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Ayo Irpin, Ukraine!
Join Date: Mar 2004
Location: Santa Cruz, CA
Posts: 12,554
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It's a function of frequency and the size of the reflector diameter. The larger the diameter, the more antenna signal gain yet, also results in a smaller signal beamwidth.
The RMS value of the reflector is determined by measuring many different points on all of the individual panels to determine how far off we are from the theoretical curve. The theoretical curve is designed to take all signal (out of phase at all points to any other point) and focus the signal by combining phase. That is how the overall power (Gain) is affected in both transmit and receive. Any deviation from the theoretical means a portion of signal is not combined (lost) and Gain goes down. It's a trade off between Transmit and Receive as we have to maintain frequency separation. The smaller the beamwith (function os diameter and frequency) determines how accurate our pointing must be. Again, stiffness in the structure helps this. Let's put it this way.. On a program I'm working on (can't give specifics).... 1/100th of a degree of pointing is the difference between being on the peak of the beam.... or not. Typically on the order of -20dB or greater. This, at at target 22k miles away.
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Harmlessly passing gas in the grassland away; Only dimly aware of a certain smell in the air Last edited by 70SATMan; 05-02-2013 at 12:10 PM.. |
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05-02-2013, 12:05 PM
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Ayo Irpin, Ukraine!
Join Date: Mar 2004
Location: Santa Cruz, CA
Posts: 12,554
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Quote:
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Harmlessly passing gas in the grassland away; Only dimly aware of a certain smell in the air |
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05-02-2013, 12:08 PM
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Registered
Join Date: May 2002
Location: Morrison, Colorado
Posts: 634
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The DSN is unique asset for planetary exploration. In recent years, some of the deep space missions have needed to work around ground station operational issues. As an interplanetary spacecraft developer I'm thrilled to see the US investing in infrastructure upgrades.
The 34M BWG antennas will support relatively high bandwidth data downlink from Mars, meaning roughly 110kb/sec with a 15W solid state transponder at Mars, D/L freq ~8.4GHz. Traveling Wave Tube Amplifiers (TWTAs) that deliver ~ 100W of RF power will support ~ 1Mb/s downlink. Each spacecraft has a unque frequency assignment so the DSN can support comm links with multiple assets at Mars. The US currently has 2 operational orbiters and 2 operational rovers on the surface. Next orbiter launches Nov 18th 2013, next lander launches March 2016. Love the DSN, it's a discriminator for the US solar system exploration effort!!!
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96 993 Cab, 73E Targa, 72S Targa |
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05-02-2013, 08:18 PM
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Ayo Irpin, Ukraine!
Join Date: Mar 2004
Location: Santa Cruz, CA
Posts: 12,554
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That gets me hot......
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Harmlessly passing gas in the grassland away; Only dimly aware of a certain smell in the air |
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05-02-2013, 09:09 PM
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