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Reduction of Aircrew Workload Through the Use of INSGPS While Employing Standoff Weapons Captain Earl W. Stolz, USAF Captain Keith J. Kosan, USAF 40th Flight Test Squadmn/DOOB 505 W Choctawhatchee Ave Ste 1 Eglin AFB FL 32542.5722 USA SUMMARY Subjective assessmentsof the value of the MCG modification Modem tighter aircraft are capable of unprecedentedattack were made using aircrew questionnaires and a modified Cooper- accuracy. However, the risk associatedwith close-in delivery Harper Scale. against well-defended targets is often high. As a result, current tactics call for delivery of precision-guided munitions from LIST OF SYMBOLS increased standoff ranges. The AGM-130 was designed to till AFB Air Force Base this need. AGL above ground level AGM air-to-ground missile The AGM-I30 evolved from the GBU-IS family of glide bombs BLU bomb live unit and is equipped with a rocket motor to increase standoff range. CCF Centralized Control Facility With the increase in launch ranges came an increased workload C/A coarse/acquisition due to difficulty locating targets within the seeker’s field of FOM figure of merit view (FOV). A launch heading offset or crosswind could FOV tield of view require the weapon systems officer (WSO) to scan a large GBU guided bomb unit area to locate both the target itself and any required waypoints. GPS global positioning system The midcourse guidance (MCG) program is an enhancement lMIRS improved modular infrared sensor designed to address this difficulty by decreasing workload with IMU inertial measurement unit an autonomous guidance capability in the midcourse portion of IMV instrumented mockup vehicle the flight and the ability to point the seeker at the target. INS inertial navigation system LOS line of sight MCG midcourse guidance The objective of the ACM-130 MCG test program is to evaluate MITL man-in-the-loop the benefits associated with reductmn of aircrew workload with nmi nautical miles the mtroduchon of an inertial navigation system (INS) that is PDOP position dilution of precision position- and velocity-aided by the global positioning system SWAT subjective workload assessmenttechnique (GPS). This paper will discuss flight test techniques and results TM telemetry obtamed from the Phase I test program, which focused on initial TSPI time-space-position information integration efforts using profiles to attack vertical targets. Phase TVGS television guidance seeker II will address the capability to attack horizontal targets and is USAF United States Air Force currently being tested. A secondary objective of demonstrating WAGE wide area GPS enhancement the advantagesof guidance using wide area GPS enhancement WGIJ weapon guidance unit (WAGE) corrections was also accomplished, wso weapon systems officer Testing involved a series of ground functional tests. captive 1. INTRODUCTION carries in which the aircraft flew the weapon’s profile. and three The AGM-130, like many standoff man-in-the-loop (MITL) live launches. munitions, is a demanding system to employ. Most of the demands placed upon the WSO occur when trying to locate the The stated goal of the MCG program is to ensure that the target target area through the small seekerFOV in the midcourse appears in the seeker’s wadeFOV at 15 secondstime-to-go 95% phase of flight. of the time. In all cases this criteria was met. Additionally, the target was within the narrow FOV 100% of the time. To assist the WSO in target acquisition, a closely coupled INS driven by GPS position and velocity updates has been added. Using the subjective workload assewnent technique (SWAT) in This system guides the weapon during the midcourse phase and a head-to-head comparison with a non-MCG-guided AGM-130. can pant the seeker at the target. This modified weapon is a 25% reduction of WSO workload was demonstrated. referred to as AGM-I30 MCG. Paper presented at the AGARD FVP Symposium on “Advances in Flight Tesfing”. held in Lisbon, Portugal, 23-26 Seprember 1996, and published in CP-593. 2. WEAPON SYSTEM DESCRIF”IJON The secondary mode of operation is MANUAL. This mode The AGM-130 (Figure I) was developed from the GBU-15 mdicates that the INS is not using the GPS navigation solution family of glide bombs. The primary difference between the due to figure of merits (FOM) not meeting the appropriate GBU-IS and the AGM-130 is the addition of a rocket motor. criteria. If the weapon is launched with MANUAL displayed, radar altimeter, and digital autopilot. Both weapons are the autopilot would not use the INS for navigation (it would use modular systems and can use either a Z,COO-lbgeneral purpose a heading hold mode) nor would it point the seeker to a set of bomb (MK-84) or a penetrator warhead (BLU-109). The target coordinates. If the weapon is launched in MANUAL and weapons are controlled via a radio frequency datalink with the GPS signal improves, a