Zarya - Soviet, Russian and International Spaceflight
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Tyneside, UK
2017 Sep 22
Friday, Day 265

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Omid Transmission Mode 1

The first transmission to be logged from Omid, 2009 Feb3, was in this format.

When seen on a software-based receiver, the signal structure is thirteen parallel lines, with a space of 1 kHz between them. To the ear, with the receiver set to FM reception mode, it comes across as a 1 kHz tone. It carries no data.

The S-shaped curvature of the lines in this plot is due to the Doppler effect. On the plot, time runs horizontally - increasing towards the right. The vertical scale is frequency and the units are Hz.


The inclination of Omid's orbit is such that the satellite has two daily periods of visibility from the middle east. In the period February 3 to February 7, Omid was observed to transmit on two consective passes in each of these windows. The first transmission of the pair was in Mode 1, the second in Mode 2.

Attempts to observe Omid from Hawaii between the Mode 1 and Mode 2 passes above Iran drew a blank, indicating that Omid was switched off between them.
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