This is a list of all frequencies reported to be associated with known SDS satellites. Not all have been verified and some satellite names are tentative, based on circumstatial evidence when associating objects from Mike McCants's "classified.tle" file with known satellite names.
In addition, earlier SDS satellites in HEO also transmitted the AFSATCOM signal near 243.7 MHz. In recent years, only the transmissions from USA 125 and USA 137 have been logged.
| Freq (MHz) |
Satellite |
Payload |
Signal Type |
Notes |
| 2242.515 |
USA 21
(SDS-1 F6)
1987-015A
17506 |
US mult--tasking intelligence-gathering and communications satellite |
CW carrier, oscillates in frequency due to satellite spinning at 4.6s per rev |
Identification very tentative - highly eccentric orbit, non-operational, the signal oscillation is probably due to the originally de-spun aerial platform having matched rotation with the satellite body, probably an SDS-1 satellite (either F4 or F6) - listed in classfd.tle as 90004 |
| 2242.500 |
USA 40
(SDS-2 F1)
1989-061B
20167 |
US mult--tasking intelligence-gathering and communications satellite |
CW carrier, oscillates in frequency due to satellite spinning at 5.2s per rev |
Tentative identification of satellite with received signals - non-operational but still transmitting, the signal oscillation is probably due to the originally de-spun aerial platform having matched rotation with the satellite body - identified as 90020 in classfd.tle |
| 2242.496 |
USA 67
(SDS-2 F2)
1990-097B
20963 |
Multi-tasking military satellite near 75° east longitude |
PSK with sub-carrier, 1024 kHz |
Originally GEO but the orbit has evolved to an inclination of 15° and is slightly elliptical so reception varies according to the sub-satellite latitude - a study by Ivan Artner 2006 March showed that the transmitter responds to eclipse periods by becoming intermittent while out of direct sunlight, indicating that the batteries are not charging properly from the solar cells |
| 2242.500 |
USA 89
(SDS-2 F3)
1992-086B
22518 |
US mult--tasking intelligence-gathering and communications satellite, now deactivated |
CW carrier plus side-bands |
During 2006, Ivan Artner tracked a spinning satellite in HEO, the times did not fit known satellites in that type of orbit - it has been tentatively identified as 90026 (last observed in 2004) but transmissions ceased during the first quarter of 2007 before an orbit could be determined, the identification of it as USA-89 is also tentative |
| 251.325 |
USA 155
(SDS-3 F1)
2000-080A
26635 |
US intelligence-related satellite near 10° west longitude, possibly including communications |
AM - 4.8 kHz data tone |
One of a triplet of similar of transmissions from a secondary payload on a US classified satellite in GEO, signal appears to be continuous and is similar to ones from USA-179 - Also transmits at 252.675 MHz, 258.775 MHz, 268.6755 MHz and 2242.486 MHz. No longer operational. |
| 268.675 |
USA 155
(SDS-3 F1)
2000-080A
26635 |
US intelligence-related satellite near 10° west longitude, possibly including communications |
AM - 4.8 kHz data tone |
One of a triplet of similar of transmissions from a secondary payload on a US classified satellite in GEO, signal appears to be continuous and is similar to ones from USA-179 - Also transmits at 251.325 MHz, 252.675 MHz, 258.775 MHz and 2242.486 MHz. No longer operational. |
| 2242.486 |
USA 155
(SDS-3 F1)
2000-080A
26635 |
US intelligence-related satellite at 10° west longitude, possibly including communications |
PSK with sub-carrier, 1024 kHz |
Geosynchronous orbit, frequency variable according to onboard power available - increases significantly at times of eclipse. Also transmitted at 251.325 MHz, 252.675, 258.775 and 268.775 MHz. No longer operational. |
| 252.675 |
USA 155
(SDS-3 F1)
2000-080A
26635 |
US intelligence-related satellite near 10° west longitude, possibly including communications |
AM - high speed (19.2 kb/s?) data transmission |
Transmissions from a secondary payload on a US classified satellite in GEO, signal appears to be continuous - Also transmits at 251.325 MHz, 258.775 MHz, 268.675 MHz and 2242.486 MHz. No longer operational. |
| 258.775 |
USA 155
(SDS-3 F1)
2000-080A
26635 |
US intelligence-related satellite near 10° west longitude, possibly including communications |
AM - 4.8 kHz data tone |
One of a triplet of similar of transmissions from a secondary payload on a US classified satellite in GEO, signal appears to be continuous and is similar to ones from USA-179 - Also transmits at 251.325 MHz, 252.675 MHz, 268.675 MHz and 2242.486 MHz. No longer operational. |
| 250.075 |
USA 162
(SDS-3 F2)
2001-046A
26948 |
US intelligence-related satellite near 144° west longitude, possibly including communications |
AM - 4.8 kHz data tone |
One of a triplet of reported frequencies carrying similar signals from satellite in geosynchronous orbit, exact frequency not known - also reported to transmit at 256.475, 263.225, 267.550 MHz and 2242.5 MHz |
| 263.225 |
USA 162
(SDS-3 F2)
2001-046A
