astronomy

TIMED

TIMED 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 TIMED rather than just read about it. In short: The TIMED (Thermosphere • Ionosphere • Mesosphere • Energetics and Dynamics) mission is dedicated to study the influences that energetics and dynamics of the Sun and humans have on the least explored and understood region of Earth's atmosphere – the Mesosphere and Lower Thermosphere / Ionosphere (MLTI). The mission was launched from Vandenberg Air Force Base in California on 7 December 2001 aboard a Delta II rocket…

Key takeaways

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

Reference excerpt

The TIMED (Thermosphere • Ionosphere • Mesosphere • Energetics and Dynamics) mission is dedicated to study the influences that energetics and dynamics of the Sun and humans have on the least explored and understood region of Earth's atmosphere – the Mesosphere and Lower Thermosphere / Ionosphere (MLTI). The mission was launched from Vandenberg Air Force Base in California on 7 December 2001 aboard a Delta II rocket launch vehicle. The project is sponsored and managed by NASA, while the spacecraft was designed and assembled by the Applied Physics Laboratory at Johns Hopkins University. The mission has been extended several times, and has now collected data over an entire solar cycle, which helps in its goal to differentiate the Sun's effects on the atmosphere from other effects. It shared its Delta II launch vehicle with the Jason-1 oceanography mission.

Atmospheric region under study

The Mesosphere, Lower Thermosphere and Ionosphere (MLTI) region of the atmosphere to be studied by TIMED is located between 60 and 180 kilometres (37 and 112 mi) above the Earth's surface, where energy from solar radiation is first deposited into the atmosphere. This can have profound effects on Earth's upper atmospheric regions, particularly during the peak of the Sun's 11-year solar cycle when the greatest amounts of its energy are being released. Understanding these interactions is also important for our understanding of various subjects in geophysics, meteorology, aeronomy, and atmospheric science, as solar radiation is one of the primary driving forces behind atmospheric tides. Changes in the MLT can also affect modern satellite and radio telecommunications.

Scientific instruments The spacecraft payload consists of the following four main instruments:

Global Ultraviolet Imager (GUVI), which scans cross track from horizon to horizon to measure the spatial and temporal variations of temperature and constituent densities in the lower thermosphere, and to determine the importance of auroral energy sources and solar extreme ultraviolet sources to the energy balance in that region. Solar Extreme ultraviolet Experiment (SEE), a spectrometer and a suite of photometers designed to measure the solar soft X-rays, extreme-ultraviolet and far-ultraviolet radiation that is deposited into the MLT region. TIMED Doppler Interferometer (TIDI), designed to globally measure the wind and temperature profiles of the MLT region. Sounding of the Atmosphere using Broadband Emission Radiometry (SABER), multichannel radiometer designed to measure heat emitted by the atmosphere over a broad altitude and spectral range, as well as global temperature profiles and sources of atmospheric cooling. The data collected by the satellite's instruments are made freely available to the public.

Specifications Mass: 660 kilograms Dimensions: 2.72 meters high 1.61 meters wide (launch configuration) 11.73 meters wide (solar arrays deployed) 1.2 meters deep Power consumption: 406 watts Data downlink: 4 megabits per second Memory: 5 gigabits Control and data handling processor: Mongoose-V Attitude: Control - Within 0.50° Knowledge - Within 0.03° Processor: RTX2010 Total mission cost: Spacecraft: US$195 million Ground operations: US$42 million

Satellite operations TIMED experienced minor problems with attitude control when, after launch, the magnetorquers failed to slow the spacecraft's spin as intended. An engineer installing the magnetorquers had mistakenly recorded the reverse of their actual polarities, which generated a sign error in the flight software. The problem was fixed by temporarily disabling the orbiter's magnetic field sensor and uploading a software patch to fix the sign error. In a separate incident, another software update fixed a problem caused by faulty testing of the Sun sensors. After these corrections, the attitude control system functioned as intended.

Kosmos 2221 conjunction At approximately 06:30 UTC on 28 February 2024, TIMED passed within 10 meters of the defunct Kosmos 2221 satellite. As neither TIMED nor Kosmos 2221 can be maneuvered, the conjunction was unavoidable. LeoLabs, a satellite tracking company, had estimated a satellite collision probability of as high as 8% prior to the encounter. A collision between the two satellites, both traveling at hypervelocity speeds relative to each other, was projected to generate between 2,500 and 7,500 fragments of space debris, a figure potentially exceeding that of the 2009 satellite collision between Iridium 33 and Kosmos 2251. This close miss was particularly concerning to NASA, which highlighted the event at the 39th Space Symposium in Colorado Springs in a broader speech on NASA's new space sustainability strategy plan.

Scientific results TIMED has improved scientific understanding of long-term trends in the upper atmosphere. The SABER instrument has collected a continuous record of water vapor and carbon dioxide levels in the stratosphere and mesosphere. SABER is able to collect 1,500 water vapor measurements per day, a vast improvement from previous satellites and ground-based observations. SABER had a flaw in its optical filter that caused it to overestimate water vapor levels; this error was discovered and the data were corrected. Based on the corrected data, SABER found that between 2002 and 2018, water vapor levels in the lower stratosphere were increasing at an average rate of 0.25 ppmv (around 5%) per decade, and in the upper stratosphere and mesosphere, water vapor levels were increasing at an average rate of 0.1-0.2 ppmv (around 2-3%) per decade. Growth in methane levels is thought to be partially responsible for the growth in water vapor levels, as methane oxidizes into carbon dioxide and water vapor, but changes driven by the solar cycle may also be responsible. SABER has also monitored carbon dioxide levels in the upper atmosphere. The instrument found that carbon dioxide levels in the upper atmosphere are increasing: at an altitude of 110 kilometres (68 mi), CO2 levels were rising at an average rate of 12% per decade. This rate is faster than what has been predicted by climate models, and suggests that there is more vertical mixing of CO2 than previously thought. By collecting upper atmosphere data, TIMED assists the modeling of environmental impacts. Water vapor and carbon dioxide are greenhouse gases and their growth in the upper atmosphere must be factored into climate models. Additionally, upper atmosphere water vapor contributes to ozone depletion.

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with TIMED

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

In research: TIMED 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 TIMED 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: TIMED is common in secondary-school and first-year university syllabi. It links to neighbouring topics Earth observation satellites of the United States, Ionosphere, NASA satellites, so understanding it makes those chapters shorter.
In everyday life: Look for TIMED 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 TIMED in 20 minutes

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

Frequently asked questions

What is TIMED in simple terms?

Why does TIMED 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 TIMED?

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 TIMED.