Galaxy 15 is an American telecommunications satellite which is owned by

Intelsat Intelsat S.A. (formerly INTEL-SAT, INTELSAT, Intelsat) is a multinational satellite services provider with corporate headquarters in Luxembourg and administrative headquarters in Tysons Corner, Virginia, United States. Originally formed as I ...

. It was launched for and originally operated by

PanAmSat The former PanAmSat Corporation founded in 1984 by Reynold (Rene) Anselmo, was a satellite service provider headquartered in Greenwich, Connecticut, United States. It operated a fleet of communications satellites used by the entertainment i ...

, and was subsequently transferred to Intelsat when the two companies merged in 2006. It was originally positioned in

geostationary orbit A geostationary orbit, also referred to as a geosynchronous equatorial orbit''Geostationary orbit'' and ''Geosynchronous (equatorial) orbit'' are used somewhat interchangeably in sources. (GEO), is a circular geosynchronous orbit in altitu ...

at a

longitude Longitude (, ) is a geographic coordinate that specifies the east– west position of a point on the surface of the Earth, or another celestial body. It is an angular measurement, usually expressed in degrees and denoted by the Greek let ...

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. Intelsat repositioned Galaxy 15 back to its original location on April 4, 2011. On 10 August 2022, Intelsat again lost control of Galaxy 15 attributing this to a

space weather Space weather is a branch of space physics and aeronomy, or heliophysics, concerned with the time varying conditions within the Solar System, including the solar wind, emphasizing the space surrounding the Earth, including conditions in the ...

event.

Satellite

Galaxy 15 was constructed by

Orbital Sciences Corporation Orbital Sciences Corporation (commonly referred to as Orbital) was an American company specializing in the design, manufacture, and launch of small- and medium- class space and launch vehicle systems for commercial, military and other governmen ...

, and was based around the

GEOStar-2 The STAR-2 Bus is a fully redundant, flight-proven, spacecraft bus designed for geosynchronous missions. It is a satellite platform, designed and developed by Thomas van der Heyden for the Indonesian Cakrawarta satellite program in the early 1 ...

satellite bus A satellite bus (or spacecraft bus) is the main body and structural component of a satellite or spacecraft, in which the payload and all scientific instruments are held. Bus-derived satellites are opposed to specially produced satellites. Bus- ...

. The contract for its manufacture was signed in 2001, and at the time it was to have been identical to the

Galaxy 12 A galaxy is a system of stars, stellar remnants, interstellar gas, dust, dark matter, bound together by gravity. The word is derived from the Greek ' (), literally 'milky', a reference to the Milky Way galaxy that contains the Solar S ...

and

Galaxy 14 A galaxy is a system of stars, stellar remnants, interstellar gas, dust, dark matter, bound together by gravity. The word is derived from the Greek ' (), literally 'milky', a reference to the Milky Way galaxy that contains the Solar S ...

satellites which were also on order. In 2003, the contract was changed to allow the addition of more

transponder In telecommunications, a transponder is a device that, upon receiving a signal, emits a different signal in response. The term is a blend of ''transmitter'' and ''responder''. In air navigation or radio frequency identification, a flight trans ...

s to support the US Government's Geostationary Communications and Control Segment (GCCS)

Wide Area Augmentation System The Wide Area Augmentation System (WAAS) is an air navigation aid developed by the Federal Aviation Administration to augment the Global Positioning System (GPS), with the goal of improving its accuracy, integrity, and availability. Essentia ...

(WAAS), a US

Federal Aviation Administration The Federal Aviation Administration (FAA) is the largest transportation agency of the U.S. government and regulates all aspects of civil aviation in the country as well as over surrounding international waters. Its powers include air traffic ...

navigation program. The communications payload aboard Galaxy 15 consisted of 24

s operating in the G and H bands of the

NATO The North Atlantic Treaty Organization (NATO, ; french: Organisation du traité de l'Atlantique nord, ), also called the North Atlantic Alliance, is an intergovernmental military alliance between 30 member states – 28 European and two N ...

electromagnetic spectrum, or the C band of the US

IEEE The Institute of Electrical and Electronics Engineers (IEEE) is a 501(c)(3) professional association for electronic engineering and electrical engineering (and associated disciplines) with its corporate office in New York City and its operati ...

spectrum. It also carried two C/ D band (IEEE

L band The L band is the Institute of Electrical and Electronics Engineers (IEEE) designation for the range of frequencies in the radio spectrum from 1 to 2 gigahertz (GHz). This is at the top end of the ultra high frequency (UHF) band, at the lower en ...

) transponders, which form part of the US Government's Geostationary Communications and Control Segment, and are used for

aircraft An aircraft is a vehicle that is able to flight, fly by gaining support from the Atmosphere of Earth, air. It counters the force of gravity by using either Buoyancy, static lift or by using the Lift (force), dynamic lift of an airfoil, or in ...

navigation. At launch, the Galaxy 15 satellite had a mass of , and an expected operational lifespan of around 15 years.

Launch

The launch of Galaxy 15 was conducted by

Arianespace Arianespace SA is a French company founded in 1980 as the world's first commercial launch service provider. It undertakes the operation and marketing of the Ariane programme. The company offers a number of different launch vehicles: the heavy ...

, using an Ariane 5GS carrier rocket flying from

ELA-3 ELA-3 (french: Ensemble de Lancement Ariane 3, lit=Ariane Launch Complex 3), is a launch pad and associated facilities at the Centre Spatial Guyanais in French Guiana. ELA-3 is operated by Arianespace as part of the expendable launch system f ...

at the

Guiana Space Centre The Guiana Space Centre (french: links=no, Centre spatial guyanais; CSG), also called Europe's Spaceport, is a European spaceport to the northwest of Kourou in French Guiana, a region of France in South America. Kourou is located approximatel ...

