astronomy

Solar-blind technology

Solar-blind technology 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 Solar-blind technology rather than just read about it. In short: Solar-blind technology is a set of technologies to produce images without interference from the Sun. This is done by using wavelengths of ultraviolet light that are totally absorbed by the ozone layer, yet are transmitted in the Earth's atmosphere.

Key takeaways

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

Reference excerpt

Solar-blind technology is a set of technologies to produce images without interference from the Sun. This is done by using wavelengths of ultraviolet light that are totally absorbed by the ozone layer, yet are transmitted in the Earth's atmosphere. Wavelengths from 240 to 280 nm are completely absorbed by the ozone layer. Elements of this technology are ultraviolet light sources, ultraviolet image detectors, and filters that only transmit the range of wavelengths that are blocked by ozone. A system will also have a signal processing system, and a way to display the results (image).

Ultraviolet sources Ultraviolet illumination can be produced from longer wavelengths using non-linear optical materials. These can be a second harmonic generator. They must have a suitable birefringence in order to phase match the output frequency doubled UV light. One compound commercially used is L-arginine phosphate monohydrate known as LAP. Research is underway for substances that are very non-linear, have a suitable birefringence, are transparent in the spectrum and have a high degree of resistance to damage from lasers.

Optical system Normal glass does not transmit below 350 nm, so it is not used for optics in solar-blind systems. Instead calcium fluoride, fused silica, and magnesium fluoride are used as they are transparent to shorter wavelengths.

Filters An optical filter can be used to block out visible light and near-ultraviolet light. It is important to have a high transmittance within the solar-blind spectrum, but to strongly block the other wavelengths. Interference filters can pass 25% of the wanted rays, and reduce others by 1000 to 10,000 times. However they are unstable and have a narrow field of view. Absorption filters may only pass 10% of wanted UV, but can reject by a ratio of 1012. They can have a wide field of view and are stable.

Ultraviolet detectors Semiconductor ultraviolet detectors are solid state, and convert an ultraviolet photon into an electric pulse. If they are transparent to visible light, then they will not be sensitive to light.

Use Solar-blind imaging can be used to detect corona discharge, in electrical infrastructure. Missile exhaust can be detected from the troposphere or ground. Also when looking down on the Earth from space, the Earth appears dark in this range, so rockets can be easily detected from above once they pass the ozone layer. Israel, the People's Republic of China (PRC), Russia, South Africa, the United Kingdom (UK), and the United States (US) are developing this technology.

References

Worked examples

Example 1 — a first encounter with Solar-blind technology

Start with the simplest possible case. Write down what Solar-blind technology 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 Solar-blind technology 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 Solar-blind technology 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 Solar-blind technology

In research: Solar-blind technology 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 Solar-blind technology 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: Solar-blind technology is common in secondary-school and first-year university syllabi. It links to neighbouring topics Military optical devices, Ultraviolet radiation, so understanding it makes those chapters shorter.
In everyday life: Look for Solar-blind technology 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 Solar-blind technology in 20 minutes

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

Frequently asked questions

What is Solar-blind technology in simple terms?

Why does Solar-blind technology 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 Solar-blind technology?

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 Solar-blind technology.