Spotlight On: RS10/RS11 and RS12/RS13

By: John A. Magliacane, KD2BD

[This article originally appeared in The AMSAT Journal, Volume 15 No. 4, July/August 1992]


Radio Sputnik (RS) satellites are favorite starting points on the road to Amateur satellite communications. These satellites provide consistent service, strong downlink signals, and have very sensitive transponders, making them easily accessible to even the most modest Amateur satellite ground stations.

Spacecraft History

The first group of RS satellites were launched back on October 26, 1978. RS-1 and RS-2 both contained "Mode A" linear transponders that were 40 kHz wide. The term "Mode A" refers to the fact that these transponders had uplink passbands in the 2-Meter Amateur band, and downlinks in the 10-Meter Amateur band. Since the Russians were limited to only a few watts of transmitter power on the 2-Meter band, the Mode A transponders carried on their RS satellites had to have very sensitive uplink receivers. Experience with RS operation proved the reliability of Mode A operation, especially during periods of low solar activity. Prior to the launch of RS-1 and RS-2, AMSAT-OSCAR-6, AMSAT-OSCAR-7, and AMSAT-OSCAR-8 all had been available for general use, and all supported Mode A linear transponder operations.

On December 17, 1981, six new RS satellites were launched together on a common launch vehicle. RS-3 and RS-4 were experimental satellites and did not contain transponders for general use. The remaining satellites contained 40 kHz wide Mode A linear transponders. In addition, RS-5 and RS-7 both contained "autotransponders" called ROBOTS. Autotransponders made it possible to carry on a CW telegraphy contact with the ROBOT computer carried on the satellite. Upon calling the satellite on a ROBOT uplink frequency, the spacecraft would respond with short message and issue a QSO number.

The autotransponders made it possible to carry out a CW contact on the satellite even if there were no ground stations available on the transponder at the time.

One Common Malady

Unfortunately, all these early Radio Sputnik satellites suffered with one common malady. Their 1700 km altitude circular orbit subjected the satellites to a great deal of radiation by flying through the lower levels of the Van Allen belts. The Van Allen belts surround the Earth at an altitude of between 1600 km and 8000 km and are comprised of high-energy sub-atomic particles that can damage sensitive electronic devices carried on satellites at this orbital altitude. Because of the radiation exposure, some RS satellites experienced unexpected transponder switching and hardware damage which made the satellites less than reliable.

After RS-5 and RS-7 had ceased operating, RS-10 and RS-11 were launched into a safer 1000 km altitude circular low-Earth orbit. Both RS-10 and RS-11 share a common power bus and space platform with COSMOS 1861, a Russian navigation satellite. Like their predecessors, RS-10 and RS-11 both contain 40 kHz wide Mode A linear communication transponders and ROBOTS, but they also contain new "Mode K" and "Mode T" transponders which have uplink passbands in the 15-Meter Amateur band. No other Amateur communications satellite had used 15-Meters for an uplink before.

On February 5, 1991 the latest group of RS satellites, RS-12 and RS-13, were launched along with COSMOS 2123, another Russian navigation satellite. These RS satellites are virtually identical in capability to RS-10 and RS-11. All four Radio Sputniks are alive and well and in operation at the present time.

Satellite Operation Made Easy

RS satellite operation is simple. For Mode A operations, just a few watts of transmitter power and a small 2-Meter antenna are all that are required for the uplink. A dipole antenna and a receiver capable of tuning the 10-Meter Amateur band are all that are needed for the downlink. Most operators use their existing HF station equipment for copying Mode A downlink signals. Converted CB rigs and portable 10-Meter transceivers lend themselves very nicely to portable Mode A operation. Uplink signals should be CW or USB voice. With a transponder bandwidth of only 40 kHz, there's not much room for FM signals on the satellite, so those operations are very much discouraged. Many 2-Meter FM rigs can be keyed for CW operation if appropriate connections are made within the transceiver. In fact, a large number of CW contacts have been made by keying the push-to-talk button on a 2-Meter handheld transceiver, although keyed FM transceivers tend to produce "chirpy" CW notes.

For Modes K and T, usually less than 100-watts of transmitter power and a dipole antenna are needed for the uplink. Regardless of the transponder mode, most of the emphasis should be placed on the sensitivity of the downlink receiver, because "if you can't hear 'em, you can't work 'em"!

Proper operating practice dictates that the transmitter or receiver operating on the highest frequency band be tuned in compensation for Doppler shift during a QSO. This means on Mode A, the transmitter VFO should be adjusted while the downlink receiver remains fixed. 0n Modes K and T, the transmitter VFO should remained fixed while the downlink receiver is adjusted for proper performance.

This practice not only applies to RS satellites, but remains valid for ALL Amateur transponder operations, and helps to avoid collisions between ground stations at geographically diverse locations as they experience varying magnitudes of Doppler shift.

