At 17:00 UTC Tuesday, the Galaxy 15 spacecraft passed Galaxy 13's 127 degree west longitude orbital location. I didn't see as many stories about potential interference as when the same satellite passed AMC-11. One reason may be that AMC-11 customers largely avoided interference thanks to the satellite shifts performed by SES New Skies. These included moving in SES-1 and using Intelsat's 19-meter uplink antenna at the Clarksburg, Md. teleport to minimize the amount of signal hitting Galaxy 15's receivers, thus setting expectations for little or no interference from Galaxy 15 at 127 degrees.
The majority of Intelsat’s customers remained on Galaxy 13 and did not face interference or service disruptions, riding out the flyby. In some cases, however, Intelsat utilized three satellites to fulfill some customers’ requests for turnaround services, according to a company spokesman. Galaxy 13 carries a Ku-band payload, which limited the amount Intelsat could move it to avoid interference from Galaxy 15. The good news is Intelsat seems to have managed to avoid interference to Galaxy 13 customers. These include TNT, Discovery Networks, the NFL, HDNet, Wealth TV, Starz, Cinemax HDTV, HBO HDTV, A&E TV Networks, BBC World News and Halogen, according to LyngSat.
Intelsat has set up Web pages with information for customers on Galaxy 13 and Galaxy 14 (the next satellite to be affected), concerning Galaxy 15's path and interference mitigation steps.
Naval Research Laboratory (NRL) researchers used observations from NASA's twin Solar Terrestrial Relations Observatory (STEREO) spacecraft to see the events that likely caused the failure of Galaxy 15. The NRL news release describes the events:
"The recent sequence of space weather events started with a moderate solar flare and prominence eruption from solar active region 1059, at 9:04 UT on April 3, 2010," said the NRL's Brian Wood. "A CME [coronal mass ejection] associated with this eruption was subsequently observed by NRL's Space Science Division (SSD) developed solar ultraviolet imagers, white light coronagraphs, and heliospheric imagers onboard the NASA STEREO satellites."
Wood further noted that "a 'halo' CME was concomitantly observed by the NRL-developed LASCO coronagraph on the SOHO spacecraft that is located at the Lagrangian L1 point between the Sun and the Earth…" This appeared to indicate that the CME was headed straight to Earth. He further noted that imagers on the two NASA STEREO spacecraft which orbit about 70 degrees "ahead and behind Earth" continuously tracked that CME from the time it appeared on the Sun's surface until it struck on April 5, 2010.
The news release includes stereo imagery from the heliospheric imagers on the two spacecraft.
Galaxy 15 may have been the first casualty of the new solar cycle, which is numbered 24. As this solar cycle is just starting, more solar storms and coronal mass ejections are likely as this latest solar cycle reaches its peak.