Galaxy 15
Encyclopedia
Galaxy 15 is an American
telecommunications satellite which is owned by Intelsat
. It was launched for and originally operated by PanAmSat
, and was subsequently transferred to Intelsat when the two companies merged in 2006. It was originally positioned in geostationary orbit
at a longitude
of 133° West, from where it was used to provide communication services to North America. In April 2010, Intelsat lost control of the satellite, and it began to drift away from its orbital slot, with the potential to cause disruption to other satellites in its path.
On 27 December 2010, Intelsat reported that the satellite had rebooted as per design and the command unit was responding to commands again. In addition, the satellite had been secured in safe mode and the potential for interference issues from Galaxy 15 had ceased.
On 14 January 2011 the satellite was located near 93° west, where further testing is scheduled to be performed. On March 18, 2011, Galaxy 15 has been re-certified from the FAA and is now sending GPS signal corrections. It will be repositioned back to its original location by about April 4, 2011.
, and was based around the Star-2
satellite bus
. The contract for its manufacture was signed in 2001, and at the time it was to have been identical to the Galaxy 12 and Galaxy 14 satellites which were also on order. In 2003, the contract was changed to allow the addition of more transponder
s to support a United States Government navigation program.
The communications payload aboard Galaxy 15 consisted of 24 transponder
s operating in the G
and H band
s of the NATO electromagnetic spectrum, or the C band
of the US IEEE spectrum. It also carried two C
/D band
(IEEE L band
) transponders, which form part of the US Government's Geostationary Communications and Control Segment, and are used for aircraft
navigation. At launch, the Galaxy 15 satellite had a mass of 2033 kilograms (4,482 lb), and an expected operational lifespan of around 15 years.
, using an Ariane 5GS
carrier rocket flying from ELA-3
at the Guiana Space Centre in Kourou
, French Guiana
. The launch occurred at 22:32 GMT on October 13, 2005, at the opening of an 84 minute launch window, and successfully placed Galaxy 15 into a geosynchronous transfer orbit. The French
Syracuse 3A military communications satellite was launched on the same rocket. During launch, Galaxy 15 was located beneath the Syracuse spacecraft, which was mounted atop a SYLDA
adaptor.
Following separation from the carrier rocket, Galaxy 15 raised itself to geostationary orbit by means of an IHI-500N apogee motor
. Its insertion into geosynchronous orbit occurred at around 19:00 on October 19, 2005.
which had to be relocated to 45.1° East for the start of a mission critical service for the United States government. Due to the necessity of relocating Galaxy 12 to 133° West, Intelsat was forced to leave 129° West vacant. On 20 April, Orbital Sciences theorized that they believed solar activity
was responsible for the satellite malfunctioning, although a later statement by the company said that the company had been unable to actually settle on "a single root cause." On May 3, an attempt at a very momentary series of strong pulses intended to cause a power system malfunction were sent to Galaxy 15. Unfortunately, this did not have the desired effect of causing a power system overload and subsequent shut down of the active transponders. It was the concern of neighboring satellite operators that this type of recovery attempt would have had the potential to permanently damage sensitive hardware onboard a satellite and could have contributed to placing a satellite into a permanent unrecoverable control state.
satellite, potentially causing interference with cable programming over the United States because the two satellites broadcast on similar frequencies. Between May 23 and June 7, 2010, Galaxy 15 passed within half a degree of AMC-11. As the two satellites passed close to each other, particularly during closest approach on May 31 and June 1, signals from Galaxy 15's still-active transponders could have interfered with signals being broadcast by AMC-11. SES maneuvered the AMC-11 satellite to reduce the possibility of interference. The SES-1
satellite followed behind Galaxy 15 during the pass to provide a backup to AMC-11 should it be needed.
