Galaxy 15

Key takeaways

Galaxy 15 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Galaxy 15 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Galaxy 15 from memory before moving on to harder problems.

Reference excerpt

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. 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 event.

Satellite Galaxy 15 was constructed by Orbital Sciences Corporation, and was based around the GEOStar-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 transponders to support the US Government's Geostationary Communications and Control Segment (GCCS) Wide Area Augmentation System (WAAS), a US Federal Aviation Administration navigation program. The communications payload aboard Galaxy 15 consisted of 24 transponders operating in the G and H bands 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 2,033 kilograms (4,482 lb), and an expected operational lifespan of around 15 years.

Launch The launch of Galaxy 15 was conducted by Arianespace, 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.

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 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 on board a satellite and could have contributed to placing a satellite into a permanent unrecoverable control state. The failure was most likely caused by an electrostatic discharge that knocked out the satellite's communications systems, as a side-effect of spacecraft charging from solar radiation.

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Galaxy 15

Start with the simplest possible case. Write down what Galaxy 15 claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In astronomy, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Galaxy 15 before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Galaxy 15 ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Galaxy 15

In research: Galaxy 15 appears in astronomy research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Galaxy 15 in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Galaxy 15 is common in secondary-school and first-year university syllabi. It links to neighbouring topics 2010 in spaceflight, Intelsat satellites, Spacecraft launched in 2005, so understanding it makes those chapters shorter.
In everyday life: Look for Galaxy 15 outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study Galaxy 15 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Galaxy 15 means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Galaxy 15 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Galaxy 15 in simple terms?

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.

Why does Galaxy 15 matter?

Because it connects several astronomy ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Galaxy 15?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Galaxy 15.