• Short Summary

    Major components consist of:
    1. Transmitter for the microwave scatterometer
    2. Receiver for the microwave radiometer/scatterometer
    3. Transmitter?

  • Description

    Major components consist of:
    1. Transmitter for the microwave scatterometer
    2. Receiver for the microwave radiometer/scatterometer
    3. Transmitter for the altimeter
    4. Receiver for the altimeter
    5. Antenna assembly
    The total assembly weight including antenna is about 260 lbs. and the total power consumption is about 150 watts.

    The mechanically scanned antenna sweeps the radar beam either along track or cross track in either a contiguous or noncontiguous mode. In the noncontiguous mode the beam moves in discrete steps from one cell to another, dwelling on each cell for a predetermined length of time. During this dwell time, the microwave instrument executes in time sequence two measurements: a passive radiometric thermal measurement with the transmitter turned off and an active scatterometer measurement with the transmitter turned on. Thus a paired measurement of apparent temperature and differential scattering cross-section are collected for each illuminated surface cell of about eight square miles. The scan period is chosen in accordance with the spacecraft velocity such that the surface cells are contiguous in the inflight direction.

    Astronauts will assist in target identification, and operate and monitor equipment. Real-time communication between astronauts and the Mission Control Center will be required for discussion during the experiment. Ground truth information desired over test sites will be obtained by the NASA Earth Resources Aircraft scatterometer team for validation and extrapolation of space-borne measurements.

    Data Return
    All data will be recorded on magnetic tape on one digitized channel. The radiometer/scatterometer data is recorded at 4 kilobits/second; the altimeter data at 10 kilobits/second.

    The experimental objective is to supplement experiment S193 in measuring the brightness temperature of the earth's surface along the spacecraft track.

    The L-Band radiometer experiment is basically the same in operating principle as the radiometer part of the microwave radiometer/scatterometer experiment (S193) except the operating frequency is changed from 13.9 GHz to 1.42 GHz. The primary function of the experiment is to supplement the measurement results of Experiment S193 by taking into consideration the effect of clouds on radiometric measurements. By using two frequencies (S193 at 13.9 GHz and S194 at 1.42 GHz) simultaneously in measurements, corrections can be made on radiometric data to include the cloud effects.

    The instruments to be used in this experiment are patterned after those which are being used on the NASA/MSC Earth Resources NP3A aircraft.

    Major components consist of:
    1. Receiver assembly
    2. Antenna assembly
    The total weight of the system is about 50 lbs. and total power consumption is about 15 watts.

    The antenna, which always points in a local vertical direction, receives noise-like signals from the thermal emission of an earth surface cell and any intervening clouds being viewed along the spacecraft track. These signals are superimposed on the instrument system noise. The noise-like signal can be recognized and its mean value accurately determined if it is observed long enough to gain a measurable signal. The signal is compared with the measured mean value of another noise source with known temperature. The comparison constitutes the radiometric measurement and can be correlated to give a measure of the brightness temperature of the surface if dielectric properties and surface roughness are known.

    When this experiment is carried out simultaneously with Experiment S193, the astronaut will be needed for equipment monitoring only.

    Data Return
    All data will be recorded on magnetic tapes. The data output is at 200 bits/second.

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    Film ID:
    Media URN:
    Reuters - Source to be Verified
    Issue Date:
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