current launch position of the aircraft. The Remote Operator Terminal display for this trial is fixed in position, displaying a map with mov- ing objects to represent the current weapon in flight and the target(s). Rather than LARs being produced for each target, a single RAR is generated for the weapon. This can then be displayed to operators to aid them in assessing the validity of re-tasking an air-to-surface weapon to a new target.
A current UK capability to re-task weapons in-flight exists in the C2 of the Hellfire missile system used in the Apache. The Hellfire uses semi-active laser homing to guide itself to the target, which is lased by either the firing platform or a third party (note some later variants of the Hellfire have been updated to include an active radar seeker). As a mechanism of aborting the weapon, an operator can, in real-time, move the laser designator away from the target to a safe location for the weapon to ditch. Similarly this technique could be used to re-task the weapon to an alternative target whilst the weapon is in-flight. Given the relatively short range, the time window for these types of re-tasking are very minimal. The operator’s terminal is not specifically configured for re-tasking roles, but this is an example of how existing systems could be used to perform such tasks.
Two methods were chosen to display decision cueing information to participants. The first, a geo-spatial graphical overlay, and the second a digital numerical display. These displays were configured to represent the maximum extended range to which the weapon in flight can be re-tasked to safely. Using a combination display was considered, how- ever, the purpose of the trial was to establish direct differences between the two displays. Using a mixed display would have removed the ability to distinguish which decision aid element participants were using to support their decision making, introducing unnec- essary confounding factors into the study.
The RAR graphical representation is a non-filled polygon shape which has the gen- eral appearance of a semicircle. This semicircle protrudes forwards in the direction of travel of the weapon with the flat edge facing the weapon, and the arc spanning from the left most extent of the weapons range if it were to turn full left, through the weapons forward maximum range, to the right most extent of the weapons range if it were to turn full right. However, due to the dynamic nature of a weapon engagement and ultimate descent into the target/surface, an air-to-surface weapon’s RAR reduces to zero over time.
In the early stages of GBU flight the RAR remains approximately the same size and shape. However, as the GBU descends the area of the RAR reduces, with the overall shape collapsing inwards to the centre. The main issue with this dynamic feature is that the reduction in area overall is not uniform in all directions. The reduction in off-boresight capability is the most obvious change in the shape of the RAR. This is the reduction in the GBU’s ability to change its heading to prosecute other targets. In Chapter 3, 3.9 shows an example of the change in shape of the RAR in 2 intervals from launch until target impact. The use of polygons is common to display this type of information (as seen in the B-1B WO display [34, 35]). It is also used in nuclear power station control rooms [148] as it has been shown that people are good at detecting departure from a ‘normal’ system state using polygon displays [149]. A detailed map is projected underneath the decision cues to ensure that all information required is in a position to allow for efficient focus and eye movement of participants [150].
The numeric display used a digital number representation rather than an analogue dial to represent the numerical values associated with the ability to re-task the GBU weapon. This is because digital displays provide greater levels of precision [151]. Ana- logue dials also rely on a participants ability to distinguish difference within graphical forms, rather than from comparing numerical values. Participants were shown two dif- ferent numbers, a numeric value representing the capability of the GBU, and a numeric value of the capability necessary to re-task to the new target. This requires participants to use basic mental arithmetic to ascertain whether the new target is within the RAR of the GBU.
This calculation could be quickly made by the computer system and a number could have been shown representing the difference between the maximum range available and the range to the target. This was avoided in order to prompt participants to make an assessment based upon the relative closeness of the new target to the maximum range of the weapon, which is not directly visible to the participant if they are only provided with a numerical value instructing them that the new target is inside or outside of the range capability of the weapon. It also does not provide the participants with direct information to assess the rate of change of the maximum range of the GBU. Any un- derstanding of the rate of change is inferred by the rate of change of the numbers on the display. The Range To Target was placed immediately above the Range Available so that the two numbers could be easily compared with each other. The numerical format provides the operator with no geo-spatial cues to build SA, however, there is still sufficient information available for an operator to develop the third ’Projection’ level of SA [56].
When using a map display it is important that the decision cues are made more easily available to participants by increasing their graphical salience on the single display [152]. The colours used for the two different decision cues were applied in order to achieve the required increase in salience, as they do not interfere with high level emergent fea- tures such as the shape of the RAR [153], and colour has been shown to increase both decision making accuracy and reaction time [154].
The data refresh rate of the user interface is dictated by the time it takes to gen- erate the RAR for the GBU. The time taken for each calculation of the RAR is based upon the resolution (number of points in the polygon) and the type of RAR calculated (open loop/closed loop solutions). This information is detailed in Chapter 3. An ap- propriate refresh rate of 10 Hz was used as it provides a suitably high frame rate to show motion, whilst allowing for a high enough resolution for a good RAR calculation. Low refresh rates have been shown not to degrade performance of participants in dy- namic tasks [155], and so a refresh rate of 10Hz should not impact on the performance of participants within this trial.
5.3.2 Network Protocol
A custom developed UDP was used to send and receive information on both the NEW and Remote Operator Terminal PCs. Chapter 3 discusses the message format in more detail.
The information sent from the NEW to the Remote Operator Terminal are Position, Attitudes and Velocity. The Remote Operator Terminal sends Target Position and Velocity information to the NEW. It is assumed, for the purpose of this trial, that the targeting information received from a third party source by the Remote Operator Terminal is both timely and accurate.
5.3.3 Weapon Simulation
The weapon simulation is a full 6DoF model of a GPS/INS GBU. The GPS/INS guided weapon is an unpowered guided bomb in the 1000lb class. It is canard controlled, uses proportional navigation guidance and standard approximations for the aerodynamic coefficients [114, 156]. This model is also discussed in detail in Chapter 3.