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TOVS PATH A DATA SUMMARY: 2. SATELLITE AND INSTRUMENT


2. Satellite and Instrument

A high-level description of the NOAA-10 platforms and the TOVS instruments is presented below. For more detailed information refer to Kidwell (1991).

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 #    Wave number(cm-1)     Channel #    Wave number(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 #    Wave number(cm-1)     Channel #    Wave number(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 wave number 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

The channels used for Path A parameter estimation are as follows:


        Temp Profile     H2O Profile     Clouds     Surf Emiss     Surf Temp
        ------------     -----------   ----------   ----------   -------------
        HIRS...1,2,4     HIRS...8,10   HIRS...4,5   MSU......1   HIRS..8,18,19
            13,14,15           11,12        6,7,8
        MSU......3,4
 
        Cloud Clearing    Ozone
        --------------   -------
        HIRS.....13,14   HIRS..9
        MSU..........2

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