The first, 244.512 MHz is relatively easy to track as the satellites generate a 0.5s long 'trigger pulse' every 60 seconds. Its purpose is to activate ground based transmitters waiting to send a message. Satellites can be identified relatively easily by measuring the time of closest approach from Doppler curve.

Received messages are then re-transmitted on the second frequency at 261.035 MHz.

From western Europe, it is unusual to hear more than a single 10-40s burst of data at 261.035 MHz on any particular pass. Transmission is usually heard near the start of a path that takes the satellite across Russia. Transmissions on passes to the west of the UK, for example, seem to be non-existent. Occasionally there are multiple bursts as a satellite triggers and retransmits two or more bursts of data from the ground but this is relatively rare.

The way to identify an individual satellite on this channel is to measure the received frequency of the data burst and compare it to the expected Doppler shifted value at that moment. Not every active satellite dumps messages on every pass and often there are several satellites above the horizon simultaneously. Simple logging of event times is not sufficient to identify the transmitter. One point to note is that NORAD has misidentified the payloads on one of the multiple-satellite launches involving both Gonets-D1 and Strela-3 payloads. It has interchanged Cosmos 2386 (a Strela-3) and Gonets D1-8, to the significant confusion of some observers.

Thanks are due to Ary Boender and Hans Oeben for their assistance in this piece of work on both the Strela-3 and Gonets-D1 satellites during a period of concentrated observations early 2009, and particularly to Ary for detecting use of the 261 MHz frequency.

Three military satellites were launched from Plesetsk 2009 July 6 at 01:26 UTC using a Rokot vehicle. Two of them (Cosmos 2451 & Cosmos 2453) were detected transmitting Strela-3 type trigger pulses at 244.512 MHz and dumping messages at 261.035 MHz. No transmissions were detected that could be determined as coming from Cosmos 2452. This led to the conclusion that two of the satellites were Strela-3 and the other was possibly a Strela-3M/Rodnik.

In 2010, transmissions from Cosmos 2452 were detected from the Zarya location at 388.6875 MHz but there was nothing from its predecessor, Cosmos 2416.

A further Rokot launch carried a Strela-3, a Strela-3M and a Gonets-M into orbit and created a small puzzle. The Strela-3 was immediately identifiable because the object by NORAD as 2010-043B/37153 was found to be transmitting at the standard Strela-3 frequencies of 244.512 MHz and 261.035 MHz.

The other two objects, 2010-043A/37152 and 2010-043C/37154 were initially reported by an observer in northern England as transmitting data at 245.0 MHz (subsequently measured as 244.999 MHz). A search by me for the Message Signal uncovered transmisions from both satellites at 388.6875 MHz.

This poses the question of why the Gonets-M and the Strela-3M seem to use the same frequencies. Based on their predecessors, Gonets D-1 and Strela-3, they would be expected to have thir own discreet pairings. One possible explanation is that the store/forward message systems have converged and that Gonets-M is being made available to commercial businesses while Strela-3M is still reserved for military/government but with the Strela-3M users having access to Gonets-M also.

After a few months, the transmissions disappeared as the satellites presumably switched to operational frequencies (as yet unreported), strengthening the convergence idea. The 245/388 MHz MHz channels may be for testing purposes with the Gonets-M and Strela-3M using similar systems.

2012 August, a short analysis of transmissions at 400.180 MHz showed them to be store-dump type trigger signals emitted every 16 seconds from the classified American satellite USA 217.