On June 2, Intelsat and SES reported that no interference had occurred during closest approach, with the satellites passing within 0.2 degrees of each other. After it had passed AMC-11, Galaxy 15 continued to drift Eastwards. Between 12 and 13 July 2010, it passed Galaxy 13/Horizons-1, a satellite located at 127.0° West which is owned jointly by Intelsat and JSAT Corporation
. The pass was not reported to have caused any disruption to broadcasts being made by Galaxy 13/Horizons-1.
On 26 July 2010, Galaxy 15 passed another Intelsat spacecraft; Galaxy 14, which is located at 125.0° West. Closest approach occurred on 30 July. On August 8, 2010, the satellite drifted toward a satellite owned by GCI
, a broadcast company broadcasting to rural Alaska
. Galaxy 15 passed Anik F2 at orbital slot 111.1° West at or near October 20 through 25th, 2010. Further, the satellite continued to be watched by telecommunications companies due to the potential for interfering with C-band frequencies.
On 9 December 2010, it was reported that Galaxy 15 had potentially caused an outage to a National Weather Service NOAAPORT feed via SES-1 located at 101 west. Then on 12 December 2010, the following advisory was issued, A RISK HAS BEEN IDENTIFIED WHEN THE GALAXY 15 ROGUE SATELLITE TRAVERSES THE SES-1 ORBITAL POSITION WHICH MAY RESULT IN A POSSIBLE LOSS OF DATA VIA THE NWS AWIPS SBN/NOAAPORT FEED. THIS POTENTIAL INTERFERENCE MAY TAKE PLACE BETWEEN 12/12/10 AND 12/18/10 INCLUSIVE. To minimize interference, signals intended for SES-1 at 101 West were routed and uplinked via an 11 meter dish from the SES Americom Master Ground Station in Hawaii, which is outside of the Galaxy 15 uplink footprint.
Throughout the failure and drift period of Galaxy 15 status information regarding the continued operation of the two L-Band Wide Area Augmentation System Space Segment transponders once utilized by the FAA for aircraft precision location remained unknown. Prior to recovery, Galaxy 15 had been expected to pass by Inmarsat 4F3 at 98 degrees west in late December 2010. Inmarsat 4F3 has since performed some of the same WAAS mission for the FAA from 98 degrees west, that Galaxy 15 once performed at 133 west.
from tracking the sun, and it would shut down. After the power reset event, further attempts would be made to recover control of the satellite.
This event was originally predicted for late August or early September 2010, then Intelsat revised its estimate to sometime between 28 November and 29 December 2010. After subsequent criticism of the actual science behind Orbital Sciences' predictions Intelsat completely abandoned the published timeline method. Instead for a period Intelsat stated Based on the revised analysis, the estimated window for a Galaxy 15 off-point and loss of power could occur as early as this month without clarifying the month indicated. The hypothesis used to calculate the timeline of any potential occurrence of loss of power was imprecise, due to the fact the satellite has experienced
erratic loading conditions of radio frequency signals since it began to drift.
Six months after the initial failure date published timelines for shut down proved to be more hopes of a public relations campaign based in theory, and in an interview conducted in October 2010 during the Satcon Conference, both Intelsat & Orbital admitted that the hoped timeline scenario was, in theory and this has been an unprecedented situation, and we are learning as we go.
On 18 October 2011, Intelsat transitioned all of its 133° West customers back from Galaxy 12 to Galaxy 15.
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
telecommunications satellite which is owned by Intelsat
Intelsat
Intelsat, Ltd. is a communications satellite services provider.Originally formed as International Telecommunications Satellite Organization , it was—from 1964 to 2001—an intergovernmental consortium owning and managing a constellation of communications satellites providing international broadcast...
. It was launched for and originally operated by PanAmSat
PanAmSat
The former PanAmSat Corporation founded in 1984 by Reynold Anselmo, was a satellite service provider headquartered in Greenwich, Connecticut. It operated a fleet of communications satellites used by the entertainment industry, news agencies, internet service providers, government agencies, and...
