astronomy

Intelsat 15

Intelsat 15 is a astronomy topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Intelsat 15 rather than just read about it. In short: Intelsat 15, also known as IS-15, is a communications satellite owned by Intelsat. Intelsat 15 was built by Orbital Sciences Corporation, on a Star-2.4.

Key takeaways

Intelsat 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 Intelsat 15 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Intelsat 15 from memory before moving on to harder problems.

Reference excerpt

Intelsat 15, also known as IS-15, is a communications satellite owned by Intelsat. Intelsat 15 was built by Orbital Sciences Corporation, on a Star-2.4. It is located at 85° E longitude on the geostationary orbit. It was launched from Baikonur Cosmodrome to a geosynchronous transfer orbit on 30 November 2009 by a Zenit-3SLB launch vehicle. It has 22 active Ku band transponders, plus eight spares. Five of those transponders are owned and operated by SKY Perfect JSAT Group under the name JCSAT-85.

Satellite description Intelsat 15 is a 3 axis stabilized geostationary communications satellite based on the Star-2.4 satellite bus. It weighed 2,484 kg (5,476 lb) at launch, had a dry mass of 1,227 kg (2,705 lb), and a design life 15 years. It had a power availability dedicated to the payload of 4.6 kW, due to its multi-junction GaAs solar cells. It also had two 4840 watt hour Li-ion batteries for surviving the solar eclipses. The satellite used a bipropellant propulsion system with an IHI BT-4 Liquid Apogee Engine for orbit circularization and thrusters and reaction wheels for station keeping and attitude control. It was filled with enough propellant for 15 years, but due to the efficient launch and transfer 17 are expected. Its payload is composed two 2.3 m (7 ft 7 in) deployable dual grid reflectors, plus one 1.4 m (4 ft 7 in) deck mounted reflector. They are fed by 22 active Ku band transponders, plus eight spares. Intelsat uses 17 transponders, which have a bandwidth of twenty 36 MHz transponder equivalents. Its footprint is arranged in a Russia beam and a Middle East beam. SKY Perfect JSAT Group owns five physical transponders under the name JCSAT-85, four have a bandwidth of 36 MHz and the other one has 72 MHz. JSCAT-85 footprint is arranged in two beams, West IOR Beam, covering middle East and the Arabic Sea, and East IOR Beam, covering the Eastern Asia coast and Pacific Ocean.

History On April 2, 2007, JSAT Corporation (now SKY Perfect JSAT Group) announced an agreement to purchase a payload consisting of five transponders on the yet to be built Intelsat 15. Intelsat and JSAT had already collaborated on the Horizons-1 and Horizons-2 satellites. The satellite, also known as IS-15, would provide services to the Asia-Pacific, Indian Ocean and Middle East regions from the 85°E longitude on the geostationary orbit, where it would replace Intelsat 709. It would have 22 Ku band transponders in total and a design life of 15 years. The JSAT payload would be known as JCSAT-85. On May 1, 2007, Orbital Sciences Corporation (now Orbital ATK) announced that it had been awarded a contract to manufacture Intelsat 15. It would be based on the STAR-2 satellite bus, generate 4.6 kW of power for its 22-transponder Ku band payload and had an expected launch date of early 2009. On February 26, 2008, Sea Launch announce a contract with Intelsat to launch two satellites manufactured by Orbital Corporation, Intelsat 15 and Intelsat 16. The contract was itself a renegotiation for repurpose two already existing reservation by Intelsat with Sea Launch for two satellites to these new spacecraft. They were expected to be launched by the Land Launch service, which used Zenit-3SLB rockets from the Baikonur Cosmodrome in Kazakhstan, during 2009. Between October 27 and November 5, 2009 Intelsat 15 was processed in the Baikonur Cosmodrome. On November 6, it was filled with propellant. On November 24, 2009, JSAT announced that the launch of Intelsat 15 was expected on November 29 at 1:00 UTC. But during the launch attempt on November 29, the automatic prelaunch issued an abort command. But the launch committee agreed to make a second attempt on the next day. On November 30, 2009, at 21:00 UTC, the Zenit-3SLB successfully launched Intelsat 15, from Baikonur Cosmodrome Site 45. After a six and a half hour mission, the DM-3SLB successfully separated the spacecraft and at 03:28 UTC, first signals from spacecraft were received. The launch put the satellite with margins of its planned geosynchronous transfer orbit with a perigee of 10,286 km, an apogee of 35,790 km and a 12° inclination to the Equator.

References

Worked examples

Example 1 — a first encounter with Intelsat 15

Start with the simplest possible case. Write down what Intelsat 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 Intelsat 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 Intelsat 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 Intelsat 15

In research: Intelsat 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 Intelsat 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: Intelsat 15 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Communications satellites in geostationary orbit, Intelsat satellites, Satellite television, so understanding it makes those chapters shorter.
In everyday life: Look for Intelsat 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.

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How to study Intelsat 15 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Intelsat 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 Intelsat 15 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Intelsat 15 in simple terms?

Intelsat 15, also known as IS-15, is a communications satellite owned by Intelsat. Intelsat 15 was built by Orbital Sciences Corporation, on a Star-2.4.

Why does Intelsat 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 Intelsat 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 Intelsat 15.