2/9/2024 0 Comments Atlas agena paper model pdfThe high wind swaths added an additional 250 km to each side. SASS had a pulse transmit frequency of 14.599 GHz and 500 km swaths on either side of the satellite. The altimeter operated at 13.56 GHz and had a swath width which varied from 2.4 to 12 km, depending on the state of the sea. Moreover, ALT measured the height of the waves below the satellite with an accuracy of 10% or 0.5 m, whichever was greater. The ALT Experiment determined the satellite’s position above the ocean surface with an accuracy of 0.1 m and it evaluated the backscatter coefficient with an accuracy of 1.0 dB. The absolute accuracy in determining the sea surface temperature was 2 K, while the accuracy of the wind speed measurements was 2 m/s for winds ranging from 7 m/s to about 50 m/s. The instrument’s antenna was a parabolic reflector, offset from the nadir by 42°. It had a swath width of approximately 600 km, while the spatial resolution ranged from 22 km at 37 GHz to 100 km at 6.6 GHz. SMMR operated at five different frequencies: 6.6 GHz, 10.7 GHz, 18.0 GHz, 21.0 GHz and 37.0 GHz. The instrument featured HH polarisation (horizontal transmit and horizontal receive) at a look angle of 20°. SAR operated in the L-band at a centre wavelength of 0.235 m, with a radiometric resolution of 5 bits of raw data and a spatial resolution of 25 m on the surface at four looks. LRR supported precision orbit determination for the spacecraft. VIRR was based on a Cassegrain-type telescope as a support instrument, capturing the visual reflection and thermal infrared emission from oceanic, coastal and atmospheric features, with the potential to aid in the interpretation of the data gathered from the other sensors. As a proof-of-concept experiment, SASS was a fan-beam dual-polarised Doppler scatterometer, with the objective of radar backscatter measurements over ocean surfaces for estimation of the wind field. The ALT instrument was a Ku-band compressed pulse radar altimeter, utilising a parabolic 1 m antenna pointed off nadir and a linear FM (Frequency Modulation) transmitter to determine sea surface profiles, currents, wind speeds and wave heights. SMMR was a multispectral, dual-polarisation microwave radiometer, observing at five different wavelengths, with the goal of monitoring sea surface temperatures, wind speeds, rain rate, atmospheric water content and ice conditions. It employed a phased array antenna, consisting of eight identical rigid fibreglass honeycomb panels. The SAR sensor is regarded as the first imaging SAR system used in Earth orbit. All sensors operated simultaneously, over the same region of the ocean. SeaSat was equipped with a Synthetic Aperture Radar (SAR), a Scanning Multichannel Microwave Radiometer (SMMR), a Radar Altimeter (ALT), the Seasat-A Scatterometer System (SASS), a Visible and Infrared Radiometer (VIRR) and a Laser Retro-Reflector (LRR).
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