earth science

QuikSCAT

QuikSCAT is a earth 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 QuikSCAT rather than just read about it. In short: The NASA QuikSCAT (Quick Scatterometer) was an Earth observation satellite carrying the SeaWinds scatterometer. Its primary mission was to measure the surface wind speed and direction over the ice-free global oceans via its effect on water waves.

Key takeaways

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

Reference excerpt

The NASA QuikSCAT (Quick Scatterometer) was an Earth observation satellite carrying the SeaWinds scatterometer. Its primary mission was to measure the surface wind speed and direction over the ice-free global oceans via its effect on water waves. Observations from QuikSCAT had a wide array of applications, and contributed to climatological studies, weather forecasting, meteorology, oceanographic research, marine safety, commercial fishing, tracking large icebergs, and studies of land and sea ice, among others. This SeaWinds scatterometer is referred to as the QuikSCAT scatterometer to distinguish it from the nearly identical SeaWinds scatterometer flown on the ADEOS-2 satellite.

Mission description QuikSCAT was launched on 19 June 1999 with an initial 3-year mission requirement. QuikSCAT was a "quick recovery" mission replacing the NASA Scatterometer (NSCAT), which failed prematurely in June 1997 after just 9.5 months in operation. QuikSCAT, however, far exceeded these design expectations and continued to operate for over a decade before a bearing failure on its antenna motor ended QuikSCAT's capabilities to determine useful surface wind information on 23 November 2009. The QuikSCAT geophysical data record spans from 19 July 1999 to 21 November 2009. While the dish could not rotate after this date, its radar capabilities remained fully intact. It continued operating in this mode until the full mission was terminated on October 2, 2018. Data from this mode of the mission was used to improve the accuracy of other satellite surface wind datasets by inter-calibrating other Ku-band scatterometers. QuikSCAT measured winds in measurement swaths 1,800 km wide centered on the satellite ground track with no nadir gap, such as occurs with fan-beam scatterometers such as NSCAT. Because of its wide swath and lack of in-swath gaps, QuikSCAT was able to collect at least one vector wind measurement over 93% of the World's Oceans each day. This improved significantly over the 77% coverage provided by NSCAT. Each day, QuikSCAT recorded over 400,000 measurements of wind speed and direction. This is hundreds of times more surface wind measurements than are collected routinely from ships and buoys. QuikSCAT provided measurements of the wind speed and direction referenced to 10 meters above the sea surface at a spatial resolution of 25 km. Wind information cannot be retrieved within 15–30 km of coastlines or in the presence of sea ice. Precipitation generally degrades the wind measurement accuracy, although useful wind and rain information can still be obtained in mid-latitude and tropical cyclones for monitoring purposes. In addition to measuring surface winds over the ocean, scatterometers such as QuikSCAT can also provide information on the fractional coverage of sea ice, track large icebergs (>5 km in length), differentiate types of ice and snow, and detect the freeze–thaw line in polar regions. While the rotating dish antenna can no longer spin as designed, the rest of the instrument remains functional and data transmission capabilities remain intact, although it cannot determine the surface vector wind. It can, however, still measure radar backscatter at a fixed azimuth angle. QuikSCAT is being used in this reduced mode to cross-calibrate other scatterometers in hopes of providing long-term and consistent surface wind datasets over multiple on-orbit scatterometer platforms, including the operational European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) Advanced Scatterometer (ASCAT) on MetOp-A and MetOp-B, India's Oceansat-2 scatterometer operated by the Indian Space Research Organization (ISRO), and the China's HaiYang-2A (HY-2A) scatterometer operated by China's National Satellite Ocean Application Service, as well as future NASA scatterometer missions in development. A NASA Senior Review panel in 2011 endorsed the continuation of the QuikSCAT mission with these modified objectives through 2018. QuikSCAT was declared fully decommissioned on October 2, 2018.

Instrument description SeaWinds used a rotating dish antenna with two spot beams that sweep in a circular pattern. The antenna consists of a 1-meter diameter rotating dish that produces two spot beams, sweeping in a circular pattern. It radiates 110 W microwave pulses at a pulse repetition frequency (PRF) of 189 Hz. QuikSCAT operates at a frequency of 13.4 GHz, which is in the Ku-band of microwave frequencies. At this frequency, the atmosphere is mostly transparent to non-precipitating clouds and aerosols, although rain produces significant alteration of the signal. The spacecraft is in a Sun-synchronous orbit, with equatorial crossing times of ascending swaths at about 06:00 LST ±30 minutes. Along the equator, consecutive swaths are separated by 2,800 km. QuikSCAT orbits Earth at an altitude of 802 km and at a speed of about 7 km per second.

Measurement description

Wind measurement accuracy

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with QuikSCAT

Start with the simplest possible case. Write down what QuikSCAT claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In earth 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 QuikSCAT 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 QuikSCAT 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 QuikSCAT

In research: QuikSCAT appears in earth 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 QuikSCAT 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: QuikSCAT is common in secondary-school and first-year university syllabi. It links to neighbouring topics Earth observation satellites of the United States, Jet Propulsion Laboratory satellites, NASA satellites, so understanding it makes those chapters shorter.
In everyday life: Look for QuikSCAT 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.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study QuikSCAT in 20 minutes

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

Frequently asked questions

What is QuikSCAT in simple terms?

Why does QuikSCAT matter?

Because it connects several earth 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 QuikSCAT?

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 QuikSCAT.