Mt. Etna Object — AARO Case Resolution Report

UNCLASSIFIED

CLEARED
For Open Publication

All-domain Anomaly Resolution Office

Apr 28, 2025

U.S. Department of Defense
Case: “Mt. Etna Object”

Department of Defense

OFFICE OF PREPUBLICATION AND SECURITY REVIEW

Case Resolution | 28 April 2025
Case Synopsis

AARO Assessment and Case Status
AARO assesses with moderate confidence
that the object was a balloon. AARO
assesses with high confidence that the
object did not exhibit anomalous behavior.
Case Overview
In December 2018, a shortwave infrared
(SWIR) camera onboard a U.S. military
uncrewed aerial system (UAS) operating
near U.S. Naval Air Station Sigonella over
the Mediterranean Sea south of Sicily,
Italy, captured 12 minutes of infrared video
of an eruption of Mt. Etna. For
approximately four and a half minutes, a
round object appears on the video and
seems to exhibit anomalous performance
characteristics by moving at high speeds
and transiting a superheated gas and ash
plume produced by the eruption.

Location: Mt. Etna, Italy
Date: December 2018
Object Altitude (reported): 500 feet
Object Altitude (assessed): 15,000 feet
Object Speed (reported): 345 mph
Object Speed (assessed): 24 mph
Object Shape (reported): Round
Object Shape (assessed): Spherical
Reporter: U.S. Military UAS operators
Data Type: Infrared
Reported Behavior: An object moving at
high speeds through Mt. Etna’s ash plume.
Assessed Behavior: The object did not
demonstrate anomalous performance
characteristics.

Confidence: Moderate confidence the object
The UAS operator reported that the
was a balloon. High confidence the object did
object’s flight behavior was seemingly
not demonstrate anomalous performance
unaffected by transiting the plume, with no
characteristics.
discernable impact on its performance,
altitude, or bearing. The operator reported
the object’s speed as approximately 555 kph (345 mph).
Key Findings
AARO assesses with high confidence that:
•

Optical effects, turbulent atmospheric conditions, and limitations in sensor capability
distorted the object’s apparent behavior, leading to an inaccurate initial assessment of
its performance characteristics.
1
UNCLASSIFIED

25-P-0694

UNCLASSIFIED
•

The object did not exhibit anomalous speeds or other behavior exceeding known state-ofthe-art performance characteristics. It did not pass through the volcano’s ash plume.

Performance Characteristics
Object Speed: AARO assessed that the object’s speed was approximately 39 kph (24 mph),
moving generally west-to-east, consistent with wind speed and direction. The object’s apparent
high speed is attributable to motion parallax. Motion parallax is an optical effect that induces an
observer to perceive that a stationary or slow-moving object is moving much faster than its
actual speed when viewed from a moving frame of reference. The more quickly an observer
moves relative to an observed object, the more pronounced this effect is. The UAS platform’s
relative motion made the object appear to move at high speeds.
Object Flight Path: AARO estimated the object's distance from the UAS platform by
comparing its speed, the cloud deck’s apparent motion, and the wind speed to plot its trajectory.
Applying this methodology, AARO created a model that accurately predicted the object’s
location later in the video, validating the conclusion that the object moved at wind speed and
heading. (Figure 1) This predictive model aligned with the findings of an independent 3-D model
produced by an AARO partner, further validating the methodology.
(UNCLASSIFIED)

(UNCLASSIFIED)

Figure 1: Predictive trajectory analysis revealed the object’s position when it was visually
undetectable. Pixel examination using post-processing filters rendered the object visible,
validating this approach.
Apparent Anomalous Material Properties: AARO applied comprehensive full-motion video
(FMV) analysis, 3-D modeling, pixel examination, and wind speed calculations to assess that the
object was much closer to the SWIR sensor than initially reported. The object did not pass
through the volcano’s ash plume. The object was approximately 170 kilometers (106 miles)
away from the plume during the recording. AARO conducted a comprehensive FMV analysis to
conclude that the object was approximately 30 km (19 miles) from the SWIR sensor. (Figure 2)
AARO also applied kinematics and photogrammetry techniques to develop a 3-D model of the
event.
2
UNCLASSIFIED

UNCLASSIFIED
(UNCLASSIFIED)

(UNCLASSIFIED)

Figure 2: AARO’s top-down reconstruction of the event depicting the object’s distance from the
UAS platform. (not to scale)
Observable Characteristics and Attribution
Size and Shape: AARO employed pixel examination to conclude with moderate confidence that
the object was spherical. Its approximate diameter was 0.3 meters (1 foot). (Figure 3)
Attribution: Due to the object’s size and performance characteristics, AARO assesses with
moderate confidence that the object is a balloon.

