AAE 450 – Senior Design
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Transcript of AAE 450 – Senior Design
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AAE 450 – Senior Design
J. Darcey Kuhn
ERV Team – Communications
January 23, 2001
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Parameters
• High Gain Antenna Sizes – Beamwidth and antenna gain
• Capacity (i.e. number of channels of each type) – or bandwidths and frequencies
• Uplink & Downlink signal strength and quality to Deep Space Network (DSN) – support communications, science data, voice, video, engineering
telemetry, and navigation
http://deepspace.jpl.nasa.gov/dsn/
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High Gain Antenna
• Beamwidth: from an antenna pattern, the angle between the half-power (3 dB) points of the main lobe, when referenced to the peak effective radiated power of the main lobe
http://132.163.64.205/fs-1037/dir-004/_0572.htm
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High Gain Antenna
A useful rule of thumb for calculating beamwidth is
3 dB beamwidth = 70λ / D (degrees)where λ is wavelength and D the antenna diameter
• Surveyor: 0.56 deg• Space Shuttle
Uplinking: 0.56 deg
Downlinking: 0.51 deg
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High Gain Antenna
• Antenna Gain (Isotropic) – for a uniformly illuminated antenna with physical area A, the directive gain at the center of the main beam is given by:
http://web.bham.ac.uk/eee1roj8/wbe/wbe031.htm
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High Gain Antenna
G = 4**A/λ2 A= d2/4
• Gain is normally expressed in dBs by taking 10*log(G)• Surveyor: 42.41 dB• Space Shuttle:
Uplinking: 42.39 dB
Downlinking: 43.14 dB
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Bandwidths & Frequencies
• Bandwidth: Amount of data that can be transferred in a fixed amount of time
• Space Shuttle uses S-band (1,700 to 2,300 MHz) & Ku-band (15,250 to 17,250 MHz) to transfer information• Ku-band located in the payload bay
• Ku-band (12-18 GHz / λ = 2.5 to 1.67 cm) can handle higher quantities of data than the S-band systems (3 channels of data)
• All transmissions broadcasted by Surveyor utilized X-band radio signals near 8.4 GHz
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Deep Space Network
• DSN is an international network of antennas that supports interplanetary spacecraft missions
• Currently consists of three deep-space communications facilities placed approximately 120 degrees apart around the world – CA, Spain, and Australia
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Antenna Mounting
• High-gain antenna sits at the end of a long boom• Two rotating joints, called gimbals, hold antenna to
boom• Gimbals will allow the antenna to automatically track and
point at the Earth
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Future Enhancements
http://deepspace.jpl.nasa.gov/dsn/array/index.html
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Future Enhancements
• Cost Analysis• Power
• Consumption• Signal
• Signal-to-Noise Ratio• Weight
• Historically low
• Failure Probability • Low Gain Antenna as back-up
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Related Skills
• Matlab, Fortran 77, UNIX, AutoCAD, C• Currently enrolled in 490E (Satellite Systems)• Two co-op tours with United Space Alliance at Johnson
Space Center – uplinking data from the MCC to ISS