26948 |
US intelligence-related satellite near 144° west longitude, possibly including communications |
AM - high speed (19.2 kb/s?) data transmission |
Reported frequency for a satellite in geosynchronous orbit, exact frequency not known - also reported to transmit at 250.075 MHz,256.475, 267.550 MHz and 2242.5 MHz |
| 267.550 |
USA 162
(SDS-3 F2)
2001-046A
26948 |
US intelligence-related satellite near 144° west longitude, possibly including communications |
AM - 4.8 kHz data tone |
One of a triplet of reported frequencies carrying similar signals from satellite in geosynchronous orbit, exact frequency not known - also reported to transmit at 250.075 MHz, 256.475 MHz, 263.225MHz and 2242.5 MHz |
| 2242.500 |
USA 162
(SDS-3 F2)
2001-046A
26948 |
US intelligence-related satellite near 144° west longitude, possibly including communications |
CW carrier (plus side-bands?) |
Reported frequency for satellite in geosynchronous orbit - also reported to transmit at 250.075 MHz, 256.475, 263.225 and 267.550 MHz |
| 256.475 |
USA 162
(SDS-3 F2)
2001-046A
26948 |
US intelligence-related satellite near 144° west longitude, possibly including communications |
AM - 4.8 kHz data tone |
One of a triplet of reported frequencies carrying similar signals from satellite in geosynchronous orbit, exact frequency not known - also reported to transmit at 250.075, 263.225, 267.550 MHz and 2242.5 MHz |
| 251.700 |
USA 179
(SDS-3 F3)
2004-034A
28384 |
US intelligence-related satellite, possibly including communications |
AM - 4.8 kHz data tone |
One of a pair of transmissions from a secondary payload on US classified satellite in HEO - Switched on and off to co-ordinate coverage with USA-198 - Prior to 2008 Mar 14, USA-179 was operating alone and was providing near 8 hours' coverage per pass at this frequency - Also transmits at 256.375 MHz and 2242.50 MHz |
| 2242.503 |
USA 179
(SDS-3 F3)
2004-034A
28384 |
US mult--tasking intelligence-gathering and communications satellite |
CW carrier plus side-bands - strong |
Part of a constellation of three satellites in highly eccentric orbit (HEO), switches to low power when over the southern hemisphere - Also transmits at 251.700 MHz and 256.375 MHz |
| 256.375 |
USA 179
(SDS-3 F3)
2004-034A
28384 |
US intelligence-related satellite - possibly including communications |
AM - 4.8 kHz data tone |
One of a pair of transmissions from a secondary payload on US classified satellite in HEO - Switched on and off to co-ordinate coverage with USA-198 - Prior to 2008 Mar 14, USA-179 was operating alone and was providing near 8 hours' coverage per pass at this frequency - Also transmits at 251.700 MHz and 2242.50 MHz |
| 251.275 |
USA 198
(SDS-3 F4)
2007-060A
32378 |
US intelligence-related satellite - possibly including communications |
AM - 4.8 kHz data tone plus various test modes |
One of a pair of transmissions from a secondary payload on US classified satellite in HEO used during the test phase of the satellite up until 2008 March 13 - on March 14, USA-198 switched to its operational frequencies at 251.700 MHz and 256.375 MHz, test transmission also at 258.800 MHz, plus transmitter at 2242.50 MHz |
| 2242.504 |
USA 198
(SDS-3 F4)
2007-060A
32378 |
US mult--tasking intelligence-gathering and communications satellite |
CW carrier plus side-bands - strong |
Part of a constellation of three satellites in highly eccentric orbit (HEO), lanched 2007 Dec 10 as a replacement for USA-125, also transmits at 251.700 MHz and 256.375 MHz, and used 251.275 and 258.800 MHz during the orbital test phase up to 2008 Mar 13
Frequency discovered independently by Bob Christy and Sven Grahn about 20 minutes after launch. |
| 251.700 |
USA 198
(SDS-3 F4)
2007-060A
32378 |
US intelligence-related satellite, possibly including communications |
AM - 4.8 kHz data tone |
One of a pair of transmissions from a secondary payload on US classified satellite in HEO - Switched on and off to co-ordinate coverage with USA-179 - Also transmits at 256.375 MHz and 2242.50 MHz |
| 256.375 |
USA 198
(SDS-3 F4)
2007-060A
32378 |
US intelligence-related satellite - possibly including communications |
AM - 4.8 kHz data tone |
One of a pair of transmissions from a secondary payload on US classified satellite in HEO - Switched on and off to co-ordinate coverage with USA-179 - Also transmits at 251.700 MHz and 2242.50 MHz |
| 258.800 |
USA 198
(SDS-3 F4)
2007-060A
32378 |
US intelligence-related satellite - possibly including communications |
AM - 4.8 kHz data tone plus various test modes |
One of a pair of transmissions from a secondary payload on US classified satellite in HEO used during the test phase of the satellite up until 2008 March 13 - on March 14, USA-198 switched to its operational frequencies at 251.700 MHz and 256.375 MHz, sharing duties with USA-179 - Test transmission also at 251.275 MHz, plus transmitter also at 2242.50 MHz |
| 2232.498 |
USA 198
(SDS-3 F4)
2007-060A
32378 |
Navy Ocean Surveillance System SIGINT |
CW carrier plus side-bands |
Navy Ocean Surveillance System |
