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The TIMED (Thermosphere • Ionosphere • Mesosphere • Energetics and Dynamics) mission is dedicated to study the influences energetics and dynamics of the Sun and humans 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.[2] TIMED Was Launched Alongside Jason-1.

TIMED

TIMED in low Earth orbit
Names	Thermosphere • Ionosphere • Mesosphere • Energetics and Dynamics
Mission type	Ionosphere Atmospheric science Space weather research
Operator	NASA
COSPAR ID	2001-055B
SATCAT no.	26998
Website	TIMED at APL
Mission duration	Planned: 2 years Elapsed: 20 years, 8 months, 13 days
Spacecraft properties
Manufacturer	Applied Physics Laboratory
Launch mass	660 kg (1,460 lb)
Dimensions	2.72 meters high 11.73 meters wide 1.2 meters deep
Power	406 watts
Start of mission
Launch date	7 December 2001, 15:07:35 UTC
Rocket	Delta II 7920-10 (Delta D289)
Launch site	Vandenberg, SLC-2W
Entered service	22 January 2002
Orbital parameters
Reference system	Geocentric orbit[1]
Regime	Low Earth orbit
Altitude	625 km (388 mi)
Inclination	74.1°
Period	97.3 minutes
Solar Terrestrial Probes program Hinode →

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.[3]

Specifications

^{[citation needed]}

• 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 ^{[citation needed]}
  • 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.[4] 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.[4]

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.[5][6]

SABER is able to collect 1,500 water vapor measurements per day, a vast improvement from previous satellites and ground-based observations.[7] 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.[8] 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.[9] Growth in methane levels is thought to be partially responsible for the growth in water vapor levels, as methane decomposes^{[clarification needed]} into carbon dioxide and water vapor, but changes driven by the solar cycle may also be responsible.[10]

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.[11] 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.[12]

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.[13]

Instrument teams

United States

See also

• Upper Atmosphere Research Satellite, 1991-2005

References

Further reading

• Rong, Pingping; Russell III, James M.; Marshall, Benjamin T.; Gordley, Larry L.; Mlynczak, Martin G.; Walker, Kaley A. (31 July 2019). "Validation of Water Vapor Measured by SABER on the TIMED Satellite". Journal of Atmospheric and Solar-Terrestrial Physics. Science direct. 194: 105099. Bibcode:2019JASTP.19405099R. doi:10.1016/j.jastp.2019.105099. S2CID 201260453. Retrieved 15 September 2020.

• Yue, Jia; Russell III, James; Jian, Yongxiao; Rezac, Ladislav; Garcia, Rolando; López-Puertas, Manuel; Mlynczak, Martin G. (16 September 2015). "Increasing Carbon Dioxide Concentration in the Upper Atmosphere Observed by SABER". Geophysical Research Letters. American Geophysical Union. 42 (17): 7194–7199. Bibcode:2015GeoRL..42.7194Y. doi:10.1002/2015GL064696. Retrieved 15 September 2020.

• Yue, Jia; Russell III, James; Gan, Quan; Wang, Tao; Rong, Pingping; Garcia, Rolando; Mlynczak, Martin (9 November 2019). "Increasing Water Vapor in the Stratosphere and Mesosphere After 2002". Geophysical Research Letters. American Geophysical Union. 46 (22): 13452–13460. Bibcode:2019GeoRL..4613452Y. doi:10.1029/2019GL084973. S2CID 210607942. Retrieved 15 September 2020.

External links

• TIMED mission page at JHU/APL
• TIMED mission page at NASA GSFC
• Solar EUV Experiment (SEE) page at the Laboratory for Atmospheric and Space Physics

На других языках

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[de] TIMED

Die Mission TIMED (englisch Thermosphere Ionosphere Mesosphere Energetics and Dynamics) ist ein Projekt, um die Dynamik in der Mesosphäre und der unteren Thermosphäre der Erdatmosphäre zu untersuchen.

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- [en] TIMED

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[es] TIMED

TIMED (acrónimo de Thermosphere Ionosphere Mesosphere Energetics and Dynamics) es un satélite artificial de la NASA dedicado al estudio de la ionosfera y termosfera terrestres. Fue lanzado el 7 de diciembre de 2001 desde la Base Aérea de Vandenberg mediante un cohete Delta.

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