[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

Re: Communication thru P5-A

In a message dated 8/28/02 12:09:26 PM EST, cvn65vf94@msn.com writes:

> Hello Chris.
>  >
>  >I don't believe you knew Mars' location without looking it up for one 
>  >moment!<<
>  Believe whatever you want.
>  But you are wrong here.

Sure and pigs have wings.

>  >The Viking Orbiter transmitter outputed 30 watts, MGS outputs 25 watts 
>  >MO
>  >outputs about 20 watts, so 50 watts with a big dish is important.
>  I did have to look this up because I wanted a source for it.
>  <<Communications were accomplished through a 20-W S-band (2.3 GHz) 
>  transmitter and 2 20-W TWTA's. An X-band (8.4 GHz) downlink was also added 
>  specifically for radio science and to conduct communications experiments. 
>  Uplink was via S-band (2.1 GHz). A 2-axis steerable high-gain parabolic 
>  antenna with a diameter of approximately 1.5 m was attached at one edge of 
>  the orbiter base, and a fixed low-gain antenna extended from the top of 
>  bus. Two tape recorders were each capable of storing 1280 Mbits. A 381 MHz 
>  relay radio was also available.
>  <<
>  Just do a google on Viking Spacecraft and you'll find it.

Yes, well your source is wrong the Landers outputted 20 watts and the 
Orbiters 30 watts.  I happen to have worked recently on one of those High 
Gain antennas used on the VIKING LANDERS.  Do you know the different between 
a Orbiter and a Lander, Robert?

Try reading this...
"[249] The goal of obtaining the greatest amount of scientific 
information possible from the Martian surface was the major influence on 
the design and structure of the lander. During 1975 and 1976, Mars and 
Earth would be at their maximum separation distance, about 380 million 
kilometers. Since the distance would vary during the mission and since 
the length of relay opportunities would also vary, several data 
transmission links were built into the lander equipment for direct 
communications with Earth (1000, 500, and 250 bits per second were 
available at a single transmitter output of 20 watts). A second 
communications link, UHF through the orbiter, was functionally redundant 
with the direct link. The orbiter relay had three transmitter power 
levels (l, 10, and 30 watts) and two data rates (4 and 16 kilobits). 
Since available communication time was severely limited by the power 
available, typical communication periods would be about 1 hour for the 
direct link transmitters and 20 minutes for the relay link transmitters. 
With these link times, data rates, and power output, the rate of 
scientific data returned to Earth would be about l million bits per day 
for the direct link and 20 million for the relay link. Since the relay 
link was the more efficient from an energy standpoint, the mission 
planners would use the orbiter link for the majority of the mission's 

Source URL: http://www.hq.nasa.gov/office/pao/History/SP-4212/ch8-3.html
>  And this
>  >is baseline.  If they fly it with advanced solar panels or increase the
>  >square area of the cells it will be closer to the 100 watts.
>  And anything is possible.

Increasing the output at Mars is easily possible and not everything is 
possible.  You would never admit a mistake!

>  Including the fact that the P5-A will fly.

Fortunately, that decision is out of your hands.  So yea it is possible.  
You're just to much of a negative BS-er to bother wasting any more bandwidth 
--Chris Vancil
Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org