Soyuz 2-1v is a three stage launch system. The first stage is the core, without strap-ons, from the standard 2-1 Soyuz version. It has a standard second stage, again from the Soyuz 2-1, and the third stage is a new unit by the name of Volga that holds the payload and is used to circularise the orbit at operational height.

Soyuz departed Plesetsk on December 5 at 14:09 UTC on a heading a little to the west of north leading to a 98° inclination, sun-sychronous, orbit. The first stage burned out over the Murmansk region and fell just off the coast in the Barents Sea, about 825 km downrange. The payload fairing fell in the Barents Sea about 1590 km from Plesetsk as the ground track approached the island of Svalbard and the second stage then took the head unit, consisting of the Volga and the two satellites, into orbit.

Eight minutes or so after lift off, the second stage with Volga and the satellites attached was above Greenland and in a 208 x 681 km orbit at 98°.2 inclination. Soon after, the Volga was to separate from the spent Soyuz stage. Success was reported by Russian news agencies shortly after 14:30 UTC.

Just before 15:00 UTC while over Antarctica the Volga fired its engine to circularise the orbit at 690 km. It then activated the satellite release mechanism.

At 15:39 UTC the Volga and the satellites came back within the view of Russian ground stations as they approached from the south above Egypt. About half an hour later news agencies again reported, this time quoting a Russian Ministry of Defence press release saying that the two satellites had been released successfully and had received the names 'Cosmos 2511' and 'Cosmos 2512' respectively.

Air and maritime navigation warnings issued for a re-entry zone over the southern Indian Ocean pointed to a plan to conduct a de-orbit firing of the Volga on that same pass over Russia. It would have led to re-entry around 16:30 - 16:35 UTC. Two objects were detected in orbit so it was assumed by that they were the two satellites and the Volga had re-entered.

Nearly 24 hours after launch, Russia's RIA-Novosti news agency quoted an "an informed source in the space industry" saying that one of the two satellites had failed to separate from the Volga, contradicting the report from the previous day. What probably happened initially is that transmissions were received from both satellites but it was only when trying to orient itself or its solar panels did it transpire that the attached mass of the Volga was inhibiting one of them.

A formal statement eventually confirmed that the 'stuck' satellite was Canopus ST. The two objects catalogued by JSpOC in the US were the combined Canopus-ST/Volga and KYuA-1.

Controllers obviously looked at taking corrective measures including instructing Volga to activate the separation mechanism again but with no result. By the time the story about non-separation surfaced, the decision had already been made that the mission could not be salvaged.

At about 15:35 UTC on December 6, the Volga's de-orbit firing was made as it passed above northern Russia. Because the additional mass of Canopus-ST was present, the resulting impulse was insufficient to lower the orbit enough to cause immediate re-entry. The resulting orbit was 114 x 591 km with perigee deep in the southern hemisphere. It would lead eventually to re-entry on December 8 but not in a predictable location.

At 18:23 UTC on Dec 7 Spacetrack issued a TIP message indicating the impending re-entry of a brand new, but anonymous, object identified only as catalogue number 41102. Its demise was predicted within an hour or so of the Volga, hinting strongly that the two were associated. About seven hours later a set of orbital elements was issued for 41102 identifying it as 2015-071D from the Soyuz 2-1v launch. The new object was in a similar orbit to the Volga and its orbit was decaying at about the same rate or a little more slowly, indicating that it was fairly dense and not just a small piece of material that had dropped off the rocket.

Two possibilities existed. One was that the Volga broke into a pair of similarly-dense pieces. With a near 100 km perigee the Volga had been dipping quite low into the sensible atmosphere and was subjected to significant stress as it passed through low density air. NOTE - the apogee and perigee derived from Spacetrack data relate to an idealised, model Earth. The 98km perigee thrown up in the Spacetrack model equates to 114 km above the true surface of the Earth.

The second possibility was that friction had caused whatever was holding Cosmos 2511/Canopus to the Volga to release its grip, meaning that both objects were being tracked as separate items.

On December 10, Spacetrack made known its interpretation of what the two items represented and lent its weight to the separation theory. It tagged 41098/2015-071A as Cosmos 2511 and 41102/2015-071D as the Volga stage. There is a summary showing the various objects from the launch in Zarya's 2015 launch table.

Spacetrack issued a final TIP message for 41098/2015-071A saying that it had re-entered the atmosphere Dec 8 at 05:43 UTC precisely. At the time it was southbound over the South Atlantic Ocean, on the Greenwich meridian at about 35° south latitude.

A TIP message for 41102/2015-071D said it re-entered about an hour earlier, around 04:37 UTC, above Antarctica on the previous circuit of the Earth.