astronomy

Sun outage

Sun outage 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 Sun outage rather than just read about it. In short: A Sun outage, Sun transit, or Sun fade is an interruption in, or distortion of geostationary satellite signals caused by interference (background noise) of the Sun when it falls directly behind a satellite which an Earth station is trying to receive data from or transmit data to. It usually occurs briefly to such satellites twice per year and such Earth stations install temporary or permanent guards to their receivi…

Key takeaways

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

Reference excerpt

A Sun outage, Sun transit, or Sun fade is an interruption in, or distortion of geostationary satellite signals caused by interference (background noise) of the Sun when it falls directly behind a satellite which an Earth station is trying to receive data from or transmit data to. It usually occurs briefly to such satellites twice per year and such Earth stations install temporary or permanent guards to their receiving systems to prevent equipment damage. Sun outages occur before the March equinox (in February and March) and after the September equinox (in September and October) for the Northern Hemisphere, and occur after the March equinox and before the September equinox for the Southern Hemisphere. At these times, the apparent path of the Sun across the sky takes it directly behind the line of sight between an Earth station and a satellite. The Sun radiates strongly across the entire spectrum, including the microwave frequencies used to communicate with satellites (C band, Ku band, and Ka band), so the Sun swamps the signal from the satellite. The effects of a Sun outage range from partial degradation (increase in the error rate) to the total destruction of the signal. The effect sweeps from north to south from approximately 20 February to 20 April, and from south to north from approximately 20 August to 20 October, affecting any specific location for less than 12 minutes a day for a few consecutive days.

Effect on Indian stock exchanges In India, the BSE (Bombay Stock Exchange) and NSE (National Stock Exchange) use VSATs (Very Small Aperture Terminals) for members (e.g. stockbrokers) to connect to their trading systems. VSATs depend upon satellites for connectivity between the terminals/systems. Hence, these exchanges are, with considerable predictability, affected by sun outages. Until 2009, both BSE and NSE interrupted trading sessions due to sun outages. As of 2009, this practice ended, with the stock exchanges urging members to "review their current connectivity set up" and making "alternative arrangements for continuing trading without any disruption".

Other locations Saint Helena suffers from island-wide loss of Internet and telecommunications connections during Sun outages because all telecommunications traffic to and from the island is carried on a single satellite link. Sun outage times are published in local newspapers. As the majority of rural Alaska is served by satellite, population centers like Utqiaġvik, Kotzebue, and Nome suffer from this as well. Nome is the terminus of the annual Iditarod Trail Sled Dog Race, and due to its timing, announcements of the finishers are often delayed during these Sun outages.

See also Satellite warfare Solar transit

References

External links What is Sun Transit Sun Interference Prediction Sun Outage Calculator Sun Outage calculator for geostationary satellites Archived 2015-09-01 at the Wayback Machine

Worked examples

Example 1 — a first encounter with Sun outage

Start with the simplest possible case. Write down what Sun outage 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 Sun outage 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 Sun outage 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 Sun outage

In research: Sun outage 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 Sun outage 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: Sun outage is common in secondary-school and first-year university syllabi. It links to neighbouring topics Autumn equinox, Satellite broadcasting, Solar phenomena, so understanding it makes those chapters shorter.
In everyday life: Look for Sun outage 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 Sun outage in 20 minutes

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

Frequently asked questions

What is Sun outage in simple terms?

Why does Sun outage 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 Sun outage?

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 Sun outage.