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Tracking the ISS


Tyneside, UK
2018 Jan 20
Saturday, Day 20

Maintained by:













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Launches to the ISS - the view from Europe

Europe is quite well placed for tracking the inital stages of launches to the ISS from both the US and from Russia. When the Shuttle was flying missions out of the Kennedy Space Center, Europe was directly in line with the ascent trajectory and, if conditions allowed, both the orbiter and the external tank could be visible like very bright stars crossing the sky from the west about 20 minutes after lift-off. A few words of conversation could also be picked up on the VHF transmission channel.

For launches from Baikonur, the majority of Europe has to wait about 4.5 hours before signals can be intercepted on rev 3. Eastern Europe sees a low elevation pass on rev 2 but interception of signals depends on co-visibility with Moscow so only the more-northerly states stand a chance. However, introduction of the new six-hour run from Baikonur to the ISS means that Soyuz or Progress are in a higher orbit by rev 2 so signals are available over a much wider area.


Soyuz and Progress

As well as the Soyuz voice channel, Soyuz and Progress transmit at two other frequencies. All three channels are relatively easy to receive. The telescopic aerial supplied with most receivers will normally be sufficient but will require some 'waving around' to find the best direction to point it.

Soyuz voice is frequency modulated with a deviation around 30-40 kHz. On most receivers the narrow FM setting will produce a result but the bandwidth is slightly narrower than ideal. Unfortunately, the FM setting is often a little too wide and the voice can get lost in the background hiss. The 166 MHz VHF frequency can be detected in both FM and AM modes but it will be necessary to tune to one of the sidebands 128 kHz above or below 166 MHz to hear the distinctive, sharp buzz with cycles of fading as Soyuz or Progress slowly rotate. The UHF frequency near 900 MHz needs the receiver set to CW and manifests itself as a rapidly falling tone.

Depending on the particular mission profile, the 166 MHz and 922 MHz transmissions are switched off when out of Russian ground stations. If the receiver is correctly tuned before hand the transmitter can be heard switching on.

Freq (MHz) Satellite Transmission Notes
121.750
Soyuz
TMA-M

30 kHz deviation FM voice ISS Crew ferry: Digital control system, three crew seats, from 2011
166.000
Progress
M-M

Telemetry transmission PCM-FM, sidebands ±128 kHz ISS supplies ferry: 2008-
166.000
Soyuz
TMA-M

Telemetry transmission PCM-FM, sidebands ±128 kHz ISS Crew ferry: Digital control system, three crew seats, from 2011
922.763
Progress
M-M

CW carrier. ISS supplies ferry: Part of the REGUL command and control system - there may be other elements of signals on sidebands around this frequency. 2008-
922.763
Soyuz
TMA-M

CW carrier. ISS Crew ferry: Part of the REGUL command and control system - there may be other elements of signals on sidebands around this frequency. Digital control system, three crew seats, from 2011

On launch day, eastern Europe gets a low elevation pass on rev 2 - about three hours after launch. Since the introduction of the six-hour trip to ISS, the chances of intercepting signals on Rev 2 has improved because the vehicle is already in a higher orbit. Rev 3 brings a pass that can be detected just about anywhere on the continent as long as Soyuz is in line of sight from the ground station at Bear Lake near Moscow. Sometimes signals appear a little earlier than expected, indicative of working with the ground station near St Petersburg. Progress craft been heard even earlier in the pass transmitting to "Cosmonaut Viktor Patsayev" a tracking ship moored in the port of Kaliningrad on the Baltic Sea.

Soyuz/Progress revs 3-5

The map above shows the tracks of Revs 3, 4 and 5 of a newly-launched Soyuz or Progress. The craft moves on a south-west to north-east track and successive orbital passes migrate to the west as the Earth rotates beneath the orbit.

Rev 4 and Rev 5 usually yield good signals at 166 and 922 MHz. One or both of Revs 4 and 5 can sometimes be detected as Soyuz or Progress rises in the west. This is because of an orbit adjustment to move Soyuz from its initial low, circular orbit to its transfer orbit for rendezvous with the ISS that takes place out of sight of ground stations. The transmitter is left on to ensure the craft can be detected in the event of the manoeuvre going awry.

One point to note about Rev 4 is that, going right back to days when Soyuz used to transmit at HF, closest approach to the UK as measured from the Doppler shift comes at 6hr 6m after launch (+/- 1 min) when using a two day approach to the ISS. With the newer six-hour approach, it stretches to 6hr 10m and the pass occurs just before Soyuz docks with the ISS. The voice channel carries details of final checks before hatch opening.

Rev 5 is the final chance for voice on day one of a two day ISS transfer. It is a low elevation pass as seen from Moscow but, being at a strategic point in the mission, voice communication is important. Equivalent passes on other days of the flight do not usually produce transmissions of any kind.

The plot below was made in real time and shows the Doppler curve from the 922 MHz transmission by Progress M-63. The fades are due to a changing viewing angle as it crossed the sky and rotation of the spacecraft as part of its regime of temperature regulation.

Progress M-63 Doppler



Space Shuttle

During the ascent and an initial period in orbit, the Space Shuttle used a straightforward VHF air-ground system for the crew to communicate with Houston. It is in the military airband, for Europe at least, and is amplitude modulated (AM). Once initial checks were out of the way and onboard systems started to be activated, the shuttle would switch to S-band.

STS Rev 0 Ground Track

There is a ground station near Madrid, Spain and it used to be possible to pick up a few terse words as the orbiter passed by on Rev 0. The content was quite often a reference to a pre-printed checklist. Occasionally there could be heard mention of an umbilical door closing. This is was a door covering one of the apertures through which a propellant line passed while the orbiter and external tank were still connected.

The shuttle would switch back to VHF prior to re-entry. Occasional bursts of unmodulated carrier or voice were noted from Europe on the final orbit.

Freq (MHz) Satellite Transmission Notes
259.700
STS

AM voice ISS Crew/payload transport: Detected over Europe occasionally prior to Shuttle re-entry from ISS operations, and with voice during the orbital injection phase from Kennedy SC to Europe - also transmitted at 2217.500 MHz, 1981-2011
2217.500
SGLS 4
STS

CW carrier plus side bands carrying data ISS Crew/payload transport: Integrated voice and data on SGLS Channel 4 - transmitter operates almost continuously while the payload bay doors are open, also transmitted at 259.7 MHz, 1981-2011

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