science

USA-85

USA-85 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-85 rather than just read about it. In short: USA-85, also known as GPS IIA-7, GPS II-16 and GPS SVN-32, was an American navigation satellite which formed part of the Global Positioning System. It was the seventh of nineteen Block IIA GPS satellites to be launched.

Key takeaways

USA-85 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-85 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of USA-85 from memory before moving on to harder problems.

Reference excerpt

USA-85, also known as GPS IIA-7, GPS II-16 and GPS SVN-32, was an American navigation satellite which formed part of the Global Positioning System. It was the seventh 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 use (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-85 was launched at 23:54:00 UTC on 22 November 1992, atop a Delta II launch vehicle, flight number D216, 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-85 into a transfer orbit. The satellite raised itself into medium Earth orbit using a Star-37XFP apogee motor.

Mission On 23 December 1992, USA-85 was in an orbit with a perigee of 20,074 km (12,473 mi), an apogee of 20,251 km (12,583 mi), a period of 717.96 minutes, and 54.8° of inclination to the equator. It was intended to broadcast signal PRN 32, but this was changed to PRN 01 on 28 January 1993 after it was discovered that receivers could not track the PRN 32 signal. The spacecraft was operated in slot 4 of plane F of the GPS constellation, and had a mass of 840 kg (1,850 lb). It had a design life of 7.5 years, and was retired from service on 17 March 2008. It is unclear whether it has been retained as a backup satellite.

References

Worked examples

Example 1 — a first encounter with USA-85

Start with the simplest possible case. Write down what USA-85 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-85 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-85 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-85

In research: USA-85 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-85 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-85 is common in secondary-school and first-year university syllabi. It links to neighbouring topics GPS satellites, Spacecraft launched in 1992, USA satellites, so understanding it makes those chapters shorter.
In everyday life: Look for USA-85 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-85 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what USA-85 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-85 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is USA-85 in simple terms?

Why does USA-85 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-85?

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-85.