science

USA-581

USA-581 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-581 rather than just read about it. In short: USA-581, also known as GPS-III SV09, NAVSTAR 85, and Ellison Onizuka, is a United States navigation satellite which forms part of the Global Positioning System. Satellite SV09 was the ninth GPS Block III satellite to launch.

Key takeaways

USA-581 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-581 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of USA-581 from memory before moving on to harder problems.

Reference excerpt

USA-581, also known as GPS-III SV09, NAVSTAR 85, and Ellison Onizuka, is a United States navigation satellite which forms part of the Global Positioning System.

Satellite

SV09 was the ninth GPS Block III satellite to launch. The spacecraft is built on the Lockheed Martin A2100 satellite bus, and weighs in at 4,331 kg (9,548 lb). The space vehicle manufacturing contract was awarded September 2016. The satellite was named "Ellison Onizuka" on 12 May 2021 following its successful core mate assembly. It was declared "Available for Launch" on 23 Aug 2022. SV09 is the first in the Block III series to use a laser retroreflector array. LRAs are a system of mirrors designed to reflect beams of light back to their source. They are used for laser ranging, a technique that enables the measurement of precise distance by observing the time it takes for a pulse of light to travel from a ground station to the mirrors and back.

Launch The satellite's launch was originally awarded to ULA but it was later switched to SpaceX because of delays in ULA's Vulcan rocket certification. In exchange, ULA was awarded another GPS launch originally planned for Falcon Heavy. SV09 was launched by SpaceX on 28 January 2026 at 04:53 UTC, atop a Falcon 9 rocket. The launch took place from SLC-40 at Cape Canaveral Space Force Station.

References

Illustrations

Worked examples

Example 1 — a first encounter with USA-581

Start with the simplest possible case. Write down what USA-581 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-581 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-581 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-581

In research: USA-581 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-581 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-581 is common in secondary-school and first-year university syllabi. It links to neighbouring topics 2026 in spaceflight, GPS satellites, Spacecraft launched in 2026, so understanding it makes those chapters shorter.
In everyday life: Look for USA-581 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-581 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what USA-581 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-581 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is USA-581 in simple terms?

USA-581, also known as GPS-III SV09, NAVSTAR 85, and Ellison Onizuka, is a United States navigation satellite which forms part of the Global Positioning System. Satellite SV09 was the ninth GPS Block III satellite to launch.

Why does USA-581 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-581?

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-581.