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INSTRUMENT

Special Observations

Special Observations can only be scheduled during the 9 or 10 orbit gaps in the Global Surveys, and are conducted in any of three basic modes:

  • Stare: In nadir mode, point at specific locations over sites for validation and other scientific interest for up to about 4 minutes. Such observations are made for as long as the target is in within ±45° of the nadir direction (up to 210 seconds).
  • Transect: In nadir mode, point at a set of contiguous areas to cover about 850 km, or indefinitely in limb mode.
  • Step-&-Stare: Point at nadir for 4 seconds (5.2 seconds with necessary reset). During that time, Aura moves 39 km in its orbit, and its nadir point on Earth's surface moves 35 km. Point at nadir again. Repeat indefinitely.

The mode used -- targeted, transect, step-and stare, or limb -- depends on the science requirement. Volcanoes, for example, would usually be targeted with the stare mode (point at the caldera and hold the view there for as long as possible). Biomass burning, on the other hand, could use any mode depending on whether we wish to measure the fire itself or look for specific gases in the plume coming from the fire. Limb transects are normally used for intercomparison with the other Aura instruments.

A visualization page provides curtain images and profile plots of Level 2 Special Observations.

Modes and Types of Special Observations

Staring Mode Observations

The Staring Mode is used for localized validation, volcano monitoring, and biomass burning observations. Adjustments to the following tables will be made at the discretion of the TES Science and Validation Teams.

Validation Sites

There are a number of permanently-instrumented validation sites around the world. Some of the most useful sites for TES are those participating in the DoE Atmospheric Radiation Measurements (ARM) program (see table below).

ARM Site Locations
ARM site TES footprint mean elevation (m) Coordinates (Decimal Degrees) Approx. Aura (Ascending) Overpass Time
Latitude E. Longitude Local Mean Solar Time Coordinated Universal Time
Southern Great Plains 314 36.617 262.500 14:02:37 20:32:37
Barrow, Alaska 2 71.323 203.384 15:19:04 1:45:32
Barrow. Alaska, off-shore pt. 0 71.400 203.200 15:19:33 1:46:45
Atqasuk, Alaska 18 70.472 202.592 15:14:01 1:43:49
Manus Island 1 -2.058 147.425 13:36:49 3:47:07
Manus Island, off-shore pt. 0 -2.180 147.450 13:36:44 3:46:56
Nauru Island 5 -0.521 166.916 13:37:42 2:30:02
Nauru Island, off-shore pt. 0 -0.500 166.820 13:37:43 2:30:26
Darwin, Australia 1 -12.425 130.891 13:30:43 4:47:09
Darwin, Australia, off-shore pt. 0 -12.320 130.780 13:30:47 4:47:39

The NASA Network for the Detection of Stratospheric Change (NDSC) also makes useful tropospheric measurements (see table below).

Selected NDSC Site Locations
NDSC site TES footprint mean elevation (m) Coordinates (Decimal Degrees) Approx. Aura (Ascending) Overpass Time
Latitude E. Longitude Local Mean Solar Time Coordinated Universal Time
Table Mountain, CA 1905 34.400 242.300 14:00:41 21:51:29
Lauder, NZ 379 -45.040 169.680 13:04:46 1:46:03
Hilo, Hawaii 11 19.720 204.930 13:49:51 0:10:08
Hilo, off-shore pt. 0 19.800 205.000 13:50 0:10
Reunion Island 10 -21.800 55.500 13:24:46 9:42:46
Reunion Island, off-shore pt. 0 -21.400 55.500 13:25 9:43

Other sites which are useful for up-welling radiance measurements, some of which are used for calibrating the Pointing Control System (PCS), are listed in the table below.

Other Radiometric Target Site Locations
Location TES footprint mean elevation (m) Coordinates (Decimal Degrees) Approx. Aura (Ascending) Overpass Time
Latitude E. Longitude Local Mean Solar Time Coordinated Universal Time
Lake Tahoe, CA 1898 39.100 239.970 14:04:50 22:04:50
Lake Tahoe, CA (N. shore) 1905 39.240 239.940 14:05 22:05
ASTER site (MN lakes) TBD TBD TBD TBD TBD
Chesapeake Lighthouse 0 TBD TBD TBD TBD
Mediterranean 0 TBD TBD TBD TBD

See TES Special Observation Target Locations (GIF, 25 KB) for a look at the locations around the world.

Volcanoes

There are 10 volcanoes that the volcanology community is interested in having TES monitor (see table below). Each of these volcanoes emits copious amounts of gas (chiefly sulfur dioxide), the exact mixture of which is believed to be an eruption predictor.

Candidate Volcanoes to be Monitored
Name Location Latitude Longitude
Colima Mexico 19.420 256.280
Erebus Antarctica -77.525 167.120
Etna Sicily 37.730 15.000
Fuego Guatemala 14.480 269.120
Kilauea/Pu'u O'o Hawai'i 19.392 204.892
Lascar Chile -23.370 292.270
Masaya Nicaragua 11.980 273.850
Pacaya Guatemala 14.380 269.400
Sakurajima Japan 31.580 130.670
White Island New Zealand -37.520 177.180

Biomass Burning & Major Industrial Accidents

Biomass burning, especially in the tropics in the September-October time frame, is a major source of atmospheric pollutants. Most burnings can be observed by TES with a delay of 48 hours or less depending on when the information is received. Major industrial accidents can be targeted if information is received in a timely manner.

Transect Mode Observations

The Tansect Mode is used primarly for regional pollution studies and validation campaigns. The following table identifies the TES transect locations (which are subject to change).

Areas for Potential Transect Measurements
Location Elevation (m) Latitude (°) Longitude (°)
Ascension Island 429 <-7.95 <-14.37
East Mediterranean 0 35.0 32.0
Saudi Arabia 777 25.0 45.0
Oklahoma 171 35.0 265.0

The schematic below shows the footprint for Transect mode.

Schematic of a segment of the TES transect mode (keystoning exaggerated for clarity)

Schematic of a segment of the TES transect mode (keystoning exaggerated for clarity)

Multiple scans can be made at each step location; however, the overall length of the transect is limited to ±45° nadir angle (see table below).

Maximum Transect Lengths
Number of scans/step Maximum Transect Length (km)
1 949
2 349
3 220
4 132

Limb transect mode observations are primarily used for instrument intercomparisons and are created by putting TES into its limb mode and making repetitive long scans.

Special Tests and Calibrations

TES has a variety of test and calibration modes. Some involve the acquisition of interferograms, many do not. All of these tests are performed regularly for the life of the mission.

Archived Special Observations Data

Archived data are available from the Aura Validation Data Center (AVDC) at the Goddard Space Flight Center. Additionally, the data may be found and ordered from the Atmospheric Science Data Center ASDC at the Langley Research Center. Specific pages for acquiring TES data are the ASDC TES Data Sets page, and the AVDC (scroll down for TES data links).