 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 |
| SATCATno. | 26998 |
| Website | TIMED at APL |
| Mission duration | Planned: 2 years Elapsed: 23 years, 11 months, 11 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, 15:07:35UTC |
| 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 |
Hinode → | |
TheTIMED (Thermosphere • Ionosphere • Mesosphere • Energetics and Dynamics) mission is dedicated to study the influences thatenergetics anddynamics of theSun and humans have on the least explored and understood region ofEarth's atmosphere – theMesosphere andLower Thermosphere /Ionosphere (MLTI). The mission was launched fromVandenberg Air Force Base inCalifornia on 7 December 2001 aboard aDelta II rocketlaunch vehicle. The project is sponsored and managed byNASA, while the spacecraft was designed and assembled by theApplied Physics Laboratory atJohns Hopkins University. The mission has been extended several times, and has now collected data over an entiresolar cycle, which helps in its goal to differentiate the Sun's effects on the atmosphere from other effects.[2] It shared itsDelta II launch vehicle with theJason-1oceanography mission.
TheMesosphere, LowerThermosphere andIonosphere (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 ingeophysics,meteorology,aeronomy, andatmospheric science, assolar radiation is one of the primary driving forces behindatmospheric tides. Changes in the MLT can also affect modernsatellite andradiotelecommunications.
The spacecraft payload consists of the following four main instruments:
The data collected by the satellite's instruments are made freely available to the public.[3]
TIMED experienced minor problems withattitude control when, after launch, themagnetorquers 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'smagnetic 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 theSun sensors. After these corrections, the attitude control system functioned as intended.[4]
At approximately 06:30 UTC on 28 February 2024, TIMED passed within 10 meters of the defunctKosmos 2221 satellite. As neither TIMED nor Kosmos 2221 can be maneuvered, the conjunction was unavoidable. LeoLabs, a satellite tracking company, had estimated asatellite collision probability of as high as 8% prior to the encounter. A collision between the two satellites, both traveling athypervelocity speeds relative to each other, was projected to generate between 2,500 and 7,500 fragments ofspace debris, a figure potentially exceeding that of the2009 satellite collision betweenIridium 33 andKosmos 2251. This close miss was particularly concerning to NASA, which highlighted the event at the 39thSpace Symposium inColorado Springs in a broader speech on NASA's newspace sustainability strategy plan.[5]
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.[6][7]
SABER is able to collect 1,500 water vapor measurements per day, a vast improvement from previous satellites and ground-based observations.[8] SABER had a flaw in itsoptical filter that caused it to overestimate water vapor levels; this error was discovered and the data were corrected.[9] 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.[10] 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.[11]
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.[12] 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.[13]
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.[14]
This article incorporates text from this source, which is in thepublic domain. This article incorporates text from this source, which is in thepublic domain.