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Zenit - Korolyov's Legacy

Tyneside, UK
2024 Jun 19
Wednesday, Day 171

Curated by:

Kettering's Bread and Butter

At Kettering Grammar School, we had never heard the name 'Zenit'. All we observed was a steady stream of satellites called 'Cosmos' going into orbit and being recovered after a week or so, sometimes emitting pseudo-morse code beacons as they descended under a parachute at the end of that time. With experience, we learned to differentiate them into types, based on the signal content, orbit height and inclination, and the pattern of the recovery beacon.

These web pages attempt to summarise the Zenit missions and look at them, in retrospect, in the light of what is now known compared with what was deduced at the time. There has been no access to the main Kettering Group files - they remain locked away. However, circulated copies of some records are held by various people. Information and statistics found here are derived from public documents, my own records (including radio tracking notes), some Kettering Group circulated records/notes, and a little help from Sven Grahn in particular.

There are still sections to be added covering, in particular, a look at how the Kettering mission analyses matched the actual types.

The Start

After successes with Korabl and some early non-recoverable satellites of the Cosmos series, Geoff Perry and Derek Slater turned their attention to the series of missions that soon became labelled "eight day wonders". They would be launched and, after a little under eight days, would disappear from orbit. Seeing that the first of the flights, labelled Cosmos 4, was announced as having been recovered from orbit, it was reasonable to assume the same for its successors. Disappearances occurred while following a ground track passing northward over the Kazakhstan and Southern Russia part of the Soviet Union - ideal for a re-entry and landing. Cosmos 12 (Zenit-2 ?6) was the first to be tracked from Kettering. From then on it was a case of waiting for new launches to occur as old ones disappeared. Cosmos 4 and Cosmos 7 (the first two Zenit to reach orbit) were tracked from Japan.


Originally, transmissions consisted of a frequency-shift-keyed signal with about 1 kHz frequency spacing and pulse lengths varying to indicate measured parameters. There was a train of measurements lasting about 1s each preceded/succeeded by a calibration train of 30 short pulses and a space for a further two. The whole telemetry frame of fifteen parameters took about 16 seconds to transmit. Later, the transmissions omitted the telemetry content and consisted of a simple FSK signal with the two tones flip-flopping' with a period around 1.5s.

Presently, this review deals mainly with the 20 MHz, HF transmissions from Zenit.

In 1966, Sven Grahn detected a morse code transmission sounding like "TK" at the end of the Cosmos 114 mission. Recovery beacons became one of the differentiators used at Kettering when trying to determine type differences.

Later, Sven discovered transmissions at the VHF frequencies used by Zenit.

From the left hand menu, you will be able to reach summaries, comparisons and descriptions of the zenit variations.

Still Going.... After a Fashion

Zenit is still with us today, in two forms - the recent Foton-M flights in co-operation with ESA, and a hybrid that uses the later Yantar Instrument Unit with Korolyov's Zenit re-entry vehicle. It is exemplified by Bion-M and Cometa. These Yantar variants are not covered here.
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