Mission Profile: TES Instrument Specifications
TES is a high-resolution, infrared, imaging Fourier-transform spectrometer with spectral coverage of 650 to
2250 cm-1 at a spectral resolution of 0.1
cm-1 (low resolution) or 0.025
cm-1 (high resolution), offering line-width-limited discrimination of
essentially all radiatively active molecular species in Earth's lower atmosphere.
| Requirement |
Specification |
Comments |
| Spectrometer type |
Connes-type four-port Fourier transform spectrometer |
Both limb and nadir viewing cpability |
| Spectral sampling distance |
Interchangeably 0.0592 cm-1 nadir and 0.0148 cm-1 limb |
Unapodized |
| Optical path difference |
Interchangeably ±8.45 cm nadir and ±33.8 cm limb |
Double-sided interferograms |
| Overall spectral coverage |
650-3050 cm-1 (3.2-15.4 µm) |
Continuous, but with multiple sub-ranges typically 200-300 cm-1 wide |
| Individual detector array spectral coverage (cm-1) |
1A (1900-3050), 1B (820-1150), 2A (1100-1950), 2B (650-900) |
All mercury cadmium telluride photo voltaic at 65 K |
| Detector array configuration |
1 X 16 |
All four arrays optically conjugated |
| Aperture |
5 cm |
Unit magnification system |
| System étandue (per pixel) |
9.45 X 10^-5 cm2sr |
Not allowing for a small central obscuration from the Cassegrain secondaries |
| Modulation index |
>0.7; 650-3050 cm-1 |
>0.5 at 1.06 µm (control laser) |
| Spectral accuracy |
±0.00025 cm-1 |
After correction fro finite field of view, off axis effects, Doppler shifts, etc. |
| Channeling |
<10% peak to peak; <1% after calibration |
All planar transmissive elements wedged |
| Spatial resolution |
0.5 X 5 km nadir; 2.3 X 23 km limb |
|
| Spatial coverage |
5.3 X 8.5 km nadir; 37 X 23 km limb |
|
| Pointing accuracy |
75 µrad pitch, 750 µrad yaw, 1100 µrad roll |
Peak-to-peak values |
| Field of regard |
45° cone about nadir plus trailing limb |
Also views internal calibration sources |
| Scan (intergration) time |
4-s nadir and calibration, 16-s limb |
Constant-speed scan, 4.2 cm/sec (optical path difference rate) |
| Maximum stare time, nadir |
208 s |
40 downlooking scans |
| Transect coverage |
885 km maximum |
|
| Interferogram dynamic range |
< 16 bits |
Plus four switchable gain steps |
| Radiometric accuracy |
< 1K, 650-2500 cm-1; < 2 K, 2500-3050 cm-1 |
Internal, adjustable, hot blackbody + cold space |
| Pixel-to-pixel cross talk |
<10% |
Includes diffraction, aberrations, carrier diffusion, etc. |
| Spectral signal-to-noise ratio |
As much as 600:1; 30:1 minimum requirement |
Depends on spectral region and target. General goal is to be source photon shot-noise limited |
| Lifetime |
5 years on orbit |
Plus 2 years before launch |
| Size |
1.0 m X 1.3 m X 1.4 m |
Earth shade stowed |
| Mass |
385 kg |
Allocation |
| Power, average |
334 W |
Allocation |
| Power, peak |
361 W |
Allocation |
| Data rate, average |
4.5 MBPS |
science only |
| Data rate, peak |
6.2 MBPS |
Allocation |
TES Optical Filters
The following table lists the optical-filter specifications and species in the atmosphere having
absoption/emission features in the filter spectral ranges. Not all the filters are used in the
global surveys. Filters 2B1, 1B2, 1A1, and 2A1 are used in nadir global
surveys, and filters 2B1, 1B2, 1A1, 2A1, 1B1, and 2A4 are used in limb global surveys.
| Filter Identification |
Filter Half-Power Points (cm-1) |
Major Species |
| Array 2B (650 - 900 cm-1) |
| 2B1 |
650 |
900 |
CO2, HNO3, CFC11, NO2 |
| Array 1B (820 - 1150 cm-1) |
| 1B1 |
820 |
1050 |
HNO3, NH3, CFC11, CFC12, O3 |
| 1B2 |
950 |
1150 |
O3, NH3, CFC11, CFC12, N2O |
| Array 2A (1100 - 1950 cm-1) |
| 2A1 |
1100 |
1325 |
O3, N2O, HNO3, CFC12, SO2, CH4 |
| 2A2 |
1300 |
1550 |
O3, HNO3, CH4 |
| 2A3 |
1500 |
1750 |
H2O, NO2 |
| 2A4 |
1700 |
1950 |
H2O, NO |
| Array 1A (1900 - 3050 cm-1) |
| 1A1 |
1900 |
2250 |
O3, CO, N2O, NO, OCS |
| 1A2 |
2200 |
2450 |
CO2, N2 |
| 1A3 |
2425 |
2450 |
N2O |
| 1A4 |
2600 |
2850 |
HDO |
| 1A5 |
2800 |
3050 |
CH4, HCl, O3 |
|
