Terra Terra About Mission Objectives
Terra launched in a sun-synchronous orbit on 18 December 1999. Terra is the flagship of the NASA Earth Observing System (EOS), a series of spacecraft that represent a landmark step in NASA's role to observe Earth from the unique vantage point of space. Terra focuses on measurements identified by a consensus of U.S. and international scientists enabling research into the ways that Earth's lands, oceans, air, ice, and life function as a total environmental system.
Instruments
ASTER – Advanced Spaceborne Thermal Emission and Reflection RadiometerCERES – Clouds and the Earth’s Radiant Energy SystemMISR – Multi-angle Imaging SpectroRadiometerMOPITT – Measurements of Pollution in The TroposphereMODIS – Moderate Resolution Imaging Spectroradiometer. MODIS delivers sea surface temperature (SST), atmospheric temperature, cloud temperature, cloud altitude, water vapor, ocean color and aerosol data. The MODIS instruments on board the Terra and Aqua EOS satellites acquire data with global coverage every 1-2 days.
MODIS Instrument
The MODIS instrument provides high radiometric sensitivity (12 bit) in 36 spectral bands ranging in wavelength from 0.4 µm to 14.4 µm. The responses are custom tailored to the individual needs of the user community and provide exceptionally low out-of-band response. Two bands are imaged at a nominal resolution of 250 m at nadir, with five bands at 500 m, and the remaining 29 bands at 1 km. A ±55-degree scanning pattern at the EOS orbit of 705 km achieves a 2,330-km swath and provides global coverage every one to two days.
A high-performance passive radiative cooler provides cooling to 83K for the 20 infrared spectral bands on two HgCdTe Focal Plane Assemblies (FPAs). Novel photodiode-silicon readout technology for the visible and near infrared provide unsurpassed quantum efficiency and low-noise readout with exceptional dynamic range. Analog programmable gain and offset and FPA clock and bias electronics are located near the FPAs in two dedicated electronics modules, the Space-viewing Analog Module (SAM) and the Forward-viewing Analog Module (FAM). A third module, the Main Electronics Module (MEM) provides power, control systems, command and telemetry, and calibration electronics.
The system also includes four on-board calibrators as well as a view to space: a Solar Diffuser (SD), a v-groove Blackbody (BB), a Spectroradiometric calibration assembly (SRCA), and a Solar Diffuser Stability Monitor (SDSM).
Primary Use
Band
Bandwidth1
Spectral2
Required3
Land/Cloud/Aerosols 1
620 - 670
21.8
128
2
841 - 876
24.7
201
Land/Cloud/Aerosols 3
459 - 479
35.3
243
4
545 - 565
29.0
228
5
1230 - 1250
5.4
74
6
1628 - 1652
7.3
275
7
2105 - 2155
1.0
110
Ocean Color/ 8
405 - 420
44.9
880
9
438 - 448
41.9
838
10
483 - 493
32.1
802
11
526 - 536
27.9
754
12
546 - 556
21.0
750
13
662 - 672
9.5
910
14
673 - 683
8.7
1087
15
743 - 753
10.2
586
16
862 - 877
6.2
516
Atmospheric 17
890 - 920
10.0
167
18
931 - 941
3.6
57
19
915 - 965
15.0
250
Primary Use Band Bandwidth1 Spectral2 Required4
Surface/Cloud 20
3.660 - 3.840
0.45(300K)
0.05
21
3.929 - 3.989
2.38(335K)
2.00
22
3.929 - 3.989
0.67(300K)
0.07
23
4.020 - 4.080
0.79(300K)
0.07
Atmospheric 24
4.433 - 4.498
0.17(250K)
0.25
25
4.482 - 4.549
0.59(275K)
0.25
Cirrus Clouds 26
1.360 - 1.390
6.00
150(SNR)
27
6.535 - 6.895
1.16(240K)
0.25
28
7.175 - 7.475
2.18(250K)
0.25
Cloud Properties 29
8.400 - 8.700
9.58(300K)
0.05
Ozone 30
9.580 - 9.880
3.69(250K)
0.25
Surface/Cloud 31
10.780 - 11.280
9.55(300K)
0.05
32
11.770 - 12.270
8.94(300K)
0.05
Cloud Top 33
13.185 - 13.485
4.52(260K)
0.25
34
13.485 - 13.785
3.76(250K)
0.25
35
13.785 - 14.085
3.11(240K)
0.25
36
14.085 - 14.385
2.08(220K)
0.35
1 2 3 4 Note: Performance goal is 30-40% better than required
Array
