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Otherwise known as Spacenet 4, SN-4


Designation 21227 / 91028A
Launch date 13 Apr 1991
Country of origin United States
Mission Telecommunications
Geostationary orbit see below
Launch vehicle Delta 2 #204

[early 1998] Would have technical malfunctions in the Ku-band


Begin End Position
L: 13 Apr 1991 Jan 2000 101°W
Feb 2000 Sep 2000 81°W
Nov 2000 Jan 2004 172°E
Jan 2004 Apr 2006 172°E, inclined

After its relocation over the Pacific, the satellite provides trans-pacific communications (mainly data). It covers Northern Pacific rim (Russia, Japan, Korea, part of China, Taiwan, The Philippines, part of Vietnam), Hawaii, Alaska, and the US & Canada West coast.

In mid-2005, the antennas are repointed North to provide Ku-band capacity for aircraft operating in the area.

End of life

Out of service Apr 2006
Cause Moved to the junk orbit

External resources

sat-index articles

Technical data

EIRP coverage (dBW) (before relocation)

C-band, 36 MHz transponders
C-band, 72 MHz transponders

C-band transponder frequency chart
Ku-band transponder frequency chart


Main transponders 18
Backup transponders  
Power 36 MHz: 12 of 8.5 W (SSPA)
72 MHz: 6 of 16 W (TWTA)
Bandwidth 12 of 36 MHz
6 of 72 MHz
Coverage Pacific
EIRP max 37 dBW
Polarization linear


Main transponders
Backup transponders  
Power 6 of 16.2 W (TWTA)
2 of 30 W (TWTA)
Bandwidth 72 MHz
Coverage Pacific
EIRP max 46 dBW
Polarization linear H
Frequencies uplink: 14.0-14.5 GHz
downlink: 11.7-12.2 GHz

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