Space Security Index

Space Security 2011
30
2010 Development
Software failure leaves Galaxy 15 adrift in the GEO belt, but it is eventually recovered
On 4 April, Intelsat General’s Galaxy 15 communications satellite experienced a malfunction
in GEO, which left it unresponsive to commands from ground operators. 12 As a result, the
satellite could not perform the station-keeping maneuvers required to maintain its orbital
slot at 133W over the Pacic Ocean between Hawaii and South America. e gravitational
forces from Earth’s bulge under the American landmass caused the satellite to slowly drift
eastward through the active GEO belt and past other satellites.
roughout April, Intelsat sent over 200,000 commands to the satellite in an attempt to
either turn o its communications payload or maneuver it to stop the drift. 13 All attempts
failed and, in early May, Intelsat announced that Galaxy 15 was too close to another
active satellite, AMC 11, to attempt further interventions. Intelsat was concerned that the
interventions would interfere with AMC 11.
Galaxy 15’s communications payload was powered by the satellite’s solar panels. As long
as the panels remained pointed at the Sun, the satellite had electrical power to retransmit
any C-Band broadcasts it picked up. e satellite’s ability to keep its antennas pointed at
the Earth and solar panels pointed at the Sun depended on the function of its momentum
wheels. Without periodic commands from the ground, these momentum wheels would
eventually saturate and the satellite would be unable to maintain its attitude pointing.
Intelsat originally predicted this “loss of Earth lock” would happen in late July or early
August. 14 However, this estimate was revised repeatedly as time went on. 15
On 29 December, Intelsat announced that it had regained full control of Galaxy 15. 16 e
satellite’s onboard battery had fully drained on 23 December, which caused the system to
perform a software reset and restored ground control. e satellite was placed in safe mode,
which prevented its payload from receiving or transmitting any signals. On 13 January 2011,
Intelsat announced that it would be moving Galaxy 15 to an orbital slot at 93W for a full
systems checkout. 17 After that, the satellite could be put back into service in its original slot.
On 20 April, Orbital Sciences, the company that built the satellite, suggested that the
malfunction could have been caused by severe space weather. 18 On the day of the failure, the
U.S. National Oceanographic and Atmospheric Administration’s (NOAA) Space Weather
Prediction Center released a space weather advisory warning bulletin that detailed signicant
solar activity. 19 However, on 13 January 2011, Intelsat announced that a failure review board
had concluded that the malfunction was caused by an electrostatic discharge (ESD) event,
and ruled out solar activity as the trigger. 20 e ESD caused a software glitch, which resulted
in the satellite’s inability to accept commands.
2010 Development
Cataloged debris field from the 2007 intentional destruction of a Chinese satellite passes 3,000 objects
In October, NASA announced that more than 3,000 pieces of trackable debris (>10 cm in
diameter) from the intentional destruction of the Chinese Fengyun-1C weather satellite in
January 2007 had been ocially cataloged. 21 In January 2011, four years after the event,
more than 95 per cent of this debris was still in orbit, where much of it is expected to remain
for several more decades. 22 e debris from the destruction of the Fengyun-1C represents
more than one-fth of all cataloged objects below 2,000 km. 23