launch point re-initialization may either an RT-lZIO/AN/AXQ-I4 datalink pod. Both the current occur and the weapon will upgrade to GOOD. If the weapon fielded versions of the GBU-15 and the AGM-130 “se ather a degradesto MANUAL after being launched with GOOD DSU-27 electro-optical or a WGU-33 imaging infrared seeker. displayed, the autopilot would still use the INS navigation Recent testing has certified two new. more advanced seekers. solution and fly to a set of coordinates. When the system Both the WGU-40 television guidance seeker (TVGS) and the degradesto MANUAL after loss of GPS, seeker pointing would WGU-42/B improved modular infrared sensor (IMIRS) will also still be available. However, the navigation solution would soon be fielded. be based strictly on the INS solution with no GPS updates (degraded accuracy). The weapon has three phasesof flight: midcourse, transition. and terminal. During the midcourse phase, the seeker is slewed The worst case is for the weapon to be in a mode with FAIL independently of the weapon platform, The only way the WSO displayed, This indicates a shutdown of the IMU, resulting in a can adjust the flightpath of the weapon in this phase is with totally inoperative weapon. discrete heading or altitude commands. In the transition phase of flight, the WSO has dmxt yaw control of the weapon via A NO KEY messageindicates that a GPS cryptokey has not slew commands. In this phase, the WSO still has no direct been loaded. and a NO SAT messageindicates that the GPS control over pitch. The final phase is the terminal phase in receiver has not yet started to track satellites. Figure 4 shows which the weapon platform steers, in both pitch and yaw, in the FOMs required for a GOOD to he displayed at different response to seeker slew inputs. See Figure 2 for a typical low- times-to-go. altitude launch profile. The MCG kit includes a GPS antenna. a GPS receiver, an INS, The MCG upgrade provides the WSO with the existing basic and an autopilot. weapon capabilities and a significant increased capability for target acquisition, especially under adverse weather conditions. The MCG upgrade will also support the attack of horizontal The GPS receiver sent accurate position and velocity to the INS. targets - a capability not currently available in the fielded This receiver used only the LI frequency, which provided time, system. position, and ephemeris data for each satellite being tracked. During preflight, the weapon will be loaded with the GPS The INS provided a navigation solution to the autopilot. The cryptokeys. The cryptokey comes on a tape that is read by a Kalman filter imbedded in the INS used inputs from both the KOI-I8 tape reader. The KOI-18 will then transfer the key to a GPS receiver set (positions and velocities) and the inertial KYK-13 or CYZ-IO for loading the weapon. A position update measurementunit (position/attitudes, velocities/rates, and may be initiated using an AN/PSN-I 1 precision lightweight accelerations) to provide the best navigation solution to the GPS receiver to speed up the inertial measurement umt’s (IMU) autopilot. alignment. Target coordmates, approximate launch coordinates, alignment data, and desired nnpact angle are loaded by slewmg The autopilot calculated both a guidance solution and a stability the target designator control (Figure 3). This obviates the need solution based on inputs from the INS, IMU. and radar for developing an expensive capability for loading this data altimeter. During the midcourse and transition phases of flight. using the aircraft’s 1760 Bus. Using the same method, targets the autopilot relied on the INS and radar altimeter to provide a may he reprogrammed inflight. guidance solution based on zeroing the line of sight (LOS) angles/ratesto the target and maintaining a programmed/ In captive or free-flight with the weapon operating normally, the commanded altitude. During terminal flight, the autopilot used WSO would see one of five messages: GOOD, MANUAL, proportional navigation to guide to the target by zeroing the FAIL, NO KEY, or NO SAT. The primary mode of operation is LOS rate to a given target coordinate, guiding the seeker lock- with GOOD displayed. In this mode, the weapon would on designation, or guiding to a manually selected seeker navigate to the target coordinates and point the seeker at the crosshair location. The autopilot used information directly from target. When GOOD is displayed, the weapon could the inertial measurement unit during all phasesof flight to autonomously (no WSO inputs) navigate to and impact the provide a stability solution to maintain a level weapon platform. target with GPS/INS accuracies. to-3 MKWE4U.I W Figure 1. AGM-130 Midcourse Transitjon Figure 2. Typical Low-Altitude AGM-130 MCG Profile LAT: N5423.!323 LNG: E138:24231 CRS: RALT ELV: 00510 MSL IAT: N54:2S.S23 VEL: 480 KTAS LNG: Et Z8zZ424231THDG: 067 DEG ALT: 30,cco MSL Figure 3.