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AAE 450 – Senior Design

AAE 450 – Senior Design. J. Darcey Kuhn ERV Team – Communications January 23, 2001. Parameters. High Gain Antenna Sizes – Beamwidth and antenna gain Capacity (i.e. number of channels of each type) – or bandwidths and frequencies

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AAE 450 – Senior Design

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  1. AAE 450 – Senior Design J. Darcey Kuhn ERV Team – Communications January 23, 2001

  2. 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/

  3. 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

  4. 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

  5. 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

  6. 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

  7. 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

  8. 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

  9. 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

  10. Future Enhancements http://deepspace.jpl.nasa.gov/dsn/array/index.html

  11. Future Enhancements • Cost Analysis • Power • Consumption • Signal • Signal-to-Noise Ratio • Weight • Historically low • Failure Probability • Low Gain Antenna as back-up

  12. 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

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