, and was subsequently transferred to Intelsat when the two companies merged in 2006. It was originally positioned in geostationary orbit
Geostationary orbit
A geostationary orbit is a geosynchronous orbit directly above the Earth's equator , with a period equal to the Earth's rotational period and an orbital eccentricity of approximately zero. An object in a geostationary orbit appears motionless, at a fixed position in the sky, to ground observers...
at a longitude
Longitude
Longitude is a geographic coordinate that specifies the east-west position of a point on the Earth's surface. It is an angular measurement, usually expressed in degrees, minutes and seconds, and denoted by the Greek letter lambda ....
of 133° West, from where it was used to provide communication services to North America. In April 2010, Intelsat lost control of the satellite, and it began to drift away from its orbital slot, with the potential to cause disruption to other satellites in its path.
On 27 December 2010, Intelsat reported that the satellite had rebooted as per design and the command unit was responding to commands again. In addition, the satellite had been secured in safe mode and the potential for interference issues from Galaxy 15 had ceased.
On 14 January 2011 the satellite was located near 93° west, where further testing is scheduled to be performed. On March 18, 2011, Galaxy 15 has been re-certified from the FAA and is now sending GPS signal corrections. It will be repositioned back to its original location by about April 4, 2011.
Satellite
Galaxy 15 was constructed by Orbital Sciences CorporationOrbital Sciences Corporation
Orbital Sciences Corporation is an American company which specializes in the manufacturing and launch of satellites. Its Launch Systems Group is heavily involved with missile defense launch systems...
, and was based around the Star-2
STAR Bus
STAR Bus is a satellite platform manufactured by Orbital Sciences Corporation with an apogee kick motor to place a communications satellite into geostationary orbit, a thruster to provide the satellite with orbital station-keeping for a 15 year mission, and solar arrays to provide the satellite...
satellite bus
Satellite bus
A satellite bus or spacecraft bus is the general model on which multiple-production satellite spacecraft are often based. The bus is the infrastructure of a spacecraft, usually providing locations for the payload .They are most commonly used for geosynchronous satellites, particularly...
. The contract for its manufacture was signed in 2001, and at the time it was to have been identical to the Galaxy 12 and Galaxy 14 satellites which were also on order. In 2003, the contract was changed to allow the addition of more transponder
Transponder
In telecommunication, the term transponder has the following meanings:...
s to support a United States Government navigation program.
The communications payload aboard Galaxy 15 consisted of 24 transponder
Transponder
In telecommunication, the term transponder has the following meanings:...
s operating in the G
G band
-NATO G band:The G band in the modern sense is the range of radio frequencies from 4 GHz to 6 GHz in the electromagnetic spectrum. This is equal to wave lengths between 7.5 cm and 5 cm...
and H band
H band
H band can refer to two different regions of the electromagnetic spectrum, in the radio and near-infrared.-Radio:The H band is the range of radio frequencies from 6 GHz to 8 GHz in the electromagnetic spectrum. This is equal to wave lengths between 5 cm and 3.75 cm...
s of the NATO electromagnetic spectrum, or the C band
C band
The C band is a name given to certain portions of the electromagnetic spectrum, including wavelengths of microwaves that are used for long-distance radio telecommunications. The IEEE C-band - and its slight variations - contains frequency ranges that are used for many satellite communications...
of the US IEEE spectrum. It also carried two C
C band
The C band is a name given to certain portions of the electromagnetic spectrum, including wavelengths of microwaves that are used for long-distance radio telecommunications. The IEEE C-band - and its slight variations - contains frequency ranges that are used for many satellite communications...
/D band
D band
IEEE D band is the range of radio frequencies from 110 GHz to 170 GHz in the electromagnetic spectrum. This is equal to wave lengths between 1.8 mm and 2.7 mm...
(IEEE L band
L band
L band refers to four different bands of the electromagnetic spectrum: 40 to 60 GHz , 1 to 2 GHz , 1565 nm to 1625 nm , and around 3.5 micrometres .-NATO L band:...
) transponders, which form part of the US Government's Geostationary Communications and Control Segment, and are used for aircraft
Aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...
navigation. At launch, the Galaxy 15 satellite had a mass of 2033 kilograms (4,482 lb), and an expected operational lifespan of around 15 years.
