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TOVS PATH B DATA SUMMARY: 2. SATELLITE AND INSTRUMENT


2. Satellite and Instrument

A high-level description of the NOAA-10 platform and the TOVS instruments is presented below. For more detailed information refer to Kidwell (1991). The Pathfinder product will eventually encompass data products derived from measurements taken aboard the NOAA Polar Orbiters launched before and after NOAA-10.

Nominal orbital parameters for the NOAA-10 spacecraft were:


        Launch date                     9/17/86
        Operational dates               11/17/86 - present
        Orbit                           Sun-synchronous, near polar
        Nominal Altitude (km)           833
        Inclination (deg)               98.8
        Nodal Period (min.)             102
        Equator Crossing Time (LST)     1930 (ascending), 0730 (descending)
        Nodal Increment (deg)           25.3

 

The TOVS system consists of 3 independent instruments, specifically:

  • the High Resolution Infrared Radiation Sounder 2 (HIRS/2)
  • the Microwave Sounding Unit (MSU)
  • the Stratospheric Sounding Unit (SSU)

All satellites in the NOAA polar orbiting series beginning with TIROS-N in 1978 contained HIRS/2 and MSU; however, both NOAA-10 and NOAA-12 contained no SSU.

The HIRS/2 is a step-scanned instrument that utilizes a 15-cm diameter optical system to gather energy emitted by the earth's surface and atmosphere in 19 infrared channels, as well as reflected radiation in a single visible channel. These channels are:



        Channel #    Wavenumber(cm-1)     Channel #    Wavenumber(cm-1)
        ---------    ----------------     ---------    ----------------
            1            667.7               11           1363.3
            2            680.2               12           1489.4
            3            691.2               13           2191.4
            4            704.3               14           2208.7
            5            716.3               15           2237.5
            6            733.3               16           2269.1
            7            750.7               17           2360.0
            8            899.5               18           2514.6
            9           1029.0               19           2665.4
           10           1224.1               20          14453.1 

  

The MSU is a step-scanned 4 channel Dicke radiometer which makes passive microwave measurements in the 50 GHz oxygen absorption region of the spectrum. Two 4-inch diameter antennas sense radiation in the following spectral channels:


        Channel #    Wavenumber(cm-1)     Channel #    Wavenumber(cm-1)
        ---------    ----------------     ---------    ----------------
            1        1.6779 (50.30 GHz)       3        1.8334 (54.96 GHz)
            2        1.7927 (53.74 GHz)       4        1.9331 (57.95 GHz)

  

The SSU is a step-scanned far-infrared spectrometer with 3 channels in the 15 micrometer carbon dioxide absorption band. It uses the pressure modulation technique in 3 individual cells to sense radiation emitted from the 1 to 20 mb region of the atmosphere. The central wavenumber for each of the 3 cells is 668 cm-1.

The instrument parameters for the TOVS sensors are:


        Instrument parameter         HIRS/2         MSU           SSU
        --------------------         ------        ------        ------
        Cross track scan angle    

        (+/- degrees from nadir)      49.5          47.4          40.0
        Number of steps                 56            11             8
        Angular FOV (degrees)         1.25           7.5          10.0
        Step Angle (degrees)          1.80           9.5          10.0
        Ground IFOV (km)
          - at nadir                  17.4         109.3         147.3 
          - at end of scan        58.5 x 29.9  323.1 x 178.8  244.0 x 186.1
        Swath width (+/- km)          1120         1174           737

  

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Last updated: Nov 23, 2009 02:26 PM ET
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