GEIPAN Case 1994-01-01345 — « AF3532 » [AERO AFR] COULOMMIERS (77) 28.01.1994

Brief

Météo-France's Division of Observation and Aerology produced this three-page analysis on January 9, 2012, placing a Trappes radiosonde assembly at 17,404 meters altitude near the vertical of Joigny at exactly 13h14 — the moment AF3532's crew reported an unexplained phenomenon. The assembly's VAISALA RS80-15L radiosonde carried no radar reflector, operating via Loran C positioning. Winds at 10,000 m reached 57 m/s and could deform the balloon's shape, but the document's own arithmetic forecloses the hypothesis: a burst balloon above 30 km cannot exceed roughly 10 meters in diameter, while witnesses described an object several hundred meters across.

Metadata

Agency

GEIPAN / CNES

Release

2007-03-22

Type

PDF • .pdf

Length

3 pages

Classification

UNCLASSIFIED

Programs

GEIPAN, SEPRA, GEPAN

Tags

radar confirmation, instantaneous disappearance, commercial aviation, lenticular/large object, France, Seine-et-Marne, 1994, AF3532, GEIPAN D1, Coulommiers

Key points

• The Trappes radiosonde was launched at 11h18 UTC on January 28, 1994 — 56 minutes before the crew sighting at 13h14.p.1
• At exactly 13h14, the assembly was calculated to be at 17,404 m altitude, 107,528 m east and 87,540 m south of Trappes, near the vertical of Joigny.p.2
• The VAISALA RS80-15L carried no radar reflector; Trappes had discontinued radar-tracked sondes after July 5, 1992, meaning the object's confirmed radar return was not from this instrument.p.1
• Wind speeds at 17,000 m reached 33 m/s (119 km/h) and at 10,000 m reached 57 m/s (205 km/h) — sufficient to deform the balloon's shape.p.2
• The balloon burst at 31,411 m after 90 minutes of flight, at 13h48, well after the sighting.p.2
• Météo-France explicitly rules out the radiosonde as a full explanation: a burst balloon above 30 km cannot reach 'several hundred meters' in diameter as witnesses described.p.2
• Page 3 contains a complete vertical wind-profile table from 168 m to 31,400 m altitude, providing the raw sensor data underlying the trajectory reconstruction.p.3

Verbatim

• La station de Trappes a procédé à un lâcher de radiosondage le 28/01/1994 pour le réseau de 12 UTC, à 11h18 UTC, soit 12h18 légales.

  p.1

• L'attelage de radiosondage était constitué d'un ballon, d'un parachute et d'une radiosonde. La distance entre le haut du ballon et la radiosonde était sans doute de l'ordre de 30 m.

  p.1

• Le modèle de radiosondes utilisé était VAISALA RS80-15L. Le positionnement des radiosondes de ce type était effectué à l'aide du réseau Loran C, ce qui signifie qu'elles n'étaient pas associées à un réflecteur destiné à un radar de poursuite comme c'était le cas à Trappes jusqu'au 05/07/1992.

  p.1

• Des vents de l'ordre de 33 m/s (119 km/h) étaient observés vers 17 000m d'altitude. Ils atteignaient 57 m/s (205 km/h) vers 10 000m d'altitude.

  p.2

• Un tel vent peut sans aucun doute provoquer des déformations de la forme du ballon.

  p.2

• Il ne peut en aucun cas atteindre un diamètre de plusieurs centaines de mètres comme indiqué par les témoins.

  p.2

Most interesting

• GEIPAN classified this case D1 — 'inexpliqué moyennement consistant avec un caractère d'étrangeté marqué' — meaning the phenomenon was confirmed by radar control and disappeared instantaneously, placing it in the marked-strangeness tier despite moderate data quality.
• Météo-France's technical note was written 18 years after the incident, on January 9, 2012, illustrating how long GEIPAN cases can remain open and under active technical review.
• The radiosonde's ascent averaged only 4.9 m/s in a northwest airflow, with a data gap near the trajectory's end — the document acknowledges the final segment's path is reconstructed from endpoints only, not continuous tracking.
• The balloon burst at over 30 km altitude before reaching the witnesses' reported size, meaning the radiosonde's own maximum possible diameter at burst — roughly 10 meters — is one to two orders of magnitude smaller than what the AF3532 crew described.
• The wind-profile table on page 3 spans 168 m to 31,400 m in over 80 discrete altitude readings, making this document simultaneously a UAP investigation input and a high-resolution atmospheric profile of northern France on January 28, 1994.