Launch
The launch of Galaxy 15 was conducted by ArianespaceArianespace
Arianespace SA is a French company founded in 1980 as the world's first commercial space transportation company. It undertakes the production, operation, and marketing of the Ariane 5 rocket launcher as part of the Ariane programme....
, using an Ariane 5GS
Ariane 5
Ariane 5 is, as a part of Ariane rocket family, an expendable launch system used to deliver payloads into geostationary transfer orbit or low Earth orbit . Ariane 5 rockets are manufactured under the authority of the European Space Agency and the Centre National d'Etudes Spatiales...
carrier rocket flying from ELA-3
ELA-3
ELA-3, short for Ensemble de Lancement Ariane 3 , is a launch pad and associated facilities at the Centre Spatial Guyanais in French Guyana. ELA-3 is operated by Arianespace as part of the expendable launch system for Ariane 5 rockets...
at the Guiana Space Centre in Kourou
Kourou
Kourou is a commune in French Guiana, an overseas region and department of France located in South America.Kourou is the location of the Guiana Space Centre, France and ESA's main spaceport.-Geography:...
, French Guiana
French Guiana
French Guiana is an overseas region of France, consisting of a single overseas department located on the northern Atlantic coast of South America. It has borders with two nations, Brazil to the east and south, and Suriname to the west...
. The launch occurred at 22:32 GMT on October 13, 2005, at the opening of an 84 minute launch window, and successfully placed Galaxy 15 into a geosynchronous transfer orbit. The French
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
Syracuse 3A military communications satellite was launched on the same rocket. During launch, Galaxy 15 was located beneath the Syracuse spacecraft, which was mounted atop a SYLDA
Sylda
Sylda is a village and a former municipality in the Mansfeld-Südharz district, Saxony-Anhalt, Germany. Since 1 January 2010, it is part of the town Arnstein....
adaptor.
Following separation from the carrier rocket, Galaxy 15 raised itself to geostationary orbit by means of an IHI-500N apogee motor
Apogee kick motor
An apogee kick motor refers to a rocket motor that is regularly employed on artificial satellites destined for a geostationary orbit. As the vast majority of geostationary satellite launches are carried out from spaceports at a significant distance away from Earth's equator, the carrier rocket...
. Its insertion into geosynchronous orbit occurred at around 19:00 on October 19, 2005.
Failure
On April 5, 2010, Galaxy 15 ceased responding to commands sent to it by controllers on the ground. However, it is unclear when the actual initial failure date was because commands are often sent by satellite operators days or even weeks apart. Without commands necessary for stationkeeping it began to drift east away from its allotted orbital slot. All television signals were transferred to other satellites and all intentional transmissions were ceased. The Galaxy 12 satellite was removed from on-orbit storage at 123° West to replace Galaxy 15 at the 133° West orbital slot. Galaxy 12 was originally slated to replace another satellite Galaxy 27Galaxy 27
Galaxy 27 is a communications satellite owned by Intelsat located at 129° W longitude, serving most of the North American market. It was built by Space Systems/Loral, as part of its FS-1300 line...
which had to be relocated to 45.1° East for the start of a mission critical service for the United States government. Due to the necessity of relocating Galaxy 12 to 133° West, Intelsat was forced to leave 129° West vacant. On 20 April, Orbital Sciences theorized that they believed solar activity
Solar variation
Solar variation is the change in the amount of radiation emitted by the Sun and in its spectral distribution over years to millennia. These variations have periodic components, the main one being the approximately 11-year solar cycle . The changes also have aperiodic fluctuations...
was responsible for the satellite malfunctioning, although a later statement by the company said that the company had been unable to actually settle on "a single root cause." On May 3, an attempt at a very momentary series of strong pulses intended to cause a power system malfunction were sent to Galaxy 15. Unfortunately, this did not have the desired effect of causing a power system overload and subsequent shut down of the active transponders. It was the concern of neighboring satellite operators that this type of recovery attempt would have had the potential to permanently damage sensitive hardware onboard a satellite and could have contributed to placing a satellite into a permanent unrecoverable control state.