Almost everyone who gives RS satellite operation a try is hooked after their first contact. After the pass is complete and the log book has been updated, you'll find them plotting out their strategy for the next pass. Since the RS series of satellites are in a circular orbit, orbital predictions are easy using OSCARLOCATORS or simple orbital prediction software.

RS Transponder Summary

Now let's look at the currently active group of RS satellites in detail. Figures 1, 2, 3 and 4.

The beacons transmit CW telegraph and provide spacecraft telemetry, ROBOT downlinks, and "Codestore" messages carrying news bulletins from the spacecraft command station RS3A.

At the present time, RS-10 is active on Mode A, while RS-12 is operating on Mode K. During periods of high solar flux, many satellite enthusiasts worked other stations a half a world away through RS-12 Mode K while the spacecraft was well below the horizon of each station. These sub-horizon contacts were made possible through F-layer propagation.

ROBOT Operation

When active, an autotransponder calls CQ and provides the uplink frequency being monitored. For example, RS-10 might be heard transmitting:

    "CQ CQ DE RS10 QSU 145820 KHZ AR"
after which the ROBOT will listen for call on 145.820 MHz. Calling the ROBOT is easy. Simply call the satellite, give your callsign, and end with AR. For example:

    "RS10 DE KD2BD AR"
The ROBOT uplink passband is several kilohertz wide, so extreme uplink frequency accuracy is unnecessary. Even chirpy CW signals have been found to work well. If the ROBOT does not copy your callsign correctly, it may ask for a repeat and respond with "QRM", "QRZ", or "RPT". Successful contacts are rewarded with ROBOT response complete with a QSO number such as:

    "KD2BD DE RS10 QSO NR 386 0P ROBOT TU USW QSO NR 386 73 SK"
High-speed CW works best for calling the ROBOT. The ROBOT will respond at the speed it is called.

QSL cards are available through the Radio Sputnik coordinating group:

Radio Sport Federation
Box 88
Moscow, Russia

Fig. 1 - Satellite: RS-10 NASA Catalog Number: 18129

Analog Transponders:
Uplink                                  Downlink
Mode K:  21.160 -  21.200 Mhz            29.360 MHz -  29.400 MHz
Mode T:  21.160 -  21.20O MHz           145.860 MHz - 145.900 MHz
Mode A: 145.860 - 145.900 Mhz            29.360 Mhz -  29.400 MHz

Mode KT: 21 MHz uplink into 29 and 145 MHz downlinks
Mode KA: 21 MHz and 145 MHz uplinks into a common 29 MHz downlink

Beacons: 29.357 MHz, 29.403 MHz, 145.857 MHz, 145.903 MHz

Robot Uplinks: 21.120 MHz, 145.820 MHz

Fig. 2 - Satellite: RS-11 NASA Catalog Number: 18129

Analog Transponders:
Uplink                                  Downlink
Mode K:  21.210 - 21.250 Mhz             29.410 MHz -  29.450 MHz
Mode T:  21.210 - 21.250 Mhz            145.910 MHz - 145.950 MHz
Mode A: 145.910 - 145.950 Mhz            29.410 MHz -  29.450 MHz

Mode KT: 21 MHz uplink into 29 and 145 MHz downlinks
Mode KA: 21 MHz and 145 MHz uplinks into a common 29 MHz downlink

Beacons: 29.407 MHz, 29.453 MHz, 145.907 MHz, 145.830 MHz

Robot Uplinks: 21.130 MHz, 145.830 MHz

Fig. 3 - Satellite: RS-12 NASA Catalog Number: 21089

Analog Transponders:
Uplink	                                 Downlink
Mode K:  21.210 - 21.250 Mhz             29.410 MHz -  29.450 MHz
Mode T:  21.210 - 21.250 MHz	        145.910 MHz - 145.950 MHz
Mode A: 145.910 - 145.950 Mhz            29.410 MHz -  29.450 MHz

Mode KT: 21 MHz uplink into 29 and 145 MHz downlinks
Mode KA: 21 MHz and 145 MHz uplinks into a common 29 MHz downlink

Beacons: 29.408 MHz, 29.454 MHz, 145.912 MHz, 145.958 MHz

Robot Upinks: 21.130 MHz, 145.830 MHz

Fig. 4 - Satellite: RS-13 NASA Catalog Number: 21089

Analog Transponders:
Uplink                                  Downlink
Mode K:  21.260 -  21.300 Mhz            29.460 MHz -  29.500 MHz
Mode T:  21.260 -  21.300 Mhz           145.960 MHz - 145.000 MHz
Mode A: 145.960 - 146.000 Mhz            29.460 MHz -  29.500 MHz

Mode KT: 21 MHz uplink into 29 and 145 MHz downlinks
Mode KA: 21 MHz and 145 MHz uplinks into a common 29 MHz downlink

Beacons: 29.458 MHz, 29.504 MHz, 145.862 MHz, 145.908 MHz

Robot Uplinks: 21.138 MHz, 145.843 MHz
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