3
UNCLASSIFIED

(UNCLASSIFIED)

UNCLASSIFIED

(UNCLASSIFIED)

Figure 3: The object at a higher magnification (0749Z) and enhanced using post-processing
tools (0753Z). The object is spherical with an approximate diameter of one foot.
Data Quality and Methodology: AARO assesses that the sensor data associated with the event
provides sufficiently detailed information to resolve this case with moderate confidence.
However, sensor limitations and atmospheric turbulence constrain the modes of rigorous analysis
that can be applied to identify the object conclusively.
Sensor Effects and Limitations: SWIR sensors identify targets by detecting differences in
infrared energy relative to the surrounding environment. Cool objects predominantly reflect
shortwave infrared energy, while hot targets predominantly emit shortwave infrared energy.
These sensors do not employ active range finding, and obtaining the accurate range to a target is
highly dependent on environmental factors. The thermally turbulent atmospheric conditions near
an actively erupting volcano likely disrupted the sensor's ability to capture accurate data.
Volcanic ash, composed of fine particulates, scatters and absorbs infrared radiation in
unpredictable ways, creating a “noisy” thermal environment. These conditions further reduce the
sensor’s accuracy by distorting the object’s signature.
The UAS platform’s SWIR camera was optimized for air-to-ground observation rather than airto-air detection during the encounter. In this configuration, SWIR sensors cannot detect and
track airborne objects reliably and cannot provide an accurate range to the object. Airborne
objects recorded by sensors configured in this way often appear indistinct, blurry, or featureless,
even if they would have visually observable surface features under different collection
conditions.
4
UNCLASSIFIED

UNCLASSIFIED
These factors likely influenced the reporter’s perceptions of the event, leading to unreliable
initial conclusions about the object’s speed and performance characteristics. AARO cautions that
the SWIR sensor’s image data should not inform any conclusion of the object’s performance
characteristics because of the significant limitations imposed by atmospheric turbulence, postprocessing effects, and contrast stretching. These effects produce visual artifacts such as
flickering, pulsating, and luminosity differences, significantly reducing the reliability of
traditional FMV analysis and pixel analysis techniques.
Alternative Hypotheses
Anomalous Performance Characteristics: An AARO partner’s initial assessment suggested
the object may have moved up to 5,470 kph (3,400 mph) and that it transited the volcano’s ash
plume. AARO and its other partners do not concur with these findings. AARO’s pixel
examination analysis determined that the object was much nearer to the sensor than initial
estimates, exacerbating the effects of motion parallax and leading to an incorrect assessment of
the object’s speed.
An AARO partner compared the luminosity of the object’s pixels to those around it and assessed
that the object’s gradient luminosity remained constant before, during, and after it appeared to
transit the plume. This conclusion would place the object within the volcano’s ash plume. AARO
and its other partners do not concur with these findings because the UAS platform’s SWIR
sensor cannot provide accurate range-finding data given the atmospheric turbulence. AARO
produced a validated 3-D model demonstrating that the partner’s assessment depends on
unreliable and inaccurate input data.
Bird: Initial assessments from AARO’s partners found that the object appears to flicker in the
sensor display at a steady frequency, which is highly suggestive of a bird flapping its wings to
maintain steady flight. On further analysis, AARO’s partners found that thermal turbulence,
post-processing effects, and contrast stretching produced visual artifacts such as flickering,
pulsating, and luminosity differences in the video footage. Therefore, AARO and its partners
discarded this initial assessment, concurring that the object was unlikely to have been a bird and
was likely a balloon.
AARO is not a member of the intelligence community. This AARO information report should
not be considered finished intelligence. It may contain references to finished intelligence
reports and/or information provided by AARO’s coordinating interagency partners to provide
context, show relevance, or substantiate AARO analytic perspectives.

5
UNCLASSIFIED