Reported Passes & Interference
On May 12, 2010, Intelsat and SES World Skies confirmed that Galaxy 15 would pass close to the latter's AMC-11AMC-11
AMC-11 , previously GE-11, is a Dutch, previously American geostationary communications satellite which is operated by SES World Skies. It is currently positioned in geostationary orbit at a longitude of 131 degrees West, from where it is used to relay cable television across North America for...
satellite, potentially causing interference with cable programming over the United States because the two satellites broadcast on similar frequencies. Between May 23 and June 7, 2010, Galaxy 15 passed within half a degree of AMC-11. As the two satellites passed close to each other, particularly during closest approach on May 31 and June 1, signals from Galaxy 15's still-active transponders could have interfered with signals being broadcast by AMC-11. SES maneuvered the AMC-11 satellite to reduce the possibility of interference. The SES-1
SES-1
SES-1 is a Dutch geostationary communications satellite which is operated by SES World Skies. It was originally ordered by SES Americom as a ground spare for AMC-5R, however in April 2008 a decision was made to launch it, and it was named AMC-1R. It was subsequently renamed AMC-4R, and finally...
satellite followed behind Galaxy 15 during the pass to provide a backup to AMC-11 should it be needed.
On June 2, Intelsat and SES reported that no interference had occurred during closest approach, with the satellites passing within 0.2 degrees of each other. After it had passed AMC-11, Galaxy 15 continued to drift Eastwards. Between 12 and 13 July 2010, it passed Galaxy 13/Horizons-1, a satellite located at 127.0° West which is owned jointly by Intelsat and JSAT Corporation
JSAT Corporation
JSAT Corporation is satellite operator with a fleet of 8 satellites in orbit. According to a 2004 report, JSAT was the fifth largest satellite operator in the world, ranked by 2003 fiscal year revenue...
. The pass was not reported to have caused any disruption to broadcasts being made by Galaxy 13/Horizons-1.
On 26 July 2010, Galaxy 15 passed another Intelsat spacecraft; Galaxy 14, which is located at 125.0° West. Closest approach occurred on 30 July. On August 8, 2010, the satellite drifted toward a satellite owned by GCI
GCI
GCI can stand for:* Georgetown Collegiate Investors* Guernsey Airport * The First Geneva Convention* Ground-controlled interception i.e...
, a broadcast company broadcasting to rural Alaska
Alaska
Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...
. Galaxy 15 passed Anik F2 at orbital slot 111.1° West at or near October 20 through 25th, 2010. Further, the satellite continued to be watched by telecommunications companies due to the potential for interfering with C-band frequencies.
On 9 December 2010, it was reported that Galaxy 15 had potentially caused an outage to a National Weather Service NOAAPORT feed via SES-1 located at 101 west. Then on 12 December 2010, the following advisory was issued, A RISK HAS BEEN IDENTIFIED WHEN THE GALAXY 15 ROGUE SATELLITE TRAVERSES THE SES-1 ORBITAL POSITION WHICH MAY RESULT IN A POSSIBLE LOSS OF DATA VIA THE NWS AWIPS SBN/NOAAPORT FEED. THIS POTENTIAL INTERFERENCE MAY TAKE PLACE BETWEEN 12/12/10 AND 12/18/10 INCLUSIVE. To minimize interference, signals intended for SES-1 at 101 West were routed and uplinked via an 11 meter dish from the SES Americom Master Ground Station in Hawaii, which is outside of the Galaxy 15 uplink footprint.
Throughout the failure and drift period of Galaxy 15 status information regarding the continued operation of the two L-Band Wide Area Augmentation System Space Segment transponders once utilized by the FAA for aircraft precision location remained unknown. Prior to recovery, Galaxy 15 had been expected to pass by Inmarsat 4F3 at 98 degrees west in late December 2010. Inmarsat 4F3 has since performed some of the same WAAS mission for the FAA from 98 degrees west, that Galaxy 15 once performed at 133 west.
