The puzzling incident took place last Tuesday, September 2 in the skies over Colorado and Wyoming. Around 10:30 p.m. local time (4:30 UTC on the 3rd), a bright fireball was observed from central Colorado into southern Wyoming, perhaps visible from as far as New Mexico, South Dakota and southern Montana. Over 30 witness reports of the event were published by the American Meteor Society. The fireball made local news last week, however, no photos or video of the event were published.
A number of witnesses, including experienced sky-watchers reported that the object was moving much slower than a usual fireball, some immediately conclude that what they were observing was the re-entry of a piece of space debris.
Spaceflight101 claims that based on the data the only possible fit is Kosmos 2495 - a Russian film-return satellite delivered to orbit on May 6, 2014 atop a Soyuz rocket launching from the Plesetsk Cosmodrome.
A relic of the soviet era, the Kobalt-M satellites originate in the Yantar photoreconnaissance project that dates back to 1964. Kosmos 2495 was likely the second to last of its kind to fly into space since Russia has started the operation of electro-optical satellites that downlink acquired imagery to the ground instead of returning physical film to Earth. Operating from a very low orbit of around 200 Kilometers, the satellite can obtain high-resolution imagery of ground targets.
Kobalt-M satellites measure 6.3 meters in length and 2.7m in diameter with a launch mass of 6,600 Kilograms, including a 900kg fuel load that is expended during the mission to maintain the satellite's extremely low operating orbit. To return film to the ground, the satellite uses two small return capsules that are separated from the satellite and land in Russia. A third capsule is part of the main satellite body to return at the end of the mission when the spacecraft performs a targeted re-entry to land in a pre-determined location within Russian territory.
With a Russian satellite weighing 6.6 metric tons, it is safe to assume that a number of components survived re-entry and reached the ground. As a relic from the older days of satellite development, the Yantar bus employs a more robust construction with heavier structural elements which has some implications on the re-entry process as dense components are known to survive longer in the high-temperature entry environment than the conventional light-weight structures used in modern spacecraft. Additionally, the film capsule of the spacecraft was specifically built to survive re-entry and protect the images it carried.
The most probable explanation for the erroneous re-entry of Kosmos 2495 is a malfunction of the satellite that led to an incorrect timing of its deorbit - possibly a software error or a partial retrofire performed at an earlier time that left the satellite in a short-lived orbit resulting in an untargeted decay.
A possible explanation could be a partial retrofire. Assuming the satellite ignited its engines for its planned deorbit burn around 17:40 UTC on September 2, but only achieved a partial burn duration, the orbital period could be easily reduced from 89 minutes to 87-87.5 minutes. Given that the satellite continued in this orbit for nearly 11 hours until re-entering explains why Kosmos 2495 was more than 15 minutes ahead of orbital predictions at the time of decay.
It remains to be seen whether any fragments of the satellite or even the film-return capsule will be found as potential surviving components are likely scattered across a long debris footprint.
