The pod appears to be previously unseen but closely resembles the Airborne Turret Infrared Measurement System III (ATIMS III), which is used to perform airborne IR signature measurements.
A U.S. Air Force F-15D has been recently spotted flying in a very unusual configuration, usually seen only for very specific tests. In fact, the aircraft was carrying on its station #2, instead of the usual external fuel tank, what appears to be a large InfraRed pod.
The photos, kindly shared with us by aviation photographer @arizona_planespotter, shows the aircraft, sporting the markings of the 144th Fighter Wing from Fresno Air National Guard Base, California, taking off from Morris ANGB in Tucson, Arizona, together with an F-15C. The two fighters apparently took part in a mission with local F-16s.
Upon closer inspection, the single-seater Eagle appears to be aircraft 83-0026, which sports on its tail the markings of the Air National Guard/Air Force Reserve Test Center. The unit is based at Morris ANGB and primarily supports F-16 operational flight program (OFP) testing, although it is tasked also with testing of other aircraft.
The large pod, which is half the length of the F-15’s external fuel tank, appears to be equipped with a ball sensor turret in the front. While some argued this might be a prototype of a directed energy weapon, the most plausible identification is an infrared measurement pod which is usually carried by twin-seater F-15Ds.
In fact, the OT- and ET-marked aircraft are able to employ a range of highly specialized pods to accurately measure infrared signatures while airborne. This capability is usually employed during the development of IR seekers or sensors, as well as IR countermeasures.
We reviewed the available imagery of the known pod, but we were not able to find a 100% match, given the nature of these pods. While the unknown pod shares similarities with the SARIS and SATIRS pods, the closest match is the ATIMS III pod, although there are some differences.
The overall shape and dimensions of the two pods appear to be the same, however there are some differences in the sensor turret and some fairings on the body of the pod. We should note that the most recent info about the pod dates back to 2020, so we cannot exclude the possibility of a newer variant.
The IR-measuring pods
According to The War Zone, which published in 2020 an in-depth report about the unusual pods, both the Air Force and Navy use these specialized pods. While the Navy’s pods, usually seen on twin-seater F/A-18s, are also used by F-15Ds, the Air Force’s ones appear to be exclusive to the F-15D.
The choice of the F/A-18 and F-15 is due to their ability to carry large and heavy loads. The latter has been particularly used throughout the years to carry outsized loads during testing and operational missions.
At the time of the 2020 report, Naval Air Systems Command (NAVAIR) maintained two podded systems, the Airborne Turret Infrared Measurement System III (ATIMS III) and the Threat Infrared Generic Emulation Radiometer (TIGER). Four more pods are available for the Air Force, with 96th Test Wing employing the Beam Approach Seeker Evaluation System (BASES), the Calibrated IR/visible/UV Ground and Airborne Radiometric Spectrometer (CIGARS), the Supersonic Airborne Tri-Gimbal Infrared System (SATIRS), and the Spectral/Spatial Airborne Radiometric Infrared System (SARIS).
ATIMS III
ATIMS III has been defined in 2020 as the latest generation of a system that dates back to at least the 1970s. The system was originally integrated aboard the A-3 Skywarrior, before being later developed into a podded variant, the ATIMS II, employed by the F-4 Phantom II.
The system, which allowed greater flexibility and more ease of use compared to the original one, had an articulating turret with various cameras and sensors installed that a single operator could point at the desired target. Today’s ATIMS III was acquired in the 1980s and offers even greater capability.
The pod’s sensor turret can hold up to four different infrared seeker types at once. The system is also equipped with one middle wavelength infrared (MWIR) imager and three visual spectrum video cameras, as well as a laser rangefinder. This allows to collect a multitude of data from multiple sensors at the same time.
The available photos show that the pod can be installed either with the turret facing forward or facing backwards, depending on the test’s requirements. TWZ reported that the pod’s design is highly modular and adaptable and features a digital data recording system.
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The report included a mention of a statement from Ampex Data Systems Corporation which provided solid-state recorders to capture the full spectrum of infrared data measured by the pod as part of an upgrade program. According to the statement, which uses the alternate Airborne Infrared Countermeasure Evaluation System (AICES) name, the pod can possibly transmit collected data to the ground via datalink.
The other pods
The second pod operated by the Navy is the Threat Infrared Generic Emulation Radiometer (TIGER), which is designed for more general aerial infrared signature measurement of fixed-wing and rotary-wing aircraft, as well as decoy flares. TIGER carries three MWIR cameras and a long-wavelength infrared (LWIR) camera, in addition to a separate infrared tracking camera and an MWIR spectrometer, along with three visual spectrum video cameras and a laser rangefinder.
TWZ reported that the spectrometer allows to verify how the infrared radiation from the test subjects interacts with the surrounding environment, enabling the pod to gather data on an object’s temperature, how that heat is distributed and how the resulting infrared signature might fluctuate under different environmental conditions and at extended distances.
Similarly to ATIMS III, the pod can be carried with the turret either facing forward or backwards. TIGER is usually seen on F/A-18s, however there are instances when it was employed by F-15s, sometimes together with ATIMS III in the same flight.
Another pod is the Spectral/Spatial Airborne Radiometric Infrared System (SARIS), focused on infrared spectroscopy. More specifically, a scientific article published online mentions that SARIS uses an Imaging Fourier Transform Spectrometer (IFTS), which permits the determination of the surface temperatures of distant objects and, combined with imaging capability, allows rapid temperature mapping.
The document says that SARIS, first delivered to Eglin AFB in 2003, is used to characterize infrared targets, such as aircraft, missiles and flares, from the air. The pod is equipped with a co-registered, high-definition infrared camera and two internal blackbody sources for performing in-flight radio-metric calibration.
There are limited freely available details about the BASES, CIGARS, and SATIRS pods, but they are understood to have general capabilities very similar to those of ATIMS III and TIGER.
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Thanks again to @arizona_planespotter for the photos he sent us! Make sure to follow him on Instagram for more!
