astronomy

Solar Wind Spectrometer

Solar Wind Spectrometer 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 Wind Spectrometer rather than just read about it. In short: The Solar Wind Spectrometer was a scientific package that flew on the Apollo 12 and Apollo 15 missions to the surface of the Moon. The goal was to characterise the solar wind near the Moon's surface and to explore its interactions with the lunar environment.

Key takeaways

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

Reference excerpt

The Solar Wind Spectrometer was a scientific package that flew on the Apollo 12 and Apollo 15 missions to the surface of the Moon. The goal was to characterise the solar wind near the Moon's surface and to explore its interactions with the lunar environment. The experiments' principal investigator was Dr Conway W. Snyder of the Jet Propulsion Laboratory.

Instrument The Solar Wind Spectrometer (SWS) experiment aimed to provide the ability "to measure energies, densities, incidence angles and temporal variations of the solar wind plasma that strikes the surface of the moon". The experiment instrument consist of seven Faraday cups, that measure the amount of charged particles. One central cup points perpendicularly to the surface. The other six cups are angled at 30 degrees from the surface, located around the central cup in 60-degree intervals. Each cup can measure incoming negatively charged electron flow and positively charged proton-alpha particle flow. The angle of the incoming particle was measured by using readings from all Faraday cups. Below the instrument was an electronics package located in a container with active thermal control. The electronics packages consists of power control circuits, sensor voltage control, ammeter circuits, and finally signal/data conditioning circuits. Thermal control was provided by three radiators, a sunshield and insulation.

Missions

Apollo 12 The Apollo 12 Solar Wind Spectrometer was deployed by astronaut Pete Conrad on the surface of the Moon on November 19, 1969. It was located at 3S, 23W. The instrument's initial state had dust covers over the Faraday cup entrances. During the early phase of the experiment's activation with the dust covers in place, background baseline data was collected. One hour after the departure of the Apollo 12 Lunar Module ascent stage at 15:25 on November 20, 1969, the dust covers were removed and the sensors exposed directly to the lunar environment.

Apollo 15 The Apollo 15 Solar Wind Spectrometer was deployed on the surface of the Moon on July 31, 1971, and was powered on at 19:37 UTC. It was located at 26N, 4E. The instrument's initial state had dust covers over the Faraday cup entrances. During the early phase of the experiment's activation with the dust covers in place, background baseline data was collected. One hour after the departure of the Apollo 15 Lunar Module ascent stage on August 2, 1971, the dust covers were removed and the sensors exposed directly to the lunar environment.

Science Analysis of the two instruments' data found that the solar plasma found near to the lunar regolith surface was broadly similar to the solar plasma measured by probes some distance from the Moon. It also found that no plasma is detectable in the shadow of the Moon during the lunar night. The instrument was also able to distinguish plasma within interplanetary space and that found in the Earth's magnetosheath. Magnetosheath plasma would exhibit large and frequent changes in plasma velocity, density and speed. Highly variable spectra were observed at lunar sunrise, potentially due to interactions with the lunar surface. Solar Wind Spectrometer data that was analysed after the landing of Apollo 14, confirmed the presence of a photoelectric layer and similar in nature to that found by the Charged Particle Lunar Environment Experiment. The instrument detected a neutral gas-ion shockwave produced by the impact of the Apollo 13 S-IVB stage on the lunar surface. It was suggested that the source of this gas shockwave may be a result of the vaporisation of 1100 kg of plastic materials contained with the rocket stage. The shockwave was estimated to have travelled 140 km at a speed of 2 km/s.

References

Illustrations

Worked examples

Example 1 — a first encounter with Solar Wind Spectrometer

Start with the simplest possible case. Write down what Solar Wind Spectrometer 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 Wind Spectrometer 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 Wind Spectrometer 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 Wind Spectrometer

In research: Solar Wind Spectrometer 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 Wind Spectrometer 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 Wind Spectrometer is common in secondary-school and first-year university syllabi. It links to neighbouring topics Apollo 12, Apollo 15, Apollo program hardware, so understanding it makes those chapters shorter.
In everyday life: Look for Solar Wind Spectrometer 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 Wind Spectrometer in 20 minutes

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

Frequently asked questions

What is Solar Wind Spectrometer in simple terms?

Why does Solar Wind Spectrometer 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 Wind Spectrometer?

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 Wind Spectrometer.