Uplink Signal Avoidance & Mitigation
Galaxy 15, like many communications satellites rebroadcasts the signals it receives on its uplink frequencies to the corresponding C-Band downlink frequencies. Therefore, the potential for interference only existed when Galaxy 15 drifted into the line of sight of a ground uplink segment intended for another communications satellite operating on the same uplink frequency range in the path of Galaxy 15. The magnitude of the interference risk depended on a large number of variables, including the size of the uplink antenna used (the larger the antenna, the lower the risk to hit Galaxy 15), the location of the uplink and whether inside the Galaxy 15 footprint, and the on board gain capabilities of the satellite proximate to Galaxy 15. Satellite operators devised a variety of strategies to mitigate the potential interference to their birds' downlink transmissions including, temporarily transferring uplinks to larger uplink antenna, deliberately off-pointing uplink antennas to put Galaxy 15 into the null, maneuvering the satellite being passed to maintain a minimum angular separation, increasing the satellite's gain sensitivity settings allowing a lowering of the uplink power needed and latterly moving the uplink to a location where Galaxy 15 had no uplink coverage (i.e. Hawaii). These techniques were successfully able to reduce, mitigate and minimize for commercial satellite operations most interference potential during a Galaxy 15 fly by. Smaller sized stationary receive only sites, like those used by amateurs or SMATV which have a wider beam width reception potential, may have experienced interference, while for the most part commercial operators experienced no adverse effects from Galaxy 15 during its failure period thanks to the execution of the mitigation practices devised in the wake of the crisis.Powerloss Predictions & Criticism
The satellite was theorized to lose attitude control when its reaction wheels became saturated. When this event occurred, it would prevent the spacecraft's solar panelsSolar panels on spacecraft
Spacecraft operating in the inner solar system usually rely on the use of photovoltaic solar panels to derive electricity from sunlight. In the outer solar system, where the sunlight is too weak to produce sufficient power, radioisotope thermal generators are used as a power source.-History:The...
from tracking the sun, and it would shut down. After the power reset event, further attempts would be made to recover control of the satellite.
This event was originally predicted for late August or early September 2010, then Intelsat revised its estimate to sometime between 28 November and 29 December 2010. After subsequent criticism of the actual science behind Orbital Sciences' predictions Intelsat completely abandoned the published timeline method. Instead for a period Intelsat stated Based on the revised analysis, the estimated window for a Galaxy 15 off-point and loss of power could occur as early as this month without clarifying the month indicated. The hypothesis used to calculate the timeline of any potential occurrence of loss of power was imprecise, due to the fact the satellite has experienced
erratic loading conditions of radio frequency signals since it began to drift.
Six months after the initial failure date published timelines for shut down proved to be more hopes of a public relations campaign based in theory, and in an interview conducted in October 2010 during the Satcon Conference, both Intelsat & Orbital admitted that the hoped timeline scenario was, in theory and this has been an unprecedented situation, and we are learning as we go.
Recovery
On 23 December 2010, Intelsat successfully regained control over the satellite after the Baseband Equipment Command Unit reset following a loss of lock and full discharge of the batteries, reportedly the most critical phases of the recovery of Galaxy 15 have been completed. The emergency command patch which would allow ground controllers to gain access to redundant BBEs in the event of a similar failure in the future has also successfully been applied to Galaxy 15 according to Intelsat. Galaxy 15 will be located at 93° West in order to conduct further in orbit testing of the viability of the payload and return to service of the satellite. On 2 September 2010, Intelsat indicated that once Galaxy 15 was fully recovered they would like to move it back to 133° West and then relocate the Galaxy 12 spacecraft for its intended mission at the currently vacant 129° West slot.On 18 October 2011, Intelsat transitioned all of its 133° West customers back from Galaxy 12 to Galaxy 15.