science

POLDER

POLDER 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 POLDER rather than just read about it. In short: POLDER (POLarization and Directionality of the Earth's Reflectances) is a passive optical imaging radiometer and polarimeter instrument developed by the French space agency CNES. Description The device was designed to observe solar radiation reflected by Earth's atmosphere, including studies of tropospheric aerosols, sea surface reflectance, bidirectional reflectance distribution function of land surfaces, and the E…

Key takeaways

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

Reference excerpt

POLDER (POLarization and Directionality of the Earth's Reflectances) is a passive optical imaging radiometer and polarimeter instrument developed by the French space agency CNES.

Description The device was designed to observe solar radiation reflected by Earth's atmosphere, including studies of tropospheric aerosols, sea surface reflectance, bidirectional reflectance distribution function of land surfaces, and the Earth Radiation Budget.

Specifications POLDER has a mass of approximately 30 kilograms (66 lb), and has a power consumption of 77 W in imaging mode (with a mean consumption of 29 W).

Imaging POLDER utilizes a push broom scanner. The device's optical system uses a telecentric lens and a charge-coupled device matrix with a resolution of 242x548 pixels. The focal length is 3.57 millimetres (0.141 in) with a focal ratio of 4.6. The field of view ranges from ±43° to ±57°, depending on the tracking method.

Spectral characteristics The device scans between 443 and 910 nm FWHM, depending on the objective of the measurement. The shorter wavelengths (443–565 nm) typically measure ocean color, whereas the longer wavelengths (670–910 nm) are used to study vegetation and water vapor content.

Data transfer It transmits data on 465.9875 MHz at bit rate of 200 bit/s, and receives on 401.65 MHz at 400 bit/s. The data rate is 880 kbit/s at a quantization level of 12 bits.

Missions POLDER was first launched as a passenger instrument aboard ADEOS I on 17 August 1996. The mission ended on 30 June 1997 when communication from the host satellite failed. POLDER 2 was launched in December 2002 aboard ADEOS II. The second mission ended prematurely after 10 months when the satellite's solar panel malfunctioned. A third generation instrument was launched on board the French PARASOL microsatellite. The satellite was maneuvered out of the A-train on 2 December 2009 and permanently shut down on 18 December 2013.

Footnotes

Sources

External links POLDER website

Worked examples

Example 1 — a first encounter with POLDER

Start with the simplest possible case. Write down what POLDER 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 POLDER 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 POLDER 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 POLDER

In research: POLDER 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 POLDER 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: POLDER is common in secondary-school and first-year university syllabi. It links to neighbouring topics Earth observation satellite sensors, Radiometry, so understanding it makes those chapters shorter.
In everyday life: Look for POLDER 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 POLDER in 20 minutes

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

Frequently asked questions

What is POLDER in simple terms?

POLDER (POLarization and Directionality of the Earth's Reflectances) is a passive optical imaging radiometer and polarimeter instrument developed by the French space agency CNES. Description The device was designed to observe solar radiation reflected by Earth's atmosphere, including studies of tro…

Why does POLDER 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 POLDER?

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 POLDER.