From: baalke@kelvin.jpl.nasa.gov (Ron Baalke)
Subject: Re: Magellan Update - 12/11/92
News-Software: VAX/VMS VNEWS 1.3-4   
Keywords: Magellan, JPL
Reply-To: baalke@kelvin.jpl.nasa.gov
Organization: Jet Propulsion Laboratory
Date: Tue, 15 Dec 1992 00:28:16 GMT

In article <1992Dec11.221949.21756@colorado.edu>, loucks@csn.org (Lord Vader) writes...
>To Ron Baalke:(or anyone else who knows)     
> 
>re:
> 
>>1.      Magellan continues to operate normally, transmitting a carrier plus
>>40 bps X-band signal which is precisely tracked by the DSN (Deep Space Network
>>stations to provide gravity data.
> 
>>2.      The present command sequence is designed to automatically shift the
>>telemetry to the 1200 bps rate if the tracking pass is over a 70 m
>>station, based on the DSN station allocation schedule as of the time
>>the reference file was prepared.  In the event the station assignment
>>is changed, some telemetry may be lost because the 34 m stations
>>cannot successfully receive the 1200 bps rate due to the Transmitter B
>>noise spur.
> 
>Which DSN stations are 34 m and which are 70?  

All three of the DSN stations have the same complement of antennas.
Each DSN complex has one 70 meter antenna, two 34 meter antennas and one
26 meter antenna.  An additional 34 meter antenna is currently under
construction at Goldstone.  The transmitter on the Goldstone 70 meter 
is more powerful of the three complexes and is often used to bounce radar
off of bodies throughout the solar system.

>Also, do some of the DSN
>stations have the capability to recieve S-band and X-band at the same time,
>and if so, which ones? 

Each *antenna* is capable of receiving S-band and X-band simultaneously.
The determining factor being whether the spacecraft was designed to 
transmit in both bands are not.  Magellan is such a dual channel mission,
and the normal mode of operation is to send the engineering data (status
& health of the spacecraft) down the S-band, and the high rate science data down
the X-band. 

>And, who can I contact to get the parameters of
>the individual DSN stations and the entire DSN capabilites?

I'll give a summary, and if you want more details then contact the
Public Information Office at JPL at (818) 354-5011.  The DSN is composed
of three parts, the Deep Space Stations (DSS) themselves located at 
Goldstone, Madrid and Canberra, the NOCC (Network Operations Control Center,
and the GCF (Ground Communications Facility).  The stations track the
spacecraft, send commands to the spacecraft, and receive and process
telemetry data from the spacecraft.  The DSN stations also perform
VLBI tests.  The NOCC is located at JPL and it controls and monitors
the operations of the three complexes.  The GCF provides the communications
circuits that link the complexes and NOCC together.

>I understand that Magellan has limited capability to transmit engineering 
>data over the X-band transmitter due to the noise spur in the subcarrier.  
>Is this data then being transmitted via the s-band, and if so, like I asked
>above, is it being recieved at the same time as the x-band gravity data,
>or does it have to be recieved separately due to limited ground capabilities?

Both the radar and gravity data are transmitted down the X-band, and they
cannot be transmitted simultaneously because of the operational modes of the
spacecraft.  The radar mapping only requires the spacecraft to point its
High Gain Antenna at the Earth to provide a steady carrier signal 
which can be at a low telemetry rate, and this is the current
operating mode of the spacecraft.  In the radar mapping mode, the spacecraft
is required to go through complicated set of maneuvers using the  High Gain
to bounce the radar off Venus, record the data  on the tape recorders,  and 
then transmit it back to Earth.  Also, because of the large volume of radar 
data collected, a higher transmission rate is required.
     ___    _____     ___
    /_ /|  /____/ \  /_ /|     Ron Baalke         | baalke@kelvin.jpl.nasa.gov
    | | | |  __ \ /| | | |     Jet Propulsion Lab |
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