Kourou Kourou () is a commune in French Guiana, an overseas region and department of France in South America. Kourou is famous for being the location of the Guiana Space Centre, the main spaceport of France and the European Space Agency (ESA). It i ...

French Guiana French Guiana ( or ; french: link=no, Guyane ; gcr, label= French Guianese Creole, Lagwiyann ) is an overseas department/region and single territorial collectivity of France on the northern Atlantic coast of South America in the Guianas ...

. 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 A geosynchronous transfer orbit or geostationary transfer orbit (GTO) is a type of geocentric orbit. Satellites that are destined for geosynchronous (GSO) or geostationary orbit (GEO) are (almost) always put into a GTO as an intermediate step f ...

. The

French French (french: français(e), link=no) may refer to: * Something of, from, or related to France ** French language, which originated in France, and its various dialects and accents ** French people, a nation and ethnic group identified with Franc ...

Syracuse 3A Syracuse may refer to: Places Italy *Syracuse, Sicily, or spelled as ''Siracusa'' * Province of Syracuse United States *Syracuse, New York **East Syracuse, New York **North Syracuse, New York *Syracuse, Indiana *Syracuse, Kansas *Syracuse, Miss ...

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 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. Following separation from the carrier rocket, Galaxy 15 raised itself to geostationary orbit by means of an

IHI Ihi, Ehee (Nepal Bhasa:ईही) is a ceremony in the Newar community in Nepal in which pre-adolescent girls are "married" to the Suvarna Kumar which is a symbol of the god Vishnu, ensuring that the girl becomes and remains fertile. It is beli ...

- 500N apogee motor. Its insertion into geosynchronous orbit occurred at around 19:00 on October 19, 2005.

2010 Failure and recovery

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 27 Galaxy 27 is a communications satellite owned by Intelsat. It was at first located at 129° West longitude, serving most of the North America market. It was built by Space Systems/Loral, as part of its LS-1300 line. Galaxy 27 was formerly kno ...

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 phenomena are natural phenomena which occur within the atmosphere of the Sun. These phenomena take many forms, including solar wind, radio wave flux, solar flares, coronal mass ejections, coronal heating and sunspots. These phenomena are ...

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 on board a satellite and could have contributed to placing a satellite into a permanent unrecoverable control state.

Reported passes and interference

On May 12, 2010, Intelsat and SES World Skies confirmed that Galaxy 15 would pass close to the latter's

AMC-11 AMC-11 , previously GE-11, is an American geostationary communications satellite which is operated by SES S.A. It is currently positioned in geostationary orbit at a longitude of 131° West, from where it is used to relay cable television acro ...

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 SKY Perfect JSAT Group. 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;

, 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 communications company broadcasting to rural

Alaska Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U ...

. Galaxy 15 passed

Anik F2 Anik may refer to: * Anik (satellite), satellites launched by Canadian telecommunications company Telesat * Anik, Iran, a village in South Khorasan Province, Iran * Anik Mountain * Anik Bissonnette, a Canadian ballet dancer * Anik Jean (born 1977) ...

at orbital slot 111.1° West at or near October 20 through 25, 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 The National Weather Service (NWS) is an agency of the United States federal government that is tasked with providing weather forecasts, warnings of hazardous weather, and other weather-related products to organizations and the public for the ...

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 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 The Wide Area Augmentation System (WAAS) is an air navigation aid developed by the Federal Aviation Administration to augment the Global Positioning System (GPS), with the goal of improving its accuracy, integrity, and availability. Essentia ...

mission for the FAA from 98 degrees west, that Galaxy 15 once performed at 133 west.

Uplink signal avoidance and 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 onboard 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 Null may refer to: Science, technology, and mathematics Computing * Null (SQL) (or NULL), a special marker and keyword in SQL indicating that something has no value * Null character, the zero-valued ASCII character, also designated by , often use ...

, 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 SMATV is Single Master Antenna Television (or Satellite Master Antenna Television), The purpose of SMATV is for supplying and controlling the number and type of channels to multiple televisions. Not only TV channels but FM channels as well. It prov ...

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.

Power loss predictions and criticism

The satellite was theorized to lose

attitude control Attitude control is the process of controlling the orientation of an aerospace vehicle with respect to an inertial frame of reference or another entity such as the celestial sphere, certain fields, and nearby objects, etc. Controlling vehicle ...

when its

reaction wheel A reaction wheel (RW) is used primarily by spacecraft for three-axis attitude control, and does not require rockets or external applicators of torque. They provide a high pointing accuracy, and are particularly useful when the spacecraft must be ...

s became saturated. When this event occurred, it would prevent the spacecraft's

solar panels A solar cell panel, solar electric panel, photo-voltaic (PV) module, PV panel or solar panel is an assembly of photovoltaic solar cells mounted in a (usually rectangular) frame, and a neatly organised collection of PV panels is called a photo ...

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 had also successfully been applied to Galaxy 15 according to Intelsat. Galaxy 15 was relocated at 93° West in order to conduct further in orbit testing of the viability of the payload and return to service of the satellite. Once Galaxy 15 was fully recovered it was moved back to 133° West and then the Galaxy 12 spacecraft was relocated for its intended mission at the 129° West slot. On 18 October 2011, Intelsat transitioned all of its 133° West customers back from Galaxy 12 to Galaxy 15.

2022 Failure and recovery

On 18 August 2022, Intelsat submitted a filing with the FCC requesting permission for the satellite to exceed its station keeping limits, indicating that control had been lost. On 31 August 2022, the spacecraft muted its transponder payloads, as it was programmed to do automatically in case of loss of ground control (21 days after last command).

References

{{Orbital launches in 2005 Spacecraft launched in 2005 2010 in spaceflight Intelsat satellites