there were some key differences in the detected optical signature from that of an actual nuclear explosion, particularly in the ratio of intensities measured by the two detectors on the satellite. The now-declassified report contains details of the measurements made by the Vela Hotel satellite. The explosion was picked up by a pair of sensors on only one of the several Vela satellites; other similar satellites were looking at different parts of the Earth, or weather conditions precluded them seeing the same event. The Vela satellites had previously detected 41 atmospheric tests—by countries such as France and the People's Republic of China—each of which was subsequently confirmed by other means, including testing for radioactive fallout. The absence of any such corroboration of a nuclear origin for the Vela incident also suggested that the "double flash" signal was a spurious "zoo" signal of unknown origin, possibly caused by the impact of a micrometeoroid. Such "zoo" signals which mimicked nuclear explosions had been received several times earlier. Their report noted that the flash data contained "many of the features of signals from previously observed nuclear explosions", but that "careful examination reveals a significant deviation in the light signature of the 22 September event that throws doubt on the interpretation as a nuclear event". The best analysis that they could offer of the data suggested that, if the sensors were properly calibrated, any source of the "light flashes" were spurious "zoo events". Thus their final determination was that while they could not rule out that this signal was of nuclear origin, "based on our experience in related scientific assessments, it is our collective judgment that the September 22 signal was probably not from a nuclear explosion". The Ruina panel did not seriously consider a detailed study done by the Naval Research Laboratory concluding that the strong signals detected by three Ascension Island MILS hydrophones supported a near surface nuclear blast that could be associated with the observed double flash. The study used French testing in the Pacific as models and placed the site in the vicinity of the Prince Edward Islands. Victor Gilinsky (former member of the Nuclear Regulatory Commission) argued that the science panel's findings were politically motivated. Some data seemed to confirm that a nuclear explosion was the source for the "double flash" signal. An "anomalous" traveling ionospheric disturbance was measured at the Arecibo Observatory in Puerto Rico at the same