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 Uplink & Downlink signal strength and quality to Deep Space Network (DSN) – support communications, science data, voice, video, engineering telemetry, and navigation

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

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

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:

High Gain Antenna G = 4*  *A/λ 2 A=  d 2 /4 Gain is normally expressed in dBs by taking 10*log(G) Surveyor: dB Space Shuttle: Uplinking: dB Downlinking: dB

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

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

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

Future Enhancements

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

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