science

USA-100

USA-100 is a science 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 USA-100 rather than just read about it. In short: USA-100, also known as GPS IIA-15, GPS II-24 and GPS SVN-36, is an American navigation satellite which forms part of the Global Positioning System. It was the fifteenth of nineteen Block IIA GPS satellites to be launched.

Key takeaways

USA-100 belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect USA-100 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of USA-100 from memory before moving on to harder problems.

Reference excerpt

USA-100, also known as GPS IIA-15, GPS II-24 and GPS SVN-36, is an American navigation satellite which forms part of the Global Positioning System. It was the fifteenth of nineteen Block IIA GPS satellites to be launched.

Background Global Positioning System (GPS) was developed by the U.S. Department of Defense to provide all-weather round-the-clock navigation capabilities for military ground, sea, and air forces. Since its implementation, GPS has also become an integral asset in numerous civilian applications and industries around the globe, including recreational used (e.g., boating, aircraft, hiking), corporate vehicle fleet tracking, and surveying. GPS employs 24 spacecraft in 20,200 km circular orbits inclined at 55.0°. These vehicles are placed in 6 orbit planes with four operational satellites in each plane. GPS Block 2 was the operational system, following the demonstration system composed of Block 1 (Navstar 1 - 11) spacecraft. These spacecraft were 3-axis stabilized, nadir pointing using reaction wheels. Dual solar arrays supplied 710 watts of power. They used S-band (SGLS) communications for control and telemetry and Ultra high frequency (UHF) cross-link between spacecraft. The payload consisted of two L-band navigation signals at 1575.42 MHz (L1) and 1227.60 MHz (L2). Each spacecraft carried 2 rubidium and 2 Cesium clocks and nuclear detonation detection sensors. Built by Rockwell Space Systems for the U.S. Air force, the spacecraft measured 5.3 m across with solar panels deployed and had a design life of 7.5 years.

Launch USA-100 was launched at 03:40:01 UTC on 10 March 1994, atop a Delta II launch vehicle, flight number D226, flying in the 7925-9.5 configuration. The launch took place from Launch Complex 17A (LC-17A) at the Cape Canaveral Air Force Station (CCAFS), and placed USA-100 into a transfer orbit. The satellite raised itself into medium Earth orbit using a Star-37XFP apogee motor.

Mission On 15 April 1994, USA-100 was in an orbit with a perigee of 19,986 km (12,419 mi), an apogee of 20,315 km (12,623 mi), a period of 716.69 minutes, and 54.9° of inclination to the equator. It broadcasts the PRN 06 signal, and operates in slot 1 of plane C of the GPS constellation. The satellite has a mass of 840 kg (1,850 lb). It had a design life of 7.5 years, but it remained in service until 21 February 2014, shortly after the launch of USA-248.

References

Worked examples

Example 1 — a first encounter with USA-100

Start with the simplest possible case. Write down what USA-100 claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, 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 USA-100 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 USA-100 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 USA-100

In research: USA-100 appears in science 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 USA-100 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: USA-100 is common in secondary-school and first-year university syllabi. It links to neighbouring topics GPS satellites, Spacecraft launched in 1994, USA satellites, so understanding it makes those chapters shorter.
In everyday life: Look for USA-100 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 USA-100 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what USA-100 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 USA-100 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is USA-100 in simple terms?

Why does USA-100 matter?

Because it connects several science 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 USA-100?

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 USA-100.