AN/APG-63 is the family of radars for the F-15 Eagle air superiority fighter. It is a family planned for continuing "spiral evolution" enhancement. The latest version, the AN/APG-63 V(3), has moved from a first, mechanically scanned version, to the first AESA radar on an operational fighter, and into the second generation of AESA.
The first three versions of the AN/APG-63 were for air combat only. The air-to-ground F-15E Strike Eagle, as well as the F-15E variants for Israel (F-15I), Singapore (F-15SG, formerly F-15T), and Saudi Arabia (F-15S), all use the AN/APG-70; the South Korean Strike Eagle variant, the F-15K, used an AN/APG-63 version.
An AN/APG-63(V)4 is planned as the next radar upgrade for the F-15E Strike Eagle. This aircraft is principally for deep attack, but retains significant air-to-air capabilities; its radar this needs ground mapping and fire control modes not required for the air superiority Eagles. Version 4 appears to take the existing AESA components of the V(3), which are fairly easily reprogrammed, and put on a "back end", or postprocessing engine, Raytheon has proposed a next generation that will take the APG-63 V(3) "front end" and mate it to a redesigned "back end" AN/APG-70 radar, which is the current Strike Eagle radar.
Mode information here is interim APG-70 air-to-air, from Serflek. It refects the tradeoffs in different modes, which include range and altitude coverage.
Range While Scan (RWS)
This the most general air search mode, but has different pulse repetition frequencies that trade off rapid detection of closing targets, medium-to-short range all-aspect coverage, and speed of detection.
Range Gated High (RGH)
RGH can find targets faster than RWS, but is confused by ground clutter and is good only for targets above 4000 feet.
Velocity Search (VS)
Velocity search is optimized for closing targets but may not detect off-threat-axis targets.
This is best for picking up low-observable targets.
Track While Scan (TWS
TWS is for specific target tracking while maintaining situational awareness.
APG-70 shares some components with the APG-63 V(2). There is a set of additional air-to-ground functions that will move to the V(4), but with the superior "front end" from the V(3).
All of these modes use variants of imaging synthetic aperture radar (SAR). SAR requires that radar signals and reflections have to be sent and received from multiple points, so the actual time base, and flight path relative to the SAR imaging, can be extremely complex.
Especially for target detection and final weapons lock, the weapons systems officer (WSO) is likely to switch among all the modes, as well as using sensors integral to weapons. Before releasing an AGM-65 Maverick missile, for example, coordinates from various radar displays are used to cue the electro-optical sensor of the Maverick onto the target. At that point, the WSO will examine the target as the missile sees it, firing only if the narrow-angle, higher-resolution sensor confirms the target.
Real Beam Mode
RBM mode is still a SAR technique built up from multiple scans, but it gives the impression of a map, the scale of which is selectable, with the aircraft at the bottom of the map. The projected flight path goes from bottom to top.
High Resolution Map
From the RBM display, the weapons system officer can select a center point fromthe RBM display, and display high-resolution imagery in a smaller area around that point. It will often be necessary to shift among the general mission plan and map as seen in the RBM, switch to HRM, and to switch among HRM, GMT, and IGMT.
Ground Moving Target
GMT mode detects areas in which there is movement on the ground, but just shows the general track of the moving object, not the object itself. This is needed since while HRM can show an object (e.g., a tank), it is very hard to see the target amidst other ground clutter. It is especially hard when the static HRM gives multiple static snapshots, and the object may have moved between scans.
Interleaved Ground Moving Target
IGMT mode adds the currently active (i.e., locked onto target, or actually fired) aimpoint indicators to the GMT display.
AESA radars can have additional applications, such as electronic intelligence and electronic warfare, and, due to the individual transmit-receive elements being independently programmable, have these applications running concurrently as long as there is adequate computing power. On the EF-18 Growler, for example, the AESA radar has a secondary role of electronic support, and may also have some electronic attack capability.
The next generation F-35A Lightning II in the Joint Strike Fighter series, often but not universally considered the Strike Eagle replacement, uses the AN/APG-81 AESA radar. A different AESA radar is the AN/APG-77 on the F-22 Raptor; the F-22 was originally seen only as the replacement for the F-15 in air superiority but now is assumed to be useful in high-performance strike and possibly electronic warfare.
- Raytheon, Raytheon’s F-15 AESA Radars: The Evolving Eyes of the Eagle; Spiral evolution
- Serflek, Szabolcs, AN/APG-70 Radar System