Sensors of X-Band Satellites

jump to information on the OCM sensor

The MODIS Sensor

The MODIS (Moderate-Resolution Imaging Spectroradiometer) instrument on Terra-1 and Aqua-1 EOS satellites is a scanning imaging radiometer with a viewing swath width of 2330 km (the field of view sweeps ± 55° cross-track) and a 10-km along-track view.

MODIS has 36 channels—11 channels in the visible range, 9 in the near-IR range, 6 in the thermal-IR range, 4 in the shortwave-IR (SWIR) range, and 6 in the longwave-IR range (LWIR).

Two channels have a spatial resolution of  250m, 5 have a resolution of 500m, and 29 have a resolution of 1000m.  The 1000m channels have 10 detectors each; the 500m channels have 20 detectors; and the 250m channels have 40 detectors.  Channels 13 and 14 have such high SNR (signal-to-noise) requirements that dual 10-element arrays are used for each.  Thus, MODIS has a total of 490 detectors.

The data rate is 13.1Mbps.  

Spectral properties of the MODIS channels are given in the following table:

Channel	Wavelength	Spectrum	Unit of Measure	Ground Resolution	Primary Use
1	0.620-0.670µm	visible	radiance3	0.25km	Land/Cloud Boundaries
2	0.841-0.876µm	near IR	radiance3	0.25km
3	0.459-0.479µm	visible	radiance3	0.5km	Land/Cloud Properties
4	0.545-0.565µm	visible	radiance3	0.5km
5	1.230-1.250µm	near IR	radiance3	0.5km
6	1.628-1.652µm	near IR	radiance3	0.5km
7	2.105-2.155µm	near IR	radiance3	0.5km
8	0.405-0.420µm	visible	radiance3	1km	Ocean Color/ Phytoplankton/ Biogeochemistry
9	0.438-0.448µm	visible	radiance3	1km
10	0.483-0.493µm	visible	radiance3	1km
11	0.526-0.536µm	visible	radiance3	1km
12	0.546-0.556µm	visible	radiance3	1km
13*	0.662-0.672µm	visible	radiance3	1km
14*	0.673-0.683µm	visible	radiance3	1km
15	0.743-0.753µm	visible	radiance3	1km
16	0.862-0.877µm	near IR	radiance3	1km
17	0.890-0.920µm	near IR	radiance3	1km	Atmospheric Water Vapor
18	0.931-0.941µm	near IR	radiance3	1km
19	0.915-0.965µm	near IR	radiance3	1km
20	3.660-3.840µm	thermal IR	radiance3	1km	Surface/Cloud Temperature
21	3.929-3.989µm	thermal IR	radiance3	1km
22	3.929-3.989µm	thermal IR	radiance3	1km
23	4.020-4.080µm	thermal IR	radiance3	1km
24	4.433-4.498µm	thermal IR	radiance3	1km	Atmospheric Temperature
25	4.482-4.549µm	thermal IR	radiance3	1km
26	1.360-1.390µm	near IR	radiance3	1km	Cirrus Clouds Water Vapor
27	6.535-6.895µm	SWIR1	radiance3	1km
28	7.175-7.475µm	SWIR1	radiance3	1km
29	8.400-8.700µm	SWIR1	radiance3	1km
30	9.580-9.880µm	SWIR1	radiance3	1km	Ozone
31	10.780-11.280µm	LWIR2	radiance3	1km	Surface/Cloud Temperature
32	11.770-12.270µm	LWIR2	radiance3	1km
33	13.185-13.485µm	LWIR2	radiance3	1km	Cloud Top Altitude
34	13.485-13.785µm	LWIR2	radiance3	1km
35	13.785-14.085µm	LWIR2	radiance3	1km
36	14.085-14.385µm	LWIR2	radiance3	1km
* Channels 13 and 14 have both high and low signal-to-noise ratios. Output datasets contain a separate variable for each. 1. shortwave IR 2. longwave IR 3. radiance = W/(m2*steradian*µm)

The OCM Sensor

The OCM (Ocean Color Monitor) sensor of Oceansat-1 (IRS-P4) is an imager with a viewing swath width of 1420 km.  OCM has 8 channels—6 channels in the visible range and 2 in the near-IR range. The data is 12-bit. The instrument can be tilted +/-20 degrees along track to avoid sun glint.

Spectral properties of these channels are given in the following table:

Channel	Wavelength	Spectrum	Unit of Measure	Ground Resolution (cross track)	Primary Use
1	0.402-0.422µm	visible	radiance1	360m	Yellow substance and turbidity
2	0.433-0.453µm	visible	radiance	360m	Chlorophyll absorption maximum
3	0.480-0.500µm	visible	radiance	360m	Chlorophyll and other pigments
4	0.500-0.520µm	visible	radiance	360m	Turbidity, suspended sediment
5	0.545-0.565µm	visible	radiance	360m	Chlorophyll, suspended sediment
6	0.660-0.680µm	visible	radiance	360m	Chlorophyll absorption
7	0.745-0.785µm	near IR	radiance	360m	O2 absorption R-branch
8	0.845-0.885µm	near IR	radiance	360m	Aerosol optical thickness, vegetation, water vapor reference over the ocean
1. radiance = mW/(cm2*steradian*µm)

Last Update: $Date: 2002/09/10 20:31:15 $