astronomy

Mars Orbiter Laser Altimeter

Mars Orbiter Laser Altimeter 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 Mars Orbiter Laser Altimeter rather than just read about it. In short: The Mars Orbiter Laser Altimeter (MOLA) was one of five instruments on the Mars Global Surveyor (MGS) spacecraft, which operated in Mars orbit from September 1997 to November 2006. However, the MOLA instrument transmitted altimetry data only until June 2001.

Key takeaways

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

Reference excerpt

The Mars Orbiter Laser Altimeter (MOLA) was one of five instruments on the Mars Global Surveyor (MGS) spacecraft, which operated in Mars orbit from September 1997 to November 2006. However, the MOLA instrument transmitted altimetry data only until June 2001. The MOLA instrument transmitted infrared laser pulses towards Mars at a rate of 10 times per second and measured the time of flight to determine the range (distance) of the MGS spacecraft to the Martian surface. The range measurements resulted in precise topographic maps of Mars. The precision maps are applicable to studies in geophysics, geology and atmospheric circulation. MOLA also functioned as a passive radiometer and measured the radiance of the surface of Mars at 1064 nanometers.

Planetary laser altimetry

A laser altimeter is an instrument that measures the distance from an orbiting spacecraft to the surface of the planet or asteroid that the spacecraft is orbiting. The distance is determined by measuring the complete round trip time of a laser pulse from the instrument to the body's surface, and back to the instrument. The distance to the object can be determined by multiplying the round-trip pulse time by the speed of light and dividing it by two. With a known attitude and position of the instrument or spacecraft, the location on the surface, which is illuminated by the laser pulse can be determined. The series of the laser spot, or footprint, locations provides a profile of the surface.

Pole-to-pole view

Above is a pole-to-pole view of Martian topography from the first MOLA global topographic model [Smith et al., Science, 1999]. The slice runs from the north pole (left) to the south pole (right) along the 0° longitude line. The figure highlights the pole-to-pole slope of 0.036°, such that the south pole has a higher elevation than the north pole from NASA Goddard Flight Center web site.

Illustrations

Mars Orbiter Laser Altimeter illustration

Worked examples

Example 1 — a first encounter with Mars Orbiter Laser Altimeter

Start with the simplest possible case. Write down what Mars Orbiter Laser Altimeter 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 Mars Orbiter Laser Altimeter 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 Mars Orbiter Laser Altimeter 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 Mars Orbiter Laser Altimeter

In research: Mars Orbiter Laser Altimeter 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 Mars Orbiter Laser Altimeter 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: Mars Orbiter Laser Altimeter is common in secondary-school and first-year university syllabi. It links to neighbouring topics Mars Global Surveyor, Space laser altimeters, so understanding it makes those chapters shorter.
In everyday life: Look for Mars Orbiter Laser Altimeter 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 Mars Orbiter Laser Altimeter in 20 minutes

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

Frequently asked questions

What is Mars Orbiter Laser Altimeter in simple terms?

Why does Mars Orbiter Laser Altimeter 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 Mars Orbiter Laser Altimeter?

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 Mars Orbiter Laser Altimeter.